泥页岩井壁水化损伤的蠕变失稳力学研究

发布时间：2018-01-31 00:47

本文关键词： 泥页岩井壁稳定水化损伤核磁共振蠕变　出处：《西北工业大学》2015年博士论文　论文类型：学位论文

【摘要】：本文针对油气钻井工程中迫切需要解决的泥页岩井壁失稳关键性问题,以长庆油田长7层西峰233井区为依托,运用损伤力学与流变力学相结合的方法,重点考察泥页岩井壁岩石内部存在的微缺陷损伤以及入井流体和地下流体物化作用造成的流变效应的影响,利用核磁共振、力学实验、理论分析和数值模拟相结合的研究方法,构建并引入由核磁共振T2谱表征的水化损伤变量,建立考虑水化损伤和蠕变损伤的泥页岩蠕变模型,揭示泥页岩井壁围岩水化后初始缺陷蔓延、传播、贯通到坍塌破坏的蠕变特性和演化过程,形成泥页岩井壁蠕变损伤失稳研究的基本理论方法。论文的主要研究内容如下:(1)岩石组分构成及力学特性分析利用X衍射和扫描电镜的实验方法,对泥页岩岩心进行矿物组分结构和地层岩石物性特征的分析。测试结果发现:该地区的泥页岩中主要原生矿物有黄铁矿、长石和石英,其中石英含量为40%左右,岩石表现为明显的脆硬性。其中粘土矿物主要成分为伊蒙混层、伊利石、绿泥石。区域地层的泥页岩压实程度较高,水平层理及微裂隙发育明显。对不同含水状态下泥页岩岩样进行单轴、三轴抗压强度力学变形实验,获得了应力—应变关系曲线。从结果可以看出:水化对岩石的力学性能影响很大,降低岩石的整体力学性能。(2)泥页岩蠕变特性实验研究对岩石进行不同含水率下三轴蠕变实验,试样在整个加载过程中,经历了衰减蠕变、等速蠕变和加速蠕变三个蠕变阶段。针对相同荷载水平不同含水条件的对比分析表明,随着含水率的提高,同级荷载情况下岩石蠕变进入稳定阶段所需的时间基本越长、蠕变加载瞬间应变越大、总应变量越大,而岩石长期强度呈减小的趋势。(3)基于核磁共振的泥页岩水化损伤特征及演化分析利用核磁共振技术对不同浸泡时间的脆硬性泥页岩试样进行测量,得到不同浸泡时间后试样质量变化、横向弛豫时间T2谱分布以及核磁成像。结果表明:水化作用会对岩石内部产生损伤,随着浸泡时间的延长,微裂缝在水化的作用下快速扩展、贯通,使岩样表面产生明显裂纹。核磁共振T2谱图和成像结果表明水化作用使岩样孔隙结构重新分布,T2曲线信号幅度发生明显变化。建立了由核磁共振T2谱图表征的损伤变量,为识别岩石材料的损伤,提供了新的方法。(4)考虑初始水化损伤和蠕变损伤的泥页岩蠕变本构模型研究分析不同含水状态下泥页岩蠕变特性,引入由核磁共振T2谱表征的水化损伤变量,建立考虑水化损伤和蠕变损伤的泥页岩蠕变模型。采用类比法,在提出的一维蠕变损伤演化方程的基础上,建立同时考虑瞬时损伤和蠕变损伤的三维流变本构模型。该模型既能描述岩石水化损伤后的衰减蠕变和稳定蠕变,又能描述岩石在高应力下的加速蠕变。是一个能反映蠕变三个阶段的水化损伤非线性蠕变模型。利用模型对长7泥页岩的蠕变试验数据拟合的结果表明,该模型可以很好地描述泥页岩水化损伤后岩石的蠕变特性。(5)泥页岩的水化损伤蠕变的有限元分析及工程应用利用FORTRAN开发环境,把建立的三维损伤流变本构模型编译成子程序,在ABAQUS中采用开发程序对泥页岩三轴蠕变实验进行数值模拟,然后通过和泥页岩的蠕变实验结果进行对比,验证非定常流变本构模型及程序编制的正确性。将所建的水化损伤蠕变模型用于长7层西峰233井区泥页岩层钻井井壁稳定分析,给出考虑损伤蠕变后泥页岩层钻进的钻井液密度图版,用以指导现场钻井。
[Abstract]:Aiming at the urgent need to solve the oil and gas drilling in shale instability problems, Changqing Oilfield 7 layer 233 wells of Xifeng area as the basis, using the method of combining damage mechanics and rheological mechanics, rheology effect focuses on the existence of the shale rock damage and micro defects into the well the fluid and underground fluid material caused by the use of nuclear magnetic resonance, mechanics experiment, research method of combining theoretical analysis and numerical simulation, construction and water damage variables introduced by T2 magnetic resonance spectroscopy characterization, a creep model of shale hydration damage and creep damage, reveal the shale rock the water after the initial defect spread, spread through to the creep characteristics and evolution process of collapse, forming shale creep damage loss theory of stabilization method research. The main contents of this paper Are as follows: (1) the rock composition and mechanics characteristics analysis and experimental methods of X diffraction and scanning electron microscope using the analysis of mineral composition structure and stratigraphic petrophysical characteristics of shale cores. The test result showed that the main minerals in the area of shale in pyrite, feldspar and quartz, quartz content around 40%, the rock is obvious brittle. The main component of clay minerals are illite smectite, illite and chlorite. Regional stratigraphic high shale compaction, horizontal bedding and micro fractures are developed. The different water condition of shale rock uniaxial deformation experiment, three axial compressive strength mechanics. To obtain the stress-strain curves. The result shows that water on Mechanical properties of