低渗透压裂水平气井多场耦合热变规律及裂缝诊断理论研究

At present, the results of fracture diagnosis and reservoir parameters identification for multi-stage hydraulically fractured horizontal gas well have shown some shortcomings, such as inaccuracy, long cycle and non-enough instantaneity. At the same time, researches on the influence of micro-thermal effect and fractures on the wellbore temperature distribution in fracturing horizontal gas well is still weak. This seriously restricts the development of staged fracturing completion optimization in low permeability gas reservoirs, and it affects the production and the later management of horizontal gas well. This project will combine the theoretical analysis, numerical simulation and case verification. Taking a fractured horizontal well in a low permeability closed boundary gas reservoir as research objects, considering the factors such as micro-thermal effect and unequal width fracture, the unsteady heat flow models for wellbore in low permeability fractured horizontal gas wells are established under multi-field coupling conditions，and analysis of the law between target parameters of fractured horizontal gas wells and wellbore temperature distribution will be conducted. This lays a model foundation for reservoir parameter identification and fracture diagnosis. Based on the nonlinear mathematical physics inversion theory, an inversion recognition method based on wellbore test data is proposed, thus clarifying the relationship between wellbore test temperature and fracture and reservoir parameters. An interpretation plate of fracture parameters and temperature distribution is drawn, and the fracture diagnosis and reservoir parameter identification theory for fractured horizontal gas wells in low permeability reservoirs, which is based on test data, are established. The investigation results have important scientific significance and engineering value for the efficient development of natural gas, the production and management of horizontal wells in China.

现有水平气井分段压裂完井裂缝诊断及储层参数识别存在结果不准确、周期长和不具有实时性等缺点，同时微热效应和裂缝对压裂水平气井井筒温度分布的影响的研究还比较薄弱，严重制约低渗透气藏水平井压裂完井优化的发展，影响水平气井的生产和后期管理。本项目拟采用理论分析、数值模拟与实例验证相结合的方法，以低渗透封闭气藏中一口分段压裂水平气井为研究对象，考虑微热效应和非等宽裂缝等因素，构建多场耦合条件下低渗透压裂水平气井井筒非稳态热流模型，分析压裂水平气井目标参数与井筒温度分布间的规律，为储层参数识别和裂缝诊断奠定模型基础。基于非线性数学物理反演理论，提出基于井筒测试数据的反演识别方法，阐明井筒测试温度与裂缝及储层参数间的关系，绘制裂缝参数与温度分布的解释图版，建立基于测试数据的低渗透水平压裂气井裂缝诊断及储层参数识别理论。研究成果对我国天然气的高效开发及水平井的生产和管理具有重要的科学意义和工程价值。

现有水平气井分段压裂完井裂缝诊断及储层参数识别存在结果不准确、周期长和不具有实时性等缺点，同时微热效应和裂缝对压裂水平气井井筒温度分布的影响的研究还比较薄弱，严重制约低渗透气藏水平井压裂完井优化的发展，影响水平气井的生产和后期管理。近年来随着光纤技术的快速发展，分布式光纤测温技术（DTS）也日趋成熟，它可以实时连续且比较准确的测试出水平井的温度分布剖面数据，然后通过对温度数据进行反演求得水平井沿程裂缝半长及导流能力，它可以避免常规生产测井注入测试难度大、耗时较长、成本较高等诸多问题。.本项目采用理论分析、数值模拟与实例验证相结合的方法，以低渗透封闭气藏中一口分段压裂水平气井为研究对象，考虑微热效应和非等宽裂缝等因素，构建多场耦合条件下低渗透压裂水平气井井筒非稳态热流模型，分析压裂水平气井目标参数与井筒温度分布间的规律，为储层参数识别和裂缝诊断奠定模型基础。基于非线性数学物理反演理论，提出基于井筒测试数据的反演识别方法，阐明井筒测试温度与裂缝及储层参数间的关系，绘制裂缝参数与温度分布的解释图版，建立基于测试数据的低渗透水平压裂气井裂缝诊断及储层参数识别理论。本文研究成果为国内气藏水平井完井综合评价提供了新的思路,对我国天然气的高效开发及水平井的生产和管理具有重要的科学意义和工程价值。