Oil and gas exploration of China Petroleum and Chemical ...Department of Oilfield Exploration &...

CHINA PETROLEUM EXPLORATION Volume 21, Issue 3, May 2016

Received date: 09 Mar. 2016; Revised date: 19 Apr. 2016. Corresponding author. E-mail: [email protected] Foundation item: China National Science and Technology Major Project “Forming Rule and Exploration Evaluation of Large/Medium Oil and Gas Fields in Marine Carbonate Reservoirs in the Tarim-Ordos Basin” (2011ZX05005-004). Copyright © 2016, Petroleum Industry Press, PetroChina. All rights reserved.

Oil and gas exploration of China Petroleum and Chemical Corporation during the 12th Five-Year Plan and the prospects for the 13th Five-Year Plan

Feng Jianhui1, Cai Xunyu1, Mou Zehui1, Gao Shanlin2

1. Department of Oilfield Exploration & Development, Sinopec; 2. Sinopec Exploration & Production Research Institute

Abstract: The China Petroleum and Chemical Corporation (“Sinopec”) has been focusing on its resource strategy and transform-ing its methods of development since the initiation of the 12th Five-Year Plan. In the past period, for the purpose of efficient ex-ploration, Sinopec funded in-depth research on hydrocarbon accumulation in structures like marine carbonates, foreland thrust belts, vast lithologic-stratigraphic reservoirs, and marine deep gas and shale gas formations. By continuously working on bottle-neck technologies, Sinopec has developed a series of characteristic techniques for data acquisition and processing, optimal and fast drilling of extra-deep wells, and reservoir evaluation of complicated reservoirs. With these supporting technologies, Sinopec achieved great breakthroughs and progress in large-scale petroliferous basins like those of the Sichuan, Ordos, Tarim, Junggar, Bohai Bay, and East China Sea, and realized the goal of stable development of oil resources and rapid development of gas re-sources. During the 13th Five-Year Plan, under the new normal of current economic conditions and the increasingly complicated internal and external environments, Sinopec will face many challenges in terms of exploration. Currently, Sinopec’s prospects in eastern China are in a stable development stage, with an average proven rate of oil resources of 46.4%, and its prospects in central and western China are still in the early exploration stage, where abundant contigent resources provide the basis for sustainable development. Thus, Sinopec’s resource strategy will consist of an increased focus on large-scale basins to make great break-throughs and discoveries and a renewed dedication to fine exploration in mature blocks to realize large-scale commercial discov-eries. Moreover, Sinopec will promote efficient exploration by creating theoretical, technical, and management innovations so as to make new contributions to the sustainable development of Sinopec and to guarantee the national energy security. Key words: oil and gas exploration, geologic cognition, exploration engineering technology, efficient exploration, Sinopec, the 12th Five-Year Plan, the 13th Five-Year Plan

The 12th Five-Year Plan marked a new period where Sinopec continued to promote efficient exploration by fully implementing the "transformation of development mode and improvement of development quality". In spite of severe challenges induced by the sharp drop of international oil prices, the new normal state of the economy in China, in-creasingly strict HSE requirements, and more complex ex-ploration targets, Sinopec adhered to the concept of bene-fit-based development, stressing the importance of discov-ering commercial oil and gas reservoirs while also shifting emphasis from focus on the reserve’s quantity to the re-serve’s quality. In regards to exploration deployment, Sinopec highlighted the preliminary exploration of traps, strengthened risk analysis, and optimized assessment ex-ploration. In regards to exploration decisions, Sinopec gave priority to optimal exploration projects, and strictly imple-mented the principle of "do not drill in these three situa-tions" (namely, don’t drill any risk wells in areas that do not have strategic guidance, don’t drill any wildcat wells in un-ascertained traps, and don’t drill any appraisal wells in areas

that may not provide any incremental economi-cally-recoverable reserves). By virtue of continuous re-search on oil and gas geological theories and technologies, Sinopec made significant breakthroughs in oil and gas ex-ploration and realized large-scale reserve increases in the subtle reservoirs of the old zones in the east, the clastic rock areas in the middle west, the marine carbonate area, and the marine shale gas area, thus creating a new period of oil and gas exploration.

1. Oil and gas exploration achievements dur-ing the 12th Five-Year Plan

1.1. Oil reserves steadily grew and gas reserves rapidly grew

In the first two years of the 12th Five-Year Plan, the cu-mulative newly-increased proven oil and gas reserves were 7.84×108 t and 6147×108 m3 respectively, and the annual newly-increased proven reserves were 3.92×108 t and 3073×108 m3 respectively. In the last three years of the 12th

2 CHINA PETROLEUM EXPLORATION Vol. 21, No. 3, 2016

Five-Year Plan, the cumulative newly-increased probable oil and gas reserves were 6.35×108 t and 9907×108 m3 re-spectively, and the annual newly-increased probable re-serves were 2.11×108 t and 3302×108 m3 respectively. The steady growth of oil and gas reserves laid a solid resource foundation for achieving a steady output of crude oil and a rapid production of natural gas (Fig.1). Of the newly-increased proven oil reserves, the east exploration area contributed 44.4% and the middle west exploration area contributed 55.05%. The crude oil output of Sinopec was stabilized at about 3300×104 t in the eastern old oil-

fields, and it increased to 161×104 t in the western new oil-fields. Of the newly-increased proven gas reserves, the Si-chuan Basin contributed 70%, the Ordos Basin contributed 17.3%, and the sea areas contributed 12%. Conventional gas output made great leaps and bounds, reaching 65×108 m3 during the 12th Five-Year Plan. Sinopec discovered and as-certained the first super-large shale gas field in China, which provided a proven shale gas reserve amount of 3806×108 m3 and a newly-established production capacity of 50×108 m3, with the cumulative gas output set at 43.9×108

m3.

Fig. 1 Petroleum initially in place and production of Sinopec from 2001 to 2015

During the 12th Five-Year Plan, Sinopec formed 11 large-scale areas with commercial reserves, including five 100-million-ton large-scale commercial oil reserve areas and six large-scale commercial gas reserve areas. In the Ji-yang exploration area, a cumulative amount of 38,600×104 t in commercial reserves were discovered in subtle reservoirs, such as the lithologic-stratigraphic oil reservoir in the southern slope of the Dongying sag, the stratigraphic oil reservoir in Sanhe Village in the Zhanhua sag, the lithologic-stratigraphic oil reservoir in the northeast part of Kendong sag, the lithologic oil reservoir in the Qingnan area, the lithologic-stratigraphic oil reservoirs in the Chengbei sag and the eastern slope, and the lithologic oil reservoir in the Linnan sag. Cumulative proven oil reserves amounting to 33,001×104 t were ascertained in the Mesozoic lithologic reservoirs in the southern Ordos Basin. Cumulative com-mercial reserves amounting to 20,305×104 t were discovered in the large karst marine carbonate reservoirs with uncon-formities in the Tahe oilfield and its periphery, mainly the main parts of the Tahe oilfield and the Yueshen block. Commercial reserves amounting to 17,960×104 t were found in the lithologic reservoirs at the west and north margins of the Junggar Basin, mainly the Neogene, Paleogene, Creta-ceous, and Carboniferous reservoirs. Cumulative commer-cial reserves amounting to 7,466×104 t were discovered in the faulted block and lithologic reservoirs in the North Ji-angsu Basin. Newly-increased proven gas reserves totaling

4,261×108 m3 were ascertained in the Upper Paleozoic lithologic gas reservoir in the northern Ordos Basin. Newly-increased proven shale gas reserve totaling 3,806×108 m3 were discovered in the Jiaoshiba area in the Fuling block. Newly-increased proven gas reserves totaling 2,710×108m3 were discovered in the middle and shallow lithologic gas reservoirs in the western Sichuan Basin. Newly-increased proven + probable gas reserves totaling 2,324×108 m3 were discovered in the middle and shallow lithologic gas reservoirs in the northeastern Sichuan Basin. Newly-increased proven + probable gas reserves totaling 2,175×108 m3 were found in the marine reef facies gas res-ervoir in the Yuanba area. Newly-increased probable gas reserves totaling 1,113×108 m3 were found in the marine gas reservoir in the Longmenshan front, in the Sichuan Basin.

