An Integrated Reservoir Study to Improve Field Performance

Abstract

Waterflood recoveries from certain areas in this large, thick carbonate reservoir were below expectations. An integrated (geological, petrophy:ical, and engineering) study was undertaken to (1) develop a geological-petrophysical model covering the areas of interest, (2) evaluate past reservoir performance, (3) predict future performance for various operating plans, and (4) make appropriate recommendations based upon technical and economic considerations. It was concluded that low oil recovery resulted primarily from low to very low formation permeabilities, injected water channeling because of fracture treatments administered during primary production, net pay intervals still behind pipe (mainly in producers), and limited control of injection/production well profiles. Results of the study indicated that oil recovery could be increased significantly by infill drilling/waterflood expansion.However, the most attractive plan from an economic viewpoint was to open the unperforated net intervals in existing producers and injectors and to monitor/improve flow profiles. Other enhanced recovery methods were not attractive because of either low permeability or low oil gravity.

Reviews on Evaluation and Prediction of Low Permeability Reservoirs’ Development Index after Infilling Well Pattern

“…我国于 1907 年陆上钻成第一口油井--延长油田 1 号井，它的产层是特低渗透层，其空气渗透率只有 0.2~0.5 × 10 -3 μm 2 [1] [2] 。这是因为油层 中的油砂体不是连续分布的，因此，在一定井网密度 条件下，注水方式不同，油井与水井的多向连通程度 也不同，即不同的注水方式将直接影响到井网的水驱 控制程度。齐与峰先生提出了水驱控制程度与井网密 度、注采井数比关系式，进而又给出了水驱采收率与 水驱控制程度关系式，计算精度得到提高 [3] 。该公式 在计算低渗透油田采收率时仍然存在问题，主要是由 于低渗透油田存在启动压力梯度，且油层渗透率越低 启动压力梯度越大，一定井网密度下，部分储层虽然 已经水驱控制，但并不能有效动用 [4][5][6] [7][8][9][10][11] 。而我国在 20 世纪 50 年代才开始对常 规水驱开发油田进行了研究。 1978 年我国学者童宪章 将水驱规律曲线介绍到我国并得到广泛的应用 [12] 。这 些指标的变化情况对油田开发有着重要的指导意义。 油田开发指标的预测方法有经验公式法、水动力学方 法、物质平衡法、油藏数值模拟方法、通用预测方法 等等 [13] 。其中在产量递减预测方面，Arps 递减曲线由 于简单易行，操作方便，在我国得到了广泛的应用。 对于 Arps 递减方程，国内外许多学者进行多年的研 究，获得了一些重要的研究成果，计秉玉运用渗流理 论进行了证明 [14] ；王俊魁给出了 3 种递减类型的判断 与初始递减率的判定方法 [15] ；裴连君确定了 Arps 曲 线与甲型水驱规律曲线的相关性 [16] ；张虎俊也提出了 相应的分析方法 [17] 。仅关于双曲递减曲线的描述和预 测，根据俞启泰先生的统计和归纳，就可分为 11 大 类、52 种单独方法 [18]…”