Quantitative Predict The Subseismic Faults And Study The Effect Of Subseismic Faults On Injection And Production

Subseismic faults are the small faults under seismic resolution,which control underground fluid flow,impact underground reservoir heterogeneity and effect of flood development of fault-blocked oilfield.Quantitative prediction on geometry and location of these subseismic faults have large significance on improving flooding effectiveness and productivity,well developing arrangement of pattern.In this paper,taking Group II of BZ34-2/4 oilfield as an example,a method for quantitative prediction of subseismic faults is proposed.This paper analyzes the relationship between injection and production,then study the effect of subseismic faults on reservoir heterogeneity.Firstly,we analyze the characteristics of seismic fault in the study area,then divide fault system and quantitatively predict the number of subseismic faults based on fractal theory.Secondly,we simulate on palaeotectonic stress field of main episode of faulting with the method of 3D geomechanics simulation.With simulating study on stress perturbation around the seismic faults,combining with coulomb failure criterion,we get advantages of fracture orientation and shear stress maximum distribution.In quantitative prediction of the subseismic faults,we use the random pattern with the constraints of the number of prediction subseismic faults based on fractal theory,and the fracture orientation and shear stress maximum distribution based on triaxial geomechanics analog.By studying the relationship between injection and production,we study the effect of subseismic faults on reservoir heterogeneity.Search Results:(1)Using the combination of Fractal geometry and the 3D geomechanics simulation,we can effectively predict the distribution of subseismic faults,and the result fit up to 90% with doubt fault we got.(2)The existence of sub seismic faults and cracks obviously enhances the heterogeneity of reservoirs.(3)The bigger the subseismic faults are,the longer the flood response time is,and the greater the ratios between flood response time and fault displacement are.The flood response time will become obviously longer,when the subseismic fault displacement is greater than 6.5m.(4)Large numbers of fractures and smaller sub-seismic faults are associated with the faults,thus improving the connectivity of reservoirs.