| Reservoir fracture is an important reservoir space and migration channel for oil and gas.The study of fracture distribution has important guiding significance for oil and gas field exploration and development.The study area has undergone multi-stage tectonic movement,with many fracture development stages and complex distribution characteristics.Quantitative fracture prediction is urgently needed to provide reference for the next work deployment of the well area.At present,many scholars have explored in the field of quantitative fracture prediction,but there are still many shortcomings in the existing fracture prediction methods,such as less consideration of multi-stage fracture development,higher simplification of fracture prediction geological model and so on.On the basis of previous studies,this paper takes Chepaizi west flank igneous reservoir as an example to carry out quantitative prediction of multi-stage fractures in the study area.The main conclusions are as follows:(1)The study area generally presents a fault-step structural pattern with east-west zoning and North-South block.The reservoir-forming conditions are favorable.Lithology is mainly tuffaceous mudstone,sedimentary tuffaceous,tuffaceous and mudstone.The reservoir space is fracture-pore type,mainly low-porosity,medium-low permeability reservoirs.(2)The period of tectonic movement in the study area includes the middle and late Hercynian movement,Indosinian movement,Yanshan movement and Himalayan movement.Through core outcrop observation,casting thin section and imaging logging data,it is determined that there are at least three stages of fracture development in the study area.The predominant trend of fracture in Carboniferous system in the study area is nearly north-south,north-east and north-west.It is judged that the time of fracture development in the near northsouth direction is the earliest,which is the middle and late Hercynian movement,followed by the time of fracture formation in the north-east direction,which is the Indosinian movement period,and the time of fracture formation in the north-west direction is the latest,which is the Yanshan movement period.(3)The maximum and minimum horizontal principal stresses of the study area in the middle and late Hercynian,Indosinian,Yanshan and Himalayan periods are determined by rock acoustic emission tests;the stress direction of each period of tectonic movement is determined by the type of in-situ stress formed by reverse faults;and the static rock mechanics parameters of the study area are determined by logging data and rock mechanics tests,based on ant pursuit.The finite element geological model of each period is obtained by the tracer tectonic interpretation technique and the tectonic stress field is simulated.(4)Based on the fracture occurrence statistics of imaging logging data,starting from the multi-period and effectiveness of fracture development in the study area,the effective coefficient of fracture development and the proportional coefficient of fracture development are introduced into the existing fracture quantitative parameter calculation model,and the new superimposed fracture quantitative prediction model suitable for multi-period fracture quantitative prediction is established and applied to the quantitative prediction of reservoir fractures in the study area.(5)Comparing the results of fracture prediction based on cylindrical deviation curvature attribute and quantitative prediction of superimposed fractures in the target reservoir of the study area,the results show that the prediction results of the two fracture prediction methods have good correlation,which indicates that the multi-stage fracture prediction method based on structural stress field simulation in this paper has high reliability.Fissures are relatively developed in the areas near well Su 13,well Su 1-13 and its western area,and northern area of Su 1-5,and relatively undeveloped in the areas from west of Su 1-5 to near well Su 1-3,well Su 2 and its western area. |
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