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Improved Recovery Techniques

Tracer Application for Water flooding

PE 4543 900

Submitted to:Dr. Deepak Devegowda

February 27, 2013

LEMMY OSHENYE

Academic Integrity StatementOn my honor, I affirm that I have neither given nor received inappropriate aid in the completion of this exercise.Lemmy OshenyeFebruary 27, 2013

Name: _________________________________ Date: ____________________________AbstractAs production from oil reservoirs matures, improving the recovery factor will play a decisive role in offsetting the decline in production. Many methods exist to improve the recovery factor. In this project, waterflooding and tracer test were simulated for an inverse 5-spot and 9-spot scenarios. Significant findings include:1. The field-wide average oil saturation for the 5-spot waterflood and 9-spot waterflood at field-wide water cut of 0.95 based on numerical solution are 0.38 and 0.469 respectively.2. The residual oil saturation for the path of each producing wells for the 5-spot waterflood and 9-spot waterflood based on the tracer method are 0.284, 0.248, 0.254, and 0.253 for producing wells P1, P2, P3, and P4 and 0.324, 0.348, 0.310, 0.377, 0.352, 0.286, 0.337, and 0.294 for producing wells P1, P2, P3, P4, P5, P6, P7 and P8 respectively. The tracer method helps to estimate changes in the residual oil saturations following each process. 3. The 5-spot waterflood is more effective in recovering the mobile oil in the field4. The 5-spot waterflood is able to recover a little bit more tracers compared to the 9-spot waterflood

IntroductionRecovering oil from a petroleum reservoir can be achieved by primary recovery, secondary recovery and tertiary recovery. Waterflooding is the most common method of secondary recovery. Waterflooding is the use of water injection to increase the production from oil reservoirs. This is accomplished by the injection of water to increase the reservoir pressure to its initial pressure and maintain it near that pressure (Warner Jr. 2007). Waterflood recovery factor is also influenced by intrinsic factors such as mobility ratio, reservoir heterogeneity, pore geometry, and initial water-/oil-saturation distribution. Connate-water saturation and residual oil saturation after waterflood are the most important numbers in waterflooding because they are used to determine the displacement efficiency. Tracer tests are often implemented prior to any improved oil recovery (IOR) process. Tracers can be used to characterize fluid migration pathways between wells, identify the distribution and location of immobile or mobile hydrocarbon and water phases, and assess the efficacy of an IOR pilot with before and after tests (Deepak 2012). There are two broad categories of tracers namely conservative and partitioning tracers. Conservative tracers are soluble in one phase and aids in identifying reservoir connectivity and barriers while partitioning tracers are soluble in more than one phase and used to identify phase saturations. During a tracer test, the partitioning tracer is usually delayed due to the oil phase. The delay of the partitioning tracer in comparison to the conservative tracer enables quantification of phase saturations and has been successfully used to infer immobile oil saturations (Deepak 2012). ProcedureA constructed simulation model is provided with an inverse 5-spot waterflood and 9-spot waterflood. For the 5-spot waterflood, the existing injection and production wells were operated using production controls of 100 bbl/day until water breakthrough occurred at the first two wells. At this time, the production in both these wells were choked back to 40 bb/day and the production in the remaining producers were increased to 160 bbl/day. Production was continued until the field-wide water cut became 0.95 and then the field-wide average oil saturation was estimated. A partitioning and conservative tracer was injected continuing the waterflood and producing all four producing wells at a rate constraint of 100 bbl/day. Injection was continued until the tracers were recovered at each of the four producing wells.For the 9-spot waterflood, four new wells were added to the 5-spot waterflood at the edges of the field at 300 days. At this time, the existing producers were shut-in and water injection was initiated at the same rate of 400 bbl/day while producing the four new wells at a rate constraint of 100 bbl/day. Production was continued from the new wells until a field-wide water cut of 0.95 was achieved and then the field-wide average oil saturation was estimated. The same process for the tracers in the 5-spot waterflood was followed for all 8 wells.

Results and Discussion of Results

Fig. 1The field-wide water cut profile for the inverse 5-spot waterflood

Fig. 2The field-wide water cut profile the inverse 9-spot waterfloodThe field-water cut for the 5-spot waterflood and 9-spot waterflood reaches 0.95 at 1125 days and 1375 days respectively.

Fig. 3The spatial distribution and location of bypassed hydrocarbon for the inverse 5-spot waterflood

Fig. 4 The spatial distribution and location of bypassed hydrocarbon for the inverse 9-spot waterfloodThere are more bypassed hydrocarbon in the inverse 9-spot waterflood compared to the inverse 5-spot waterflood. This can be seen in Fig. 3 and Fig. 4.

Fig. 5The tracer elution profile for well P1 from the 5-spot waterflood.