1.2. Fuling shale gas field, the first super-large shale gas field in China, was discovered and ascertained

Sinopec started its shale gas play appraisal and explora-tion in 2006. Its strategic concepts have experienced three major changes since then. Firstly, through play appraisal across China (mainly South China, the Tarim Basin, and the eastern faulted basin) based on the experiences of North America, the marine (Cambrian and Silurian) formations in South China were selected as the main exploration layers[1]. Secondly, after drilling of some exploration wells (e.g. Xuanye 1, Huangye 1, and Xiangye 1), it was suggested that

Feng Jianhui et al., Oil and gas exploration of China Petroleum and Chemical Corporation during the 12th Five-Year ... 3

the marine formations in South China had complex struc-tures, poor preservation conditions, and a high thermal evo-lution degree. Thus, Sinopec turned its shale gas exploration towards the marine facies of the Longmaxi Formation res-ervoirs in the Sichuan Basin and its periphery, together with their Cambrian and continental strata. Thirdly, the drilling and evaluation of Well Pengye 1, Well Jiaoye 1, Well Jinshi 1, Well Xinye 1 (continental facies), Well Jianye 1, and Well Fuye 1 showed that the continental shale strata were characterized by abrupt facies changes, a small thickness, a low maturity, and other conditions that would have realized difficult commercial development, and additionally, the target marine strata outside of the basin had a normal pres-sure system with poor preservation conditions. So, these strata could not be commercially developed with the current technology and budget available. Following the commercial development of Well Jiaoye 1, Sinopec turned its shale gas exploration focus to the marine Silurian Longmaxi Forma-tion in the southeastern and southern Sichuan Basin. Break-throughs were made in Wells Jiaoye 1, 2, 3, 4, 5, 6, 7, and 8, which laid a solid foundation for capacity construction evaluation in the first and second phases. Additionally, in the Weiyuan-Rongxian, Rongchang-Yongchuan, Dingshan, Jingyan-Jianwei, Pengshui, and Wulong areas, commercial discoveries were obtained in Well Weiye 1 and Well Yongye 1, and important discoveries and breakthroughs were made in Well Dingye 1, Well Dingye 2, Well Jinye 1, Well Pengye 1, and Well Longye 1, which implied the po-tential for fast shale gas development in the southeastern and southern Sichuan Basin.

On the basis of comprehensive study and evaluation, Well Jiaoye 1HF was drilled in the Silurian Longmaxi For-mation in the Jiaoshiba block in February 2012. On No-vember 28 of the same year, this well provided a high-yield industrial gas flow of 20.3×104 m3 per day in production testing, recording a major strategic breakthrough in China’s

shale gas exploration[2]. In January 2013, Sinopec deployed a pilot well cluster in a 43 km2 shale gas play in the Jiaoshiba area in the Fuling block. In the same year, the newly-increased shale gas output capacity was 5×108 m3; in 2014, the production capacity was 25×108 m3. On December 29, 2015, Sinopec officially announced that the available production capacity of the Fuling shale gas field was up to 50×108 m3. By the end of 2015, the proven shale gas area was 383.54 km2, with proven shale gas reserves totaling 3,805.98×108 m3. Thus, the first large shale gas field was born in China.

Sinopec obtained a series of new achievements in shale gas exploration and development. Firstly, a series of inno-vative theories and technologies were developed. By study-ing the differences between the marine shale gas of the southern exploration area and the shale gas of North Amer-ica, Sinopec proposed that deep continental-shelf shale was the foundation for the enrichment of marine shale gas, or-ganic pores were the main reservoir spaces of shale gas, and good preservation conditions were critical for the enrich-ment and high yield of marine shale gas (Fig.2). Sinopec reinforced its analysis regarding the main controlling factors for shale gas enrichment by forming the marine shale gas evaluation system and standard with consideration to “the quality of shale, preservation conditions, and the economy”, thus providing theoretical guidance for selecting marine shale gas zones/layers in China. Secondly, five technical systems were innovated and developed specifically for the Fuling marine shale gas, i.e., comprehensive evaluation of shale gas reservoir, efficient and fast drilling of horizontal wells, staged fracturing and gas testing of long horizontal wells, supporting technologies for production testing, and supporting technologies for green development[3]. Thirdly, the equipment and technologies for the development of shale gas in China were improved. Sinopec independently developed some movable and efficient “well factory” drilling

Fig. 2 TOC vs. gas content and pressure coefficient vs. gas production of high-quality shale in the Wufeng Formation – the first member of Longmaxi Formation, the Sichuan Basin


rigs, such as the stepwise rig, the wheel-track rig and the rail rig. Sinopec also launched its high-power 3000 hp fractur-ing unit, its coiled tubing operating vehicle, and its efficient drilling assembly, drillable bridge plug and supporting downhole tools. Sinopec realized that the localization of en-gineering and technical equipment was suitable for reser-voirs shallower than 3500 m. Thus, the R&D and manufac-turing capacities of domestic petroleum machinery and equipment were greatly improved.

The Fuling national shale gas demonstration zone is the first large scale shale gas field that has been commercially developed within China, and the second largest only to that of North America’s. The high level, high speed, and high quality development & construction of the demonstration zone demonstrate the theoretical innovation, technical in-novation, and management innovation capacities of China’s shale gas exploration and development process. It success-fully reflects the concept of "innovative, coordinative, green, open, and sharing" development. Therefore, led by its guiding concepts, China’s shale gas exploration and development process will vigorously drive the process of shale gas explora-tion and development, optimize energy structure, promote en-ergy conservation and emissions reduction, and improve envi-

ronmental quality. Moreover, the theory, technology, and management systems thus formed provide a replicable and re-peatable experience for China's shale gas exploration and de-velopment as the technical equipment, standard specifications, enterprise-local area cooperation, and industry-study-research combinations have already been facilitated under the develop-ment of this demonstration zone.

