本文關(guān)鍵詞： 深水鉆井 高溫地層 淺部地層 溫度應(yīng)力 坍塌破裂壓力　出處：《長(zhǎng)江大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：20世紀(jì)70年代末期,世界油氣勘探開始涉足深水海域,近年來我國(guó)南海周邊地區(qū)的深水油氣勘探開發(fā)也在廣泛地進(jìn)行之中。向深水進(jìn)軍,開發(fā)我國(guó)深水油氣資源已成為國(guó)內(nèi)油氣工業(yè)發(fā)展的必然趨勢(shì)。然而深水鉆井面臨著特殊地質(zhì)環(huán)境,淺部地層塑性強(qiáng),井筒溫壓場(chǎng)復(fù)雜,鉆井作業(yè)窗口窄,保持深水鉆井井壁穩(wěn)定是關(guān)系到深水鉆井安全的關(guān)鍵。建立深水環(huán)境下井壁穩(wěn)定評(píng)價(jià)方法,能為實(shí)現(xiàn)我國(guó)南海深水油氣資源的高效安全開發(fā)提供理論依據(jù)。論文主要完成工作有:1.深水環(huán)境下孔隙壓力預(yù)測(cè)孔隙壓力預(yù)測(cè)一般基于有效應(yīng)力原理,即其等于上覆巖層壓力減去基巖有效應(yīng)力。因此孔隙壓力預(yù)測(cè)之前首先進(jìn)行上覆巖層壓力預(yù)測(cè)。在穩(wěn)定的沉積速率下沉積物密度與埋深之間具有一定的數(shù)學(xué)關(guān)系,基于該原理國(guó)內(nèi)外學(xué)者建立了多種深水環(huán)境下的地層密度模型,其中Power Law模型在深水環(huán)境下應(yīng)用良好。其次以地震層速度為數(shù)據(jù)來源,以聲波速度與基巖有效應(yīng)力之間的正相關(guān)性為理論基礎(chǔ),建立了層速度預(yù)測(cè)孔隙壓力方法。2.高溫地層溫度分布規(guī)律以地層導(dǎo)熱基本理論和流體力學(xué)基本理論入手,根據(jù)熱力學(xué)第一定律,在鉆柱內(nèi)、環(huán)空內(nèi)、地層內(nèi)、井壁圍巖建立基本的溫度場(chǎng)控制方程。以全隱式差分理論保證其離散的收斂性,有效割裂鉆井液與地層之間的相互熱交換,以進(jìn)口鉆井液初始溫度首先建立井筒溫度場(chǎng),再建立井壁和地層溫度場(chǎng),有效地簡(jiǎn)化了溫度場(chǎng)建立過程。3.井壁穩(wěn)定分析針對(duì)于深水淺部塑性軟泥巖地層,以塑性變形為基本假設(shè),根據(jù)塑性破壞準(zhǔn)則,結(jié)合力學(xué)平衡方程,進(jìn)入超孔隙壓力理論,建立軟泥巖地層的破裂壓力計(jì)算公式;針對(duì)井底井壁附加的溫度應(yīng)力對(duì)井壁的影響,以導(dǎo)熱學(xué)和流體力學(xué)為基本理論,以熱力學(xué)第一定律為基礎(chǔ),建立溫度場(chǎng)控制方程,采用全隱式差分理論保證離散收斂,得到溫度場(chǎng)分布。結(jié)合熱力學(xué)平衡方程、井壁圍巖應(yīng)力-應(yīng)變關(guān)系、協(xié)調(diào)方程后,得到井底附加溫度應(yīng)力,最終得到溫降后的井壁坍塌、破裂壓力,完成井壁穩(wěn)定性研究。
[Abstract]:In the end of 1970s, world oil and gas exploration began to set foot in deep-water waters. In recent years, deep-water oil and gas exploration and development in the surrounding areas of the South China Sea are also being carried out extensively. Exploitation of deep-water oil and gas resources in China has become an inevitable trend in the development of domestic oil and gas industry. However, deep-water drilling is faced with special geological environment, strong plastic shallow formation, complex wellbore temperature and pressure field and narrow drilling window. The key to the safety of deep water drilling is to maintain the wellbore stability in deepwater drilling. It can provide a theoretical basis for the efficient and safe exploitation of deep-water oil and gas resources in the South China Sea. The main work accomplished in this paper is: 1.The prediction of pore pressure in deep-water environment is generally based on the effective stress principle. That is, it is equal to the overburden pressure minus the effective stress of the bedrock. Therefore, the overlying strata pressure is predicted first before the pore pressure prediction. There is a certain mathematical relationship between the sediment density and the buried depth at the stable deposition rate. Based on this principle, many kinds of stratigraphic density models in deep-water environment have been established by domestic and foreign scholars, among which Power Law model has been applied well in deep-water environment. Secondly, seismic layer velocity is taken as data source. Based on the positive correlation between acoustic velocity and effective stress of bedrock, the pore pressure prediction method of reservoir velocity is established. 2. The distribution of high temperature formation temperature is based on the basic theory of thermal conductivity and hydrodynamics. According to the first law of thermodynamics, the basic governing equations of temperature field are established in the drilling string, the annulus, the formation, the surrounding rock of the shaft wall. The discrete convergence is guaranteed by the fully implicit difference theory, and the heat exchange between the drilling fluid and the formation is effectively severed. First, the wellbore temperature field is established with the initial temperature of the imported drilling fluid, then the wellbore and formation temperature fields are established, which effectively simplifies the process of establishing the temperature field .3.The wellbore stability analysis is aimed at the deep water shallow plastic mudstone formation. Taking plastic deformation as the basic hypothesis, according to the plastic failure criterion, combining with the mechanical equilibrium equation and entering into the theory of excess pore pressure, the formula for calculating the fracture pressure of the mudstone formation is established, and the effect of the additional temperature stress on the borehole lining is discussed. Based on the basic theories of heat conduction and fluid mechanics and the first law of thermodynamics, the governing equation of temperature field is established. The discrete convergence is guaranteed by using the fully implicit difference theory, and the temperature field distribution is obtained. After the stress-strain relation of wall rock is coordinated, the additional temperature stress is obtained, and finally the wall collapse and fracture pressure after temperature drop are obtained, and the stability of wellbore is studied.
【學(xué)位授予單位】：長(zhǎng)江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TE21

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