Fracture Characteristics And Prediction Of Carboniferous Volcanic Rocks In Shixi Oilfield, Junggar Basin

Fractures have an important influence on the quality of volcanic reservoirs.Based on the theory of structural geology and reservoir geology,the development characteristics and main controlling factors of the Carboniferous volcanic rock fractures in the Shixi Oilfield are studied.Fracture fractal method,paleo-tectonic stress field numerical simulation method and seismic attribute three techniques are used to carry out fracture prediction;the results of three technical means are superimposed and evaluated by information superposition method,predicting fracture development area and exploring fracture the effectiveness and analysis of production dynamic data analysis,to determine the impact of fractures on oil and gas enrichment,provide recommendations for the next development and deployment.This paper mainly achieved the following results:The fracture types of volcanic reservoirs in the study area are mainly shear fractures with structural genesis.The fractures have the characteristics of medium development scale,large dip angle,large width,low filling degree,small density and large spacing.The fracture orientation mainly includes EW direction,NW direction,SN direction and NE direction,EW and SN trending fractures are planar "X"-type conjugate shear joints formed under the tectonic action of the first phase(middle-late Herzeian);NW and NE trending fractures are planar "X"-type conjugate shear joints fonned under the tectonic action of the second phase(Indosinian).The degree of fracture development is mainly affected by lithology,structural parts and weathering and dialysis,Fractures in agglomerates,breccia lavas and strip lavas are well developed,structural high-point fractures and fractures in the vicinity of 30-120 m below the top of the Carboniferous are well developed.According to the analysis of conventional logging interpretation results of fractures,The area with the best fracture growth thickness mainly includes the fan-shaped area surrounded by Shi 001 well and Shixi 2 well,and the surrounded by the wells of Shixi 1-SHW01-SH1104-SH1019-SH1024 region.The development degree of fracture in the study area are predicted by using fractal method,numerical simulation method of paleo-tectonic stress field and seismic attributes.According to the results of fractal fractal dimension prediction,the fractures are mainly concentrated in the area surrounded by SH1036 well-SH 1203 well-SH 1201 well-SH 1032 well-Shixi 1 well and around Shi 011 well and Shi 001 well;The results of simulated fracture prediction of paleo-tectonic stress field show that the degree of fracture development is higher in the area where is mainly distributed in the SH1109 well-SH 1024 well-SH 1020 well-SH 1032 well and the central micro-structure is mainly SH1117 well and SH1104 well.Fracture prediction result of the seismic attribute shows that the volcanic rock fractures in the study area are mainly developed along the EW.Such as SH1024 well-SH1019 well-SH1109 well-SH 1034 well maintained area and SH1025 well-SH 1020 well-Shixi 1 well and SH1114 well-SH1117 well located at the central micro-structure.The fracture prediction results obtained by the three technical means are superimposed and evaluated.The evaluation results show that the central part of the study area is the main fracture development area,including the SH1035 well-SH1024 well-SH1019 well,it is located around the structural high point SHW10 well-SH1020 well-SH1104 well-SHWO1 well-Shixi 1 well and The local structural high point area dominated by the SH1114 well-SH1117 well and the surrounding Shi 001 well near the north fault of Shixi 2 well,generally distributed in a linear pattern.The fractures near EW direction in the study area have better effectiveness,the effective fractures are mainly concentrated around the SH1115 well-Shixi 1 well-SH1024 and SH1019 wells.The obvious law is mainly affected by the current maximum principal stress orientation.Compare the relationship between fracture development level and productivity,the fracture prediction results have a good match with the actual production situation.The optimal target selection principle is established to provide suggestions for the next development and deployment.According to various results,next step is advantageous to tap potential target area are SH1037-SH1114 wells and SH1115-SHW10 wells.