复杂泥页岩地层地应力的确定方法研究

掌握地层原始地应力状态是有效控制钻井过程中泥页岩地层井壁失稳的前提。在分析水压致裂法、Kaiser效应法、差应变法和多极子测井方法测量地应力的技术现状的基础上，发现利用单一方法获取复杂泥页岩地层的地应力比较困难，将多种方法组合在一起才能较好地解决问题。如果地层破裂试验层段有钻井岩芯，可通过差应变方法获得主地应力的比值；如果地层破裂试验层段没有钻井岩芯，可通过多极子测井方法得到两个水平主地应力的差值。将两个水平主地应力的相对值代入地层破裂试验的破裂压力计算模型，可分别确定出两个水平主地应力的大小。利用地层破裂试验与差应变试验组合测地应力方法和地层破裂试验与多极子测井组合测得应力的方法，分别较为成功地测试地应力。

STUDY ON DETERMINATION METHOD OF IN-SITU STRESS FOR COMPLEX SILT FORMATIONS

In-situ stress is critical to well instability in silt formations during drilling.Based on the analysis of in-situ stress measurement methods such as hydraulic fracturing method,Kaiser effect method,differential strain analysis(DSA) method and multi-pole logging method,it is difficult to acquire in-situ stress of complex silt formations through any method mentioned above.The best way is the combination of the advantages of these methods.Two methods to determine the in-situ stress are presented in this paper.The in-situ stress ratio can be measured by DSA method if there are drilling cores in the fracturing test,while the in-situ stress difference can be measured by multi-pole logging method if there is no drilling core in the fracturing test.Combined the acquired in-situ stress relative value with the fracture pressure mode for fracturing test,the horizontal in-situ stress can be determined.These two combined methods,in which one is the combination of formation fracturing test with DSA method and the other is the combination of formation fracturing test with multi-pole logging method,are feasible in field application.