Abstract
Most multilayer sandstone reservoirs in the Bohai Sea have already entered the middle or high water cut production stage with large amounts of remaining oil being scattered distributed. Therefore, there is an urgent need to find a suitable countermeasure to reduce water cut and increase oil recovery. In this study, taking the narrow-channel reservoirs in the M oilfield as an example, we qualitatively described the sand body scale and the contact relationships between different sand bodies, in addition to carefully analyzing the material base and remaining oil distribution characteristics. Accordingly, we proposed a countermeasure based on the injection-production structural adjustment to reduce water cut and increase oil recovery from high water cut, narrow-channel reservoirs. Herein, three optimization strategies were developed based on the proposed development mode: a seepage field optimization strategy was developed based on the quantified injection-production index; a well pattern optimization strategy for narrow-channel reservoirs was developed to overcome the production energy refueling problem; an injection-production measure optimization strategy was developed to tap the different types of remaining oil. Additionally, the well pattern optimization and injection-production optimization strategies were integrated to optimize and adjust the seepage field system. The findings reported herein this paper help understand the development of similar offshore oilfields with a high water cut.
Highlights
Until 2019, the Bohai Oilfield had undergone a decade of steady development, and the annual oil output reached 30 million tons in 2010
The oilfield has entered into the high water cut production stage, and adjusted development measures are urgently needed
The physical experiment on interlayer interference showed that when the permeability ratio was greater than 3, the interlayer interference increased [27], and the oil displacement efficiency was low
Summary
Until 2019, the Bohai Oilfield had undergone a decade of steady development, and the annual oil output reached 30 million tons in 2010. The oilfield has entered into the high water cut production stage, and adjusted development measures are urgently needed. Conducting countermeasures, including adjusting the allocation of displacement energy in narrow-channel reservoirs with middle or high water cuts, developing effective injection-production optimization strategies, and effectively tapping the remaining oil, is very important for further development of such oilfields. In order to determine reasonable countermeasures to decrease water and increase oil, a comprehensive study on the optimization of seepage field, injection-production well pattern, and auxiliary technology was conducted in this study. To overcome the aforementioned problems while considering the interwell connectivity, we optimized the seepage field, well pattern, and countermeasures through the SPSA optimization algorithm, numerical simulation, and remaining oil analysis, respectively. The complexity of the calculation was significantly reduced, the calculation cycle was shortened, and the optimal countermeasures to decrease water and increase oil have been proposed
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