【摘要】：下志留統(tǒng)龍馬溪組的富含有機(jī)質(zhì)黑色頁巖,普遍被認(rèn)為是中上揚子地區(qū)最佳的頁巖氣研究對象。前人已對這套黑色頁巖進(jìn)行了系統(tǒng)的烴源巖分析,但針對川東地區(qū)龍馬溪組的沉積特征和頁巖氣資源潛力評價的研究還比較薄弱,勘探程度較低。本文針對川東地區(qū)龍馬溪組開展了野外露頭剖面觀察和采樣,收集了區(qū)內(nèi)及鄰區(qū)已有剖面資料和鉆井資料,并對黑色頁巖進(jìn)行了鏡下薄片鑒定、有機(jī)地球化學(xué)、全巖X射線衍射、掃描電鏡等室內(nèi)測試分析,在此基礎(chǔ)上系統(tǒng)研究了區(qū)內(nèi)龍馬溪組黑色頁巖的沉積特征及頁巖氣評價參數(shù),優(yōu)選出頁巖氣有利目標(biāo)區(qū),并對有利目標(biāo)區(qū)進(jìn)行綜合評價。研究區(qū)五峰組-龍馬溪組沉積環(huán)境總體為陸棚環(huán)境,處于淺水陸棚與深水陸棚的交替期,可細(xì)分為五段:①澗草溝組(或臨湘組)為灰質(zhì)淺水陸棚沉積,②五峰組下部黑色頁巖段為泥質(zhì)深水陸棚沉積,③五峰組上部觀音橋段為灰泥質(zhì)淺水陸棚沉積,④龍馬溪組下部為泥質(zhì)深水陸棚沉積,⑤龍馬溪組上部為砂泥質(zhì)淺水陸棚沉積。平面展布上從酉陽黑水到巫溪田壩,沉積相從深水陸棚逐漸向半深海-深海盆地變化。沿此剖面兩端向中心:龍馬溪組泥頁巖厚度逐漸變厚。研究區(qū)龍馬溪組黑色頁巖有機(jī)質(zhì)類型以I型-II型為主;有機(jī)質(zhì)豐度較高,黑色頁巖TOC集中在1%~4%之間,平均值約1.7%;Ro值大于2.2%,一般在2.4%~4.3%,已處于過成熟演化階段,核心地區(qū)的Ro≥3.6%(最大達(dá)4.3%)。TOC縱向上從五峰組到龍馬溪組下段有逐漸降低的趨勢,橫向上TOC的展布與川東地區(qū)構(gòu)造形跡相似,呈北東-南西向的濃集中心展布,向中心有頁巖厚度變厚且有機(jī)碳質(zhì)變大的趨勢。研究區(qū)龍馬溪組黑色頁巖段礦物以石英礦物、粘土礦物為主,其次為黃鐵礦、碳酸鹽巖。粘土礦物含量平均分布在24.2%~60.6%,平均含量為44.14%,粘土礦物成分主要有伊蒙間層、伊利石和綠泥石,其中尤以伊利石含量最高。石英礦物平均分布在27.5%~60.9%,平均含量為40.01%。頁巖BET比表面積為8.156m2/g~30.54m2/g,平均為14.796m2/g。研究區(qū)龍馬溪組黑色頁巖段孔隙度較低,主要集中在4%~8%,平均值為6.17%。微觀孔隙為開放型,連通性較好�？紫额愋椭饕獮榱ｉg孔、粒內(nèi)孔、有機(jī)質(zhì)孔以及微裂縫。其中粒間孔分為粒間格架孔、粘土片間孔、粒緣孔、表生溶孔,粒內(nèi)孔分為草莓狀黃鐵礦粒內(nèi)晶間孔、粘土粒內(nèi)孔以及成巖溶孔。依據(jù)頁巖氣有利目標(biāo)區(qū)劃分標(biāo)準(zhǔn),綜合分析泥頁巖有效厚度、有機(jī)碳含量、有機(jī)質(zhì)成熟度、頁巖出露與埋深及有利構(gòu)造等條件,在川東地區(qū)出圈定3個有利目標(biāo)區(qū)并進(jìn)行評價:分別是位于合江-習(xí)水一帶的習(xí)水目標(biāo)區(qū)、位于涪陵-石柱一帶的石柱目標(biāo)區(qū)、位于開縣-巫溪一地的巫溪目標(biāo)區(qū)。
[Abstract]:The black shale rich in organic matter in the Longmaxi formation of Lower Silurian is generally considered as the best shale gas research object in the middle and upper Yangtze area. The former has carried out systematic source rock analysis of the black shale, but the study on sedimentary characteristics of Longmaxi formation and evaluation of shale gas potential in east Sichuan is still weak and the exploration degree is relatively low. In this paper, the outcrop profile of Longmaxi formation in eastern Sichuan is observed and sampled, the existing profile data and drilling data are collected in the area and adjacent areas, and the black shale is identified by microscopic thin section, organic geochemistry, and organic geochemistry. On the basis of the whole rock X-ray diffraction and scanning electron microscope, the sedimentary characteristics and shale gas evaluation parameters of the black shale of Longmaxi formation are systematically studied, and the favorable target area of shale gas is selected. A comprehensive evaluation of the favorable target area is carried out. The sedimentary environment of Wufeng formation and Longmaxi formation in the study area is generally continental shelf environment, which is in the alternate period of shallow water shelf and deep water shelf, and can be subdivided into five sections: Wei 1 Jian Cao Gou formation (or Linxiang formation) as gray shallow water shelf deposit. (2) the black shale formation in the lower part of Wufeng formation is a muddy deep-water shelf sediment. The upper Guanyinqiao section of Wufeng formation is a shallow-water silty shelf sediment. The lower part of the Longmaxi formation is a muddy deep-water shelf deposit, the upper part of the Longmaxi formation is a sandy shallow-water shelf deposit. From Youyang Heishui to Wuxi Tianba, the sedimentary facies gradually changed from deep water shelf to semi-deep sea-deep sea basin. Along the two ends of this section, the shale thickness of Longmaxi formation becomes thicker and thicker. The organic matter type of black shale in Longmaxi formation in the study area is mainly type I -II, and the abundance of organic matter is relatively high, the TOC of black shale is concentrated in the range of 1% or 4%, the average value is about 1.7% and the Ro value is more than 2.2, and generally at 2.4% and 4.3%, it is already in the stage of over-maturation and evolution. In the core area, the Ro 鈮，

本文編號：2226578