稠油油藏热采井出砂机理与流固热耦合计算方法研究

With the increasing requirement of oil and gas, the high effective development of heavy oil reservoir has been a hot spot. Due to the high viscocity of crude oil and shallow burial depth, the sand production of heavy oil thermal recovery is severe, including the coupling of well completion method, seepage, heat transmission, the change of rock mechanical characteristics and physical property, in-situ stress, etc. The study of sand production of heavy oil thermal recovery well is of a great theoretical and engineering practice significance. With the background of heavy oil thermal recovery well completion and production, and based on the rock mechanics, percolation mechanics, thermodynamics, etc., the mathematical model of coupled thermo-hydro-mechanical processes of rock dilatancy damage that may exist in the near-wellbore area in heavy oil thermal recovery well with gravel packer completion is built and validated by the means of experimental analysis, theoretical modeling and numerical calculation. In addition, the numerical solution of the model is discussed. The multi-filed coupling response including thermal field, seepage field and rock mechanical field during the steam injection and thermal recovery of heavy oil well is systematically studied. Furthermore, the interaction mechanism of the heat transmission between stream and formation, seepage, rock property, sieve tube or gravel layer and the change of borehole stress state is uncovered. Finally, an integrated theory system of numerical modeling of coupled thermo-hydro-mechanical processes considering the near-wellbore reservoir stability during the hot steam injection is built, and it provides a scientific method for the safe injection and recovery and optimized production of heavy oil thermal recovery in poorly consolidated sand.

随着油气资源需求的增加，稠油油藏的高效开发已成为重点。由于稠油油藏储层原油粘度高、埋深浅，热采出砂问题严重，主要包括完井方式、渗流、传热、地层岩石力学特征及物性变化、地应力等多因素互相耦合作用，研究稠油热采井的出砂问题具有重要的理论意义和工程实际意义。本研究以稠油热采井完井及生产为工程背景，采用实验分析、理论建模、数值计算相结合的方法，利用岩石力学、渗流力学、热力学等理论，建立稠油热采井砾石充填完井方式下近井地带储层岩石扩容破坏的流固热耦合数学模型及简化验证，并探讨其数值求解，系统研究稠油热采井在蒸汽注采过程中的热场、渗流场及岩石力学场的多场耦合响应，揭示地层注入蒸汽与地层间的传热、渗流、地层性质、筛管或者砾石层和井眼应力状态变化及彼此间相互作用的内在机理，构建完整的注热蒸汽条件下近井地带储层稳定的流固热耦合数值模拟研究理论体系，为弱固结砂岩稠油热采地层安全注采和优化生产提供科学方法。

随着油气资源需求的增加，稠油油藏的高效开发已成为重点。由于稠油油藏储层原油粘度高、埋深浅、热采出砂问题严重，主要体现在完井方式、渗流、传热、地层岩石力学特征及物性变化、地应力等多因素互相耦合作用，研究稠油热采井的出砂问题具有重要的理论意义和工程实际意义。本研究以稠油热采井完井及生产为工程背景，采用了实验分析、理论建模、数值计算相结合的方法，将实验和现场参数相结合的方法进行了研究，主要完成了以下几个方面的工作：首先根据现场取芯和人工岩样在温压条件下进行常规三轴压缩试验，分析了疏松砂岩岩石的变形及强度特征，建立了弱固结砂岩的损伤扩容模型；同时基于温度控制方程、渗流模型及固体变形方程建立了稠油油藏饱和岩体的流固热耦合模型，利用有限元法对流固热耦合问题进行求解，将建立的流固热耦合模型与一维热固结过程中的理论模型进行对比，两者吻合；再者基于渤海湾的现场资料及岩心实验，结合热采井钻完井及生产过程的相关材料及模型参数，建立了综合考虑钻井—下筛管—砾石充填过程及砾石充填完井方式下的出砂计算模型；最后基于在渤海湾热采井开发过程中已统计的极限注入参数值，根据优选的稠油热采出砂预测方法及出砂界定条件，分析了不同注热参数（注热时间、注热速度、注热温度、注热压力）在注采阶段对地层应力、孔隙压力、温度及塑性变形的影响规律，评价了各参数对出砂的影响程度，提出了基于储层发生等效塑性应变后影响其塑性区域大小扩展的最优注入速度和注入压力。本项目通过实验和理论相结合，认识了在稠油热采井开发过程中现场注采工艺参数对出砂的影响规律，并在一定程度上对现场的注采工艺参数进行评价分析，得出结论即生产过程中有效控制注采工艺参数，可以有效控制稠油油藏生产井的出砂区域面积的扩大。本文理论、实验和现场应用相结合，形成了稠油热采生产井的出砂面积预测技术，为渤海湾稠油热采井的施工设计提供理论基础。