本文關(guān)鍵詞： 二次壓裂 轉(zhuǎn)向壓裂 誘導(dǎo)應(yīng)力 裂縫軌跡 數(shù)值模擬　出處：《西南石油大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：對于采用壓裂投產(chǎn)的油氣井而言,由于老裂縫控制的油氣已接近全部采出,必須實施轉(zhuǎn)向二次壓裂,才能有效開采出老裂縫控制區(qū)以外的油氣,提高油氣產(chǎn)量和油氣田最終采收率。本文針對垂直裂縫氣井二次壓裂前應(yīng)力場的分布特征、新裂縫的重定向以及新裂縫延伸軌跡等問題開展了系統(tǒng)的、深入的研究,取得了如下主要研究成果： (1)應(yīng)用彈性力學(xué)理論,建立并求解了氣井初次人工裂縫的誘導(dǎo)應(yīng)力數(shù)學(xué)模型,進而完成了人工裂縫誘導(dǎo)應(yīng)力的影響因素分析,分析表明：人工裂縫誘導(dǎo)應(yīng)力和誘導(dǎo)應(yīng)力差隨作用于裂縫壁面的凈壓力的增大和縫高的增加而增大；人工裂縫誘導(dǎo)應(yīng)力隨泊松比的增加而增大,誘導(dǎo)應(yīng)力差卻隨之減小。 (2)綜合應(yīng)用滲流力學(xué)和巖石力學(xué)理論,建立了流—固耦合應(yīng)力場計算模型。該模型中的耦合滲流方程考慮了儲層滲透率各向異性,采用有限差分法求解,而對巖土變形方程則采用有限元法求解,并采用顯式交替求解方式將它們結(jié)合起來整體求解,實現(xiàn)了對垂直裂縫氣井二次壓裂前由長期生產(chǎn)活動產(chǎn)生的誘導(dǎo)應(yīng)力場的定量分析和模擬。 (3)根據(jù)建立的流-固耦合計算模型,對影響氣井生產(chǎn)誘導(dǎo)應(yīng)力的因素進行了分析,分析表明：生產(chǎn)時間越長,井底流壓越小以及滲透率各向異性越強都有利于井周圍各點產(chǎn)生更大的誘導(dǎo)應(yīng)力差值,使得應(yīng)力重定向區(qū)域越大；縫長、泊松比和彈性模量對生產(chǎn)誘導(dǎo)應(yīng)力的影響相對較小,泊松比和彈性模量的增大不利于應(yīng)力重定向,而縫長主要影響裂縫遠處應(yīng)力重定向。 (4)采用最大周向拉應(yīng)力起裂判據(jù)分析了新縫延伸軌跡,完成了新縫延伸軌跡的影響因素分析,分析表明：生產(chǎn)時間、井底流壓、滲透率各向異性和原始水平主應(yīng)力差是影響新裂縫轉(zhuǎn)向的主要因素,且生產(chǎn)時間越長,井底流壓越小,滲透率各向異性越強和原始水平主應(yīng)力差越小都有利于二次壓裂新裂縫具有更大的轉(zhuǎn)向距離,進而盡可能地溝通儲層的未動用區(qū)域。 (5)在理論推導(dǎo)的基礎(chǔ)上,通過VB6.0語言編制了氣井二次壓裂前應(yīng)力場分布及新裂縫延伸軌跡計算程序,實現(xiàn)了二次壓裂氣井應(yīng)力場變化及新裂縫延伸軌跡的定量分析。 本文的研究可以為氣井二次壓裂優(yōu)化設(shè)計提供一定的理論基礎(chǔ),以及指導(dǎo)二次壓裂施工,提高其工藝可行性和經(jīng)濟可行性,這對老油氣田綜合治理、穩(wěn)產(chǎn)增產(chǎn)具有較為重要的意義。
[Abstract]:For oil and gas wells with fracturing production, since the oil and gas controlled by old fractures have been nearly all produced, it is necessary to implement secondary fracturing in order to effectively produce oil and gas outside the control area of old fractures. Aiming at the distribution characteristics of stress field before secondary fracturing of vertical fractured gas wells, the reorientation of new fractures and the trajectory of new fractures, etc., this paper has carried out a systematic study on the improvement of oil and gas production and the final recovery of oil and gas fields. The main research results are as follows: 1) based on the theory of elasticity, a mathematical model of induced stress of primary artificial fracture in gas well is established and solved, and the factors influencing the induced stress of artificial fracture are analyzed. The results show that the induced stress and induced stress difference increase with the increase of net pressure and crack height. The induced stress increases with the increase of Poisson's ratio, but the induced stress difference decreases with the increase of Poisson's ratio. (2) based on the theory of seepage mechanics and rock mechanics, a computational model of fluid-solid coupling stress field is established. The coupled seepage equation in this model takes account of reservoir permeability anisotropy and is solved by finite difference method. The deformation equations of rock and soil are solved by finite element method, and they are solved by alternating explicit solution. The quantitative analysis and simulation of induced stress field produced by long-term production activities before secondary fracturing of vertical fractured gas wells are realized. 3) according to the fluid-solid coupling calculation model established, the factors influencing the induced stress in gas well production are analyzed. The analysis shows that the longer the production time is, the longer the production time is. The smaller the bottom hole flow pressure and the stronger the permeability anisotropy are, the greater the induced stress difference is, and the larger the stress reorientation area is. The effect of joint length, Poisson's ratio and elastic modulus on the induced stress is relatively small. The increase of Poisson's ratio and elastic modulus is not conducive to the stress reorientation, while the joint length mainly affects the stress reorientation in the distance of the crack. 4) using the criterion of maximum circumferential tensile stress to analyze the trajectory of new fracture extension, the factors influencing the trajectory of new crack extension are analyzed. The analysis shows that: production time, bottom hole flow pressure. The anisotropy of permeability and the difference of primary horizontal principal stress are the main factors affecting the new fracture turn, and the longer the production time is, the smaller the bottom hole flow pressure is. The stronger the permeability anisotropy and the smaller the primary horizontal principal stress difference are, the greater the turning distance of the new fracture is, and then the unproduced area of the reservoir can be communicated as much as possible. 5) on the basis of theoretical derivation, a program for calculating stress field distribution and new fracture extension trajectory before secondary fracturing in gas wells is compiled by VB6.0 language. The quantitative analysis of stress field change and new fracture extension trajectory of secondary fracturing gas well is realized. The research in this paper can provide a certain theoretical basis for the secondary fracturing optimization design of gas wells, and guide the secondary fracturing operation to improve its technological and economic feasibility, which can comprehensively control the old oil and gas fields. It is of great significance to stabilize production and increase production.
【學(xué)位授予單位】：西南石油大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TE357

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