Wellbore Stability Evaluation Study for Continental Shale Oil Reservoir in Northern Jiangsu
In order to solve the technical problems such as frequent stuck drilling and difficult well completion in the continental shale oil reservoir in northern Jiangsu Province,the geological characteristics analysis and laboratory experiment evaluation were carried out.The results indicate that the Funing Formation in northern Jiangsu Province has high clay mineral content,which is dominated by I/M mixed layer,has quite a certain extent hydration and dispersion performance,and has obvious amphiphilic characteristics.The shale of the second layer of Funing Formation has strong bedding,and the filtrate of drilling fluid can easily intrudes into the formation along the micro-cracks under the pressure difference and imbibition effect,which causes local hydration of the shale and generates hy-dration expansion pressure,resulting in the extension and expansion of a large number of micro-cracks,rock integrity damage,and sig-nificant deterioration of mechanical parameters,resulting in wellbore instability.The technical measures for wellbore stability control of"enhanced inhibition+efficient plugging+wetting inversion"are specifically developed,which can achieve the wellbore stability effect of"external waterproof invasion and internal control expansion",which can provide reference for the later development of conti-nental shale oil and gas.
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