深层异常高压致密砂砾岩油藏衰竭式开采渗流规律研究

As 100 million tons of tight oil reservoirs in Karamay oilfield, it is very important to develop the abnormal pressure glutenite reservoir efficiently. In order to obtain higher economic benefits, the fracturing operation and early full use of natural energy should be considered. However, the presences of low effective stress and widely distributed granule make the fracture forecast and describe difficult; meanwhile, the combined effect of the stress sensitivity of reservoir and the change of fracture conductivity while producing also increase the difficulty to reveal the law of fluid flow in deeply tight glutenite reservoir with abnormally high pressure under depletion condition. .The project focuses on the Ma Lake reservoir in Karamay oilfield. The 3-axis stress experiments of the core, 3D hydraulic fracturing experiment of the outcrop and the fracture conductivity experiments with small scale will be used to reveal the stress sensitivity of glutenite reservoir, fracture feature of outcrop and the change of the fracture conductivity. Based on the results of the 3D hydraulic fracturing experiment, the topological theory will be introduced to describe the characteristics of fracture distribution. According to the mathematical characteristics of the topology, the large-scale fracture model will be constructed and effectiveness of the fracture structure will be estimated with the production. The transient pressure analysis, the trend of rate declining and the optimization of productivity index can be achieved by coupling the reservoir model with stress sensitivity and the fracture model with varying conductivity. Based on the project, a set of theory methods for glutenite reservoir description, evaluation of the fracture effectiveness, scale transformation, production prediction and parameter optimization can be established which can be used for the production of Ma Lake reservoir in Karamay oilfield.

玛湖深层异常高压砂砾岩油藏是我国新发现的亿吨级致密油藏。在油井压裂的基础上，早期利用天然能量衰竭式开发能获得较高的经济效益。但异常高压带来的低有效应力和砾岩颗粒的广泛分布增大了裂缝延展预测和描述的难度；同时，异常高压导致的储层应力敏感与裂缝导流能力动态变化的共同作用也加大了揭示油藏渗流规律的难度。.项目选取岩心和露头开展小尺度三轴应力实验、三维水力压裂实验和导流能力实验，揭示砂砾岩储层应力敏感性、裂缝延展特征和导流能力变化规律；在水力压裂模拟实验的基础上，引入拓扑学理论，描述砂砾岩储层压后裂缝展布特征；基于拓扑网络的数学特征，构建大尺度裂缝网络模型，结合导流能力实验结果，预测裂缝结构的动态变化特征及有效性；耦合油藏应力敏感模型和裂缝变导流数学模型，揭示衰竭式生产时油井生产动态特征，建立一套针对砂砾岩储层裂缝描述、有效性评价、尺度转换、生产预测和参数优化的研究方法，为现场生产提供理论基础。

物理模拟实验表明，玛湖地区砂砾岩露头具备形成复杂缝网的条件。通过重新定义裂缝系统，建立了复杂裂缝形态描述通用数学模型，结合裂缝内非均质导流能力流动模型，实现对各种复杂裂缝形态与复杂流动的准确表征。在此基础上，揭示了不同裂缝形态组合下的生产特征、产能变化规律以及裂缝网络演化规律。研究成果从理论上论证了玛湖十亿吨大油田压裂衰竭式开发的可行性，为现场生产提供了理论支撑。