Pore pressure prediction in front of drill bit based on grey prediction theory

Abstract

Abstract At present, the method of formation pressure is mainly divided into pressure prediction before drilling, pressure monitoring while drilling, and post-drilling pressure detection. The drilling monitoring method and the post-drilling pressure detection method cannot predict the pressure value of the formation in front of the drill bit. The pre-drilling prediction method is used to predict pressure by seismic data, but the accuracy of the result is not high. How to infer the pressure information of complex and unknown drilling strata based on very limited known formation pressure information is the key technical problem to be solved in this paper. In order to solve this problem, a method based on grey theory is proposed to predict the formation pressure in front of the drill. The prediction results of formation pore pressure based on the method in this paper are compared with the monitoring results of formation pore pressure while drilling: the maximum error is 3.408%, and the average relative error is 3.038%, which indicates that the model has high accuracy. It can meet the requirements of field drilling construction. Through the research of this paper, it can provide more accurate pore pressure information of the formation to be drilled under the bit. Based on the pressure prediction results of the formation to be drilled, dynamic engineering risk assessment can be carried out, so as to assist the drilling operators to make quick and accurate decisions and prevent drilling risk caused by inaccurate understanding of pressure information.

Keywords

• Pore pressure prediction
• Pore pressure monitoring
• Grey prediction theory
• Drilling safety