随钻地震技术在异常高压地层预测中的应用

随钻地震（SWD）技术的原理是：钻进过程中牙轮钻头破碎地层产生冲击波，经过地层反射到达地面，通过地面接收系统来采集井下的地层信息。SWD技术能够实时提供钻头下部几百米内的地层信息，利用这些地层信息可以准确地计算地层孔隙压力，并能准确地预测异常高压地层的深度，为钻井过程中合理选择钻井液密度和确定套管合理下入深度提供科学依据。通过对南中国海域某试验井SWD采集信息的处理和分析，预测地层孔隙压力，及时调整钻井液密度，并根据异常高压面的预测深度确定技术套管的下入深度。现场实践表明，利用SWD技术预测的异常压力面深度与实钻情况比较吻合，其地层压力的预测精度较高。图4表1参11

Application of seismic while drilling technique in prediction of abnormally high pressure formation

The principle of SWD (Seismic While Drilling) is that the shock waves generated by cone bits breaking formation in the process of drilling are reflected to the surface of the earth by borehole formation, and then the stratigraphic information is collected by a ground receiving system. SWD can provide real-time information of several-hundred-meter formation below the drill bit, which can be used to calculate formation pore pressure accurately, predict abnormal pressure formation's depth, and provid a scientific foundation for the reasonable selection of drilling fluid density and casing setting depth. SWD is applied in a pilot well in South China Sea, and the result indicates that the abnormal pressure face's depth predicted by SWD nearly coincides with the actual drilled depth, and the formation pressure predicted by SWD is of high accuracy.