Research on the Collaborative Method of Underground Gas Storage and Single Well Self-drive for Enhanced Oil Recovery

The injection and production characteristics during the construction and operation of underground gas storage are periodic injection of gas into sealed geological bodies, followed by regular extraction. Underground gas storage has injection production characteristics and displacement mechanisms such as advanced energy replenishment, periodic injection production, gravity displacement, oil gas mixing, large PV displacement, and nano dispersion. The injection production characteristics and displacement mechanism advantages of underground gas storage help to improve oil displacement efficiency, expand sweep coefficient, and increase diversion capacity. Self drive development to improve oil recovery is a one well self drive development mode that can supplement energy, strengthen activation, make full use of the spontaneous displacement force of underground rock fluid, and achieve the integration of injection and production of Injection well and production well. According to the dominant factors of different spontaneous displacement forces, self drive can be divided into two types: fracturing type inter fracture self drive and throughput type dredging self drive. The underground gas storage is a self driving drainage system with a throughput type. Both underground gas storage and self driving development to improve oil recovery require geological body sealing evaluation. This article first addresses the challenges of evaluating geological body gas tightness and its dynamic sealing, inventing a fault dynamic sealing evaluation method, and innovating the four-dimensional geomechanical modeling technology for cover layer tensile failure and shear deformation, enhancing the scientific nature of dynamic sealing evaluation of faults and cover layers. Quantitatively determining the risk index of caprock, fault, and wellbore under alternating load stress conditions has achieved quantitative evaluation of the dynamic sealing performance of the “three in one” gas storage. Secondly, in response to the complex mechanism of natural gas oil displacement collaborative reservoir construction and the low efficiency of underground gas storage space expansion, through indoor experimental research and field experiments, the multi-scale collaborative displacement mechanism of “nanometer to kilometer level” has been revealed. A new method for efficient oil displacement collaborative reservoir expansion has been invented, and a three-stage collaborative reservoir construction model of “gas injection extraction+throughput expansion+capacity and production” has been established. The collaborative method of underground gas storage and self driving for enhanced oil recovery has supported the industrial testing of new gas storage reservoirs such as Tarim Donghe 1 and Jidongdongbao 1–29. The Liaohe Shuang-6 gas storage reservoirs have significant drainage and expansion effects during the gas injection period, forming three major oil reservoir type gas storage groups in Northeast, North China, and Northwest China, with a storage capacity of 10.1 billion cubic meters and a central well group crude oil recovery rate of over 70%.