Study On The Formation Of Shear Bands In Weakly Consolidated Sandstone Reservoir During Production

Due to the differences in mechanical properties between unconsolidated sandstone and weakly consolidated sandstone,sand production characteristic are significant difference.At present,there are few studies,which cannot be enough to guide production,on the sand production characteristics of weakly consolidated sand reservoirs.The key factor affecting the sand production characteristics of weakly consolidated sandstone reservoir is the shape of shear bands.In this thesis,the problems of shear bands formation in weakly consolidated sandstone reservoirs are studied,and some laboratory experiments are conducted.The deformation parameters and strength parameters are obtained,and the mechanical constitutive formula suitable for weak consolidated sandstone is selected.On these basic,the model of shear bands formation in weakly consolidated sandstone reservoir is formed.The model combines with the theory of strain localization and seepage mechanics.With the ABAQUS secondary exploration interface,the fluid solid coupling element is setup to simulate the formation of the shear bands in the weakly consolidated sandstone reservoir.Based on the data of H oilfield,the finite element model of the shear bands around the wellbore in the weakly consolidated sandstone is established.The influence of the residual strength,softening modulus,the horizontal in-situ stress state and the production pressure on the shear bands is analyzed.The results show that,with the increasing of the residual strength of the rock,the decreasing of the softening modulus,the decreasing of the difference between the horizontal in-situ stress and the decreasing of the production pressure,the number of the shear bands increases in the direction of the minimum horizontal in-situ stress,the control depth of the shear bands increases,and the falling cuttings is likely to occur.On the contrary,it is more likely to produce granular sand.The analysis results in this thesis can provide guidance for the completion and sand control design of weakly consolidated sandstone reservoirs.