Geological Feasibility and Operating Index Design of Volatile Oil Reservoir into Underground Gas Storage: Case Study of M Block in Jidong Oilfield

At present, there is no precedent for reconstruction of Volatile Oil Reservoir into Underground Gas Storage (UGS) at home and abroad. Utilizes oil reservoirs to rebuild gas storage can fully utilize the mechanisms of gravity, miscibility, viscosity reduction, and imbibition, which can greatly enhancing crude oil recovery and gradually collabo-rate to build gas storage. This is a new approach to the rapid development of gas storage construction in China. Taking M Block in Jidong Oilfield as an example, The study starts from the geological characteristics of the reservoir, Analyzes the sealing condition, reservoir property, fluid feature and well productivity. Study results show that Es1 formation of the study area yield excellent reconstruction condition for its great sealing property, medium to high permeability, high productivity, no obvious interlayer and good internal connectivity, Furthermore, study also indicates there contain low hydrogen sulfide content. In response to the collaborative needs of gas drive oil recovery and UGS construction, Adopts the construction and operation mode of “initial top mild gas injection + pressure recovery → differential gas drive + efficient collaborative oil production → enhanced injection and production + long-term liquid carrying”. The UGS will be operated in pressure range of 17.5–40.0 MPa, with a effective storage capacity of 18.6 × 108 m3, constructs a three-dimensional injection and production well network of “high injection and low production, horizontal and vertical differentiation injection and production”, gradually form and expand secondary gas cap by gas injection and oil drainage in batches and stages, the study area is designed to be reconstructed with a mixed well pattern of 7 directional wells and 3 horizontal wells, Meets the effective control of gas storage capacity and the demand for unbalanced peak shaving gas production. It is estimated that the maximum production rate may yield 956 × 104 m3 and, the working gas may reach 9.0 × 108 m3, which is 48.4% of the total reserves and it can enhance crude oil recovery by 27.7%. In conclusion, volatile oil reservoirs have the geological feasibility of rebuilding underground gas storage, and can form relatively efficient gas production and peak shaving capabilities while injecting gas for enhancing crude oil recovery, resulting in significant economic benefits.