压裂水平井线性复合分析模型
发布时间：2019-06-18 19:26
【摘要】：近些年来,我国对陆上石油的勘探程度及难度不断增加,低渗透油田越来越受到人们的重视。对于低渗透油田,人们通常利用水平井分段压裂技术来提高油井的产油能力。压裂水平井提高油层产能的机理是将普通水平井中原来的流体径向渗流转变成线性渗流。然而低渗透油藏由于存在启动压力梯度,会导致流体出现非线性——拟线性的非Darcy渗流规律,在不定常渗流过程中压力扰动的传播存在一个动边界,这将导致相应的不稳态渗流带有非齐次性和非线性。本文首先明确了低渗透油藏的渗流特征,考虑启动压力梯度的影响,通过改进无量纲压力定义,结合复合线性流动理论,建立了考虑启动压力梯度的垂直裂缝井之双线性流模型,分别得到井底定产量及定流压条件下不同启动压力梯度、导流能力的动边界传播规律,以及井底压力、储层压力分布剖面和井底产量图。计算分析表明,利用线性复合模型可以有效地模拟矩形油藏有限导流垂直裂缝井模型,将结果与精确解进行对比后,结果发现该解在前期与精确解拟合情况较好,但在中期渗流阶段可能会产生渗流模型上的差异,即可能的平面径向流动段不会发生,代之而来的是平面线性流动。在低渗油藏中,动边界传播速度随地层的启动压力梯度的增大而逐渐减慢。对于固定井底流压条件,动边界随着时间的延长向外传播,裂缝中点处动边界传播速度最快,两边逐渐递减,整体呈坡锥型曲线,达到最大动外边界后停止传播;当最大动边界满足xm D=1.0/λD时,单井最大动用面积为yf(pi-pwf)/λ;如果地层的启动压力梯度越大,那么压降漏斗将会越陡,同时产量的递减速度也将会越来越快。最后,利用线性复合模型之不对称泄流面积模型、三区、五区模型可近似地模拟分段压裂水平井,得到的解与数值模拟的结果对比,给出了解析解模型的适用范围。
[Abstract]:In recent years, the degree and difficulty of onshore oil exploration in China has been increasing, and people pay more and more attention to low permeability oil fields. For low permeability oil fields, horizontal well subsection fracturing technology is usually used to improve the oil production capacity of oil wells. The mechanism of fracturing horizontal well to improve reservoir productivity is to transform the original fluid radial seepage into linear seepage in ordinary horizontal well. However, due to the existence of start-up pressure gradient in low permeability reservoir, the fluid will appear nonlinear-quasilinear non-Darcy seepage law, and there is a moving boundary for the propagation of pressure disturbance in the process of unstable seepage, which will cause the corresponding unstable seepage to be non-homogeneous and nonlinear. In this paper, the seepage characteristics of low permeability reservoir are clarified, and the influence of starting pressure gradient is considered. by improving the definition of dimensionless pressure and combining with the compound linear flow theory, the bilinear flow model of vertical fracture well considering starting pressure gradient is established, and the dynamic boundary propagation law of different starting pressure gradient and diversion capacity under the condition of constant bottom hole production and constant flow pressure, as well as the bottom hole pressure, are obtained respectively. Reservoir pressure distribution profile and bottom hole production map. The calculation and analysis show that the linear composite model can effectively simulate the finite conductivity vertical fracture well model of rectangular reservoir. After comparing the results with the exact solution, it is found that the solution fits well with the exact solution, but the difference in the seepage model may occur in the middle seepage stage, that is, the possible plane radial flow section will not occur, but the plane linear flow will be replaced by the solution. In the low permeability reservoir, the propagation velocity of the moving boundary slows down with the increase of the starting pressure gradient of the formation. For the fixed bottom hole flow pressure condition, the moving boundary propagates outward with the prolongation of time, the propagation speed of the moving boundary at the midpoint of the fracture is the fastest, the two sides decrease gradually, and the whole slope cone curve stops when the maximum moving boundary satisfies xm D 鈮，
本文编号：2501727
[Abstract]:In recent years, the degree and difficulty of onshore oil exploration in China has been increasing, and people pay more and more attention to low permeability oil fields. For low permeability oil fields, horizontal well subsection fracturing technology is usually used to improve the oil production capacity of oil wells. The mechanism of fracturing horizontal well to improve reservoir productivity is to transform the original fluid radial seepage into linear seepage in ordinary horizontal well. However, due to the existence of start-up pressure gradient in low permeability reservoir, the fluid will appear nonlinear-quasilinear non-Darcy seepage law, and there is a moving boundary for the propagation of pressure disturbance in the process of unstable seepage, which will cause the corresponding unstable seepage to be non-homogeneous and nonlinear. In this paper, the seepage characteristics of low permeability reservoir are clarified, and the influence of starting pressure gradient is considered. by improving the definition of dimensionless pressure and combining with the compound linear flow theory, the bilinear flow model of vertical fracture well considering starting pressure gradient is established, and the dynamic boundary propagation law of different starting pressure gradient and diversion capacity under the condition of constant bottom hole production and constant flow pressure, as well as the bottom hole pressure, are obtained respectively. Reservoir pressure distribution profile and bottom hole production map. The calculation and analysis show that the linear composite model can effectively simulate the finite conductivity vertical fracture well model of rectangular reservoir. After comparing the results with the exact solution, it is found that the solution fits well with the exact solution, but the difference in the seepage model may occur in the middle seepage stage, that is, the possible plane radial flow section will not occur, but the plane linear flow will be replaced by the solution. In the low permeability reservoir, the propagation velocity of the moving boundary slows down with the increase of the starting pressure gradient of the formation. For the fixed bottom hole flow pressure condition, the moving boundary propagates outward with the prolongation of time, the propagation speed of the moving boundary at the midpoint of the fracture is the fastest, the two sides decrease gradually, and the whole slope cone curve stops when the maximum moving boundary satisfies xm D 鈮，
本文编号：2501727
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