The Study On Prediction Technology Of Formation Pressure In Ledong Block Of Yingqiong Basin

The temperature and pressure conditions in the Yingqiong Basin are extremely poor.Complex conditions such as wellbore collapse,gas intrusion,and downhole leakage often occur during the drilling process.During the production test,due to the high pore pressure and the low permeability of the reservoir,the test pressure difference is very large,the formation stability is poor,and the test process is difficult.The pore pressure of the target reservoir is abnormally high,and even gas intrusion and overflow may occur at the same time,resulting in extremely difficult,high operational risks,and high operating costs in drilling and completion operations.This paper studies the abnormal high-pressure mechanism of the block and the stability of the borehole during the drilling and testing process,and provides theoretical guidance and suggestions for the drilling operation of the Ledong block.Based on the geological,log information,drilling and cutting logging data of Ledong block in Yingqiong Basin,combined with indoor rock acoustic experiments,this paper analyzes the abnormal high-pressure mechanism of Ledong block;the seismic velocity data and acoustic time difference data of the site are used to analyze the formation pore pressure based on Eaton model,Bower’s model,Equivalent depth model and difference method.then optimize the difference method and select the appropriate regional index to analyze the pore pressure of the exploration well by comparing the real pore pressure and the calculated value;according to the indoor rock mechanics experiment and the on-site test data,the geostress and strength profile are established.Based on the previously calculated formation stress,strength parameters,real pore pressure and adjacent working conditions data,FLAC^3D finite difference software is used to simulate the stability of target well,such as mudstone section under drilling conditions and sandstone sections under production test conditions.Through research and analysis,laboratory experiments,numerical simulation,case analysis,theoretical calculations and other methods,the main cause mechanism of abnormal high pressure of Ledong block is clarified,and the difference method is optimized to precisely analyze the pore pressure of LD area,and establish the pore pressure profile of two drilled wells in LD10-X area.Based on the comparation between the calculated value and the real pore pressure,it is known that the accuracy of optimized method is high,and the maximum error is only 2.56%.