【摘要】：泥頁巖井壁穩(wěn)定問題是鉆井工程中一個復雜的世界性難題,也是制約我國油氣田勘探開發(fā)效率的重要問題。泥頁巖地層的水化作用會造成孔隙壓力升高、巖石強度降低等變化,容易造成井壁剪切坍塌破壞。因此,研究泥頁巖水化對井壁穩(wěn)定的影響具有重要意義。 本文所做的主要工作如下： (1)在研究泥頁巖理化性能及水化作用機理的基礎上,根據(jù)泥頁巖自發(fā)滲析實驗和泥頁巖吸水擴散模型研究泥頁巖地層的吸水規(guī)律。 (2)根據(jù)泥頁巖吸水規(guī)律,研究泥頁巖水化時,彈性模量、泊松比、內(nèi)聚力、內(nèi)摩擦角與膨脹應變隨時間、空間的變化規(guī)律。 (3)在對孔隙彈性力學耦合模型和力學-化學耦合模型的大量調(diào)研基礎上,根據(jù)泥頁巖井壁穩(wěn)定力-化耦合機制與滲透井壁的井周圍巖彈性應力模型,在彈性力學本構方程的基礎上,考慮膨脹應變和孔隙壓力對井壁穩(wěn)定性的影響,建立了泥頁巖井壁穩(wěn)定新模型。新模型不僅考慮泥頁巖水化對巖石力學參數(shù)與孔隙壓力產(chǎn)生的影響,而且考慮了由于孔隙壓力的變化對井壁圍巖產(chǎn)生的附加應力。水化后井周有效總應力由三部分組成：考慮水化膨脹作用后均勻地應力場導致的井周應力,非均勻地應力部分導致的井周應力以及由井周壓力傳遞產(chǎn)生的附加井周應力。 (4)新模型依據(jù)現(xiàn)場數(shù)據(jù)分析鉆井時時井周圍巖彈性模量、泊松比、內(nèi)聚力、內(nèi)摩擦角與膨脹應變隨時空的變化規(guī)律。得到泥頁巖地層不同位置、不同時間徑向應力與切向應力,結(jié)合強度準則對在不同時間與位置泥頁巖地層的穩(wěn)定性進行分析。泥頁巖水化導致巖石強度降低與孔隙壓力升高,這會導致井周應力的改變,井周應力的改變導致井壁穩(wěn)定性的改變。隨著鉆井時間的增加,泥頁巖地層發(fā)生剪切坍塌破壞會造成更為嚴重的井眼擴徑。
[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.
【學位授予單位】：西南石油大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TE28

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