高温高压致密气藏基质--裂缝系统传质与流动规律实验研究

The deep naturally fractured tight reservoir is of great resources, whereas, the reservoir pressure and temperature is very high, significantly affecting gas flow mechanism in the system of matrix, activated natural fracture and hydraulic fracture. The gas flow models are generally established based on the experimental data, however, due to the constraint of experimental methodology, most of the experiments are conducted under the room temperature and relatively low pressure, while the physical simulation technology under the high pressure and high temperature is not well developed, impeding the understanding of the gas flow mechanism in the deep reservoir and the development and advancement of gas flow models. In this study, the Keshen naturally fractured tight gas reservoir in the Tarim Basin is targeted as our research area. Our study will be mainly conducted through physical simulation, combined with the theoretical modeling. The pressure and temperature condition and the matrix-fracture connecting way will be improved to physically simulate the processes of gas flow from matrix to natural and hydraulic fractures as well as matrix-fracture mass transfer under the high pressure and high temperature conditions. The gas flow under different thermal and stress conditions will be compared and analyzed, and the combined influences of fracture connectivity, stress and flow regime on gas flow mechanism under conditions of high pressure and temperature will be identified, Moreover, the multiphysical coupled model of gas flow in the system of matrix, natural fracture and hydraulic fracture will be modified. Our study will thoroughly improve the understanding of gas flow mechanism after hydraulic fracturing, and provide experimental and theoretical foundation for the effective development of tight gas in deep reservoir.

我国深层裂缝性致密气藏资源潜力大，但储层高温超高压，对压裂改造后气体在基质、天然裂缝和人工裂缝系统中的流动有较大影响。目前气体流动模型一般基于实验数据建立，由于实验条件的限制，流动实验大多在常温常压下进行，高温高压条件下的物理模拟技术尚不成熟，制约了对深井储层中气体流动规律的认识以及气体流动模型的发展与完善。本项目以塔里木库车山前克深裂缝性致密气藏为研究对象，采用物理模拟为主，结合理论建模的研究手段，通过改进常规气体渗流测试方法中的温压条件及基质-裂缝连通方式，物理模拟高温高压条件下气体从基质到天然裂缝和人工裂缝的流动及基质—裂缝传质过程，对比分析不同温压条件下的气体流动差异性，明确高温高压条件下裂缝系统连通性、应力和流态对气体流动规律的综合影响，完善基质--天然裂缝--人工裂缝的多物理场耦合渗流模型，为深层致密气的高效开发提供实验基础和理论依据。

以塔里木克深气藏为代表的我国深层裂缝性致密气藏资源潜力大，但储层高温超高压，对压裂改造后气体在基质、天然裂缝和人工裂缝系统中的流动有较大影响,然而目前影响机制并不明确。本项目自主研发了高温高压基质-天然裂缝-人工裂缝气体流动物理模拟装置，建立了高温高压基质-天然裂缝-人工裂缝气体流动物理模拟方法，该装置和方法已经申请了国家发明专利。基于该装置和方法，阐明了温度和压力对基质-天然裂缝-人工裂缝气体流动与传质的影响规律。对于高温高压气藏，温度升高会导致气体流量减少，高压加剧了气体流量对温度的敏感性；另外，基质-天然裂缝渗透率极差对气体流动也有显著影响，极差越大，气体流量整体相对越低，气体流动对温度和压力越敏感；在此基础上，揭示了不同温度条件下岩石应力敏感曲线的变化机制，提出了一种新的定量评价致密气藏渗透率应力敏感和滞后性的方法，申请了国家发明专利，确定了应力敏感的临界有效应力；最后，明确了温度和压力对气体的滑脱流及在人工裂缝中流动规律的影响，低压下温度升高，渗透率降低，有效应力的增大和温度的升高都会导致非达西渗流系数的减小，降低了人工裂缝的渗透率。该项目的研究成果对于高温高压致密气藏压裂改造后优化生产制度、设置合理的生产压差，注水时机和注水效果的评价提供了重要的理论基础和实验依据，具有重要的参考意义。