四川盆地中二叠统茅口组一段泥灰岩源内非常规天然气成藏条件及有利勘探方向  

Accumulation conditions and favorable exploration orientation of unconventional natural gas in the marl source rock of the fi rst member of the Middle Permian Maokou Formation,Sichuan Basin

作　　者：江青春[1] 汪泽成[1] 苏旺[1] 黄士鹏[1] 曾富英[1] 冯周[1] 毕赫 鲁卫华[1] Jiang Qingchun;Wang Zecheng;Su Wang;Huang Shipeng;Zeng Fuying;Feng Zhou;Bi He;Lu Weihua(PetroChina Research Institute of Petroleum Exploration&Development)

机构地区：[1]中国石油勘探开发研究院

出　　处：《中国石油勘探》2021年第6期82-97,共16页China Petroleum Exploration

基　　金：中国石油天然气股份有限公司前瞻性与基础性重大科技项目“海相碳酸盐岩致密储层成藏机理、富集规律与勘探评价技术研究”(2021DJ0504)。

摘　　要：早期研究认为四川盆地中二叠统茅口组一段(茅一段)为一套较好的碳酸盐岩烃源岩,忽略了其作为类似页岩非常规储层的油气勘探潜力。近期多口探井先后在茅一段获工业气流,揭示其可能成为四川盆地一个油气勘探新领域。通过对该层系钻井含油气性与油气分布、气源特征与烃源条件、岩相类型与有利岩相分布、储集条件与储层分布、成藏特征与富集规律五方面研究,指出茅一段泥灰岩中“碳酸盐岩源内非常规天然气”富集:油气具有区域大面积连续分布,在构造高部位、斜坡区、向斜区连续富集;茅一段天然气以自身烃源岩供烃为主,茅一段具有有机质丰度高、天然气富集程度高的“双高”特征,揭示其源内成藏、原位富集的特点;茅一段主要发育眼球灰岩相、含眼皮的眼球灰岩相、含眼球的眼皮灰岩相和眼皮灰岩相4类岩相,物性分析表明最有利的储集岩相为眼皮灰岩相,其储集空间主要为有机质纳米孔和白云石晶间微米孔,储层孔隙度普遍小于10%,渗透率小于1mD,具有典型的低孔、低渗致密储层特征。研究发现茅一段甜点纵向和平面分布连续稳定,纵向分布于茅一a亚段和茅一c亚段,平面上在全盆地普遍分布。茅一段超压特征显著,含气性好,结合埋深及储层分布对该层系有利区进行了综合评价,评价优选3个I类有利区和4个Ⅱ类有利区,认为南川—合川I类有利区勘探潜力最好,建议在该区进行风险探井部署,采取水平井体积压裂方式对该领域进行规模化生产。The early study regarded that the carbonate of the fi rst member of the Middle Permian Maokou Formation(hereinafter referred to as Mao 1 member)is a set of high-quality source rock in Sichuan Basin,but ignored its potential as an unconventional reservoir similar to the shale.Recently,commercial gas fl ows have been achieved of Mao 1 member in several exploration wells,probably indicating a new exploration fi eld.Five aspects of geological studies are conducted,including oil and gas bearing properties in wells and oil/gas distribution,gas source analysis and evaluation of source rock conditions,lithofacies types and distribution of favorable lithofacies zones,reservoir performance and its distribution,gas accumulation conditions and enrichment characteristics,by which the unconventional natural gas is considered to be enriched of marl source rock of Mao 1 member.It is continuously accumulated in a large area in structural highs,slope and syncline.The natural gas is mainly supplied by source rock of Mao 1 member itself,which is featured by high TOC and high degree of gas enrichment,indicating the characteristics of gas accumulation inside the source rock and in-situ gas enrichment.Four types of lithofacies are mainly developed in Mao 1 member,i.e.,the augen limestone lithofacies,eyelid bearing augen limestone lithofacies,augen bearing eyelid limestone lithofacies and eyelid limestone lithofacies.The study of rock physical properties shows that the eyelid limestone is the most favorable facies with reservoir space of mainly organic nanopores and dolomite intercrystal micropores.The reservoir porosity and permeability are generally less than 10%and 1mD respectively,which is a typical tight reservoir of low porosity and low permeability.The reservoir sweet spots are continuously distributed in a and c sub-members of Mao 1 member vertically,and widespread laterally in the whole basin.The reservoir has distinct characteristics of overpressure and good gas bearing property.Combined with burial depth and reservoir distrib

关 键 词：四川盆地 中二叠统 茅一段 富集规律 有利勘探区带 

分 类 号：TE122.2[石油与天然气工程—油气勘探]