缝洞型油藏井组注气体示踪剂解释模型研究

针对常规砂岩油藏注气体示踪剂解释方法基于储层连续介质假设，不适用于大尺度缝洞离散组合的缝洞型油藏问题，考虑了气体示踪剂在大尺度溶洞区中径向迁移扩散及裂缝中一维迁移二维扩散的传输方式，引入了井间分配系数、相间分配系数及裂缝分配系数，建立起缝洞型油藏注采井间气体示踪剂解释物理和数学模型，求解模型并绘制了气体示踪剂浓度理论采出曲线。对该模型进行了参数敏感性分析，探索了溶洞大小、裂缝条数与长度、扩散系数、注气速度及示踪剂注入量对产出曲线的影响规律。研究表明，溶洞越大，浓度曲线峰值出现时间越迟；裂缝长度增加，峰值滞后，条数增多，峰值越多。对塔河油田TK425井组注气体示踪剂实测响应曲线进行了拟合解释，计算了溶洞区体积及注采井间裂缝流道。缝洞型油藏注气体示踪剂解释模型能够有效判断井间连通性，计算地层参数，认识储集体分布情况，为井组注气提高采收率提供理论支撑。

Interpretation Model of Gas-injected Tracer for Well Groups in Fracture-vuggy Reservoirs

The conventional gas injection tracer interpretation method for sandstone reservoirs is based on the assumption of continuum, which is not suitable for large-scale fracture-vuggy reservoirs with discrete combinations of fractures and caves. A physical and mathematical model of gas tracer interpretation between injection and production wells in fractured-vuggy reservoirs has been established. The model considers the radial migration and diffusion of gas tracers in large-scale cave areas and the transmission of one-dimensional migration and two-dimensional diffusion in fractures. In this way, the distribution coefficient between wells, phases, and fractures are introduced. The model is solved and the theoretical recovery curve of gas tracer concentration is drawn. The parameter sensitivity analysis of the model is carried out, and the influence of the size of the cavern, the number and length of fractures, the diffusion coefficient, the gas injection rate, and the amount of tracer injection on the output curve is explored. Studies have shown that the larger the cave, the later the peak of the concentration curve appears; the longer the crack length, the lagging of the peak, the more the number of bars and the more the peak. The measured response curve of gas injection tracer in the TK425 Well Group of Tahe Oilfield is fitted and interpreted, and the volume of the karst cave area and the fracture channel between injection and production wells are calculated. The gas injection tracer interpretation model for fractured-vuggy reservoirs can effectively determine the connectivity between wells, calculate formation parameters, understand the distribution of reservoirs, and provide theoretical support for gas injection to improve recovery.