Paleoenvironment and organic matter enrichment of the Carboniferous volcanic-related source rocks in the Malang Sag,Santanghu Basin,NW China

Volcanic activity was quite frequent during the deposition of the Late Carboniferous Ha’erjiawu Formation in the Santanghu Basin.The petrology and organic and inorganic geochemical indicators were used to investigate hydrocarbon potential,paleoenvironmental conditions and organic matter enrichment of the mudstones.The results show that the oil generation capacity of the Ha’erjiawu Formation mudstones,which has abundant oil-prone organic matter(TypeⅡkerogen with hydrogen index values mainly ranging from 250 to 550 mg HC/g TOC)in mature stage(Tmax values mainly ranging from 435 to 450℃),is considerable.The Ha’erjiawu Formation was deposited in a dysoxic,freshwater-mildly brackish,and warm-humid environment.During its deposition,the Ha’erjiawu Formation received hydrothermal inputs.The volcanic hydrothermal activities played an important role in the organic matter enrichment.In addition,the total organic carbon(TOC)is significantly positively correlated with the felsic mineral content,but it is negatively correlated with the carbonate mineral content and C27/C29 ratios,indicating that terrigenous organic matter input also contributed to the primary productivity in the surface water.Therefore,the formation of the high-quality source rocks in the Ha’erjiawu Formation was jointly affected by the hydrothermal activity and the terrigenous organic matter input.

The Characteristics of the Hydrothermal Exhalative Dolostone of Lucaogou Formation in Santanghu basin and its Geology Setting Indication

The NW-SE trending Santanghu basin is located in Xinjiang,NW China,between Tianshan Mountains and Altai Mountains.The tectonic evolution history of north Xinjiang has long been debated,especially the question when did that area began its intraplate rift evolution stage.This abstract discusses the features and possible origin of the hydrothermal exhalative dolostone of Lucaogou Formation in Santanghu basin,aiming to provide relevant information about this question.The target dolostone are characterized by extreme thin lamina of 0.3cm–1 cm thick.Dolomite,ankerite,potassium feldspar and analcite are dominant composition.Most dolomite is poor crystallized and is in anhedral or subhedral shapes.Ankerite is generally porphyritic,few is in irregular shapes.It has to be noted that the porphyritic ankerite commonly develop zonal textures characterized by rings with various Fe O content.Potassium feldspar and analcite（<50%）are commonly observed in dolostones.Thin sections show some analcite is tetragonal trisoctahedron with harbour–like corrosion rims.Besides,few fragments of carbonatite rocks are observed in Lucaogou Formation and they perform intermittent or scattered distribution in rock layers.Previous work done by our study team showsδ13C PDB values are 4.8‰;1.4‰,6.93‰on average.Theδ18 O PDB values are between-5‰;21.1‰,-10.94‰on average.Paleosalinity calculated byδ13C andδ18 O is between 128.35 and 136.81,134.42 on average.Sr content of dolostones in study area reaches to164×10-6;37×10-6（379.1×10-6 on average）,most dolostone in target area are between 0.70457;.706194, average at 0.705360.Considering either accompanying residual tuff or residual leucite is found via electron probe,this indicates the analcite may derive form analcime phonolite.Furthermore,fragments of carbonatite rocks proves mantle-derived magmatism exist.The rapid variation ofδ18 O indicates multiple interactions of hydrothermal fluids with lake water during Lucaogou sedimentary period.87Sr/86Sr values are much lower than that of crustal silica rocks while are more close to mantle derived rocks,which indicates diagenetic hydrothermal fluid is mantle-origin.It has been reported that dolostone does not intergrow with iron-rich dolostone in study area.According to the latest X diffraction results of cores,iron-rich dolostone distributes rather locally.Given that ankerite commonly develop zonal textures characterized by various Fe O content,we confirm it is due to multiple hydrothermal fluids activities in different hydrothermal vents.There should be abundant hydrothermal vents during Lucaogou period.Deep faults and its relevant fractures built plenty paths for mantle-origin hydrothermal fluids to run up.Different vents owned various fluid properties,so did relevant sedimentation products.Hence we inclined to believe Santanghu basin was at intraplate rift evolution stage,under regional extension condition in late Carboniferous.During early-mid Permian the basin was a starved,deep lacustrine intracontinental rift basin.Accordingly,in northern Xinjiang,ocean basin may close in late Carboniferous and started continental sedimentary development in early Permian.

