The Study On The Analysis Of Physicochemical Characteristics Of Shale In Jiangsu Oilfield And Optimization Of Oil-based Drilling Fluid

Oil and gas drilling have a major impact on the stability of wellbore. Shalehydration often leaves the wall expansive, peeling off the block and so on, resulting inthe occurrence of the underground complex situations. After exploration, JiangsuOilfield has large potential, but there exists the formation of organic-rich mud shalesystem. Therefore, the stability of shale formations in Jiangsu Oilfield should beprotected.Based on a comprehensive geological data collected on Jiangsu Oilfield, thedetermination of the whole rock and SEM are conducted for couplets X38well, X26well, and158well. For X38well, the permanent dispersion of rock samples and theexpansion of testing are completed. The perfect physical and chemical propertiesanalysis Jiangsu Oilfield shale formations are made. The crystalline clay minerals,amorphous clay minerals and non-clay mineral composition, as well as their relativeand absolute content of clay content of the shale are known. The characteristics ofstrata cements are clear.A deviated wellbore stress model is developed. Tri-axial stress test is conductedfor X26well. The angle of internal friction and cohesion size formations CoupletsX38wells is known. The wall shear failure prone is determined. Meanwhile, theinfluencing factors in situ stress, formation properties, drilling, well trajectory,construction and other wellbore stability of shale are analyzed.Finally, according to an orthogonal experimental design, domestic, Chevron,COSL different oil-based drilling fluids were tested at room temperature and hightemperature performance. A set of best oil-based drilling fluid formulations are given:320ml5#white oil+80ml water+26.7gCaCl2+1.5%+0.5%of primary breast withmilk+2.5%+1.5%organic soil wetting agents+3.0%+1.2%fluid loss Tiqie agent+152g barite, which meets all the requirements of Jiangsu Oilfield shale wellbore stability.