挤压作用形成异常高压的定量研究

Quantitative Study on Abnormal High Pressure by Extrusion Effect

周鹏高 李亚双 刘燕

ZHOUPenggao LIYashuang LIUYan

克拉玛依职业技术学院, 新疆 克拉玛依 834000 中国石油新疆油田分公司采油一厂, 新疆 克拉玛依 834000 中国石油新疆油田分公司新疆技师学院, 新疆 克拉玛依 834000

Karamay Vocational & Technical College, Karamay, Xinjiang 834000, China NO.1 Oil Production Plant, Xinjing Oilfield Company, PetroChina, Karamay, Xinjiang 834000, China Institute of Xinjiang Technicians, Xinjing Oilfield Company, PetroChina, Karamay, Xinjiang 834000, China

封闭地层受挤压后孔隙体积变小，孔隙中的流体受到压缩却无法排出引起压力升高。基于这一理解，许多文献认为构造挤压作用是形成异常高压的主要原因之一，但目前的研究均只是定性分析，未进行定量计算。以双重有效应力理论和多孔介质弹性力学理论为基础，通过缜密的推导，对挤压作用导致的地层弹性压缩量进行了研究，得到了孔隙压力系数增量的理论计算公式。定量计算结果表明，在特定地质条件下，封闭地层受挤压作用后能使孔隙压力小幅度增大，产生轻微的压力异常，挤压作用导致的孔隙压力系数增量十分有限；挤压作用形成异常高压的条件极为苛刻，只有当地层埋藏较深、强度足够大、围岩的密封性能好、挤压作用发生在最小水平主应力方向、且外挤压力足够大，这些条件同时满足时，才可能产生较大的异常高压；挤压作用难以形成异常高压，一般不是异常高压形成的主要原因。

Pore volume in closed formation reduces when it is squeezed, and the compressed fluid that cannot be discharged in the pores causes the pressure to rise. A number of previous studies have argued that the tectonic compression effect is one of the main factors that lead to abnormal pressure. However, instead of a quantitative analysis, current studies have paid attention solely to qualitative analysis. In this study, stratum elastic compression caused by extrusion effect was investigated by close reasoning based on the double effective stress theory and the poroelasticity theory, by which the theoretical calculation formula of pore pressure coefficient increment was calculated. Quantitative calculation suggest that, under certain geological conditions, squeezed closed formation leads to a small increase in pore pressure and a slight pressure abnormality, with a limited increment of pore pressure coefficient. It was possible to cause abnormal high pressure by the extrusion effect only when the following occurred simultaneously:stratigraphic burial was sufficiently deep, the strength was sufficiently high, the sealing property of the surrounding rocks was excellent, extrusion occurred in the direction of minimum horizontal stress, and the external extrusion was sufficiently high. The extrusion effect could not generate abnormal high pressure, nor did it serve as the main cause.

10.11885/j.issn.1674-5086.2015.08.14.02