1.3. Conventional gas exploration maintained a vigor-ous trend

Since the 12th Five-Year Plan, Sinopec has strengthened its natural gas exploration. Specifically, Sinopec deepened the study on hydrocarbon accumulations and enrichment in superimposed basins in central and western China, such as the Tarim, Sichuan, and Ordos Basins, as well as in the hydrocarbon-rich areas in the East China Sea, and Sinopec has also enhanced its research on seismic tech-niques to define multi-level and multi-type targets. In the marine facies of the western Sichuan Basin, the northern Ordos Basin, and the north slope of the central Tarim Basin, Sinopec achieved three major discoveries and ascertained a number of large and medium commercial gas reserve areas (Table 1).

Table 1 Sinopec’s achievements of gas exploration (including shale gas) during the 12th Five-Year Plan Newly-increased gas in place/108 m3

Basin Block/play Type of gas reservoir Horizon Lithology Proven Probable Possible

Western Sichuan Lithologic, structural- lithologic Jurassic, Triassic Clastic rock, carbonate 2661 5402 8545

Northeastern Sichuan Lithologic Permian-Triassic, Jurassic Clastic rock, carbonate 2392 4632 4857 Sichuan

Jiaoshiba Shale gas Silurian Shale 3806

Ordos Hangjin Banner Lithologic, structural- lithologic Permian Shanxi Fm, Shihezi Fm Clastic rock 58 4408 3780

Tarim North slope of Central Tarim Structural- lithologic Ordovician Carbonate 52 582 603

1.3.1. Significant exploration discovery was made in the Marine Leikoupo Formation of the Longmenshan piedmont zone in western Sichuan Basin

Gas exploration in the Leikoupo Formation of the Si-chuan Basin began in the 1970s. After more than 50 years, a series of small and medium gas reservoirs and gas-bearing structures have finally been found. “As there is no large-scale weathering crust type reservoir or pore type reservoir and the underlying Permian source rocks are far away, therefore there must not be any hydrocarbon source developing in this area.” Such traditional concepts restrict exploration in this area.

After the discovery of large marine gas fields, such as the Puguang and the Yuanba, Sinopec deployed 22 regional seismic profiles for the marine strata in the western Sichuan Basin. Combined with the regional research results, it was thought that the Marine Leikoupo Formation might have good accumulation conditions. In 2007, in the Xinchang

structural belt in the western Sichuan Basin, Well Chuanke 1, a research and study well, was drilled, and it obtained a high-yield gas flow of 86.8×104 m3/d in the weathered crust on the top of the Leikoupo Formation. Since then, the ma-rine facies exploration in the western Sichuan Basin has ramped up. Subsequently, Well Xiaoshen 1 and Well Xin-shen 1 both revealed high quality reservoirs in the Leikoupo Formation. Well Xinshen 1 obtained a high-yield gas flow of 68×104 m3/d, and Well Xiaoshen 1 produced a low-yield gas flow due to its lower location in the structure[4]. In 2012, Sinopec made efforts in seismic acquisition scheme optimi-zation, complex structure imaging, and fine modeling and interpretation in the mountain front of the western Sichuan Basin, and Sinopec used the "extension frequency + inver-sion" prediction technology to accurately ascertain the res-ervoir’s location. Important progress was made in research relating to source rocks, reservoir characteristics, and for-


mation mechanisms. On this basis, Well Dushen 1, Well Tongshen 1, and Well Pengzhou 1 were respectively de-ployed in the south and north slopes of the Xinchang struc-tural belt and in the Longmenshan piedmont zone (Fig.3). All three of these wells encountered high-quality reservoirs in the Leikoupo Formation, which indicated that the Leik-

oupo Formation reservoirs are widely distributed in the western Sichuan Basin. Upon its construction’s completion in the Leikoupo Formation, Well Pengzhou 1 obtained a high-yield industrial gas flow of 121×104 m3/d in testing, which is a great discovery for marine exploration in the Longmenshan piedmont zone.

Fig. 3 Exploration of the Leikoupo Formation in the western Sichuan Basin

After the breakthrough was made in Well Pengzhou 1, according to the deployment guidelines of focusing on the Jinma-Yazihe River structural belt of the Longmenshan piedmont zone to confirm the scale of the gas reservoir to find the large marine gas field, Sinopec deployed Well Ya-shen 1 and Well Yangshen 1 in 2014. Actual drilling re-vealed that the reservoirs of these two wells are thick, with a cumulative thickness of more than 100 m, which can be di-vided into upper and lower reservoir intervals. The dissolu-tion pores/cavities develop in the lower reservoir interval. High-yield gas flow was obtained in the test. The discover-ies from the marine Leikoupo Formation in the western Si-chuan Basin broke the traditional idea that the hydrocarbon sources of the Leikoupo Formation gas reservoir are insuffi-cient; instead, new knowledge was gained; namely, large-scale reservoirs exist in this area and hydrocarbons were accumulated from multisources in multi-phases. The

Indosinian movement made the top of the Leikoupo Forma-tion suffer from erosion, thus causing the development of a large-scale dissolution fracture-pore dolomite reservoir[5]. The reservoir’s space is dominated by intercrystalline dis-solution pores, irregular dissolution pores, and dissolution fractures. It is predicted that the favorable reservoir area of the Leikoupo Formation is 5280 km2 and the reservoir thickness is 10-60 m. The Leikoupo Formation gas reservoir is characterized by a hydrocarbon supply from multiple sources in multiple phases, preservation controlled by dolomite dissolution, accumulation controlled by struc-tural-stratigraphic traps, and enrichment in the uplifted zone and slope zone.

After seven years of efforts from 2007, when Well Chuanke 1 was deployed in marine formations in the west-ern Sichuan Basin, to 2014, when Well Pengzhou 1 achieved its breakthrough, great breakthroughs were finally


made in the marine facies in the western Sichuan Basin. Thus, the presence of a reserve increasing belt with reserves totaling 3000×108 m3 has basically been confirmed. 1.3.2. A new reserve increasing belt with the reserves of 5000×108 m3 was formed in the Hangjin Banner in northern Ordos Basin

The Paleozoic gas exploration in the Hangjin Banner be-gan in the 1980s. In 2003, important discoveries and large-scale natural gas reserves were obtained in the Upper Palaeozoic of the Daniudi gas field in the south of the adja-cent block. Accordingly, a study suggested that the Hangjin Banner stretches across the Yimeng uplift, Yishan slope, and Tianhuan syncline, and that multi-phase large deltas have long been located at the paleo-uplift slope. Good Up-per Palaeozoic source rocks develop in the west and south of the slope. So, the Hangjin Banner has the accumulation conditions similar to that of the Daniudi gas field.

During the 12th Five-Year Plan, Sinopec continued the G&G study and the integrated deployment of exploration & development. Several widely-distributed overlapping gas reservoirs were found via the exploration and development method of “fine 3D reservoir prediction + staged fracturing horizontal well", thus realizing the leapfrog development of

Upper Palaeozoic gas exploration in the northern Ordos Ba-sin. In the early stage of the 12th Five-Year Plan, guided by the concept of “source-oriented exploration”[6], the explora-tion focused on the coal-measure source rocks in the south of the Boerjiang Haizi fault, and breakthroughs were made in Wells Jin 6, 7, 8, 9, and 10. In the late stage of the 12th Five-Year Plan, it was determined that the north area of the Boerjiang Haizi fault had been in the structural high throughout the basin evolution process and was thus a fa-vorable destination for gas migration. The rapid lateral changes of the delta sand body and the fracture development made it easy for the formation of structural traps and lithologic-structural composite traps, and small faults are conducive to vertical hydrocarbon migration into the He 2 and He 3 Members and the upper Shihezi Formation sand body for accumulation. With regards to this knowledge, Sinopec reinforced the accuracy of this prediction by utiliz-ing geophysical multi-attribute sand body and gas-bearing properties detection. Commercial air flow was obtained from several wells and the gas-bearing area was greatly ex-panded (Fig.4). During the 12th Five-Year Plan, 3P gas re-serves totaling more than 5000×108 m3 cumulatively were booked.