Geochemical characteristics and geological significance of picritic rocks in Permian Tiaohu Formation from Santanghu Basin, Xinjiang, NW China

1 Introduction Santanghu Basin is located between the Armantai and Karamaili suture zone,at the junction of the Siberia,Kazakhstan and Tarim plates(Chen and Jahn,2004;Xiao et al.,2008).As an important part of the Central Asian

Characteristics and genesis of tuffaceous shale oil lithofacies:A case study of Lucaogou Formation in Santanghu Basin

Lucaogou Formation in the Santanghu Basin is a special lacustrine fine-grained sedimentary deposits rich in volcanic debris and carbonate,with abundant shale oil resources.However,understanding of shale oil characteristics and genesis remains unclear.Lithofacies,sedimentary environment,and formation mechanisms of tuffaceous shale oil are investigated based on core and thin section observations,X-ray diffraction,field emission SEM and geochemical analysis.Results show that three mixed lithofacies types are developed in Lucaogou Formation:blocky tuff,laminated tuffaceous dolomite,and laminated dolomitic tuff.These lithofacies types are characterized by high content of felsic and dolostone,widespread organic matter,and low clay content.Formation of tuffaceous shale oil sweet spots is primarily influenced by four factors:inputting of volcanic ash as a high-quality source rocks and reservoirs provides good material basis;devitrification of volcanic glass,calcitization,and dissolution are crucial for formation of reservoirs;expulsion of source rocks with high-abundance organic matter expulsion facilitates migration and accumulation of hydrocarbon in adjacent reservoirs;fracture development improves reservoir permeability to form highly productive sweet spots.By analyzing characteristics and genesis of tuffaceous shale oil,the main controlling factors of reservoir physical property and oil saturation are clarified,which is of great significance for selection of shale oil exploration zones.

Source Rock Potential and Organic Geochemistry of Carboniferous Source Rocks in Santanghu Basin, NW China

Carboniferous source rocks identified by drilling in Santanghu （三塘湖） Basin were evaluated for their source potential, employing organic geochemistry and RockEval pyrolysis. The organic matter origin and depositional environment of these samples were also determined through biomarker analysis. Most of the Carboniferous source rocks in Santanghu Basin are characterised by high values of total organic carbon （TOC） content and high extractable organic matter content and hydrocarbon yields, indicating that they are organicrich source rocks with high oil generative potential. The organic matter is predominantly Type I and Type II kerogen with a minor contribution of Type III kerogen, as demonstrated by its pyrolysis parameters and carbon isotope values. According to Ro （%） and T max values, most of the studied samples are at earlyto middle-thermal mature stage; only a few of the samples are at a highly mature stage （past peak oil generation）. The biomarker analysis reveals a dominance of algal/bacterial organic matter input, with a minor contribution of land plant material. Pr/Ph ratio supports a suboxic depositional condition, consistent with a neritic or marine-continental alternating environment proposed by predecessor.

