准噶尔盆地莫索湾地区深层压力预测

Prediction of Deep Pressure in Mosuowan Area of Junggar Basin

莫索湾凸起井下侏罗系下部普遍表现为超压特征,但井底以下地层压力特征不清楚。莫深1井是莫索湾凸起上以深层石炭—三叠系大型背斜圈闭为勘探目标的一口重点科学探索井,钻前开展压力预测,对莫深1井钻井工程的合理设计具有十分重要的意义。采用地震层速度法预测地层压力在正常压力段比较准确,但在超压段,地震层速度与真实地层速度之间的系统误差较大,预测压力明显小于实测压力值。VSP测井速度较地震层速度对超压段更为敏感,利用VSP速度对地震速度进行校正,可以大大降低这种系统误差。采用校正后的地震层速度进行地层压力预测,其预测精度有较大提高。

The wells in Mosuowan Uplift area indicate the wellhole overpressure characteristics of Jurassic. But it is not clear about the pressure characteristics of the formations below the well bottom. Moshen-1 well is a key scientific study well targeted at exploration of the large-scale deep Carboniferous-Triassic anticline trap on Mosuowan Uplift. The pre-drilling pressure prediction is of great significance to reasonable drilling engineering design of Moshen-1 well. Adoption of the seismic horizon velocity method for prediction of formation pressure is comparatively accurate for the normal pressure section. However, as for the overpressure section, the systematic errors between the seismic horizon velocity and the real formation velocity are considerable. The predicted pressure is obviously lower than the actual pressure. VSP logging velocity is more sensitive to the overpressure section as compared to seismic horizon velocity. Use of VSP velocity for correction of the seismic velocity can substantially reduce the systematic errors. Use of the corrected seismic horizon velocity for prediction of formation pressure can greatly raise the accuracy of prediction.