Fig. 4 Profile of the upper Paleozoic gas reservoir in the Hangjin Banner, the northern Ordos Basin

1.3.3. Great discovery was made in exploration of ma-rine carbonate gas reservoir in the Shuntuoguole low uplift in the north slope of the Central Tarim area, the Tarim Basin

The Central Tarim area is one of the major hydrocar-bon-rich belts in the Tarim Basin. At the end of the 11th Five-Year Plan, the comparative research of the Central Tarim uplift belt and the Tahe area accumulation conditions suggested that this area had superior accumulation condi-tions. Firstly, during the middle Caledonian, the Northern Tarim, Central Tarim, and Shuntuoguole areas were entirely lifted and corroded. The Yijianfang Formation-Yingshan Formation in the coverage area of the upper Ordovician in

the heading side of the Central Tarim I slope-break belt has Caledonian karst reservoir development conditions similar to that of the Northern Tarim uplift (See the bead-shaped re-flections of the Yijianfang Formation-Yingshan Formation on the two-dimensional seismic section). Secondly, near the Manjiaer hydrocarbon depression, several NE-trending shear faults developed in the Suntuoguole area, which are helpful for oil and gas migration and reservoir improvement. In Well Shunnan 1, deployed in 2010, a daily output of 3.87×104 m3 of natural gas was obtained in the test of the Yingshan Formation, breaking the traditional ideas that “no large-scale karst reservoir develops in the coverage area of the upper Ordovician in the heading side of the Central


Tarim I slope-break belt” and that “oil and gas in the slope area adjusts to the high structural fault zone of the Central Tarim I slope-break belt”. In 2011, a large area of 3D seis-mic exploration was conducted, providing high quality data for meticulously describing the carbonate fracture/cavity bodies of this area. Seismic data showed that truncated re-flector characteristics are obvious near the Central Tarim I slope-break belt and Guchengxu uplift, the denudation of the Yijianfang Formation is reduced, and plenty of deeply buried beads along the layers were reflected on some seis-mic sections. Analysis shows that this area has a frac-ture–pore reservoir in the upside of the Yijianfang Forma-tion-Yingshan Formation, and the fracture–pore reservoir in the downside of the inner Yijianfang Formation-Yingshan Formation. The development of the reservoir body is con-trolled by the sequence interface, fractures, and hydrother-mal conditions, which vary. The high part of the ancient landform and NE-trending fault zone is the favorable area

for the development of reservoirs. Wells Shunnan 4, 5, 6, and 7 were deployed and high-yield industrial gas flow was obtained in the lower member of the Yingshan Formation and the Penglaiba Formation. In 2014, the Shuntuoguole uplift slope area was further explored northward. High-yield gas flow was obtained in the Yingshan Formation from Well Shuntuo 1, marking a new discovery in the exploration of the Shuntuoguole low uplift belt. Exploration results showed that the heading side of the Central Tarim I slope-break belt, the Shuntuoguole and Guchengxu areas, are likely to be a large gas field that is controlled by the fracture-pore reservoir, displays a high gas column and mul-tiple longitudinal superposed layers, and is composed of relatively independent gas accumulation groups[7] (Fig.5). All of the gas reservoirs are over 6000 m deep, and they are characterized by high temperatures and high pressures. It is expected that the reservoirs have geological reserves total-ing over 100 billion m3.

Fig. 5 Profile of N-S geological structure and reservoir in the east of central Tarim Basin

1.4. New progress was made in fine oil exploration in mature areas

Oil exploration is concentrated in the complex fault blocks in the eastern mature exploration areas, the litholo-gic-stratigraphic reservoir, the carbonate reservoir in the Tarim Basin, the vast clastic rock reservoir in the south of the Ordos Basin, and the complex and subtle reservoirs in the Junggar Basin and other areas. A number of large-scale commercial reserve zones were found (Table 2). 1.4.1. Important progress was made in fine exploration in the eastern oil-rich sags

At the beginning of the 12th Five-Year Plan, the eastern exploration area was confronted with numerous difficulties. The exploration rate was high in mature exploration areas,

and major oil-rich sags, with an exploratory well density greater than 0.2 well/km2, were almost completely mapped with 3D seismic technology. With a high level of both hy-drocarbon discoveries and proven resources, these areas had an average proven reserve rate of 47.78%, and 16 oil-rich depressions among them had a proven rate of 55.6%. There was a large amount of remaining resources, with a remain-ing quantity of 70.38×108 t. The sixteen oil-rich sags had a remaining amount of 55.3×108 t between them and a re-source abundance of 9.89×104 t/km2. The resource explora-tion rate did not match the discovery rate in different zones and different strata, and the depressions’ periphery along with reserves blank areas became major exploration tar-gets[8]. Main exploration layers were buried deeply, around 2800 m underground. Reservoir strata had a thin


Table 2 Sinopec’s achievements of petroleum exploration during the 12th Five-Year Plan Newly-increased oil reserves/108 tBasin

(depression) Block/play Type of oil reservoir Horizon Lithology Proven Probable Possible

Junggar Northwestern margin Lithologic-stratigraphic Neogene, Paleocene, Cretaceous, Jurassic, Carboniferous Clastic rock, volcanic 0.98 1.98 1.97

Ordos Zhenjing (Zhenyuan -Jingchuan) Lithologic Triassic, Jurassic Clastic rock 1.84 1.21 1.78

Tarim Tahe Lithologic-stratigraphic Neogene, Paleocene Carbonate 2.80 2.35 1.74

Dongying sag Neogene, Paleocene Clastic rock 1.78 1.81 1.63 Jiyang

Zhanhua sag Neogene, Paleocene Clastic rock 0.81 1.86 1.82 Gaoyou sag Fault block lithologic Neogene, Paleocene, Cretaceous Clastic rock 0.17 0.30 0.51

Northern Jiangsu Hai’an sag Fault block lithologic Neogene, Paleocene Clastic rock 0.13 0.13 0.23

Qintong sag Fault block lithologic Neogene, Paleocene Clastic rock 0.15 0.28 0.24

Jianghan Qianjiang sag Fault block lithologic Neogene, Paleocene Clastic rock 0.12 0.13 0.18

thickness, generally less than 10 m. Glutenite, beach bar sand bodies, turbidite, river sand, and small complex fault-blocks became complicated main target types. The trap area was small, mostly less than 0.1 km2.