Formation of the Permian basalts and implications of geochemical tracing for paleo-tectonic setting and regional tectonic background in the Turpan-Hami and Santanghu basins,Xinjiang

The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoicreworked intracontinental basins that superposed on the folded basement of the Paleozoic orogenicbelt. ^(40)Ar/^(39)Ar geochronological study of the basalts developed in the basins reveals that theformation period is Permain (293—266 Ma). From geochemical comparison of the basalts, theSantanghu basalts exhibit a strong depletion in Nb and Ta, and a selective enrichment in HFSE,reflecting that the source region is influenced by the subducted components related to subduction ofthe ancient oceanic crust and characterized with ''lagged arc volcanic rocks''. In contrast, theTurpan-Hami basalts show a slight depletion in Nb and Ta, high Th/Ta ratio, similar to the basaltsformed in an intracontinental ex-tensional zone or in an initial rift. Combined with the formationperiod of the ophiolite and ophiolite melange zones and regional magmatic activities occurring onthe post-orogenic extensional background in northern Xinjiang, it can be inferred from thesegeochemical characteristics that the tectonic background for forming the Turpan-Hami and Santanghubasins is closely related to the regional extension after the continent-continent collisionalorogeny. The basalts of the two basins came from different sources on the post-orogenic extensionalbackground of the similar basin-forming dynamics. Although the settings are all intracontinentalrift, the source for the Santanghu basalts is obviously subjected to the metasomatism of thesubducted components, implying the existence of the previous subduction.

三塘湖盆地油气勘探历程与启示

三塘湖盆地油气勘探始于20世纪50年代,50—80年代基本以地面地质调查和局部勘探为主,大规模油气勘探始于90年代并取得了丰硕成果。回顾六十多年的油气勘探实践,系统梳理了三塘湖盆地石油地质研究与认识、勘探领域及勘探成果,基于钻井、地震、储量及产量等数据分析,将三塘湖盆地油气勘探历程划分为地质普查、砂岩油藏勘探、火山岩油藏勘探、致密油勘探4个阶段。以油气勘探各阶段勘探思路、科技创新、勘探技术、重大勘探成果为主线,系统总结了各个阶段的勘探启示以及对勘探产生重要影响的成果及认识,形成了侏罗系低渗低压砂岩油藏、火山岩油藏和凝灰岩致密油藏的成藏地质理论和勘探开发技术,有效推动了三塘湖盆地油气勘探的持续突破,同时期望指导三塘湖盆地下一步油气勘探工作。

东准噶尔三塘湖盆地中侏罗统砂岩碎屑锆石U-Pb年龄、Hf同位素特征及对铀成矿的意义

三塘湖盆地汉水泉地区是东准噶尔地区砂岩型铀矿找矿的有利地段,为揭示该地区中侏罗统西山窑组和头屯河组沉积物物源体系,分析地层铀源条件,对西山窑组和头屯河组砂岩开展碎屑锆石LA-ICP-MS U-Pb测年和Hf同位素分析。分析结果显示西山窑组砂岩的碎屑锆石年龄集中于晚古生代,2个样品年龄峰值分别为328 Ma和340 Ma,碎屑锆石ε_(Hf)(t)为8.9~14.7,二阶段模式年龄介于690~415 Ma之间;头屯河组砂岩的碎屑锆石年龄可划分出238~163 Ma、505~259 Ma和1950~744 Ma 3个区间段,碎屑锆石ε_(Hf)(t)为-6.5~12.1,二阶段模式年龄介于1709~575 Ma之间。物源分析表明西山窑组砂岩物源单一,主要来自于研究区西部卡拉麦里—麦钦乌拉和野马泉地区;头屯河组砂岩物源相对复杂,除了有来自于卡拉麦里地区的碎屑物质外,还接受了其他区域的物源供给。二者之间碎屑锆石年龄特征的突变,代表了东准噶尔地区中侏罗世一次剧烈的构造变形事件,物源特征指示汉水泉地区中侏罗统地层铀含量相对有限,铀源是限制该地区砂岩型铀矿成矿的重要因素。

