水溶性ポリマー生産微生物を用いたＭＥＯＲにおける油層内挙動と石油増進回収機構に関するシミュレーション研究

Abstract

Our research group has carried out experimental studies to analyze the performance and the mechanism of MEOR with TU-15A, a microbe that produces water-soluble polymer. In the previous study, a mathematical model for this MEOR was developed, including almost all important phenomena such as growth and death of microbe, consumption of nutrient, production of water-soluble polymer, increase of water viscosity and the flow of reservoir fluids.In this study, the validity of the MEOR simulation model was firstly examined by comparison between experimental and computed results. The results of the numerical simulation agreed with the experimental results in terms of oil recovery, injection pressure, oil cut and flow profile of injection water.Next, numerical simulation was carried out to analyze the performance and mechanism of this MEOR process for five-spot pattern flooding. The procedure and the conditions used are as follows.Step 1: Conduct water flooding until water cut becomes 90%.Step 2: Inject microbe and nutrient solution into reservoir up to 0.1 PV.Step 3: Shut-in and wait for cultivation in the reservoir for 10 days.Step 4: Conduct postflash until water cut becomes 95%.The quantitative changes of microbe, nutrient, water viscosity and oil saturation were analyzed. Regarding the alteration of flow pattern in the reservoir, it was found that (1) the water-soluble polymer produced by the microbe flowed into the main flow channel along the shortest way between the injection well and the production well and water viscosity there increased, (2) subsequently more uniform flow profile of injected water for oil recovery was established, and (3) then the residual oil was mobilized to the production well. The more than 10% additional oil recovery was obtained in the early phase of postflash in this MEOR process compared with waterflooding.