Seismic prediction and well trajectory design for ultra-deep fault-controlled carbonate fractured cave reservoirs:Taking the north-central part of fault zone No.4 in the Shunbei Oilfield as an example
The fault-controlled fracture-cave reservoir in Shunbei is mainly controlled by strike-slip faults,and the activity intensity of the fault zone controls the degree of reservoir development.The reservoir space is mainly fractured to form caves,pores,and fractures.The spatial distribution of the reservoir is highly heterogeneous,and the spatial positioning and quantitative characterization of the fractures-cave reservoir is the key to restricting the selection and efficient use of well location and well type.Based on the comprehensive logging,seismic,and geological data,the three-dimensional and semi-quantitative characterization of the carbonate reservoirs in the northern section of the Shunbei Zone No.4 fault is carried out.The results show that the carbonate reservoirs in Shunbei are irregularly distributed along the fault zone,with large longitudinal extension(height of 50 to 800 m)and strong heterogeneity along the fault surface.The size and composition of the reservoirs in different sections of the strike-slip fault zone are different.The tensioning section has the largest reservoir volume space,with the highest proportion of holes(35%)and cracks(65%).The volume space of the translation section is smaller,with a lower proportion of caves(44%)and cracks(56%),the well trajectory classification design is carried out according to the reservoir prediction and reservoir space distribution.The width of the pull segment plane is large,the angle between the fracture plane and the reservoir is 0 to 30°,and the vertical angle of large inclination is adopted to cross the fracture zone to maximize reservoir drilling.The translation section has a narrow section,a small reservoir size,and an angle between the section and the reservoir group of 30 to 50°.The vertical mid-slope angle is used to cross the fault zone,and the drilling reveals that the length of the reservoir group can be increased by 1.8 times compared with the cross-zone to achieve high and stable production.The above techniques and methods have achieved good drilling results.
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