富油煤焦油产率测井评价方法研究

【目的】富油煤作为一种集煤、油、气属性为一体的煤基油气资源,对于保障我国油气资源供应、实现煤炭清洁高效利用具有重要意义。目前富油煤的识别主要依靠格金干馏试验测量的焦油产率来判断,而利用地球物理手段准确识别与评价富油煤的研究则相对薄弱。【方法】以新疆三塘湖盆地侏罗系西山窑组和八道湾组煤层为研究对象,基于岩石物理实验,在明确富油煤典型测井响应特征基础上,创新建立了一种煤焦油产率测井定量评价方法。【结果和结论】结果表明:(1)相比含油煤,富油煤具有富氢结构物质含量高、孔隙结构差的特点,这造成富油煤具有“低密度、高中子和高电阻率”的常规测井响应特征;(2)通过多状态二维核磁共振实验测量分析,明确了富油煤具有“二维核磁T1谱双峰,T_(2)<1、T_(1)/T_(2)>10区域信号强”的核磁测井响应特征,而含油煤相应区域信号不明显,这与富油煤中富氢结构物质含量高有关;(3)基于富油煤典型测井响应特征,提出利用电阻率和中子2个参数构建富油煤指示因子Z,Z越大,表明煤焦油产率越高。在煤焦油产率刻度基础上,建立了煤焦油产率与指示因子间的线性关系,实现了煤焦油产率的准确方便计算,可操作性强。上述认识为基于地球物理测井手段识别和评价富油煤提供了理论指导。

东疆地区石炭纪—二叠纪构造古地理与原型盆地演化

石炭纪—二叠纪是东疆地区洋-陆转换的关键构造转折期,期间发生了多次洋壳闭合和陆陆碰撞活动。基于东疆地区洋盆性质、沟-弧-盆俯冲事件和陆陆碰撞的复杂性,目前针对东疆地区盆地晚古生代地层格架对比以及沉积充填特征认识不足。文中以活动论构造古地理思想为指导,复原东疆地区盆山构造带的构造-沉积面貌,厘定各构造地层单元的构造-沉积环境,从沉积充填、构造演化复原、周缘构造环境等角度来综合地、动态地开展原型盆地恢复。研究结果表明:东疆地区经历了早石炭世伸展、早石炭世末期—晚石炭世早期弱伸展、晚石炭世末期挤压、早二叠世早期伸展、早二叠世末期挤压5期伸展聚敛旋回,随后经历了晚二叠世、晚三叠世、晚侏罗世、晚白垩世—古近纪、晚新生代5期构造改造过程。盆山构造复原揭示了石炭纪吐哈盆地南部边界距现今盆山边界向南46~70 km,石炭纪准东盆地北部克拉美丽山距现今向北约30 km,三塘湖盆地北部造山带石炭纪边界距今约55 km。东疆地区沉积环境经历了从石炭纪海相到早二叠世海陆过渡相再到中晚二叠世陆相的沉积演化,石炭纪发育海相的弧相关断陷盆地、裂谷边缘盆地、断陷盆地,早二叠世以发育海相、陆相断陷盆地为主,中二叠世主要发育陆相坳陷盆地,晚二叠世发育挤压型坳陷盆地。解析东疆地区盆山构造格局及石炭纪—二叠纪构造古地理演化,为探究东疆地区主要沉积盆地石炭系—二叠系成藏条件、源-储组合分布奠定良好基础。

三塘湖盆地条湖-马朗凹陷煤层气甜点预测

三塘湖盆地煤层气勘探开发工作仍处于初期阶段,通过建立煤层气资源地质工程一体化评价方法,预测煤层气开发甜点区。结果表明,条湖-马朗凹陷煤层气赋存条件优越,9^(#)煤层主体埋深600~2600 m,含气量1.3~4.5 m^(3)/t,煤层厚度5.0~60.9 m,构造较为简单,顶底板岩性均以泥岩为主。优选煤层厚度、埋藏深度、顶底板岩性、构造、沉积相带、孔隙度、渗透率、脆性指数、破裂压力、泥质含量10个参数作为评价指标,预测煤层气甜点区(Ⅰ类区)主要分布于条湖凹陷东北部和马朗凹陷西部。

