石油与天然气地质 ›› 2025, Vol. 46 ›› Issue (4): 1233-1249.doi: 10.11743/ogg20250414

• 油气地质 • 上一篇    下一篇

川中地区二叠系茅口组深层灰岩基质孔隙发育与保持机理

文龙1(), 罗冰1, 张本健1, 彭瀚霖1, 李文正2,3,4, 刘一锋5, 沈安江2,3,4(), 张玺华1, 袁海峰1, 胡安平2,3,4   

  1. 1.中国石油 西南油气田公司 勘探开发研究院，四川 成都 610400
    2.国家能源碳酸盐岩油气重点实验室，浙江 杭州 310023
    3.中国石油集团碳酸盐岩储层重点实验室，浙江 杭州 310023
    4.中国石油 杭州地质研究院，浙江 杭州 310023
    5.浙江大学，浙江 杭州 316021
  • 收稿日期:2024-07-05 修回日期:2025-02-17 出版日期:2025-08-30 发布日期:2025-09-06
  • 通讯作者: 沈安江 E-mail:wenlong@petrochina.com.cn;shenaj_hz@petrochina.com.cn
  • 第一作者简介:文龙（1977—），男，博士、高级工程师，天然气勘探地质综合研究。E-mail：wenlong@petrochina.com.cn。
  • 基金项目:
    国家自然科学基金企业创新发展联合基金项目(U23B20154);国家自然科学基金面上项目(42372169)

Formation and preservation mechanisms of matrix pores in deep limestones： A case study of the Maokou Formation， central Sichuan Basin， China

Long WEN1(), Bing LUO1, Benjian ZHANG1, Hanlin PENG1, Wenzheng LI2,3,4, Yifeng LIU5, Anjiang SHEN2,3,4(), Xihua ZHANG1, Haifeng YUAN1, Anping HU2,3,4   

  1. 1.Research Institute of Exploration and Development，Southwest Oil & Gasfield Company，PetroChina，Chengdu，Sichuan 610400，China
    2.State Energy Key Laboratory of Carbonate Oil and Gas，Hangzhou，Zhejiang 310023，China
    3.Key Laboratory of Carbonate Reservoirs，CNPC，Hangzhou，Zhejiang 310023，China
    4.Hangzhou Research Institute of Geology，PetroChina，Hangzhou，Zhejiang 310023，China
    5.Zhejiang University，Hangzhou，Zhejiang 316021，China
  • Received:2024-07-05 Revised:2025-02-17 Online:2025-08-30 Published:2025-09-06
  • Contact: Anjiang SHEN E-mail:wenlong@petrochina.com.cn;shenaj_hz@petrochina.com.cn

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摘要：

目前，已发现的深层碳酸盐岩大油气田大多分布于孔隙型白云岩储层和岩溶缝洞型灰岩储层中。但近年来四川盆地蓬深12井和南充2井的发现证实，深层二叠系茅（茅口组）二段发育一套孔隙型灰岩储层，这一发现突破了传统的储层地质认识，成为当前的研究热点。基于岩心和薄片观察、储层地球化学特征分析以及井-震联合的储层识别和追踪，取得3项地质认识：①深层茅二段发育孔隙型生屑灰岩储层，储集空间以粒间孔、生物体腔孔、铸模孔和溶孔为主，这些孔隙形成于沉积和表生环境。其中，蓬深12井储层厚度为24.80 m，实测孔隙度平均值为5.1%，渗透率平均值为0.05 × 10-3 μm2。②揭示早期油气充注和异常超压（超压封存箱）是沉积和早表生期形成的孔隙在深层得以保持的关键因素。断续分布的多孔生屑灰岩被相对致密的泥晶灰岩包裹，在深层超高温的夹持下导致生屑滩内部局部异常超压的形成，茅二段储层的底板为茅一段致密泥晶灰岩、顶板为吴家坪组互层的致密泥岩和灰岩，在致密顶底板的夹持下，形成了茅二段区域异常超压。③孔隙形成与保持机理揭示，断续分布的多孔生屑滩、早期油气充注、单滩体异常超压和区域异常超压是茅二段孔隙型灰岩储层规模发育的条件，该储层具有侧向断续分布特点，通过井-震联合，在顶底板和生屑滩体识别的基础上，预测有利生屑灰岩滩储层分布面积为9.5 × 104 km2。上述认识奠定了深层发育孔隙型灰岩储层的理论基础，拓展了四川盆地深层灰岩储层勘探新领域，对其他盆地深层灰岩储层勘探具重要借鉴价值。

关键词: 孔隙形成与保持, 异常超压, 孔隙型灰岩储层, 深层, 茅口组, 川中地区

Abstract:

Presently， large-scale oil and gas fields discovered in deep carbonate rocks are predominantly distributed within porous dolomite reservoirs and fractured-vuggy karst limestone reservoirs. However， recent discoveries in wells Pengshen 12 and Nanchong 2 in the Sichuan Basin confirm the presence of porous limestone reservoirs in the 2nd member of the deep Maokou Formation （also referred to as the Mao 2 Member）. This finding challenges the traditional geological understanding of reservoirs， establishing the porous limestone reservoirs as a hot research topic. In this study， geological insights are gained using core and thin section observations， geochemical analysis of reservoirs， and reservoir identification and tracking through well-tied seismic interpretation. The results indicate that porous bioclastic limestone reservoirs are present in the Mao 2 Member. The dominant storage spaces include intergranular pores， biological cavity pores， moldic pores， and dissolved pores， which are formed in sedimentary and supergene environments. Specifically， the reservoir encountered in drilling well Pengshen 12 exhibits a cumulative thickness of 24.80 m， an average measured porosity of 5.1%， and an average measured permeability of 0.05 × 10-3 μm2. Early hydrocarbon charging and the presence of anomalous overpressure （overpressured compartments） are identified as key factors contributing to the deep preservation of pores formed during the sedimentary and early supergene stages. The intermittently distributed porous bioclastic limestones are wrapped by relatively tight micritic limestones， resulting in the formation of local anomalous overpressure within bioclastic shoals under the influence of ultra-high temperatures at great depths. Reservoirs in the Mao 2 Member are sandwiched by the floor of tight micritic limestones of the Mao 1 Member and the roof of tight mudstones interbedded with limestones from the Wujiaping Formation. This configuration facilitates the formation of regional anomalous overpressure in the Mao 2 Member. The mechanisms underlying pore formation and preservation suggest that the large-scale porous limestone reservoirs in the Mao 2 Member are developed under a combination of favorable conditions： intermittently distributed porous bioclastic shoals， early hydrocarbon charging， local anomalous overpressure within individual shoals， and regional anomalous overpressure. These reservoirs exhibit a laterally intermittent distribution. Based on the identification of bioclastic shoals， the roof and floor of the member， it is predicted through well-tied seismic interpretation that favorable bioclastic limestone shoal reservoirs cover an area of 9.5 × 104 km2. These insights provide a theoretical foundation for the occurrence of porous limestone reservoirs in deep parts， expanding the exploration targets of deep limestone reservoirs in the Sichuan Basin. Additionally， this study offers a valuable reference for the exploration of deep limestone reservoirs in other basins.

Key words: pore formation and preservation, anomalous overpressure, porous limestone reservoir, deep-buried reservoir, Maokou Formation, Central Sichuan Basin

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