泥页岩水化对井壁稳定影响研究

发布时间：2018-07-25 11:29

【摘要】：泥页岩井壁稳定问题是钻井工程中一个复杂的世界性难题,也是制约我国油气田勘探开发效率的重要问题。泥页岩地层的水化作用会造成孔隙压力升高、岩石强度降低等变化,容易造成井壁剪切坍塌破坏。因此,研究泥页岩水化对井壁稳定的影响具有重要意义。本文所做的主要工作如下： (1)在研究泥页岩理化性能及水化作用机理的基础上,根据泥页岩自发渗析实验和泥页岩吸水扩散模型研究泥页岩地层的吸水规律。 (2)根据泥页岩吸水规律,研究泥页岩水化时,弹性模量、泊松比、内聚力、内摩擦角与膨胀应变随时间、空间的变化规律。 (3)在对孔隙弹性力学耦合模型和力学-化学耦合模型的大量调研基础上,根据泥页岩井壁稳定力-化耦合机制与渗透井壁的井周围岩弹性应力模型,在弹性力学本构方程的基础上,考虑膨胀应变和孔隙压力对井壁稳定性的影响,建立了泥页岩井壁稳定新模型。新模型不仅考虑泥页岩水化对岩石力学参数与孔隙压力产生的影响,而且考虑了由于孔隙压力的变化对井壁围岩产生的附加应力。水化后井周有效总应力由三部分组成：考虑水化膨胀作用后均匀地应力场导致的井周应力,非均匀地应力部分导致的井周应力以及由井周压力传递产生的附加井周应力。 (4)新模型依据现场数据分析钻井时时井周围岩弹性模量、泊松比、内聚力、内摩擦角与膨胀应变随时空的变化规律。得到泥页岩地层不同位置、不同时间径向应力与切向应力,结合强度准则对在不同时间与位置泥页岩地层的稳定性进行分析。泥页岩水化导致岩石强度降低与孔隙压力升高,这会导致井周应力的改变,井周应力的改变导致井壁稳定性的改变。随着钻井时间的增加,泥页岩地层发生剪切坍塌破坏会造成更为严重的井眼扩径。
[Abstract]:Mud shale wellbore stability is a complex worldwide problem in drilling engineering and an important problem restricting the exploration and development efficiency of oil and gas fields in China. The hydration of shale formation will lead to the increase of pore pressure and the decrease of rock strength, which will easily lead to shear collapse of wellbore. Therefore, it is of great significance to study the influence of shale hydration on wellbore stability. The main work of this paper is as follows: (1) on the basis of studying the physical and chemical properties and hydration mechanism of shale, According to the experiment of shale spontaneous dialysis and the model of shale absorption and diffusion, the water absorption law of shale formation is studied. (2) according to the law of shale water absorption, the elastic modulus, Poisson's ratio and cohesion of shale hydration are studied. The variation of internal friction angle and expansion strain with time and space. (3) on the basis of a large number of investigations on the porous elastic coupling model and the mechanical-chemical coupling model, According to the coupling mechanism of shale-wall stability and the elastic stress model of the surrounding rock, the influence of dilatation strain and pore pressure on the wellbore stability is considered on the basis of the constitutive equation of elastic mechanics. A new model of shale wellbore stability is established. The new model not only considers the influence of shale hydration on rock mechanics parameters and pore pressure, but also takes into account the additional stress caused by the variation of pore pressure on wall rock. The effective total stress around the well after hydration consists of three parts: the stress around the well caused by uniform ground stress field after consideration of hydration expansion. (4) the new model analyzes the elastic modulus, Poisson's ratio and cohesion of surrounding rock according to the field data. The variation of internal friction angle and expansion strain with time and space. The radial stress and tangential stress in different position and time of shale formation were obtained, and the stability of shale formation at different time and position was analyzed in combination with strength criterion. Shale hydration leads to the decrease of rock strength and the increase of pore pressure, which will lead to the change of the stress around the well and the change of the stress around the well to the stability of the wellbore. With the increase of drilling time, shearing collapse in shale formation will result in more serious hole expansion.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE28

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