Experiment and Simulations of Steam Flooding in Offshore Heavy Oil Reservoir with Bottom Water

Abstract

Abstract LD27-2 block, located in the Bohai Bay, is a heavy oil reservoir with bottom water, average thickness of the oil zone is 18m and the bottom water zone is five times the thickness of oil zone. As the oil viscosity at reservoir temperature is 1000mPa·s, thermal recovery methods are necessary. Steam flooding has been widely used for heavy oil recovery in the worldwide, it can produce oil significantly faster than can the cyclic stimulation process, but can also have a significant economic impact. In order to investigate the effect of steam flooding in LD27-2 block, experiment and simulations of steam flooding are performed in this study. In this study, parameters of LD27-2 block are transformed into physical model parameters with similarity criteria firstly, and with the high temperature and pressure three-dimensional experiments apparatus, the steam flooding process in LD27-2 block is simulated and production data is achieved. Then, based on the physical model, an identical numerical model is built, and history matching is conducted according to the production data. With this numerical model, a set of numerical simulations are performed to optimize the parameters which have influences on the steam flooding performances, and these optimal parameters are referred back to the real reservoir lastly. The steam flooding physical simulation shows that the production process can be divided into three stages: in the first stage, oil production increases at rapid speed while water cut goes down slightly (in order to decrease the oil zone pressure and preheat the formation, before the steam flooding, cyclic steam stimulation has been carried out and water cut has gone up greatly); in the second stage, oil production and water cut decrease and increase, respectively; and then they both gradually stabilize in the third stage, and the ultimate recovery is 27.74%(instantaneous oil steam ratio is 0.1). The numerical simulations indicate that the optimal steam injection rate is 60-70mL/min, production injection ratio is 1.3-1.4, height of water avoidance is 4.5cm and the injection and production wells should be deployed at the same height of the reservoir. Based on these results, the optimal parameters for the real reservoir can be confirmed by inversion calculation, in this condition, the ultimate recovery of the LD27-2 block can be more than 36%. In summary, this study is beneficial for the application of thermal recovery in the LD27-2 block, and it is also a reference for the effective and efficient development of heavy oil reservoirs with bottom water.