Evaluation Of Drill-in Fluid For Complex Gas Reservoirs In Jilin Oilfield

Based on the geological conditions of blocks,the adaptability of reservoir specialized technology is studied in this paper.It includes the research and evaluation of hole stability technology and reservoir specialized drilling fluid technology.First,the reservoir geological characteristics,pore parameters and reservoir sensitivity were systematically analyzed according to the standard test procedures.The results show that the sensitivity of the study block is: moderate to strong water sensitivity,moderate to strong salt sensitivity,weak speed sensitivity,weak acid sensitivity,weak alkali sensitivity and weak stress sensitivity.Based on the data of formation physicochemical properties,the chemical stability of strata was discussed.The shale content of the She Ling formation in the Yitong area(about 3000 meters)is only 5.5%,and the content of expansive clay minerals is relatively low in terms of mineral composition.The morphology of typical clay minerals was not observed from the 12000-fold electron microscope photographs.The cation exchange capacity is low and has weak swelling property.The expansion rate of shale in Yitong She 1 group is between 6.56% and 7.89%,which is a relatively weak expansion.According to the analysis,the instability pattern of the hole in this layer is dominated by crushing and flaking.The anti-sloughing effect of three drilling fluid systems that was commonly used at the site was analyzed,and it was consider that: the recovery rate of oil-in-water drilling fluid is the highest,and the recovery rate of clay free drilling fluid is higher than that of polymer drilling fluid.Under the condition of shale contact with the drilling fluid,the strength of the rock sample after the contact of the clay free drilling fluid is higher than that after the contact of the polymer drilling fluid,and the decrease of the core strength after the contact of the oil-in-water drilling fluid is the smallest.The above studies laid a good foundation for further research and application of drilling fluid technology for complex gas reservoirs in Jilin oilfield.