烃源岩中类胡萝卜烷系列化合物的检出及其地质意义——以三塘湖盆地马芦1井芦草沟组为例

【目的】γ-和β-胡萝卜烷属于类胡萝卜烷,广泛分布于沉积物和原油中,但是低碳数的类胡萝卜烷系列化合物在烃源岩中较为少见,γ-和β-胡萝卜烷以及低碳数类胡萝卜烷系列化合物的来源及其在地质载体中的指示意义尚不明确。【方法】基于三塘湖盆地马朗凹陷马芦1井芦草沟组12件代表性烃源岩样品,通过气相色谱—质谱、岩石热解、镜质体反射率、总有机碳分析,详细表征其地球化学特征,以此获得目标化合物的生源信息。【结果和结论】马芦1井芦草沟组烃源岩有机质丰度高、类型好、处于成熟阶段,并且这些烃源岩样品中富含γ-和β-胡萝卜烷以及低碳数(碳数范围为C_(13)~C_(25))的类胡萝卜烷系列化合物。根据正构烷烃、萜烷、甾烷等系列生物标志化合物的分布特征,并综合分析其他地球化学参数,认为γ-和β-胡萝卜烷主要来源于细菌。此外,结合烃源岩热演化、微生物化石及火山爆发的证据,提出低碳数类胡萝卜烷系列化合物可能是γ-和β-胡萝卜烷受微生物或热演化作用的产物,该研究可以为探索烃源岩的有机质来源、沉积环境和热演化程度提供新的思路。

反应温度及压力对三塘湖盆地褐煤热解产物分布影响

煤在气化通道中气化反应效率是影响煤炭地下气化气体组分与热值的关键问题。为揭示反应温度和压力对三塘湖盆地褐煤在水蒸气中气化行为和产物分布特征影响,基于固定床热解炉对三塘湖盆地西山窑组褐煤进行不同反应温度和压力热解试验。结果表明:随反应温度升高(300~900℃),气体质量分数由3.84%增至24.29%,水和焦油质量分数先增后减;高温下反应温度升高,加剧二次反应,H_(2)和CH_(4)体积显著增加,900℃体积最大分别为100.89、106.09 mL/g,污染物总质量减少,900℃质量分数相对小,17.72 mg/g。增加反应压力(1.5~3.0 MPa),利于提高半焦转化率和增加气体质量分数。高温下反应压力增加,加剧二次反应,利于反应加氢气化和甲烷化发生,导致CH_(4)体积显著增加,700℃CH_(4)体积最多增加26.89 mL/g,但在700℃会促进自由基加氢饱和反应,污染物总质量增加。建议在实际生产中,通过控制注汽移动速度适当增加反应温度并提高反应压力,且控制气化反应区的温度远离700℃,利于H_(2)和CH_(4)生成,以提高煤炭地下气化工艺高效清洁开发。研究成果可为三塘湖盆地西山窑组褐煤煤炭地下气化工艺提供指导。

三塘湖盆地侏罗系西山窑组褐煤储层孔隙结构特征及脱水演化规律

查明干燥前后煤孔隙结构差异及演化规律有助于准确预测煤炭地下气化炉运行效果。通过选择水、煤油作为饱和流体进行低场核磁共振实验,测试并对比同一样品分别在饱水和干燥状态下的孔隙结构差异;通过X-CT技术观察了煤样孔隙结构的脱水演化过程并建立了演化模式;通过脉冲衰减渗透率测试与低温液氮吸附实验评估了煤样的传质能力变化。研究结果表明:(1)褐煤干燥发生孔隙收缩的同时会产生裂缝,总孔容由0.630 cm^(3)/g降至0.481 cm^(3)/g,而大孔体积显著增加,由0.070 cm^(3)/g增加至0.420 cm^(3)/g,脱水导致孔隙集中,大孔体积占比达88%。(2)褐煤干燥时的孔隙收缩受基质收缩程度控制,不同煤岩组分脱水的孔隙结构演化模式不同,易收缩的基质煤脱水时,其组分边缘或内部产生大量裂隙,而木质煤或丝质煤脱水收缩较弱,保留大量原生孔隙,裂隙发育较少。(3)褐煤干燥后,水分脱除、空孔体积增加,渗流状态由单相水向气水两相、单相气流转变的同时形成了良好的连通孔隙网络,煤层渗流能力显著改善,渗透率由0.248 mD增加至48.080 mD,扩散传质贡献增大,干燥褐煤在温度为200℃、压力为0.5 MPa时中孔及大孔的扩散系数约为0.09 cm^(2)/s。

