关键词:

孔隙压力, 地应力场, 层速度, 高压气井, 钻井液密度窗口, 准噶尔盆地南缘, 三压力曲线

Abstract:

There are two major difficulties in safe drilling of a new block in the southern margin of Junggar Basin：the first is the lack of logging data，which makes it impossible to calculate pore pressure values using a conventional method；the second is that the anticline structure has complex stress variations locally and it is hard to give accurate stress values through a single-well in-situ stress analysis. In order to overcome the two difficulties，this paper puts forward a method for pore pressure and drilling fluid weight window predictions based on 3D in-situ stress numerical solutions. It has been successfully applied in the drilling operation of LT1，a high-pressure gas well in Tugulu anticlinal block in the south margin of Junggar Basin. The structural details derived from the seismic formation data were introduced into the calculation model of the 3D in-situ stress field of the block to obtain the accurate numerical solution of its 3D in-situ stress. The predicted formation pore pressure values and drilling fluid weight windows were calculated accordingly. The predicted formation pore pressure data covering LT1's total depth of 8，000 m were given according to the numerical results of the 3D in-situ stress field with the velocity data of intervals，and the corresponding drilling fluid weight windows for safe drilling were calculated，thus providing theoretical guidance and accurate reference data for performing the drilling operation of this well safely，quickly，and excellently. The successful drilling operation of LT1 shows that the method proposed here is effective and the predicted pore pressure and drilling fluid weight window data are accurate.

Key words:

pore pressure, in-situ stress field, interval velocity, high-pressure gas well, drilling fluid weight window, southern margin of Junggar Basin, three pressure curve