422. 二氧化碳提高近枯竭边底水油藏采收率与储存研究

Study on CO₂-Enhanced Oil Recovery and Storage in Near-Depleted Edge–Bottom Water Reservoirs

 

本研究针对一个典型的老油田边底水油藏进行了CO2提高采收率和储存的模拟研究，该油藏已经开发多年，采收率为51.93%。通过模拟，研究了在近枯竭阶段，通过比较四种不同的注入方式（水驱、气驱、水气交替注入和双向注入）来提高采收率和CO2储存的新生产方案。

结果表明，双向注入方案实现了最高额外采收率3.62%。提高注入压力可以提高气油比和产液量。从近枯竭阶段过渡到枯竭阶段后，提高CO2储存能力最有效的方法是增加储层压力。在初始储层压力的1.4倍时，最大储存能力为6.52 × 10^8 m^3。然而，过度提高压力可能会带来储存和泄漏风险。因此，预计较低的注入速率和较长的间歇注入将有助于实现更长期的CO2储存。

通过数值模拟研究，对于所考虑的方案，每天80,000 m^3的气注入速度和4-6年的注入计划（1年关井）被证明是有效的。在31年的CO2注入期间，溶解CO2的百分比从5.46%增加到6.23%，而在枯竭期增加到7.76%。本研究为老油田边底水油藏的CO2地质储存提供了指导。

CMG软件应用情况

本研究中，使用了CMG-GEM模拟器进行数值模拟，该模拟器广泛应用于CO2储存和提高采收率研究。数学模型基于质量守恒、动量守恒和能量守恒的原则，用于分析流体、裂缝和基岩之间的相互作用。模拟包括累积项、流动项和源/汇项，由连续性方程表示。模拟使用了商业软件CMG 2022版进行。

Abstract

The geological storage of carbon dioxide (CO₂) is a crucial technology for mitigating global temperature rise. Near-depleted edge–bottom water reservoirs are attractive targets for CO₂ storage, as they can not only enhance oil recovery (EOR) but also provide important potential candidates for geological storage. This study investigated CO₂-enhanced oil recovery and storage for a typical near-depleted edge–bottom water reservoir that had been developed for a long time with a recovery factor of 51.93%. To improve the oil recovery and CO₂ storage, new production scenarios were explored. At the near-depleted stage, by comparing the four different scenarios of water injection, gas injection, water-alternating-gas injection, and bi-directional injection, the highest additional recovery of 3.62% was achieved via the bi-directional injection scenario. Increasing the injection pressure led to a higher gas–oil ratio and liquid production rate. After shifting from the near-depleted to the depleted stage, the most effective approach to improving CO₂ storage capacity was to increase reservoir pressure. At 1.4 times the initial reservoir pressure, the maximum storage capacity was 6.52 × 10⁸ m³. However, excessive pressure boosting posed potential storage and leakage risks. Therefore, lower injection rates and longer intermittent injections were expected to achieve a larger amount of long-term CO₂ storage. Through the numerical simulation study, a gas injection rate of 80,000 m³/day and a schedule of 4–6 years injection with 1 year shut-in were shown to be effective for the case considered. During 31 years of CO₂ injection, the percentage of dissolved CO₂ increased from 5.46% to 6.23% during the near-depleted period, and to 7.76% during the depleted period. This study acts as a guide for the CO₂ geological storage of typical near-depleted edge–bottom water reservoirs.

作者单位

中国石油大学（华东）教育部非常规油气开发重点实验室

中国石化胜利油田分公司勘探开发研究院

沙特阿拉伯国王科技大学物理科学与工程部（PSE）