南方古生界典型區塊頁巖氣勘探潛力評價研究進展報告

黃保家 夏斌 盧鴻 蔡東升 李緒深

摘 要：為評價皖南蕪湖區塊古生界頁巖氣勘探潛力、優選勘探層系，根據鉆井巖心、露頭巖樣地化、巖石學分析數據及野外調查等資料，對該地區古生界3套富有機質層系的頁巖氣形成地質-地球化學條件進行初步研究，厘定了下揚子蕪湖地區三套頁巖的厚度和埋深，對比研究了三套烴源巖的地球化學特征，揭示了頁巖脆性、孔隙類型及其發育的控制因素，進而對頁巖氣儲層及勘探潛力進行了初步評價。從最近鉆探的4口參數井中采集了365個頁巖樣品進行TOC和Rock–Eval分析，采用低溫N2吸附和場發射掃描電鏡（FE-SEM）方法對其中的57個樣品進行了研究。結果表明，古生界上奧陶統五峰組-下志留統高家邊組、二疊系（孤峰組+龍潭組+大隆組）富有機質泥頁巖層系在區內分布廣、厚度較大、有機質豐富（TOC普遍>2%），且以偏腐殖型為主、熱演化程度較高（Ro=1.3%～3.0%），具有形成頁巖氣的良好物質基礎。它們的礦物基質孔和有機質空隙發育，大小從幾個納米-上百納米，56柱心樣品總孔隙度主體在2.03%～6.5%之間，其中以介孔和微孔為主；總比表面積為7.19～20.84 m2/g，這些特征與四川盆地志留系龍馬溪組頁巖儲層特征相似。同時，其埋深適中且泥頁巖與硅質巖相伴生，利于人工壓裂和勘探開發，有較大勘探潛力。另一方面，古生界寒武統黃柏嶺組富有機質頁巖有機質豐度高且以腐泥型為主，也有良好的成氣潛力，但因其普遍深埋、成熟度偏高，該區后期發生的多期強烈構造運動等因素對早期形成頁巖氣的富集及保存可能有一定影響，其勘探潛力有待進一步深究。

關鍵詞：安徽蕪湖地區 古生界 富有機質泥頁巖 孔隙結構 頁巖氣 形成條件 勘探潛力

A Study on Exploration Potential of Paleozoic Shale Gas in the Typical Block，Southern China

Huang Baojia1 Xia Bin2 Lu Hong3 Cai Dongsheng4 Li Xushen1

（1.Zhanjiang Branch，China Offshore oil （China） Co.， Ltd.； 2.Sun Yat-sen University；3.Guangzhou Institute of Geochemistry，Chinese Academy of Sciences；4.CNOOC Research Institute）

Abstract：In order to investigate the exploration potential of the Paleozoic shale gases in the South Anhui， geochemical and reservoir petrologic analysis were made on the representative core samples from the study area. A preliminary study was performed on the geological-geochemical conditions of Paleozoic shale gas formation， by the combination of the data with geological information and outcrop data. it can be found that three sets of organic-rich shale strata， including the lower Cambrian Huangpaling Formation（∈1h）， the upper Ordovician Wufeng Formation（O3w） to the lower Silurian Gaojiabian Formation（S1g），and the Permian Formation（Gufeng Formation（P1g），Longtan Formation （P2l），Dalong Formation （P2d） are developed within Paleozoic. The 365 black shale core samples from 4 wells drilled recently were obtained for TOC and Rock–Eval analysis， and the geochemistry and pore structures of about 57samples were investigated using low pressure N2 adsorption analysis， field emission scanning electron microscopy （FE-SEM） observations. The results show that the O3w- S1g and P1g+P2l+P2d shales with a wide distribution in the studied area have relatively big thickness， high TOC（>2%）， type IIb-III kerogens，high thermal maturity （Ro=1.3%～3.0%）， and high quartz contents. Both mineral matrix and organic matter pores are well developed with pore sizes ranging from several to several hundred nanometers. The total porosity for the 56 samples ranges mainly from 2.03% to 6.5% with majorities of mesoporous and microporous. The total surface area ranges from 7.19～20.84 m2/g.These characteristic are similar to those of Lower Silurian Longmaxi Formation shales in Southern Sichuan Province.Therefore， they could have favorable geological conditions for forming shale gas and relatively big exploration potentia1. On the other hand，∈1h organic-rich shale with type I kerogens should also have relatively great gas generation potential， but its deep burial and over- maturity， especially late multiphase tectonic movement may have some influence on the generation， accumulation and preservation of shale gases within the strata， so its exploration potential of shale gases need further study.

Key Words：South anhui area； Paleozoic； Shale gas； Organic-rich shale； Pore structure； Geological condition； Exploration potential

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