含夹层气顶底水油藏开发技术对策

Discussion on the development technology policy of gas cap and bottom water reservoirs with interlayer

气顶底水油藏在开发过程中面临气窜、水窜的风险,夹层发育可以延长单井无气、无水采油期,控制含水上升速度,提高油藏采收率,因此“寻夹避窜”为此类油藏高效开发的关键。Z油藏为典型的气顶强底水油藏,具有统一的油气界面及油水界面,该油藏中部连续分布具有一定渗透性的夹层,且位于夹层上下的储层物性差异较大。本文应用油藏数值模拟技术,研究了夹层对于开发指标的影响以及Z油藏的开发技术对策,创新性地提出了采用“划层系、分区域”的开发策略和先底部采油后边部采油的开发方式,即以夹层为界限将油藏分为两套层系、三个区域,其中层系Ⅰ按照气顶底水油藏进行开发并且尽量避免油气同采,层系Ⅱ按照强底水油藏进行开发,紧贴夹层底部布井。研究认为:在夹层底部布井可极大程度减少产气量以抑制气窜,但是在气顶区域布井不能阻碍油侵气顶的发生。综合考虑油藏采收率和初期产量贡献,推荐先底部采油后边部采油的开发方式。底部油藏最优布井数量为4口,单井最优配产1500 m^(3)/d,边部油藏最优布井数量为2口,单井最优配产100 m^(3)/d。

Reservoirs with gas cap and bottom water are exposed to the risk of the situation that the oil and gas are mutually turbulent in the development process.The development of the interlayer can prolong the gas-free and water-free oil recovery period in a single well,control the bottom water coning speed and improve the oil recovery.Therefore,the key to efficiently explore such reservoirs is to seek the interlayer and avoid the turbulence.The Z reservoir is a typical reservoir with gas cap and strong bottom water containing a uniform oil-gas interface and oil-water interface.Interlayers with certain permeability are continuously distributed in the middle part of the reservoir,and it is quite different between the reservoir above the interlayer and below the interlayer in terms of properties.The development technology policy of such reservoirs was established by means of reservoir numerical simulation.The influence of the interlayer on the development index and the development technology strategy of the Z reservoir were studied.According to the research,it is believed that the development of such reservoirs should adopt the method of“drawing the layer system and making regional separation”.According to the reservoir feature,the reservoir is separated to two development systems and three zones by interlayer.The zone I of reservoir above the interlayer is developed according to the reservoir with gas cap and bottom water,and try to avoid the way of oil and gas producing together.The zone II of reservoir below the interlayer is developed according to the reservoir with bottom water.The wells are mostly located closed to the interlayer.The research results show that when the well is drilled under the interlayer,it can slow the gas coning speed and control the gas production rate.But when the well is drilled at the top gas zone,it cannot stop the oil from going back to the top gas zone.Reservoir above the interlayer was developed according to the reservoir with gas cap and bottom water,and reservoir below the interlayer was developed according to the reservoir with bottom water.In addition,it had better development effect on firstly develop of the bottom layer considering the maximum oil recovery factor and high initial oil rate.The optimum number of wells in bottom reservoir is four,and the optimal production allocation is 1500 m^(3)/d.The optimum number of wells in edge reservoir is two,and the optimal production allocation is 100 m^(3)/d.