气顶强边水油藏气顶区剩余油分布与挖潜——以渤海埕北油田为例

Remaining oil distribution and potential tapping in the gas-cap area of gas-cap strong edge water reservoirs:A case study of CB Oilfield in Bohai Sea

埕北油田为气顶强边水油藏,油田经过30多年开发后气顶区域内经历了长期的气窜、水进、油侵等复杂驱替,剩余油分布复杂,挖潜难度大。基于埕北油田地质油藏特征与开发生产特征,设计并开展物理模拟实验,同时进行了相应的油藏数值模拟机理模型研究与扩展分析,研究油气互侵机理及剩余油分布规律。研究结果表明,油气互侵规律主要表现为两方面:一是能量水平强弱,当地层能量较弱时(衰竭开发)以气侵为主,当地层能量较强时(强边水或人工注水)以油侵气顶为主;二是生产井的位置影响,对于气顶强边水油藏,在靠近气顶区有生产井存在的条件下,油井快速气窜,在强边水推动作用下气顶萎缩、油侵气顶,边水主要沿储层底部向构造高部位推进,剩余油主要分布在油侵气顶区和储层顶部。根据研究认识,在埕北油田原始气顶区实施水平井加密调整,挖潜原始气顶区剩余油,取得了较好效果。

The CB Oilfield is a gas-cap reservoir with strong edge water.After more than 30 years of development,the oilfield has experienced long-term complex displacements such as gas channeling,water inflow,and oil intrusion in the gas-cap area,and the remaining oil distribution is complex and difficult to tap the potential.Based on the geological reservoir characteristics and development and production characteristics of CB Oilfield,physical simulation experiments were designed and carried out,and the corresponding numerical simulation mechanism model of the reservoir was studied and extended to study the mechanism of oil and gas mutual intrusion,and the distribution law of remaining oil.The results show that the oil and gas mutual invasion law is mainly manifested in two aspects:first,the energy level is strong or weak.When the formation energy is weak(depleted development),gas invasion is dominant;when the formation energy is strong(strong edge water or artificial water injection),oil invasion into the gas-cap is dominant.The second is the influence of the location of producing wells.For a gas-cap strong edge water reservoir,under the condition that there are producing wells near the gas-cap area,the oil wells will be rapidly gas channeled,the gas-cap shrinks and oil invades the gas-cap under the push of strong edge water,the edge water mainly advances along the bottom of the reservoir to the high part of the structure,and the remaining oil is mainly distributed in the oil-invaded gas-cap area and the top of the reservoir.According to the research understanding,the infilling adjustment of horizontal wells in the original gas-topped area of CB Oilfield was implemented to tap the remaining oil in the original gas-cap area,and good results were achieved.