井筒多相流瞬态流动数值算法及响应特征研究

发布时间：2018-12-13 20:11

【摘要】：深层油气资源目前是我国油气勘探开发的重要领域。深层油气储层、尤其是深层海相油气储层,地质条件复杂、缝洞发育、压力高产量高,具有窄安全窗口的特点。钻进中井筒与地层间容易发生物质交换,导致溢流、漏失以及溢漏同存频发,从而引发井筒内的复杂多相流动。为了精确控制井筒压力,需要掌握各种工况条件下井筒多相流动规律和各相流动参数之间的动态响应特征。钻井中地层流体侵入井筒而导致的多相流动的过程是瞬态流动,数值仿真模拟是研究井筒多相流瞬态流动规律及响应特征的重要手段。为了精确数值仿真模拟气体流量实时变化的复杂流动情况,要求数值计算方法具有高精度、高稳定性、高分辨率,能够精确捕捉流域内的各种间断。目前,国内的井筒多相流瞬态流动模型和计算软件有一定研究,主要针固定气体流量的气侵及其压井过程。采用的数值计算方法较为落后,缺少严格的数值算例验证,并且缺少对计算结果中井筒内各处流体质量流量守恒精度的讨论,而该性质是影响计算精度的关键因素之一。本文针对精确数值计算井筒多相流瞬态流动问题开展研究,主要研究如下：(1)考虑井筒温度,基于气液两相流漂移模型和Shi漂移参数预测模型,结合相关辅助模型,建立储层-井筒多相流瞬态流动耦合模型,用于数值仿真模拟分析井筒内的流动规律和各流动参数的动态象性特征。(2) AUSM (Advection Upstream Splitting Method)类格式不需要(近似)Riemann求解器或计算Jacobian矩阵,具有形式简单,计算量小的优点。结合经典保单调的MUSCL (Monotone Upstream-Centred Schemes for Conservation Laws)方法和van Leer斜率限制器获得具有二阶空间精度的AUSMV格式,并采用Runge-Kutta方法离散得到二阶时间精度,应用于求解气液两相流漂移模型。(3)利用经典数值算例验证所编写的程序,计算结果与参考值吻合良好表明了本文构建的改进AUSMV格式耗散效应和色散效应小,没有明显的数值振荡,间断没有被拉宽或抹平。二阶精度格式比一阶精度格式具有更好的间断捕捉能力。研究表明该二阶AUSMV格式计算气液两相流动具有计算量小、精度高、分辨率高、计算稳定的优点。(4)利用大型实验台架模拟了连续气侵过程,观察了该过程井筒内的流动特征,并测量了井筒内的压力演变过程。进而,利用室内实验数据和现场实验数据验证了所编程序的计算精度,结果分析表明两种情况下程序压力计算误差分别在±10%和±5%之内,满足工程需求。(5)采用已验证的程序数值仿真模拟研究了定气量连续气侵、变气量连续气侵、单股气侵、间歇气侵,以及控压钻进薄储层和厚储层等典型工况,分析了井筒内各流动参数间的动态响应特征,揭示了复杂井筒多相流动的规律。
[Abstract]:Deep oil and gas resources are an important field of oil and gas exploration and development in China. Deep oil and gas reservoirs, especially deep marine oil and gas reservoirs, are characterized by complicated geological conditions, developed fractures and cavities, high pressure and high production, and have the characteristics of narrow safe window. Material exchange between wellbore and formation is easy to occur in drilling, which leads to overflow, leakage and leakage co-occurrence frequently, thus causing complex multiphase flow in wellbore. In order to accurately control wellbore pressure, it is necessary to master the characteristics of multi-phase flow and the dynamic response between the parameters of the multi-phase flow in the wellbore under various working conditions. The process of multiphase flow caused by formation fluid intruding into wellbore in drilling is transient flow. Numerical simulation is an important means to study the transient flow law and response characteristics of wellbore multiphase flow. In order to simulate the complex flow of gas flow in real time, it is required that the numerical method has high accuracy, high stability and high resolution, and can accurately capture all kinds of discontinuities in the basin. At present, there are some researches on the transient flow model and calculation software of multi-phase flow in wellbore, mainly on the gas invasion of fixed gas flow rate and its well killing process. The numerical calculation method adopted is backward, lacks strict numerical example verification, and lacks the discussion of the conservation accuracy of fluid mass flow throughout the wellbore in the calculation results. This property is one of the key factors affecting the calculation accuracy. In this paper, the problem of accurate numerical calculation of transient flow in wellbore multiphase flow is studied. The main research is as follows: (1) considering wellbore temperature, based on gas-liquid two-phase flow drift model and Shi drift parameter prediction model, combined with relevant auxiliary model, The coupled model of reservoir and wellbore multiphase flow transient flow is established. It is used for numerical simulation and analysis of flow law and dynamic imaging characteristics of flow parameters in wellbore. (2) AUSM (Advection Upstream Splitting Method) scheme does not need (approximate) Riemann solver or calculate Jacobian matrix, so it has simple form. The advantage of less computation. Combined with the classical monotone preserving MUSCL (Monotone Upstream-Centred Schemes for Conservation Laws) method and the van Leer slope limiter, the AUSMV scheme with second-order spatial accuracy is obtained, and the second-order time accuracy is obtained by using the Runge-Kutta method. It is applied to solve the drift model of gas-liquid two-phase flow. (3) A classical numerical example is used to verify the program. The calculated results are in good agreement with the reference values. It is shown that the improved AUSMV scheme constructed in this paper has less dissipative effect and less dispersion effect. There is no obvious numerical oscillation and the discontinuity is not widened or leveled. The second order precision scheme has better discontinuous capture ability than the first order precision scheme. It is shown that the two-order AUSMV scheme has the advantages of low computational complexity, high precision, high resolution and stable calculation. (4) the continuous gas invasion process is simulated by using a large scale experimental bench. The flow characteristics in the wellbore are observed and the pressure evolution in the wellbore is measured. Furthermore, the calculation accuracy of the program is verified by indoor and field experimental data. The results show that the calculation error of program pressure is within 卤10% and 卤5%, respectively. (5) using the verified numerical simulation to study the typical conditions such as constant gas flow continuous gas invasion, variable gas flow continuous gas invasion, single flow gas invasion, intermittent gas invasion, and controlled pressure drilling into thin and thick reservoirs, etc. The dynamic response characteristics of various flow parameters in the wellbore are analyzed, and the law of multiphase flow in complex wellbore is revealed.
【学位授予单位】：西南石油大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TE21;TE52

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