Study Of Well Test Interpretation Method In Low Permeability Oil Reservoir

Recently, with a growing proportion of low permeability oil resource in oil/gas fielddevelopment, more and more attention is paid on layer characteristics and flow feature in lowpermeability reservoirs. Well test is an effective method to guide oilfield reasonableexploration and efficient development. Currently, well test method based on Darcy flowtheory is very mature. But, there are errors when using traditional well test method in lowpermeability reservoir. A new well test method considering characteristics of lowpermeability reservoirs needs to be established.Based on the review of domestic and international documents, the geology and flowcharacteristics in low permeability reservoirs are analyzed, and the non-linear flow and layerstress-sensitivity description method are established. Considering non-linear flow and layerstress-sensitivity, well test models are established. The models involve three well types, twoporous media types and different boundary conditions. Influence of well storage and skinfactor are introduced using mathematical transformation. The models are solved using finiteelement method, and the well test curves are drawn with programming. The incidence ofseveral parameters on curves is studied. The difference between pressure buildup anddrawdown well test considering non-linear flow and stress-sensitivity is also studied.The result of parameters sensitivity shows: considering non-linear flow andstress-sensitivity in low permeability reservoir, pressure and pressure derivative curves willproduce upturn. And the effect of non-linear flow to curves is more sensitive than that ofpermeability modulus. There are differences between the extent and time of effects which arecaused by non-linear flow and permeability modulus. While in dual porosity media reservoir,non-linear flow affects the depth and position of pressure derivative sunken. Stress sensitivityof formation affects the upturn of curves. Besides, wellbore storage coefficient, elastic energystorage ratio and cross flow coefficient have some special impact to curves. In the actual well test data analysis, geological condition, core testing data and well test data should beconsidered comprehensively. Making a right judgment to the affecting factors can bring aboutproper well test interpretation.