深层裂缝性异常高压气藏高速非达西渗流建模及非线性渗流特征研究

Deep fractured overpressured gas reservoir has the distinctive “4-high” characteristics of high temperature, high pressure, high stress sensitivity and high-velocity non-Darcy. The traditional linear flow theory is not suitable for fractured overpressured gas reservoirs and the existed nonlinear flow theory is extremely immature, so we need to further study the nonlinear flow theory as soon as possible. Therefore, we will carry out the stress sensitivity experiments under the high temperature and high pressure conditions of real deep gas reservoir using the full diameter matrix cores, the full diameter cores with natural fractures and the full diameter cores with the manmade packed fracture; and according to the experimental results, we will divide the pressure into the high, mid and low pressure ranges and search for the best nonlinear relationship of porosity and permeability with the pore pressure for each pressure range. We will design the long-core depleted flow experiment under high temperature and high pressure conditions to study the high-velocity non-Darcy flow law of gas in the matrix, natural fractures and manmade fracture. Then we will establish the mathematical model of one dimensional nonlinear flow and simulate the pressure dynamics to validate the model by comprising the simulated pressure transients with the experimental pressure transients. Based on the validation, we will put the relationship equations of stress sensitivity and high-velocity non-Darcy of the one dimensional model into the nonlinear flow model establishment of gas well production in deep fractured overpressured gas reservoir. We will respectively establish the nonlinear flow models for the preliminary, middle and late stages of gas reservoir development, and then simulate the transient pressure and rate to study the nonlinear flow characteristics. We will implement real case analysis to validate the theoretical models. The research results could lay the foundation for the high-efficient development of deep fractured overpressured gas reservoir.

深层裂缝性异常高压气藏具有高温、高压、高应力敏感、高速非达西的“四高”特性，传统线性渗流理论已不再适用，且现有的非线性渗流理论极不成熟，急需深度研究其非线性渗流理论。对此，拟开展深层高温高压环境下全直径基质岩芯、含天然裂缝的岩芯、人造支撑裂缝岩芯的应力敏感实验，按照高压、中压和低压三个不同的压力区间，分别研究岩芯孔隙度和渗透率随内压变化的非线性关系式。创新设计高温高压长岩芯衰竭式渗流实验，分别研究基质、天然裂缝、人造裂缝的高速非达西渗流规律。建立一维非线性渗流数学模型，理论计算并对比实验结果，验证理论模型。将一维模型中的应力敏感和高速非达西关系式扩展到气井开采生产的渗流建模中，分别建立适用于开发初期、中期及后期的深层裂缝性异常高压气藏非线性渗流模型，模拟不稳定的压力及产量动态，研究非线性渗流特征。通过实例应用分析，验证理论模型。研究成果可为深层裂缝性异常高压气藏的高效开发奠定基础。

深层裂缝性异常高压气藏具有高温、高压、高应力敏感、高速非达西的“四高”特性，传统线性渗流理论已不再适用，且现有的非线性渗流理论极不成熟，急需深度研究其非线性渗流理论。因此，本项目从渗流力学基本原理出发，根据深层裂缝性异常高压气藏地质特征，开展了高压环境下的全直径基质岩芯和含天然裂缝的岩芯的应力敏感实验；创新设计了高压长岩芯衰竭式渗流实验，研究基质和天然裂缝的非线性渗流规律；建立了深层裂缝性异常高压气藏高速非达西渗流模型，利用点源函数理论、拉氏变换等数学方法对模型进行了求解；模拟并分析了深层裂缝性异常高压气藏不同井型下的生产压力动态特征。.取得的主要研究进展有：完成了变围压定内压和变内压定围压两种方法的应力敏感性测试试验，对实验结果进行分析与评价，揭示了分别由岩石围压变化和内压变化引起的应力敏感性的变化规律；完成了基质和裂缝长岩芯在高压条件下非线性渗流的测试试验，有效评价了天然气分别在基质和裂缝中衰竭式渗流的动态变化规律，对比分析了基质和裂缝在高压条件下非线性渗流试验结果的差异性；针对不同井型(直井、压裂直井和压裂水平井)，建立并求解了深层裂缝性异常高压气藏的非线性渗流模型，编程绘制了井底压力动态特征曲线，揭示了非线性渗流规律。.项目的研究成果为深层裂缝性异常高压气藏提供新的实验方法和渗流模型；揭示了深层裂缝性异常高压气藏的非线性渗流规律和水动力学行为特征；深化认识了深层裂缝性异常高压气藏开发特征；揭示了流体在基质、人工裂缝和天然裂缝之间流动的不稳定压力瞬态变化规律，为深层裂缝性异常高压气藏的高效开发奠定了坚实的理论基础。项目的研究还扩大了现代数学理论方法在工程技术领域中的应用，在一定程度上促进了地下油气藏渗流力学理论的发展，无疑具有重大的科学意义和价值。