三塘湖盆地中二叠统芦草沟组油页岩热重特性及影响因素

为了研究油页岩加热过程中的热重特性和热解过程及其影响因素,对三塘湖盆地芦草沟组油页岩的含油率、总有机碳、热解、主量元素和热重分析等进行测试。结果显示,三塘湖盆地芦草沟组油页岩为具有较高有机质丰度、高灰分和中等发热量的中等品质油页岩,且灰分主要元素组成为SiO_(2)、Al_(2)O_(3)、CaO,属于高熔灰分。油页岩热重分析显示其热解过程主要为低温、中温和高温失重段3个阶段,中温失重段为油页岩主要失重段和油页岩热解反应阶段,温度范围为300~580℃。其中油页岩热解过程中油气大量生成阶段的温度范围为430~500℃,为油页岩热解过程中生油关键阶段,而500~580℃为页岩气生成阶段,可以形成一定量的页岩气。

三塘湖盆地汉水泉凹陷新近系砂岩型铀矿成矿条件及找矿方向

三塘湖盆地地处东准噶尔构造带的东南部,是我国北方重要的产煤、产油气盆地。依据煤田钻孔测井数据,盆地北侧汉水泉凹陷中部中、新生代地层显示大量放射性异常,为铀矿找矿提供了重要线索。为深入了解区内砂岩型铀矿成矿潜力,本次研究针对汉水泉地区中部放射性异常集中区开展钻探验证,查明了储铀层位和铀矿化情况,分析汉水泉地区砂岩型铀矿成矿潜力和找矿方向。研究认为:(1)三塘湖盆地汉水泉地区铀矿化及异常主要分布于昌吉河群中段底部的灰色、黄色细砂岩和西山窑组上段顶部的灰色细砂岩中,铀异常分布范围广,但储铀砂体厚度较薄,铀品位偏低;(2)汉水泉地区昌吉河群地层具备有利的沉积建造条件和完善的“补-径-排”体系,后生蚀变及铀矿化显示良好,具备较好的找矿潜力,蚀源区铀源相对匮乏和地层还原剂含量不足是限制成矿的不利因素;(3)汉水泉凹陷异常区中部断裂带附近及其北侧可作为后续找矿的重点地区。

三塘湖盆地原油地球化学特征及其成因类型

依据生物标志物分布和组成特征， 把三塘湖盆地的原油和油显示划分为中生界煤成油和上古生界湖相成因原油两大类。中生界煤成油以塘参１ 井中侏罗统西山窑组的原油为代表，含蜡量高（３０％ 以上） ， 其正构烷烃系列具有明显的奇碳优势，Ｐｒ／Ｐｈ 值高（ 大于４．０） ，四环萜烷／三环萜烷值大于１．０，三环萜烷系列中Ｃ１９ 、Ｃ２０ 相对丰度高于Ｃ２１ 、Ｃ２３ ，有Ｃ３１ 六环藿烷，无伽马蜡烷，Ｃ２９ 甾烷占绝对优势，此类原油源于中生界煤系烃源岩。上古生界湖相成因原油包括塘参３ 井、条２ 井、条３ 井油显示，其正构烷烃系列没有明显的奇偶优势，Ｐｒ／Ｐｈ 值低，三环萜烷／四环萜烷（ 仅检测到Ｃ２４ 一个化合物）值大于１．０，且Ｃ２１ 、Ｃ２３ 三环萜烷的相对丰度高于Ｃ１９ 、Ｃ２０ ，无Ｃ３１ 六环藿烷，但伽马蜡烷和β胡萝卜烷的含量高，Ｃ２７ 甾烷丰度较高， 此类原油源于上古生界湖相烃源岩。依据成熟度， 又可把上古生界原油分成未熟－ 低熟油和成熟油。