Facing the above problems and challenges, Sinopec needed new innovative ideas in exploration. Firstly, by re-evaluating the potential of oil and gas resources in certain locations[9], increases ranging from 11% to 35% in regards to oil resources were made in seven depressions (Dongying, Zhanhua, Chezhen, Dongpu, Qianjiang, Biyang, and Gaoyou). Thus, the amount of total resources increased by 31.52×108 t, an increase of 30%, which enhanced the de-velopment confidence. Secondly, Sinopec deepened its un-derstandings on the underlying causes for differences in hy-drocarbon accumulation, and it established similarities and differences regarding the distribution mode of hydrocarbon accumulations in continental fault basins, which effectively guided fine exploration in mature areas. Thirdly, Sinopec developed and improved high precision 3D seismic explora-tion technology and then applied it to oil and gas regions in the east. During the 12th Five-Year Plan, high precision 3D seismic technology was applied in the eastern oil and gas regions over an area of 8404 km2, with the basic frequency increased by 10 Hz on average, the broadband broadened by 8 to 23 Hz, and the resolution improved by 50%. The minimum distinguishable fault displacement reached 8 m, and the identification of fault block traps was accurate to 0.02 m2. To meet new requirements for fine exploration, Sinopec constantly carried out research and improved tech-nology, and importantly, it innovated a series of exploration technology used in complex fault blocks, beach bar sand-bodies, glutenite, turbidite, river sand, basin margin forma-tions, and others, which guaranteed efficient development of fine exploration. Fourthly, by innovating exploration man-agement mechanisms, strengthening investment benefit evaluation, adhering to the integration of exploration and

development, making efforts to identify scale high-quality reserves, and focusing on commercial discoveries and effec-tive uses for those discoveries, Sinopec sought to continue to advance its exploration efforts.

During the 12th Five-Year Plan, new discoveries were made in “three new domains”. Firstly, new exploration dis-coveries were made in new areas such as in the small sags near oil-rich sag margins. Taking the Sanhecun oilfield in the Jiyang depression as an example, from the Guantao Formation to the Sanhejie Formation in Sanhecun Village, there were oil and gas shows from an unknown source. Thus, no substantial discoveries were made in the past. By ana-lyzing the geological factors in the accumulation stage, however Sinopec was able to discover that the region pos-sessed early accumulation conditions (Fig.6). Then, by fine evaluation, Sinopec made breakthroughs in the third mem-ber of the Shahejie Formation and the upper Guantao For-mation, and found the 75th oilfield in eastern Shengli: The Sanhecun oilfield[9]. As a result, the newly-increased prob-able and possible oil reserves amount rose to 4211.4×104 t, and the oilfield’s planned production capacity is 16.26×104 t. Breakthroughs were also made in other areas such as Chen-jiazhuang area and Kendong area of the Jiyang depression, the southwest low-lying land of the Dongpu sag, the south slope of the Jiangling sag, and the Jinshan area of the Lishu fault depression. Secondly, subtle reservoir exploration de-veloped in depth and new discoveries were made in new fields. By further improving knowledge of the hydrocarbon accumulation mode of subtle reservoirs, exploration guide-lines gradually changed from searching “along faults, fol-lowing sources, and exploring sand” to “going down de-pressions, following sand, and exploring fan areas. As a re-sult of these new exploration ideals, Sinopec made break-throughs in new types of sublacustrine fans and pinch-outs of updip sandstone, which both demonstrated Sinopec’s new ideas, namely “point to the surface” and “from single to


Fig. 6 Hydrocarbon accumulation mode in the Sanhecun oilfield, the Jiyang depression

multiple”, and expanded new areas for "second time explo-ration" in fault basins. New discoveries were respectively made in the Gaoyou sag sublacustrine fan, the northern Qi-jiang fault zone lithology in the Qianjiang sag, the Qingnan sag beach-bar sandbody, the south slope of the Jiangling sag, the Shigang fault zone in the Jinhu sag, and other new fields. Thirdly, new breakthroughs were achieved in the deep strata of oil-rich sags and other new strata. Although the eastern fault basins have superior hydrocarbon geological condi-tions, there was little progress made in preliminary explora-tion due to the poor quality of the deep stratum seismic data, small-fault identification difficulties, and multiple results regarding reservoir location prediction. In recent years, through fine interpretation of high-precision 3D seismic data, fine characterization of sand, and low resistivity of reservoir identification, breakthroughs were made in the lower part of the fourth member of the Shahejie Forma-tion-the Kongdian Formation of the Zhanhua sag, the fourth member of the Shahejie Formation of the Bonan sag, the Permian in the Huzhuangji of the Dongpu sag, and the lower He-3 member of the Biyang depression, all of which highlighted a huge exploration potential.

During the 12th Five-Year Plan, Sinopec obtained 10 large-scale commercial discoveries in the eastern explora-tion areas and discovered 5 reserves-increasing areas with cumulative reserves totaling 5000×104 t, contributing to newly-increased 3P reserves totaling 17.6×108 t. 1.4.2. New discoveries were made in oil exploration in the lower Paleozoic of the Tarim Basin

By the end of the 11th Five-Year Plan, the Tahe oilfield provided an OOIP of over 10×108 t, which was mainly dis-tributed in the main part of the oilfield. Exploration rates were low in the deep, southern, and subsalt layers of the Tahe oilfield. During the 12th Five-Year Plan, the oil explo-

ration goal was to deepen the exploration in the Tahe mature area, and to actively expand new periphery areas. By im-plementing high-precision 3D technology in the subsalt area of the southern Tahe to further finely characterize faults and clarify the location of unconformable surfaces and abnormal reflexes of fracture-caves, Sinopec focused on exploring the distribution of fault zones along strike-slips and laterally sealing good targets. Well TP39, Well TP42, and Well AT27X were deployed in the Tuofutai area in the eastern Tahe oilfield, and they obtained high-yield hydrocarbon flows which essentially controlled the oil and gas reserves in the entire subsalt eastern region. Well S1181, Well AT5, Well AT22, and other wells in the western Tahe oilfield also obtained high-yield oil flow, forming a new capacity front. By positively assessing reserves blank areas in the northern region, Sinopec made new discoveries in the Yuqi area. Meanwhile, Sinopec strengthened the exploration of oil-gas rich regions under the main karst reservoirs, and Well Tashen 3 obtained an industrial oil and gas flow during rou-tine testing of the fracture-cavern body of the upper part of the inner Yingshan Formation, which provided new motiva-tion for exploring the lower Ordovician inner carbonate rock structure of the Tahe oilfield. During the 12th Five-Year Plan, the Tahe oilfield submitted proven oil reserves totaling 27,380×104 t and gas reserves totaling 18.92×108 m3.

