The Research On The Stability Of The Borehole Wall In Longhupao Oilfield

In the process of drilling in the Longhupao oilfield, there occurs some complex drilling accidents which include borehole wall sloughing and borehole sticking because of the more complex nature of rock and formation structure in this area and the larger collapsed pressure in mud shale. These complex drilling accidents not only have a serious impact on the efficiency of drilling and on increasing of the drilling costs, but also make borehole quality seriously affected as well as the cement job quality. Initially, this paper analyzes the main form of instability of borehole wall and researches the key element of making the borehole wall instability in the process of drilling to calculate the rock elastic parameters and mechanical parameters by sonic logging and to set up the relationship model of dynamic and static elastic parameter based on laboratory. By using the data of density logging, the thesis calculates the overburden rock pressure, inverts the earth stress combining the fracture experiment data to regress the tectonic stress factor of Longhupao oilfield in order to establish the calculation model of three-dimensional stress. In addition, thesis also sets up the mechanical model of stability of borehole wall by using linear elasticity theory. By choosing reasonable destruction guideline, the thesis calculates the caving pressure and the fracturing pressure in order to make the borehole wall stability as well as the establishment of the security drilling fluid density window, hence, it provides effective technological guidance for drilling engineering in Longhupao oilfield to ensure the further exploration and development of oilfields and reduces drilling accidents in order to enhance economic efficiency. The paper is a systematic theoretical research on the stability of the borehole wall in Longhupao oilfield.