孤东油田孤东281块特低渗油藏开发优化技术研究

The Optimized Technique for Development of Extremely Low-permeability Reservoirs in Block Gudong 281 of Gudong Oilfield

孤东油田孤东281块沙河街组三段中亚段(Esm3)油藏是典型的特低孔低渗油藏,具有自然产能低的特点,但压裂后产能得到明显提高,并且有一定的有效期,产量递减符合指数递减规律。孤东281块Esm3油藏天然能量弱,弹性采收率低,并且该油藏属于低含油饱和度油藏,出现多数油井投产即含水的现象。为改变孤东281块采收率低的现状,开展了注水开发可行性评价,经济极限出产及动用厚度分析,合理井型、井网、井距等一系列开发优化技术分析;分析认为该区天然能量开发采收率为10.7%,比注水开发采收率20.6%低,并且注水开发可行性评价结果显示,注水开发具有可行性,在现有的开发政策条件下,经济极限初产为8.6t/d,布井厚度界限确定为8.0m。通过井型、井网、井距分析显示孤东281块方案适宜采用大井距小排距的矩形井网,采用大型压裂仿水平井开发,井距为600m,排距为150m。

Reservoir in the middle section of the third member of Shahejie Formation in Fault Block 281of Gudong Area was a typical reservoir with low porosity and low permeability and with the characteristics of low natural productivity, but it was obviously improved after fracturing was carried out,and it had certain effective period,its production depletion was consistent with the law of index depletion.The natural deliverability of Gudong Fault Block 281was weak with low elastic oil recovery,and the reservoir was low oil saturation,water-cut was appeared in the most of wells when they were put into production.For the purpose of changing the current situation,optimization techniques such as feasibility study on waterflooding,the economic limit rate and producing thickness,rational well spacing,well pattern and well types were analyzed.The analysis shows that the oil recovery ratio of natural energy is 10.7%,injection and producing ratio is 20.6%,and the feasibility study indicates that it is feasible for waterflooding,the economic limit rate is 8.6t/d under current limit,the limit producing thickness is 8.0m.The analyses of well type,well pattern and well spacing indicate that the producing scheme of Fault Block 281is suitable for tranangular well pattern with big well spacing and small well array,large fracturing and horizontal wells are used for oil development,well spacing is 600m,well array is 150m.