Fracture Identification And Prediction Of Glutenite Reservoir In Xuxi Sag,Songliao Basin

Natural fractures increase the reservoir ability and permeability and are the key factors for the high oil and gas production.Therefore,accurate prediction of the spatial distribution of natural fractures has always been the key and difficulty in oil and gas exploration.In particular,the small size of natural fractures in glutenite reservoirs further increases the difficulty of fracture prediction.This paper takes the glutenite reservoir of the fourth member of the Yingcheng Formation(referred to as the YING-4 section)in Xuxi Sag of Songliao Basin as the research object,guided by the theories of structural geology,sedimentology,logging geology,etc.,and based on the fracture data such as core and imaging logging,uses mathematical methods,geophysical methods and geological methods to identify and predict the fractures.The main conclusions are as follows:(1)The research zone mainly develops high-angle structure fractures.The fractures in this area have the characteristics of small scale,strong direction,good effectiveness,and small development density.The structural fractures were formed at the end of the Yingcheng Formation,the Quantou-Qingshankou Formation and the Nenjiang Formation;Non-structural fracture type is diagenetic fracture,and no secondary fracture caused by other factors is found;(2)The fractal dimension difference of DT and GR is obtained by R/S analysis method for fracture identification.The calculation result is sensitive to fracture response and has a good correspondence with productivity,indicating that it can be used for the fracture identification work,and semi-quantitatively characterizes the fracture development intensity in areas without core or imaging logging data;(3)In order to improve the accuracy of fracture prediction of seismic post-stack attributes,the frequency division technology is used to improve the ability of seismic identification of smallscale fractures,and the fracture distribution is predicted by combining the complementary nature of coherence body and curvature body in fracture prediction advantages.The prediction result of this method has a good correspondence with the fracture calibration of the YING-1 section,but a poor correspondence with the unit productivity of the YING-4 section,indicating that this method improves the ability of post-stack attributes to identify fractures,however,the recognition and prediction of small-scale fractures need to be improved;(4)In order to break through the limitation of seismic resolution,the geological genesis method is used to predict the distribution of structural fractures,and the finite strain distribution of each fracture formation period is calculated.The results show that the end of the Yingcheng Formation and the Quantou-Qingshankou Formation are the main forming periods of structural fractures.According to the productivity,the study area is divided into three types of fracture development zones.The type I fracture development zone has been verified by well-drilling.The type Ⅱ fracture development area can be used as an important direction for further tapping potential of deep natural gas.The type Ⅲ fracture development area has low productivity.There are 63 figures,5 tables and 124 references in this paper.