First Attempt of the Multi-Well Simultaneous Steam Stimulation for Offshore Heavy Oilfield: A Case Study

Abstract Limited by platform space and equipment capability, thermal fluid injection was conducted for each individual well during heavy oil development with cyclic steam and flue gas stimulation in NB35-2 Oilfield. The single well injection mode results in severe gas channeling from injection well to adjacent production wells caused by areal pressure imbalance and high development cost. Measures must be taken to improve the recovery effect and economic benefits, especially in the low oil price environment. The idea of multi-well simultaneous steam stimulation for offshore heavy oilfield was proposed and applied for actual practice in NB35-2 Oilfield. According to reservoir simulation results, formation pressure distribution could be much more even when thermal fluid was injected into the formation from different wells simultaneously. Besides, the overall developing cost could be greatly reduced by lowering the integral operating cost. For further controlling the gas channeling, the foam and temperature-sensitive gel were also used for gas channeling plugging. Based on the capacity of current steam and gas generator, two thermal wells were selected for field trail. During the simultaneous steam and flue gas injection process of well X1 and X2, no gas channeling phenomenon occurred from the injection wells to adjacent wells which means that no negative impact on the production wells was induced by the injection operation. And the multi-well simultaneous steam stimulation combined with chemical plugging has displayed positive effects in controlling gas channeling. The daily oil production rate of these two wells were increased from 28.77 m3/d to 38.87m3/d, and 23.68 m3/d to 35.71 m3/d, respectively when compared with its value before steam injection. The predicted overall incremental oil production amount is about 5250 m3, and the period of validity is about 180 days. More importantly, compared with the operating cost of previous single well injection mode, the commuted operating cost of the multi-well simultaneous stimulation for one single well is greatly decreased by about 45 % and this kind of operating mode will surely bring more economic benefits. This is the first time that multi-well simultaneous steam stimulation for offshore heavy oilfields is proposed and put into field trial. The favorable application result indicates that this technology could provide a useful guidance for the high-efficient heavy oil exploitation of offshore oilfield.