石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (6): 1590-1604.doi: 10.11743/ogg20240607

• 油气地质 • 上一篇    下一篇

鄂尔多斯盆地上古生界本溪组8#煤岩煤岩气与致密砂岩气主要气藏特征对比

李明瑞1,2(), 史云鹤1,3(), 范立勇1,3, 戴贤铎1,3, 荆雪媛1,3, 张沂4   

  1. 1.低渗透油气田勘探开发国家工程实验室,陕西 西安 710018
    2.中国石油 长庆油田公司勘探事业部,陕西 西安 710018
    3.中国石油 长庆油田公司 勘探开发研究院,陕西 西安 710018
    4.中国石油 长庆油田公司采气一厂,陕西 西安 710018
  • 收稿日期:2024-05-26 修回日期:2024-07-01 出版日期:2024-12-30 发布日期:2024-12-31
  • 通讯作者: 史云鹤 E-mail:lmrui_cq@petrochina.com.cn;syhe_cq@petrochina.com.cn
  • 第一作者简介:李明瑞(1975—),男,博士、教授级高级工程师,油气勘探综合研究和勘探管理。E‑mail: lmrui_cq@petrochina.com.cn
  • 基金项目:
    中国石油天然气股份有限公司科技专项(2023ZZ18);中国石油长庆油田公司“揭榜挂帅”项目(2022D-JB01)

Comparison of main reservoir characteristics between deep coal-rock gas of the No. 8 coal seam of the Upper Paleozoic Benxi Formation and tight sand gas reservoirs, Ordos Basin

Mingrui LI1,2(), Yunhe SHI1,3(), Liyong FAN1,3, Xianduo DAI1,3, Xueyuan JING1,3, Yi ZHANG4   

  1. 1.National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gas Fields,Xi’an,Shaanxi 710018,China
    2.Petroleum Exploration Division,Changqing Oilfield Company,PetroChina,Xi’an,Shaanxi 710018,China
    3.Research Institute of Exploration and Development,Changqing Oilfield Company,PetroChina,Xi’an,Shaanxi 710018,China
    4.No. 1 Gas Production Plant,Changqing Oilfield Company,PetroChina,Xi’an,Shaanxi 710018,China
  • Received:2024-05-26 Revised:2024-07-01 Online:2024-12-30 Published:2024-12-31
  • Contact: Yunhe SHI E-mail:lmrui_cq@petrochina.com.cn;syhe_cq@petrochina.com.cn

摘要:

鄂尔多斯盆地长庆油田在盆内煤岩气领域取得了良好的勘探进展,发现CH4多以吸附态和游离态赋存于煤岩中,形成自生自储型煤岩气藏。针对上古生界本溪组8#煤岩为代表的煤岩气藏特征进行了深入研究。结果表明:鄂尔多斯盆地自上而下发育10套煤岩,其中5#和8#煤岩为主力煤岩,分布稳定,厚度大。本溪组煤岩气相较于浅层煤层气表现出“高压力、高温度、高含气、高饱和、高游离”等5高特征。气藏平均地层压力22 ~ 35 MPa,压力高但压力系数为1.0 ~ 1.1,为正常压力系统。气藏平均地层温度为67 ~ 92 ℃,地温梯度为29. 4 ℃/km,属于正常地温梯度。气体组分中CH4含量平均值为96.92 %,C2H6含量平均值为0.61 %,CO2含量平均值为0.85 %,N2含量平均值为1.47 %,为干气气藏。气藏地层水矿化度为41 644 ~ 89 776 mg/L,平均值为62 228 mg/L,为CaCl2型原生地层水,未受浅层水的影响。煤岩气试气产量高,生产阶段控压生产情况下产量稳定、压降速率低、稳产效果好。通过对煤岩气与苏里格气区石盒子组8段与山西组1段内致密砂岩气的系统性对比分析,发现两者在气藏类型、气藏压力和温度、气体成分、地层水性质及产能特征等主要气藏特征方面具有相似性,这个规律对后期煤岩气的大规模开发和建产具有指导意义。

关键词: 气藏特征, 致密砂岩气, 煤岩气, 煤岩, 本溪组, 鄂尔多斯盆地

Abstract:

The Changqing Oilfield Company of PetroChina has achieved significant advances in exploring deep coal-rock gas within the Ordos Basin, discovering that methane (CH4) largely occurs in coals as both adsorbed and free gas, which contributes to the formation of self-sourced coal-rock gas reservoirs. In this study, we comprehensively investigate the characteristics of coal-rock gas reservoirs represented by the No. 8 coal seam of the Benxi Formation. The results indicate that the Ordos Basin contains 10 coal seams from top to bottom. The Nos. 5 and 8 coal seams, among others, predominate, exhibiting stable distribution and great thickness. Compared to shallow coalbed methane (CBM), the deep coal-rock gas occurring in the No. 8 coal seam of the Paleozoic Benxi Formation is characterized by high formation pressure, high formation temperature, high gas content, high gas saturation, and high free gas content. Specifically, these coal-rock gas reservoirs exhibit average formation pressure ranging from 22 to 35 MPa, suggesting high formation pressure. However, their formation pressure coefficients vary between 1.0 and 1.1, indicating a normal pressure system. The coal-rock gas reservoirs present average formation temperatures ranging from 67 to 92 ℃ and an average geothermal gradient of 2.94 ℃/km, suggesting normal geothermal gradients. The composition of coal-rock gas in these reservoirs manifests an average CH4 content of 96.92 %, average C2H6 content of 0.61 %, average CO2 content of 0.85 %, and average N2 content of 1.47 %, establishing these reservoirs of dry gas type. The formation water in these reservoirs has total dissolved solids (TDS) concentrations ranging from 41 644 to 89 776 mg/L (average: 62 228 mg/L), indicating primary CaCl2-rich formation water. Unaffected by shallow groundwater, the coal-rock gas reservoirs exhibited high gas production rates in tests and stable production at a low pressure drop rate. A systematic comparison between deep coal-rock gas reservoirs in the No. 8 coal seam of the Benxi Formation and tight-sand gas reservoirs in the 8th member of the Xiashihezi Formation (He 8 Member) and the 1st member of the Shanxi Formation (Shan 1 Member) in the Sulige gas field reveals similarities in major reservoir characteristics, including reservoir type, reservoir pressure and temperature, gas composition, formation water properties, and production capacity. These similarities will provide a valuable guide for future large-scale exploitation and production capacity construction of deep coal-rock gas.

Key words: tight-sand gas, coal-rock gas, gas reservoir characteristics, coal seam, Benxi Formation, Ordos Basin

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