rock impact, reducing the overall mechanical properties of rock. (2) experimental research on the creep characteristics of mud shale rock Three axis creep experiments of different moisture samples during the whole loading process, experienced attenuation creep, steady creep and accelerated creep creep stage three. The comparative analysis for the same load level of different water conditions show that, with the increase of moisture content, the rock creep loads into the stable stage of the time required for the more basic long, creep loading instantaneous strain increases, the total strain is larger, and the long-term strength of rock decreases. (3) shale hydration damage characteristics and evolution of nuclear magnetic resonance analysis using nuclear magnetic resonance technology in different soaking time of brittle shale samples based on the measurements of different soaking time after sample quality change of transverse relaxation time T2 spectral distribution and magnetic resonance imaging. The results show that the hydration will cause damage to the rock, with the extension of soaking time, micro cracks in the water Through with the rapid expansion of the rock surface, obvious cracks. Nuclear magnetic resonance T2 spectrum and imaging results show that the hydration of the rock pore structure re distribution curve of T2 signal amplitude changes obviously. The damage variables characterized by nuclear magnetic resonance T2 spectrum, for the identification of rock material damage, provided the new method. (4) constitutive model analysis of creep properties of shale in different moisture conditions of shale hydration initial creep damage and creep damage, water damage variable is introduced by T2 magnetic resonance spectroscopy characterization, a creep model of shale hydration damage and creep damage. By analogy method. In the one-dimensional creep damage evolution equation based on established considering three-dimensional rheological instantaneous damage and creep damage constitutive model. The model can describe the rock water damage after the decay creep and steady Creep, and can describe the accelerated creep of rock under high stress. A water damage can reflect the nonlinear creep model of three stages of creep. The creep test data fitting model of Chang 7 shale. The results show that the model can well describe the shale hydration after rock creep damage characteristics. (5) FORTRAN was developed using the finite element analysis and engineering application of shale hydration creep damage, the three-dimensional damage rheological constitutive model is developed to compile the subroutine, used in ABAQUS development program for numerical simulation of three axis creep test and creep test results of shale and shale by by contrast, verify the correctness of non steady rheological constitutive model and the program. The water damage creep model is built for analyzing the 7 layer of Xifeng 233 well area of mud shale borehole instability, creep damage are given After the mud shale drilling mud density diagram, used to guide the on-site drilling.

【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE21

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