Sinopec has always insisted on deepening the overall evaluation of the northern Tarim Basin. Palaeotectonic analysis shows that the Yuejin and Shuntuoguole-Manjaer areas are located in the south wing of the Northern Tarim palaeohigh formed at the end of the Middle Ordovician. The Yijianfang Formation has a vast area of karst reservoir de-velopment conditions similar to that of the southern Tahe oilfield. The karst fracture-cavern body is controlled by the NE and NW strike-slip faults, and it is located on a


long-term path used for transporting western oil sources to the northeast, which indicates that the reservoir has excel-lent accumulation conditions. Well Yuejin 1x and Well Yuejin 2x, deployed in 2012, made breakthroughs in oil and gas exploration and submitted proven oil reserves totaling 1100×104 t. Sinopec further confirmed that the NE and NW deep fault zones at the south of the Northern Tarim pa-laeohigh were favorable locations for reservoir development

and oil-gas accumulation. Well Shunbei 1-1H, deployed in 2013, obtained a daily crude oil output of 184.95 t and a gas output of 9.07×104 m3, which marked a major breakthrough in the exploration of the Tahe periphery. Thus, the hydro-carbon-bearing area in the Northern Tarim palaeohigh was further expanded (Fig.7), consolidating Sinopec’s confi-dence in exploring the Ordovician carbonate rocks of the Shuntuoguole low uplift.

Fig. 7 Hydrocarbon accumulation mode in the Yuejin – northern Shuntuoguole, the Tarim Basin

1.4.3. Important achievements were made in the ex-ploration of the Mesozoic Yanchang Formation low-porosity and extra-low-permeability sandstone res-ervoir in the south of the Ordos Basin

The exploration area in the South of the Ordos Basin in-cludes Zhenyuan, Jingchuan, Changwu, Binxian, Fuxian, and other areas. Besides being close to the Chang 7 Member source rocks, which have a certain thickness, the exploration area is also close to the Chang 7 Member and the source rock development center of the whole basin. The over pres-suring of the Chang 7 Member of the main source rocks provides adequate migration power for two-way hydrocar-bon expulsion, and it also provides conditions for multiple layer accumulation. With the advances of exploration tech-nology, the economic value of low porosity/extra-low po-rosity and extra-low permeability resources in the Yanchang

Formation in the Ordos Basin is further highlighted. During the 12th Five-Year Plan, Sinopec strengthened their explora-tion work in the Ordos Basin, which served as a major front for increasing reserves and production. Firstly, Sinopec deepened their understanding towards hydrocarbon accu-mulation, centering on the characteristics of low poros-ity/extra-low porosity, extra-low permeability resources in the Yanchang Formation. Studies suggested that the Yanchang Formation has developed a large river delta sys-tem with a large average sand body thickness in multiple periods. Favorable sedimentary microfacies and favorable diagenetic facies jointly control the extra-low permeability reservoirs in the Yanchang Formation at the south of the ba-sin. Favorable sedimentary microfacies determine the res-ervoir rock fabric, the mineral components, and the sand thickness while favorable diagenetic facies determine the


relative size of the physical properties of the reservoirs within the same sedimentary microfacies while also playing a dominant role in determining the effectiveness of the res-ervoirs. Its tectonic structure is characterized by being low in the west and high in the east, and southeast fractures and northeast fractures are likely to be web-intersected, which constitutes a fracture pathway system and also improves the pore structure of the reservoirs. On the whole, the Yanchang Formation is a low porosity and extra-low permeability res-ervoir which has a strong reservoir heterogeneity, a large displacement pressure, and a median pressure; that means that it has large resistance to oil and gas lateral migration and, as a result, low well production. On this basis, Sinopec proposed a new insight for low permeability oil reservoir accumulation; namely, the “primary source setting, fa-cies-controlled reservoir with two-way hydrocarbon expul-sion and near-source reservoir accumulation”, which effec-tively guided the exploration deployment work. Secondly, Sinopec carried out research and formed a set of key 3D seismic acquisition technologies suitable for the Loess Pla-teau region, and established a comprehensive evaluation technology series for the area’s vast amount of lithologic traps. This effectively solved problems facing the seismic reservoir identification description and helped to forecast high-yield enrichment zones. At the same time, Sinopec learned lessons from unconventional oil-gas exploration, carried out staged fracturing tests of horizontal wells to strengthen technological research for improving single-well productivity, and made efforts to improve reserve utilization rate to enhance reserves’ value. Thirdly, based on the vast area’s lithologic reservoir characteristics, in accordance with the idea of “overall evaluation, overall deployment, and overall control,” Sinopec implemented an operation method involving the integration of progressive exploration and de-velopment to promote efficient exploration. Sinopec devel-oped 4 hundred-million-ton sized reserves and increased production in-the Zhenjing, Weibei, Jinghe River, and Luohe River zones, with 3P oil reserves totaling nearly 10×108 t. 1.4.4. New discoveries were made in the subtle reser-voir exploration at the western margin of the Junggar Basin

Oil and gas exploration at the western margin uplift zone of the Junggar Basin started in the 1950s. Then, Sinopec successively found more than 10 oilfields, such as the Karamay, Hongshanzui, Urho, and Xiazijie, around the pe-riphery of the uplift zone, with proven oil reserves totaling nearly 20×108 t. These discoveries are concentrated in places near the hydrocarbon-generation depression of the uplift zone. Although Sinopec had drilled several wells near

the basin margin, no oil and gas were discovered. This place was thought to be far away from the hydrocarbon source re-gion and the exploration prospects were not promising. Sinopec had registered the site’s mining rights in 2000, however, and Sinopec thought that the basin margin was both in a positive structural development zone and a favor-able area for long-term hydrocarbon migration. Oil and gas could be migrated along unconformable surfaces, but the key was to find favorable reservoir sand bodies. In 2005, a breakthrough was made in Well Pai 2, which was deployed with the Neogene Shawan Formation as the target. During the 11th Five-Year Plan, exploration results were further ex-panded, and Sinopec successively discovered and proved the existence of two oilfields (Chunguang and Chunfeng), opening up new prospects for efficient, high quality oil ex-ploration at the western basin margin regions.

During the 12th Five-Year Plan, Sinopec adhered to fine exploration at the western margin of the Junggar Basin and constantly expanded its search for reserves to the west and north to find new types of reserves, explore new strata, and form new reserve locations. In the existing reserve areas, Sinopec insisted on the integration of exploration and de-velopment along with the increased usage of prediction and evaluation technology in the lithologic-stratigraphic traps of the Shawan Formation. Sinopec made full use of the “side lobes” seismic waves technology, amplitude attributes, and other means to describe the distribution of sand bodies at different stages. Thus, it ensured an increase in reserves and a stable yield. Meanwhile, Sinopec intensified research on sedimentary facies, unconformable traps, and fine charac-terizations of palaeogeomorphology, and eventually discov-ered new oil-bearing strata such as the Jurassic, the Creta-ceous, and the Carboniferous, which had ten-million-ton scale reserves.

