Performance evaluation and mechanisms study of near-miscible CO2 flooding in a tight oil reservoir of Jilin Oilfield China
Performance evaluation and mechanisms study of near-miscible CO2 flooding in a tight oil reservoir of Jilin Oilfield China
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DOI：
10.1016/j.jngse.2015.11.005
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发表时间：
2015-11-01
影响因子：
--
通讯作者：
Zhang, Hua
中科院分区：
文献类型：
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作者：
Ren, Bo;Zhang, Liang;Zhang, Hua
吉林油田在中国进行了大规模的二氧化碳三次采油及封存示范工程。从附近天然气藏分离出的CO2(体积分数为15-30%)已注入H-59区块北部，渗透率为3.0 md，孔隙度为12.7%。经过6年的运行，在混相或近混相驱方式下，已注入近26万吨CO2(032个碳氢化合物孔容)，CO2利用率为63mscf/bbl，预计可提高采收率10%以上。进行了系统和彻底的水库监测计划，以促进有效的运行和评估。为了监测生产井的气窜，对套管环空气体成分进行了分析。以及气体示踪剂，以检测穿过储集层的二氧化碳流动。结合井底压力测量和流体取样，结合注采资料分析，评价混相效果。结果表明，由于注采井压差较大，设计的混相驱最好描述为近混相驱，混相不稳定性主要是由于气窜和裂缝/非均质性造成的。在注水过程中，油藏的下倾部分可能会发生重力稳定驱替。通过室内岩心驱油和矿场采出油成分分析，观察和证实了汽化和冷凝效果。评价研究的一个关键发现是，与混相相比，二氧化碳近混相驱更灵活、更容易实现，特别是在致密油藏中。在近混相驱设计下，油藏开发方案的优化还需要进一步研究。(C)2015爱思唯尔B.V.保留所有权利。
Jilin Oilfield has been conducting a large-scale demonstration project on CO2 EOR and storage in China. CO2 separated from a nearby natural gas reservoir (15-30 vol% CO2) has been injected into the northern part of H-59 oil block with the permeability of 3.0 mD and porosity of 12.7%. After six years of operation, nearly 0.26 million ton of CO2 (032 Hydrocarbon Pore Volume) has been injected under a miscible or near-miscible flooding mode with CO2 utilization efficiency of 63 MScf/bbl, and an expected enhanced oil recovery of over 10% would be achieved. A systematic and thorough reservoir surveillance program has been conducted to facilitate efficient operation and evaluation. Casing annulus gas composition was analyzed to monitor gas breakthrough in production wells. as well as the gas tracer to detect CO2 flow across the reservoir. Bottom hole pressure (BHP) survey of producers and fluid sampling were combined to evaluate the miscibility effect in conjunction with the injection-production data analysis. It is revealed that the designed miscible flooding is best described as near-miscible due to the large pressure difference between injector and producer, and the gas channeling and fractures/heterogeneities cause the miscibility instability. Gravity-stabilized displacement may develop in the downdip part of the reservoir during the flooding process. The vaporization and condensation effects have been observed and confirmed through laboratory core flooding and field produced oil compositions analysis. A key insight from the evaluation study is that CO2 near-miscible flooding is more flexible and easily realizable relative to miscible, particularly in the tight oil reservoir. Further study would be necessary to optimize the reservoir development program under the near-miscible flooding design. (C) 2015 Elsevier B.V. All rights reserved.