Study On Optimal Design Of Shaft Trajectory For Shale Gas Horizontal Well In South

The horizontal shale gas well borehole wall stability in the process and the fracturing in the later period are the keys of the shale gas development. How to balance the borehole wall stability and fracturing effect,and how economic and efficient development of shale gas are the current problems to be solved.Because of the geologic structure in the southern part of Sichuan reservoir with complex stress and the shale stratification is developed,it’s easy to have some complex situations such as the borehole wall caving and drilling sticking,it’s disadvantage to develop the shale gas efficiently and securely.This article is proved by multi-disciplinary theories and technologies such as rock mechanics, drilling engineering, mathematical optimization method and the geophysical logging. Combined with actual geological data to research in the work area,and achieved some research achievements as follow:found out the difficulties and key problems in the horizontal Shale gas well design and drilling by investigating the current situation of horizontal shale gas well. The major factors to consider about borehole trajectory optimization are horizontal azimuth, horizontal segment length and the spacing between the horizontal segments, etc.Collected geology, geological characteristics, lithologic characteristics,the development of reservoir fracture in the W-N work zone and analyzed the borehole wall sloughing. Found out the problems which in the process of drilling horizontal shale gas Wells in the block and provided the basis for optimization design of horizontal well borehole trajectory.Analyzed of well logging and on-site hydraulic fracturing data, revised the ground stress size and direction in the W-N work area. Combined with the stratification collapsing model and provided the basis for the orientation of the horizontal segment in the work area. Use the productivity index to describe the fluid flow in the horizontal wellbore, Combined fluid friction calculation and horizontal well models to deduce the optimal length calculation model which is suitable for shale gas reservoir horizontal well’s horizontal segment.Take the horizontal shale gas wells in W-N as research objects, used of the related research results above-mentioned to carry out the optimization design of horizontal shale gas well borehole trajectory method of application research. According to the actual data for optimization design of3wells the work area,analyzed and verified the optimal well track results,put forward a general method of optimization design of horizontal shale gas well borehole trajectory in the work area.Through the above research to ensure the work area safe and efficient development of shale gas.