Sinopec carried out research on prototype basin restora-tions, recognizing the existence of a large area of Permian source rocks under the Nappe structure of the Sahara Hart Mountain, which has a source rock distribution that extends west for nearly 10 km, an area of over 1000 km2. The Mesozoic and Cenozoic in the area were in a single-sloping state for a long time with undeveloped faults and relatively simple structural forms, which constituted favorable condi-tions for large-scale Jurassic and Cretaceous stratigraphic reservoirs. Through detailed study of 3D data, Sinopec chose relatively shallow favorable stratigraphic traps to de-ploy and drill in with their deployment of Well Haqian 1, and it made a breakthrough in the Jurassic system, discov-ering the Chunhui oilfield with 5000×104 t in reserves. By exploring westward, Sinopec obtained industrial oil flows in multiple strata of the Jurassic, Triassic, and Carboniferous,


eventually discovering the ten-million-ton Arad oilfield. In the southwest of the Chepaizi uplift, by comparing oil and gas sources, Sinopec thought that the Sikeshu sag had a good hydrocarbon potential. The updip direction area was liable to form lithologic-stratigraphic reservoirs as oil and gas were transported along faults and unconformable sur-faces. Sinopec made a breakthrough by applying fault-sand

stone matching and directional technology to identify favor-able zones and targets (Fig.8). In the past 5 years, Sinopec has discovered composite hydrocarbon accumulation zones in multiple strata of the Neogene, Paleogene, Cretaceous, Jurassic, Carboniferous, and Permian, with 3P reserves to-taling nearly 4×108 t. This place has become a crude oil production base with a production totaling 200×104 t.

Fig. 8 Hydrocarbon accumulation mode in the Chepaizi region at the western margin of the Junggar Basin

2. Prospects for the 13th Five-Year Plan

During the 12th Five-Year Plan, Sinopec vigorously pro-moted efficient exploration and achieved a major break-through in shale gas. Conventional gas exploration contin-ued to rapidly develop and oil exploration made significant progress, creating a new and better situation for oil and gas exploration. Facing the new normal of economic develop-ment, and the severe situation and major challenges induced by increased difficulties in exploration, Sinopec will have a difficult path in regards to oil and gas exploration during the 13th Five-Year Plan.

2.1. New challenges for oil and gas exploration

Firstly, the external economic environment poses serious challenges. There is still no recovery sign from the precipi-tous fall of international oil prices and low oil prices could become the new normal during the 13th Five-Year Plan, which would have a huge impact on the upstream business. China has implemented more stringent environmental pro-tections and energy-saving policies, and for exploration ac-tivities, there are always diplomatic, military, special plan-ning, and other sensitive risks. China’s new management law on mining rights puts forward higher requirements on block management. Out of the big basin areas over which

Sinopec possesses mining rights, oil-rich sags account for just 27.9% of the basin area, and most mining rights in big basins are centered on the basin margins or deep hinterland areas while other mining-right blocks are eastern outlying areas with poor oil and gas geological conditions, western small and medium-sized basins, or southern regions with a high evolution degree[10]. Hydrocarbon accumulation condi-tions are complex, and conflicts may arise between different companies regarding investments and the mining rights & interests in many blocks.

Secondly, oil and gas exploration objectives are more complex. Oil-rich sags in the eastern oil and gas-bearing ba-sins are faced with challenges of clastic rock porosity, lower permeability, increased depth, smaller targets, lower grades, special reservoirs, and the fact that old seismic data cannot meet the requirements for fine exploration. Western regions with a low level degree of exploration may encounter many challenges such as a poor surface condition around the basin margin, poor overall preservation conditions of oil and gas, deep-buried target strata in basins, great difficulties in res-ervoir prediction, high-sulfur content natural gas, and the fact that drilling and completion techniques have high re-quirements. Take oil exploration in the east as an example: low permeability and extra-low permeability reserves ac-counted for 75% of the newly-increased probable reserves


during the 12th Five-Year Plan and the ratio of mid-deep strata reserves to the total number of reserves increased from 35% in the 10th Five-Year Plan to 57% in the 12th Five-Year Plan.

Thirdly, low oil prices raise higher requirements on effi-cient exploration. Oil prices have stayed low for a long time while exploration fields constantly extended to ultra-deep strata, areas with ultra-high pressure, ultra-high temperature, and complex structure zones, and ultra-tight reservoirs. The cost of new, innovative engineering technology to maintain oil and gas discoveries has become increasingly demanding, resulting in a substantial increase in the cost of oil and gas discoveries and highlighting conflicts between comprehen-sive benefits and resource discovery.

Faced with these challenges, Sinopec should go forward with an open mind, reducing resistance to changes in con-cepts, strengthening research on zones and belts, intensify-ing technology research, reinforcing economic evaluations, focusing on quality and efficiency, and insisting on oil-gas breakthroughs and commercial discoveries in order to maintain substantial development.

2.2. Potential of oil and gas exploration

2.2.1. It is at the early and mid-stage of exploration dis-covery and there is still great resource potential in the future

In the eastern oil-rich sags, the average proven rate of oil resources is 46.4%, with remaining resources totaling 89.22×108 t. There is still a rich resource base for sustain-able development if the world’s current amount of proven oil resources discovered is calculated at 70%. The proven rate of oil resources in western China is 16.8% because it is still at the early and middle stages of exploration. Sinopec’s exploration areas currently possess probable reserves of 14.62×108 t, possible reserves of 17.27×108 t, contingent resources of 43.8×108 t, and remaining resources of 203.79× 108 t, which provide a good resource base for efficient, sta-ble development. The proven, probable, and possible gas reserves are 2.18×1012 m3, 2.0×1012 m3, and 2.1×1012 m3 respectively; the contingent resources are 8.62×1012 m3, and remaining resources amount to 19.91×1012 m3; the proven rate is 9.86%. The proven rates of natural gas resources in the Sichuan Basin and Ordos Basin are 16% and 16.3% re-spectively, and 4.45% and 2.95% respectively in the East China Sea shelf and the Tarim Basin. Natural gas resources have a high abundance, a large upgrade potential, and pos-sess conditions for rapid development. 2.2.2. Zones and layers with low exploration degree have great potential in exploration

There is an unbalanced relationship between degree of

exploration and degree of resources proven in oil-gas rich regions in sags, zones, layers, and types, which constitutes as potential for deepening exploration in the next step. Tak-ing the Jiyang depression as an example, the Jiyang depres-sion and beach areas are highly explored on the whole, with a relatively high exploratory density. But, different sags and zones have different degrees of exploration and there are still many blank areas of reserves. According to statistics, the proportion of regions having a proven rate of less than 50% is up to 70%, and there still exists a high abundance of remaining resources. As exploration targets are more com-plex and hidden, it is increasingly difficult to obtain new exploration discoveries. Although Linqing, eastern Liaodong and other peripheral exploration areas have a low degree of exploration, a low exploration wells density, a low resource discovery degree, and a relatively low resource abundance, they still have good potential for exploration discoveries. As for layers, the main exploration areas of Ji-yang, they still have the largest amount of resources and proven reserves in the Paleogene, followed by the Neogene and then the Pre-Tertiary. In terms of proven degree, in ac-cordance with the criteria for reserve discovery stages, the proven degree in the Neogene has reached 78.89% at the last stage after reserves discovery; it is currently in the mid-dle-stage of reserves growth in the Paleogene while the proven rate in the Pre-Tertiary is only 2.5%, which is almost fully in the early discovery stage. The exploration degree is imbalanced inside various layers. For example, the Paleo-gene, the second member of the Shahejie Formation and the upper part of the fourth member of the Paleogene, has a relatively high degree of exploration and awareness. The Dongying Formation and the first member of the Shahejie Formation, which both mainly serve as concurrently-pro-specting layers, have relatively low levels of awareness and exploration, with a relatively small reserves discovery. The lower part of the fourth member of the Shahejie Forma-tion-the Kongdian Formation have an overall low explora-tion level. But, even the second member of the Shahejie Formation-the upper part of the fourth member of the Sha-hejie Formation, and the Guantao Formation, which have high levels of awareness and exploration, also have many blank reserves areas among each oil-bearing formation. There are many “oil spots” or “oil wells” in these blank ar-eas and the exploration imbalance indicates a huge potential for tapping these reserves and vast room for exploration.

