Study On Increasing Oil Recovery By Adding Natural Gas In X Block

As an important technique of enhancing oil recovery, gas flooding has good adaption in developing low permeability reservoirs, which have low recoveries by natural depletion and difficulties by water flooding. The means of natural gas injection for EOR has no harmful to the reservoir and could be recycled. Thus, this article takes X block, low permeability reservoir as the research object, combining laboratory experiment and numerical simulation methods to study the mechanism of natural gas injection for EOR and optimize the gas injection parameters. The main contents and understandings are as follows:(1) The block of X was analyzed and summarized in this paper, for the reservoir characteristics and fluid properties and analyzed the appropriateness of gas injection that combined with gas injection screening criteria. As a result, block X has a good adaptability of gas injection exploiting.(2) Combined with the basic knowledge of phase theory, based on the formation of crude oil phase and the gas injection of natural gas-formation crude oil expansion experiments, proceeded the simulation study of the experimental results of phase state characteristics as follows, PVT high pressure physical properties, constant composition expansion and swelling test of formation crude oil system, provided reliable parameters filed for the later study of pseudo-ternary phase diagram simulation, tubule simulation and numerical simulation.(3) Carried out the indoor tubule experiment, tubule simulation and the simulation study of pseudo-ternary phase diagram of natural gas injection, determined the minimum miscible pressure by taking the average value of these three methods. on the current geological condition, the injected natural gas could be miscible with the crude oil.(4) The six-well group model of block X was established, the reserves and production history matching has been completed, and has done correlation analysis to the monolayer remaining oil saturation. As a result, the remaining oil saturation of the target stratum of block X was higher, satisfied the requirements of gas injection exploiting.(5) Optimized the engineering parameters included that gas injection speed, gas injection working system, the size of injection slug in the cycle, the time ratio of the well injected gas and stopped injecting in the cycle, the fracture half length, fracture section of production well, horizontal section length, injecting layer and so on by using single factor and multiple factors orthogonal methods, and has predicted the optimized solutions. The forecasts showed that natural gas injection increased11.5percent point than exhausting exploiting, gas injection can enhance oil recovery to a certain extend.Through the study of gas injection suitability assessment, the determination of the minimum miscible pressure and the research of phase state change in the process of gas injection of block X, deepened the understanding of miscible natural gas injection flooding of block X. Besides, it was carried out the parameter optimization and project forecasts for the gas injection of block X, The optimized development project is significant to the actual development for X block reservoir and it has important reference value considering the development of similar reservoir as well.