Oil Wellbore Strengthening: New Experimental and ...

2020年9月23日-25日中国·成都 23–25 September 2020 in Chengdu, China

2020 油气田勘探与开发国际会议International Field Exploration and Development Conference 2020

Oil Wellbore Strengthening:

New Experimental and Theoretical

Approaches

Musaed N. J. [email protected]

King Saud University, College of Engineering,

Petroleum and Natural Gas Engineering Department,

Riyadh, Saudi Arabia

2020年9月23日-25日中国·成都

23–25 September in Chengdu, China2020 油气田勘探与开发国际会议International Field Exploration and Development Conference 2020

Outlines

1. Introduction

2. Objectives

3. Experimental Work

4. Discussion of Results

5. Conclusions

IFEDC - Oil Wellbore Strengthening: New Experimental and Theoretical ApproachesMusaed N. J. AlAwad, KSU, Riyadh, Saudi Arabia

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1. Introduction


1) Expenses for drilling represent 25% of the total oilfield exploitation costwhich depends on whether it is onshore or offshore.

2) Drilling fluids represent 20% of the total cost of petroleum well drillingoperations.

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1. Introduction


The main drilling fluids problem is the loss into formations with:

2) Induced fractures

3) Cavernous and Vugs

4) Natural fractures

1) High permeability

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1. Introduction


The Lost circulation can be divided into the following categories:

3) Severe Loss: > 50 barrels/hr.

2) Partial Loss: 10 - 50 barrels/hr.

1) Seepage: up to 10 barrels/hr.

DANGEROUS

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4) Total Loss: 100%



1. Introduction


Prevention or mitigation of lost circulation is a main challenge whiledrilling in these formations where conventional lost circulation materials(LCM) are not able to mitigate these losses.

LCM Function: Mitigate lost circulation problem

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Graphite, Mica, Fibers, Cellulose, Walnut shell, etc.



1. Introduction


Prevention or mitigation of severe lost circulation using conventional lostcirculation materials (LCM) is not possible. Therefore, fractures sealmaterials (FSM) are required in conjunction with LCM.

FSM Function: Mitigate lost circulation problem + Wellbore strengthening

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Nut plug, Crushed limestone, coarse mica, etc.



1. Introduction


Fracture seal materials (FSM) can seal (plug) the existing naturalfractures and vugs, hence:

1) Prevent or mitigate drilling fluid losses.

2) Provide wellbore strengthening effect.

Wellbore Strengthening is the term generally used in drillingengineering to artificially increase the maximum pressure a wellborecan withstand without intolerable mud losses.

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1. Introduction


FSM: Mitigate lost circulation problem + Wellbore strengthening

Tooth ImplantationFracture Seal

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2. Study Objectives

The main objectives of this study are:

1. Develop practical laboratory setup and testing procedure to examine

potential applicability of fracture seal materials.

2. Develop a simple, practical and technically valid approach suitable

for theoretical and experimental understanding and evaluating of

wellbore strengthening process.

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3. Experimental Work

FSM & LCM Selection Criteria

1) Environmentally friendly, Cheap and readily available.

2) Suspend in the drilling mud and can go through the mud circulationsystem to the fractured zone.

3) Withstand mechanical effects of the mud circulation system.

4) Withstand downhole pressure and temperature.

5) Pass specialized laboratory tests.

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3. Experimental Work (Testing Cell)

Modifying the conventional API HT-HP filtration cell to accommodatefractured core plugs of 38.1 mm (1.5 inch) diameter and 38.1 mm (1.5inch) thickness instead of filter paper or ceramic disc.

API HT-HP Filtration Cell Modified HT-HP filtration cell with sleeve

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Photograph and properties of the utilized artificial sandstone

3. Experimental Work (Core Samples)

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3. Experimental Work (Fracture Simulation)

Appropriately simulating severely fractured or vuggy formations usingreal core plug with manmade fracture.

Artificial sandstone plugs with manmade fractureArtificial sandstone with man-made fracture

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3. Experimental Work (Potential FSM)

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In Saudi Arabia, there are more than 20 million dates palm trees with

more than 320 types occupying approximately 160,000 hectares.

Saudi Arabia produce more than 1,000,000 tons of dates annually.

Dates palm fruit Dates palm seeds Dates palm tree






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Date seeds are considered to be about 15% of the weight of the fruit .

At present, dates palm seeds are used mainly as animal feeds.

Plus other minor applications (coffee additive, medicine, etc.).





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Date palm seeds are environmentally friendly.

Date palm seeds available annually in huge quantities.

Potential use of crushed date palm seeds as a fracture seal material.





Date palm seeds are considered to be about 15% of the weight of the fruitcurrently used mainly as animal feeds

Crushed date palm seeds

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3. Experimental Work (Results)

Fractures seal

Testing FSM and LCM Seal Quality, i.e. (Pw)max = ?

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Experimental setup


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Example experimental results


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Relationship between pressure difference and spurt volume @ 90oC

(Pw)max = 1000 psi = 6.9 MPa

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Optimum FSM size required for complete seal





Wellbore Strengthening Interpretation

Using

Rock Mechanics Principles

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The Multi-Stage Triaxial Compression TestThe Brazilian Tensile Test

Rock Mechanics Tests: UCS, BTS and MS-TCS

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Experimental results for the BTS and UCS tests

Rock Mechanics Tests: UCS, BTS and MS-TCS





Test type Sample shape after testing

Sample dimensions Confining pressure, MPa

Axial stress at failure, MPa # D, mm L, mm t, mm

MS-TCS

3 38.1 95.25 ---

CP1= 3.45 18.5

CP2= 6.89 25.5

CP3= 10.35 42.9

Experimental results for the MS-TCS test

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4. Results and Discussion (Results)

MS-TCS test result (failure criteria) for the tested sandstone

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4. Results and Discussion (Results)

Wellbore strengthening estimated from the MS-TCS test

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4. Discussion of Results (Results)

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Oil Wellbore Strengthening:

New Experimental and Theoretical

Approaches

Suitability of the tested new FSM

Filtration control

% Success in tensile strength recovery

(Wellbore Strengthening)





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(Pw)max = 6.9 MPa

(RTS) = 2.56 MPa

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(Pw)max = 6.9 MPa

(RTS) = 2.56 MPa

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5. Conclusions & Recommendations

1. Wellbore strengthening process for a particular rock (formation) can be easily

evaluated if samples from the same rock (formation) are tested at laboratory using

MS-TCS, UCS, and BTS tests.

2. For the tested sandstone, a wellbore strengthening effect generated by a complete

fracture seal using crushed dates palm seeds is equivalent to applying a 6.9 MPa

confining pressure on a fractured rock specimen during a multi-stage triaxial

compression test.

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5. Conclusions

3. For the tested sandstone, using crushed dates palm seeds as a fracture seal

material has improved wellbore strengthening from zero tensile strength (complete

mud lost circulation) to 2.56 MPa (zero mud lost circulation) which is approaching

the intrinsic tensile strength of the non-fractured similar rock (BTS=2.7 MPa).

4. The low tensile strength of formations due to the existence of natural fractures

and/or vugs can be improved using proper wellbore strengthening materials.

Hence, a wide, safe and economic mud weight window for oil and gas well drilling

can be obtained.

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2020年9月23日-25日中国·成都 23–25 September 2020 in Chengdu, China

2020 油气田勘探与开发国际会议International Field Exploration and Development Conference 2020

Thanks for your attention

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