Coupled effects of stress damage and drilling fluid on strength of hard brittle shale

Abstract

During well drilling process, original stress state of hard brittle shale will be changed due to stress redistribution and concentration, which leads to stress damage phenomenon around the borehole. Consequently, drilling fluid will invade into formation along the tiny cracks induced by stress damage, and then weaken the strength of hard brittle shale. Based on this problem, a theoretical model was set up to discuss damage level of shale under uniaxial compression tests using acoustic velocity data. And specifically, considering the coupled effect of stress damage and drilling fluid, the relationship between hard brittle shale strength and elapsed time was analyzed.

Keywords

hard brittle shale / stress damage / drilling fluid / time effect / strength

References

[1] WangJ-h, YanJ-n, SunS-lin. New method for evaluating borehole stability in brittle shale [J]. Oil Drilling & Production Technology, 2006, 28(2): 28-30

[2] DarleyH A. Laboratory investigation of borehole stability [J]. Journal of Petroleum Technology, 1969, 21(7): 883-892

[3] O'brienD E, ChenevertM E. Stabilizing sensitive shales with inhibited potassium-based drilling fluids [J]. Journal of Petroleum Technology, 1973, 25(9): 1

[4] LiuE-l, ShenZ-jiang. Study on brittleness of geomaterials [J]. Chinese Journal of Rock Mechanics and Engineering, 2005, 24(19): 3449-3453

[5] LeiY-c, XiangX-jin. Brief introduction of the classi fication of shales [J]. Drilling Fluid & Completion Fluid, 2007, 24(2): 63-66

[6] ShaoJ F, RudnickiJ W. A microcrack-based continuous damage model for brittle geomaterials [J]. Mechanics of Materials, 2000, 32(10): 607-619

[7] KondoD, JiaY. A coupled elastoplastic damage model for semi-brittle materials and extension to unsaturated conditions [J]. Mechanics of Materials, 2006, 38(3): 218-232

[8] ZhouJ J, XuW Y. Coupled modeling of damage growth and permeability variation in brittle rocks [J]. Mechanics Research Communications, 2006, 33(4): 450-459

[9] ShaoJ, AtaN, OzanamO. Study of desaturation and resaturation in brittle rock with anisotropic damage [J]. Engineering Geology, 2005, 81(3): 341-352

[10] MaT-s, ChenPing. Analysis of wellbore stability for horizontal wells in stratification shale [J]. Journal of Central South University: Science and Technology, 2015

[11] ParkB Y. Interbed modeling to predict wellbore damage for big hill strategic petroleum reserve[J]. Rock Mechanics & Rock Engineering, 2014, 47(5): 1-11

[12] DusseaultM B. Geomechanical challenges in petroleum reservoir exploitation [J]. KSCE Journal of Civil Engineering, 2011, 15(4): 669-678

[13] LiP, RaoQ-h, LiZhuo. Thermal-hydro-mechanical coupling damage model of brittle rock [J]. Journal of Central South University, 2014, 21(3): 1136-1141

[14] GutierrezM, NygardR. Shear failure and brittle to ductile transition in shales from P-wave velocity [C]. American Rock Mechanics Association, 2008

[15] OdaM, TakemuraT, AokiT. Damage growth and permeability change in triaxial compression tests of Inada granite [J]. Mechanics of Materials, 2002, 34(6): 313-331

[16] SouleyM, HomandF, PepaS. Damage-induced permeability changes in granite: a case example at the URL in Canada [J]. International Journal of Rock Mechanics and Mining Sciences, 2001, 38(2): 297-310

[17] LuY-huStudy on mechanism of wellbore instability of gas-liquid conversion [D], 2011BeijingChina University of Petroleum

[18] WuS, AbelA. Fatigue crack stress intensity factors: The influence of residual stresses [J]. International Society of Offshore and Polar Engineers, 199292-355

[19] GaoQingEngineering fracture mechanics [M], 1986ChongqingChongqing University Press

[20] YangC-h, MaoH-j, WangX-chao. Study on variation of microstructure and mechanical properties of water-weakening slates [J]. Rock and Soil Mechanics, 2006, 27(12): 2090-2098