新疆三塘湖盆地二叠纪火山岩岩石地球化学及其构造环境分析

对新疆东北部地区二叠纪构造动力学背景的研究,前人已经做过很多工作,但争议较大。本文通过对位于新疆东北部边缘的三塘湖盆地二叠纪火山岩常量、微量元素的分析测试及讨论,为恢复二叠纪盆地性质与古构造环境提供岩石地球化学约束。研究区内火山岩主要岩石类型为玄武岩、安山玄武岩、辉绿岩、安山岩以及少量英安岩和流纹岩,显示亚碱性系列特征。玄武岩常量元素总体显示高Ti的特征,轻、重稀土元素分馏明显,含量比值(LREE/HREE)在3．8和8．35之间变化,不同岩石类型均具有LREE富集的特征,玄武岩和玄武安山岩Eu异常不明显(δEu=0．92～1．13)；微量元素LILE富集,Nb、Ta相对于La强烈亏损,具有较明显“TNT”负异常,不相容元素丰度并不很高,判别图解投入板内玄武岩及火山弧玄武岩区域,总体上既显示板内的构造环境,又携带俯冲带地球化学信息,与“滞后弧火山岩”特征类似,但是缺少CFB端元,综合区域地质特征及前人的研究结果,新疆北部地区晚石炭世至二叠纪处于造山后期伸展裂陷的构造背景。

三塘湖盆地火成岩储集空间类型及特征

三塘湖盆地的上、下二叠统和石炭系发育 3套典型的火成岩 ,主要岩类有玄武岩、安山岩和辉绿岩等 ;储集空间包括原生孔隙和裂缝以及次生溶孔和裂缝 ,进一步可分为原生气孔、残余气孔、原生粒间孔隙、冷凝收缩缝、收缩节理、颗粒爆炸纹缝、斑晶溶蚀孔、铸模孔、粒间溶孔、基质溶蚀孔、蚀变物溶蚀孔、裂缝充填再溶蚀孔、杏仁体溶孔、构造裂缝、风化裂缝、溶缝等。火成岩在成岩和后生变化过程中 ,发生了交代蚀变作用、充填作用和溶解作用等成岩事件 ,原生孔隙经历了复杂的充填和溶蚀过程才形成现今的面貌。火成岩的岩相、成岩作用和构造运动控制了火山岩的储集性能。图 1参

火山岩风化体储层控制因素研究——以三塘湖盆地石炭系卡拉岗组为例

针对火山岩风化壳储层控制因素和成因复杂的难题,以三塘湖盆地石炭系卡拉岗组为例,在搞清晚石炭世构造环境和岩性特征基础上,提出风化淋滤和断裂改造是火山岩风化壳形成有利储层的主要控制因素。不同火山岩岩性经风化淋滤后储层物性均增大并能形成有利储层,储集层孔隙类型以次生溶蚀孔隙和裂缝为主,具双峰分布特征。建立了5层结构模型,并提出通过岩芯识别火山岩风化体方法,指出不同风化体结构层中的孔隙类型和岩石结构不同,其中溶蚀带和崩解带是有利储层发育段,火山岩风化体厚度可达380 m,受断裂控制的火山岩风化体发育中低角度裂缝,储层物性更好、厚度更大,火山岩风化体主要发育于古地貌高部位和斜坡带,沿断裂处更发育。该认识改变了古生界火山岩成岩作用强、储集性能差,不能形成有利储层的认识,扩大了油气勘探领域,对指导火山岩风化体油气勘探具有重要的科学意义,并指出中国中西部含油气盆地古生界发育大规模火山岩风化体,是今后油气勘探的新领域。