基于地震资料的探井钻前孔隙压力预测——以伊拉克A油田为例

钻前压力预测在保障钻井安全、选取合理的钻井液密度、设计科学的井身结构、降低钻井成本和保护油气层方面都具有十分重要的意义。由于测井资料不足和地震资料的多解性，钻前压力预测的精度常常达不到钻井的要求。本次研究以伊拉克西南部的A油田为研究区，针对该区深层探井资料少和地震响应复杂的两个难点，以地震资料为基础，充分结合区域地质和浅层测井资料，从压力的成因研究出发，查明了研究区超压主要受侧向构造挤压和深部断裂引起的流体充注两种因素的控制，在此基础上优选出了基于地震资料的钻前压力预测方法，开展了井震联合上覆地层压力预测、地质一致性精细速度解释和地震速度变化率分段求取三项参数精度提升工作，预测出了深层探井侏罗系的孔隙压力系数为1.95~2.05。经钻井验证，压力预测成果与实测结果的相对误差小于3%，证实该方法能够提高钻前孔隙压力预测的精度。

Pre-drilling pore pressure prediction based on seismic data for exploratory well: Oilfield A in Iraq

Pore pressure prediction before drilling is of great significance for ensuring drilling safety,choosing reasonable drilling mud density,designing well configuration,reducing drilling cost and protecting reservoirs.The accuracy of pressure prediction usually is not sufficient for drilling requirement due to a lack of logging data and multi-interpretation of seismic data.This paper focuses on an oilfield A in southwest of Iraq.To tackle the problem of inadequate exploration well data of deep layers and complicated seismic responses,we combined seismic data with regional geology and shallow well logging data to study the mechanisms behind pressure.We found out that the study area was controlled by fluid charging caused by lateral tectonic extruding and deep faulting.An optimized method for pre-drilling pressure prediction was picked out and improvement on the precision of the pore pressure calculating parameters was achieved through overburden pressure prediction based on seismic-well-integration,seismic velocity analyses based on geological consistency,and variation rate of seismic velocity estimation.Pore pressure coefficient of exploratory well in deep Jurassic was predicted to range between 1.95 and 2.05.The prediction was verified by actual measurement with an error less than 3% only.