2.3. Oil and gas exploration strategy

2.3.1. Concept Sinopec earnestly implements the national energy strat-

egy action plan and the general requirements for transform-


ing its own development mode and improving development quality. Sinopec also fully carries out innovation-driven and resource development strategies. By centering on oil-gas discoveries and commercial discoveries, developing both oil and gas resources, and paying attention to conventional and unconventional resources, Sinopec will strive to achieve a strategic breakthrough in oil and gas exploration and scale reservoir increases, provide a resource base for upstream sustainable development, and make contributions to ensur-ing the national energy security. 2.3.2 Priorities

During the 13th Five-Year Plan, oil exploration will focus in the eastern oil-rich sags, the Tarim Basin, the Junggar Basin, the Ordos Basin, and etc. which have the potential to increase annual probable reserves to (1.52.0)×108 t. Natu-ral gas exploration will focus in the Sichuan Basin, the Or-dos Basin, the Tarim Basin, and the East China Sea shelf Basin, with the potential to increase annual probable natural gas reserves to (20002400)×108 t.

Oil and gas exploration in the east is mainly around the Dongying sag, the Zhanhua sag, the Chezhen sag, the Huimin sag, the offshore area, and the Dongpu sag, which are in the Bohai Bay Basin, as well as the Qianjiang sag in the Jianghan Basin and the Qintong sag in the North Jiangsu Basin. Sinopec should make additional breakthroughs in the “three new domains”. The first is to discover deep Neogene stratigraphic reservoirs in layers represented by subtle res-ervoirs in the lower part of the fourth member of the Sha-hejie Formation-the Kongdian Formation in the Jiyang de-pression. Second is to discover reservoirs in the low buried hills and inner buried hill of the Jiyang and Dongpu areas, etc, as they have layered and inner buried hill reservoirs. Third is the volcanic rock fields, which have a large explo-ration potential, represented by the near-source reservoir combinations in the Songliao Basin, the Bohai Bay Basin, and the North Jiangsu Basin. Sinopec should deepen re-search on the differential evolution of zones and prepare for the detailed implementation of targets.

Large-scale breakthroughs and commercial discoveries should be made in the mid-west basins, centering on the Tarim Basin, the Junggar Basin[11], the Sichuan Basin, the Ordos Basin, the Qaidam Basin, and other large superim-posed basins. Exploration in the Tarim Basin centers on the Ordovician in the northern Shuntuoguole uplift, the Ordovi-cian of Maigaiti slope, and the Cambrian of the Central Tarim and Bachu uplifts. Exploration in the Junggar Basin focuses on new types of Mesozoic in the central Junggar Basin, the Carboniferous weathering crust of the western and the northern margin of the basin, and the Mesozoic and the Paleozoic of the Huainan piedmont zone[12]. Exploration

in the Sichuan Basin focuses on the marine Permian in the western Sichuan Basin, the upper Sinian-Cambrian strata in the Sichuan Basin, the southeast Sichuan Basin, the Central Sichuan uplift, the western Hubei, and the eastern Chongqing areas[1316]. Exploration in the Ordos Basin fo-cuses on Xinzhao in the Hangjingqi region, clastic rocks in the Azhen region, Tabamiao, the Ordovician subsalt in Fuxian, and the Upper Paleozoic in the southern basin. Sinopec should actively explore the Quaternary bio-gas in the eastern Qaidam Basin and the Jurassic self-generating and self-preserving reservoirs. 2.3.3. Measures

Firstly, be brave in exploring in order to promote devel-opment with large hydrocarbon discoveries. The key to ob-taining resources lies in exploration and the essence of ex-ploration is discovery. Sinopec should further emancipate the mind, strengthen exploration work to realize the goal of developing mature regions, open up new areas, and break through restricted areas and ensure the steady progression of the resource strategy.

Secondly, strengthen scientific and technological innova-tion to drive development with innovation and to promote exploration with scientific and technological innovations. Sinopec should comprehensively deepen understandings of the basin structure, tectonic evolution, sedimentary filling, hydrocarbon accumulation conditions, and distribution laws. On this basis, Sinopec should pay attention to evaluation research on zones, traps, and reservoirs to guide exploration deployment with deepened insight. Sinopec should carry out research focused on moving past the bottleneck technology restricting exploration, and strive to achieve remarkable re-sults during the 13th Five-Year Plan and eventually improve the success rate of exploratory wells, reserves upgrades, and utilizations while also working to reduce the cost of discov-eries.

Thirdly, strengthen innovation management to accelerate development by improving quality and efficiency. Sinopec should continuously promote efficient exploration and fur-ther establish and improve decision-making mechanisms and new mechanisms of two-level management for opti-mizing exploration deployment. Sinopec should highlight the main responsibilities and comprehensively intensify key exploration project management, improve exploration ap-praisal management to motivate workers’ initiatives in ex-ploration, strengthen risk identification and control, and en-hance the integration of geological research and exploration production, exploration and development, geological studies and engineering, and technical and economic aspects in or-der to realize efficient sustainable development of oil and gas exploration.


3. Conclusions

Sinopec deepened its geological knowledge in the fields of marine shale gas, marine carbonate rocks, tight clastic rocks, oil-gas rich depression continental clastic rocks, and etc. Because of innovation developments in exploration technology, Sinopec achieved a major breakthrough in shale gas, large-scale development of conventional natural gas, and steady growth of oil exploration, which created a better oil and gas exploration situation for Sinopec in the 12th Five-Year Plan. Facing the new normal in economic devel-opment, and other severe situations and major challenges induced by increasing difficulties in exploration during the 13th Five-Year Plan, Sinopec still has a long way to go in regards to oil and gas exploration. On the whole, it is still at the early and mid-stage of exploration discovery, and there are still great resource potentials in the future for Sinopec. Oil exploration focuses on the eastern oil-rich sags, the Tarim Basin, and the Junggar Basin while natural gas ex-ploration focuses on the Sichuan Basin, the Ordos Basin, the Tarim Basin, and the East China Sea Shelf Basin. Centering on oil-gas and commercial discoveries, Sinopec should fully carry out innovation-driven and resource development strategies, be brave in exploring, promote development with scale hydrocarbon discoveries, lead development with in-novations, continue to promote efficient exploration, and strive to achieve strategic breakthroughs in oil and gas ex-ploration to increase reservoirs, to provide a resource base for upstream sustainable development, and to make contri-butions towards ensuring the national energy security.

Acknowledgements

We appreciate Liu Jinlian, Quan Shujin and Zhou Dehua from Department of Oilfield Exploration & Development, Sinopec, Cai Lixue, Cheng Zhe, Qin Weijun and Liu Chaoying from Sinopec Exploration & Production Research Institute, as well as other oil and gas companies for their support and help in writing this paper.

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