双鱼石构造地层三压力剖面的建立及应用

Establishment and Application of Three-pressure Profile in Shuangyushi Tectonic

双鱼石构造钻井工程地质环境复杂,纵向上存在多套压力系统且地层微裂缝发育,喷漏卡塌等复杂井下事故频发,很有必要开展其地层三压力(孔隙压力、坍塌压力和破裂压力)剖面变化特征的研究。文章结合该构造的地质特征和实钻资料,利用常规和偶极声波等测井资料,针对不同岩性地层的压实机理建立了地层孔隙压力预测模型;基于摩尔—库仑剪切破坏准则和拉应力破坏理论建立了地层坍塌压力和破裂压力计算模型,由此建立了双鱼石构造的地层三压力剖面。据此,以ST1井为例分析了其井壁失稳的原因,并结合实钻资料确定了安全钻井液密度窗口。研究结果表明,砂泥岩层段具有较宽的安全钻井液密度窗口,要注意防塌、防漏,而碳酸盐岩地层微裂缝发育,安全钻井液密度窗口窄,要注意防喷防漏。

The formation of Shuangyushi tectonic have comlex drilling engineering geological environment,and there are many pressure systems existing on the vertical profiles and developing micro fissures, which caused frequently tough downhole accidents such as spurting, leakage, clipment, collapse. So it's significant for safe drilling to predict three-pressure(Pore pressure、collapse pressure and fracture pressure)profile. Combining with the geological characteristics and real drilling data, the text used conventional and dipole acoustic logging data predicting the pore pressure of different lithology compacted mechanism; Based on Moore-coulomb shear failure criterion and the tensile stress theory, the collapse pressure and fracture pressure calculation model was founded, thus the three-pressure profile of Shuangyushi tectonic was established. On this basis, take the ST1 well of the tectonic for the example, the instability of ST1 well was analyzed, and the safety window of drilling fluid density was determined. The reseachment shows that the sand mudstone layer in in Shuangyushi tectonic has a wide safety window of drilling fluid density, the attentions should be paid to prevent collapse, the carbonate formation develops micro fissures and abnormal high pressure exits, attentions should be paid to the leakage and spray.