火山岩地层孔隙压力测井预测方法研究

火山岩地层孔隙压力测井预测方法研究

刘之的;汤小燕

【摘要】针对火山岩地层孔隙压力预测相对较难,充分考虑到火山岩剖面的地层特性,在岩石力学参数室内测试分析的基础上提出了利用有效应力法预测地层压力的方法;讨论了模型中利用岩石泊松比室内测试数据刻度测井资料计算的泊松比计算岩石有效应力,进而预测地层孔隙压力.建立的整套方法模型对准噶尔盆地×1井等井的火山岩井段进行了地层压力测井预测处理,给出了合理的地层压力剖面与泥浆密度,计算出不同井深与不同层位的地层压力.基于火山岩岩性复杂,不同岩性的泊松比变化较大,应分岩性建立地层孔隙压力预测模型,对具体模型进行检验修正,以逐步解决火山岩地层孔隙压力预测的难题.与实测地层压力对比表明,该方法从测井信息中提取火山岩地层压力是可靠的,且精度较高、实用性较强,能够用于火山岩地层地层压力剖面的建立和钻井液密度的设计.%It is vital to accurately determine three-formation pressure for designing drilling mud density, stabilizing borehole and drilling safety. Predicting formation pressure with well logging data is a comparatively more valid method. Presently, the technique of predicting formation pressure in mud-sand profile is relatively perfect. However, there are definite problems to estimate accurately formation pore pressure of volcanic rock profile. Based on different formation characteristics of volcanic rock and the analysis of the rock mechanics parameters in indoor test, an effective stress method is presented to predict the formation pore pressure in the volcanic rock. The transverse wave time difference and rock Poisson ratio are used to calculate effectiveness stress, from which obtained is the formation pore

pressure. Formation pressures of ×1 well and other wells in ZhunGaEr basin, are predicted based on effectiveness stress method using logging data. The reasonable formation pressure profile and mud density are given; the formation pressures in different well-depths and different intervals are calculated. Due to lithology of volcanic rock is very complex and the Poisson ratios of different lithologies change greatly, so the formation pore pressure prediction model should be set up according to different lithologies; at the same time, the model should be tested and corrected so as to gradually solve the problems in predicting the formation pore pressures of the volcanic rocks. The calculated formation pressure of the volcanic rock is reliable based on the method using logging data. Predicting precision is high, and practicability is better. The calculated result can act as the guide of establishing formation pressure and designing the mud density of volcanic rock formation.

【期刊名称】《测井技术》

【年(卷),期】2011(035)006

【总页数】4页(P568-571)

【关键词】测井资料;火山岩;有效应力;地层压力;泊松比

【作者】刘之的;汤小燕

【作者单位】西安石油大学油气资源学院,陕西西安710065;西安科技大学地质与环境学院,陕西西安710054

【正文语种】中文

【中图分类】P631.84

直接从测井信息中准确提取地层压力一直得到人们的高度重视［1－3］。用测井

资料估算砂泥岩剖面地层压力的技术较为成熟［4－6］。火山岩剖面中泥页岩层少，很难找到纯泥页岩层构建正常压实趋势方程，等效深度法已失去意义。本文充分利用测井资料，基于有效应力定理，利用岩石泊松比室内测试数据刻度测井资料计算的岩石泊松比，进而计算岩石有效应力和地层孔隙压力，并探讨模型中所涉及的岩石力学参数的测井求法。将所建立的一整套方法模型应用到准噶尔盆地×1井等井的地层压力测井解释处理中，给出了合理的地层压力剖面与泥浆密度，取得了良好的应用效果。

从力学角度，沉积压实的原动力来源于上覆岩层的压力，但又受孔隙压力的影响。Terzaghi经过多年对饱和多孔介质力学特性的研究，考虑2种力的综合影响提出

了有效应力定理［2－4］。

式中，σ为岩石的有效应力，MPa；p 0为上覆岩层压力，MPa；pφ为地层孔隙压力，MPa。

由Terzaghi有效应力定理可知，若已知某地层的上覆岩层压力和有效应力，则可以求出地层孔隙压力。上覆岩层压力可以通过已钻井的密度测井资料等求得。因此，只要设法求出有效应力即可以确定孔隙压力。

研究发现［2－3］，岩石的有效应力σ与某些岩石力学参数密切相关，而岩石力

学参数又可以由声波测井资料求取。这样，利用测井资料就可以间接地求得有效应力。实际资料表明［1－3］，有效应力与泊松比存在良好的指数函数关系。已有

实验研究表明［1］，当应力方向与声波测量方向一致时，对声波速度大小的影响较大；而当应力方向与声波测量方向相互垂直时，对声波速度大小几乎没有什么影