Miscible CO2 Flooding Using Horizontal Multi-Fractured Wells in San Andres Formation, TX – a Feasibility Study
本文针对德克萨斯州约阿克姆县圣安德烈斯地层低渗透碳酸盐岩油藏，开展了利用水平多裂缝井进行二氧化碳混相驱的可行性研究。通过建立油藏模型并进行历史拟合，对多种开发参数进行敏感性分析，包括裂缝簇间距、井间距、注入方式等。研究发现，300 - 400ft 的裂缝簇间距在长期生产中效果最佳，160 英亩的井间距能实现较好的产量效益。连续二氧化碳注入和水交替气（WAG）注入方案均能显著提高采收率，其中连续二氧化碳注入时，优化后的注入井设计可使采收率达 22%，二氧化碳利用率在 7 - 8 之间；WAG 方案中，7 口注入井且 WAG 比在 0.9 - 0.8 时效果较好，且该方案对裂缝半长不敏感，但长裂缝易导致二氧化碳过早突破。本研究为低渗透油藏二氧化碳混相驱开发提供了重要参考。
CMG 软件应用情况
在油藏模拟过程中使用了 CMG 的 GEM 模拟器。利用该软件构建油藏模型，包括设置水平和垂直方向的网格尺寸、层数，确定水力裂缝几何形状，并通过局部网格加密（LGR）技术准确捕捉近裂缝区域的压力瞬变和流体流动。在模型中输入通过 PVT 建模得到的包含八个集总组分的组成型 PVT 模型等相关参数，对不同开发方案和参数组合进行模拟计算，以分析油藏生产动态、采收率及二氧化碳驱替效率等，为研究提供关键的模拟数据和分析结果。
中文作者单位：
Junjie Yang、Yagna Deepika Oruganti、Pierre Karam：贝克休斯公司（Baker Hughes）
Dan Doherty、Jim Doherty：莱利勘探公司（Riley Exploration）
Abstract
The San Andres is a well-known dolomitic enhanced oil recovery target with low matrix permeabilityin the area of interest. A reservoir simulation study was undertaken to investigate the feasibility of using horizontal multifractured wells in low permeability miscible floods. A reservoir model was developed for the area of interest and was history matched with the primary production data from the field. The model was then used to illustrate the CO2 miscible flood potential by quantifying the incremental recovery over the primary production scenario.
Compositional modeling was used in the study to evaluate CO2 flooding feasibility and efficiency. A holistic workflow including PVT modeling, petrophysical analysis, geomodeling, and hydraulic fracture modeling, provided integrated input into the reservoir model. Continuous CO2 flooding was explored as an operating strategy. Furthermore, water alternating gas (WAG) cases were designed and run as a more realistic and cost-effective method of implementing miscible flooding. Based on the history-matched model, sensitivity analyses were conducted on hydraulic fracture geometry, well spacing, injection patterns and operating conditions for the primary production scenario, continuous CO2 flooding and WAG scenarios.