Fig. 6The tracer elution profile for well P1 from the 9-spot waterflood.The delay of the partitioning tracer (green) in comparison to the conservative tracer (red) is longer for the 5-spot waterflood compared to the 9-spot waterflood. This can be seen in Fig. 5 and Fig. 6.TABLE 1Field-wide average oil saturation for both scenarios using numerical solution

Field-wide Average Sor

5-spot Waterflood0.38

9-spot Waterflood0.469

TABLE 2Conservative and partitioning tracer recovery for 9-spot waterflood

Conservative TracerPartitioning Tracer

WellsBreakthroughTracer RecoveryWellsBreakthroughTracer Recovery

days%days%

P1112925.6P1112925.6

P2112924.6P2113824.7

P3112924.7P3113824.6

P4112924.9P4113824.8

TABLE 3Residual oil saturation for 5-spot waterflood using tracer method

WellsSor

fraction

P10.2380.284

P20.1980.248

P30.2040.254

P40.2040.253

TABLE 4Conservative and partitioning tracer recovery for 9-spot waterflood

Conservative TracerPartitioning Tracer

WellsBreakthroughTracer RecoveryWellsBreakthroughTracer Recovery

days%days%

P11440.215.8P11386.816.0

P21381.53.6P21381.53.4

P31386.814.4P31386.814.9

P41431.87.3P41386.87.1

P513767.2P513766.9

P6137621.2P6137921.5

P7137610.9P7137610.2

P8137619.4P8137619.4

TABLE 5Residual oil saturation for 9-spot waterflood using tracer method

WellsSor

fraction

P10.2880.324

P20.3200.348

P30.2690.310

P40.3630.377

P50.3260.352

P60.2400.286

P70.3040.337

P80.2500.294

The water breakthrough for the 5-spot waterflood occur at 475 days at wells P2 and P3. This is as a result of higher permeability in that direction.ConclusionThe 5-spot waterflood is more effective in recovering the mobile oil in the field compared to the 9-spot waterflood. The tracer method helps to estimate the residual oil saturation for the pathways of each of the producing wells.ReferencesDevegowda, D. 2013. Tracer Tests. Lecture notes on tracer tests. The University of Oklahoma,Oklahoma, United States.Warner Jr., H.R. 2007. Petroleum Engineering Handbook, Vol. 5, V-1037V-1096. Richardson, Texas, SPE.

AppendicesEquation

Supplemental Tables and Figures5-spot WaterfloodConservative Tracer

WellsPeak TimeProduction TimeProduction rateQ/(1+)Tracer Production TotalPartitioning Coefficient (Ki)Field-wide Tracer Injection Total

daysdaysbbl/daybbldimensionless

P1160147210047200103.670.6404.49

P215263971003970099.590.6404.49

P31513.5384.510038450100.040.6404.49

P4157644710044700100.760.6404.49

Partitioning Tracer

WellsPeak TimeProduction TimeProduction rateQTracer Production TotalPartitioning Coefficient (Ki)Field-wide Tracer Injection Total

daysdaysbbl/daybbldimensionless

P11713.5584.510058450103.470.6404.49

P21613.5475.51004755099.730.6404.49

P316014631004630099.670.6404.49

P4167653810053800100.390.6404.49

Fig. 7The tracer elution profile for well P4 from the 5-spot waterflood.

9-spot WaterfloodConservative Tracer

WellsPeak TimeProduction TimeProduction rateQ/(1+)Tracer Production TotalPartitioning Coefficient (Ki)Field-wide Tracer Injection Total

daysdaysbbl/daybbldimensionless

P11863.6476.81004768063.780.6404.64

P22513.5113210011320014.440.6404.64

P31851464.21004642058.410.6404.64

P42313.5881.71008817029.340.6404.64

P519515751005750028.980.6404.64

P616763001003000085.720.6404.64

P71663.5287.51002875044.250.6404.64

P815762001002000078.410.6404.64

Partitioning Tracer

WellsPeak TimeProduction TimeProduction rateQTracer Prod TotalPartitioning Coefficient (Ki)Field-wide Tracer Inj Total

daysdaysbbl/daybbldimensionless

P12001614.21006142064.620.6404.64

P228761494.510014945013.630.6404.64

P31976589.21005892060.480.6404.64

P42588.51201.710012017028.730.6404.64

P52138.5762.51007625027.880.6404.64

P617513721003720087.140.6404.64

P717513751003750041.280.6404.64

P816262501002500078.540.6404.64

Fig. 8The tracer elution profile for well P3 from the 9-spot waterflood.

Fig. 9The tracer elution profile for well P4 from the 9-spot waterflood.

Fig. 10The tracer elution profile for well P5 from the 9-spot waterflood.

Fig. 11The tracer elution profile for well P6 from the 9-spot waterflood.

Fig. 12The tracer elution profile for well P7 from the 9-spot waterflood.

Fig. 13The tracer elution profile for well P8 from the 9-spot waterflood.