Acta Petrolei Sinica ›› 2022, Vol. 43 ›› Issue (3): 355-363,398.DOI: 10.7623/syxb202203003

• PETROLEUM EXPLORATION • Previous Articles     Next Articles

Multilayer caprock natural gas diffusion capacity of Longwangmiao Formation gas reservoir in Anyue gas field,Sichuan Basin

Tian Hua1,2, Lu Xuesong1,2, Zhang Shuichang1,2, Liu Shaobo1,2, Tian Xingwang3, Ma Xingzhi1,2, Liu Qiang1,2   

  1. 1. PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China;
    2. State Key Laboratary of Enhanced Oil Recovery, Beijing 100083, China;
    3. PetroChina Southwest Oilfield Company, Sichuan Chengdu 610051, China
  • Received:2020-11-30 Revised:2021-08-31 Published:2022-04-06

四川盆地安岳气田龙王庙组气藏多层盖层天然气扩散量

田华1,2, 鲁雪松1,2, 张水昌1,2, 柳少波1,2, 田兴旺3, 马行陟1,2, 刘强1,2   

  1. 1. 中国石油勘探开发研究院 北京 100083;
    2. 提高石油采收率国家重点实验室 北京 100083;
    3. 中国石油西南油气田公司 四川成都 610051
  • 通讯作者: 鲁雪松,男,1982年11月生,2009年获中国石油勘探开发研究院博士学位,现为中国石油勘探开发研究院高级工程师,主要从事油气成藏综合地质研究与实验分析工作。Email:luxs@petrochina.com.cn
  • 作者简介:田华,男,1986年12月生,2020年获中国石油勘探开发研究院博士学位,现为中国石油勘探开发研究院高级工程师,主要从事深层与非常规油气地质实验研究。Email:tianhua86@petrochina.com.cn
  • 基金资助:
    国家自然科学基金项目(No.42002177)、国家重点研发计划项目(2017YFC0603101)和中国石油天然气股份有限公司科技专项(2021DJ0104)资助。

Abstract: Anyue gas field in Sichuan Basin is known as an ancient large gas field of oil cracked gas with high thermal evolution, where the large amount of oil cracked gas and gas reservoirs were formed in the Jurassic to Cretaceous period. According to the accumulation characteristics of large gas fields in China and due to small natural gas molecules and easy diffusion, the loss of natural gas in large gas fields with early accumulation will increase with the increase of diffusion time. In view of the problem that the Anyue gas field can be preserved as a large gas field even though it was formed in the early stage, the analysis of deep gas diffusion model and the evaluation of the diffusion capacity of ancient gas reservoirs are the key to understand whether the deep ancient gas field can be effectively preserved. The multi-layer caprock model uses the comprehensive diffusion coefficient of the overlying strata of the gas field and takes into account the comprehensive sealing effect of the multiple strata overlying the deep gas field. Taking Anyue gas field as an example, single-layer and multi-layer caprock diffusion models are used to calculate the diffusion capacity of the Cambrian Longwangmiao Formation gas reservoir, and the total gas diffusion capacity is calculated by the gas density ratio between the ancient gas reservoir and the present gas reservoir. The results show that according to the classical single-layer caprock diffusion model, the cumulative diffusion capacity of the gas field after 90 Ma is 3 340×108m3, far exceeding the upper limit of the total gas diffusion capacity (1 020×108m3), indicating that the single-layer model is not applicable. The cumulative diffusion capacity calculated by the multi-layer caprock diffusion model is 920×108m3, which is much lower than that calculated by the single-layer diffusion model. In fact, the deep gas field is covered with multiple regional caprocks, which can greatly reduce the gas diffusion. These results provide a method to evaluate the diffusion capacity of deep gas reservoirs and help to deepen the understanding of the preservation conditions of deep ancient gas fields.

Key words: deep layer, natural gas, caprock, diffusion, Sichuan Basin, Anyue gas field

摘要: 四川盆地安岳气田是古老高热演化程度原油裂解气大气田,其原油大量裂解生气及气藏定型时间在侏罗纪-白垩纪。根据中国大气田成藏特征以及对天然气分子小、易扩散特点的认识,早期成藏的大气田随着扩散时间增长,其天然气散失量也会不断增加。针对安岳气田在早期成藏但仍能保存为大气田的问题,开展深层天然气扩散模型分析和古老天然气藏扩散量评价,目前已成为认识深层古老气田能否有效保存的关键问题。多层盖层模型利用了气田上覆地层的综合扩散系数,考虑了深层气田上覆多套地层的综合封盖效应。以安岳气田为例,采用单层盖层和多层盖层扩散模型分别计算寒武系龙王庙组气藏的扩散量,并通过古气藏与现今气藏的天然气密度比例计算天然气散失总量。按照经典的单层盖层扩散模型进行计算,气田经历从90 Ma至今的累积扩散量(3 340×108m3)将远远超过天然气散失总量的上限(1 020×108m3),这表明单层模型不适用。而多层盖层扩散模型计算的累积扩散量为920× 108m3,比单层盖层扩散模型的计算结果大幅降低。深层气田上覆多套区域盖层,可大幅降低天然气扩散量。研究结果提供了一种评价深层气藏扩散量的方法,有助于深化对深层古老气田保存条件的认识。

关键词: 深层, 天然气, 盖层, 扩散, 四川盆地, 安岳气田

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