石油学报 ›› 2011, Vol. 32 ›› Issue (4): 697-703.DOI: 10.7623/syxb201104021

• 石油工程 • 上一篇    下一篇

深井超深井井底应力场

常德玉 1,2  李根生 1  沈忠厚 1  黄中伟 1  田守嶒 1  史怀忠 1  宋先知 1   

  1. 1中国石油大学油气资源与探测国家重点实验室  北京  102249; 2中国石油化工集团国际石油工程有限公司  北京  100011
  • 收稿日期:2010-09-29 修回日期:2011-03-23 出版日期:2011-07-25 发布日期:2011-09-22
  • 通讯作者: 常德玉
  • 作者简介:常德玉,男,1984年9月生,2005年毕业于青岛农业大学农业机械化及自动化专业,现为中国石油大学(北京)在读博士研究生,主要从事石油工程和高压水射流的研究工作。
  • 基金资助:

    国家重点基础研究发展规划(973)项目“深井复杂地层安全高效钻井基础研究”(2010CB226704)资助。

The stress field of bottom hole in deep and ultra-deep wells

CHANG Deyu 1,2  LI Gensheng 1  SHEN Zhonghou 1  HUANG Zhongwei 1  TIAN Shouceng 1  SHI Huaizhong 1  SONG Xianzhi 1   

  • Received:2010-09-29 Revised:2011-03-23 Online:2011-07-25 Published:2011-09-22

摘要:

深井超深井钻井技术对加快我国石油勘探开发进程具有重要意义,深井超深井井底应力场是破岩机理研究进而提高机械钻速的基础。针对井深4500~7000 m时3种不同地应力状态下的井底岩石应力分布规律进行研究,在井底岩石力学分析的基础上,建立了考虑孔隙压力和垂直、水平最大和最小三向地应力差下的流固耦合模型,并采用数值方法进行求解。结果表明,岩石内部孔隙压力以约呈井眼径向距离的–0.055次幂减小;当井深一定时,垂直总地应力为最小地应力时,岩石所受围压最大,为中间主应力时次之,为最大地应力时最小;当地应力状态相同时,随着井深增加,岩石所受围压呈线性增加,导致岩石塑性强度增加,这是深井超深井机械钻速低的主要原因之一。深井超深井井底应力场的定量研究对深井超深井破岩机理研究和提高机械钻速具有重要的理论指导意义。

关键词: 深井超深井, 应力场, 孔隙压力, 流固耦合, 机械钻速

Abstract:

The drilling technology of deep and ultra-deep wells is of great significance in speeding up petroleum exploration and development of China. Study on the stress field of bottom-hole rocks in deep and ultra-deep wells is one of the bases to investigate rock-breaking mechanisms and the enhancement of the rate of penetration (ROP). Here, we examined the stress field distribution of bottom-hole rocks under three different in-situ stress states in wells at depths from 4500 to 7000 meters. On the basis of mechanical analysis of well bottom-hole rocks, a fluid-solid coupling model that considers the pore pressure and differences between the maximal and the minimal values of vertical and horizontal triaxial stress was established, and a numerical method was applied to solve the model. The results indicated that the pore pressure within rocks decreased approximately by the -0.055th power of the borehole radial distance. When the well depth was constant, the confining pressure suffered by rocks decreased from the maximum to the minimum in order of the vertical total in-situ stress equal to the minimum in-situ stress, the intermediate principle stress and the maximum in-situ stress, respectively. When the in-situ stress state was constant, the confining pressure suffered by rocks increased linearly with the increase of well depth, leading to the increase of rock plasticity, which was defined as one of the main reasons why the drilling of deep and ultra-deep wells had a low rate of penetration. Finally, a couple of feasible drilling modes used for deep and ultra-deep wells were summarized. Quantitative studies on the stress field of bottom-hole rocks in deep and ultra-deep wells are of theoretical significance in guiding investigations of rock breaking mechanisms and the enhancement of the rate of penetration.

Key words: deep and ultra-deep well, stress field, pore pressure, fluid-solid coupling, rate of penetration