Main Structural Styles and Deformation Mechanisms in the Northern Sichuan Basin,Southern China

The Triassic Jialingjiang Formation and Leikoupo Formation are characterized by thick salt layers. Three tectono-stratigraphic sequences can be identified according to detachment layers of Lower-Middle Triassic salt beds in the northern Sichuan Basin, i.e. the sub-salt sequence composed of Sinian to the Lower Triassic Feixianguan Formation, the salt sequence of the Lower Triassic Jialingjiang Formation and Mid-Triassic Leikoupou Formation, and the supra-salt sequence composed of continental clastics of the Upper-Triassic Xujiahe Formation, Jurassic and Cretaceous. A series of specific structural styles, such as intensively deformed belt of basement-involved imbricated thrust belt, basement-involved and salt-detached superimposed deformed belt, buried salt-related detached belt, duplex, piling triangle zone and pop-up, developed in the northern Sichuan Basin. The relatively thin salt beds, associated with the structural deformation of the northern Sichuan Basin, might act as a large decollement layer. The deformation mechanisms in the northern Sichuan Basin included regional compression and shortening, plastic flow and detachment, tectonic upwelling and erosion, gravitational sliding and spreading. The source rocks in the northern Sichuan Basin are strata underlying the salt layer, such as the Cambrian, Silurian and Permian. The structural deformation related to the Triassic salt controlled the styles of traps for hydrocarbon. The formation and development of hydrocarbon traps in the northern Sichuan Basin might have a bearing upon the Lower-Middle Triassic salt sequences which were favorable to the hydrocarbon accumulation and preservation. The salt layers in the Lower-Middle Triassic formed the main cap rocks and are favorable for the accumulation and preservation of hydrocarbon.

Reservoir characteristics and genetic differences between the second and fourth members of Sinian Dengying Formation in northern Sichuan Basin and its surrounding areas

This study investigated the characteristics and genesis of reservoirs in the 2^(nd) and 4^(th) members of Sinian Dengying Formation in northern Sichuan and its surrounding areas, on the basis of outcrop, drilling cores and thin section observation and geochemical analysis. The reservoirs of 2^(nd) member are distributed in the middle part of the stratum. The reservoir quality is controlled by supergene karst and the distribution of mound-shoal complex. The bedded elongated isolated algal framework solution-cave and the residual "grape-lace" cave, which are partially filled with multi-stage dolosparite, constituted the main reservoir space of the 2^(nd) member. There is no asphalt distribution in the pores. The pore connectivity is poor, and the porosity and permeability of the reservoir is relatively low. The reservoirs of 4^(th) member were distributed in the upper and top part of the stratum. The reservoir quality is controlled by burial dissolution and the distribution of mound-shoal complex. The bedded algal framework solution-pores or caves, intercrystalline pores and intercrystalline dissolved pores constituted the main reservoir space of the 4^(th) member. It's partially filled with asphalt and quartz, without any dolosparite fillings in the pores and caves. The pore connectivity is good. Most of the 4^(th) member reservoirs had medium-low porosity and low permeability, and, locally, medium-high porosity and medium permeability. Affected by the development of mound-shoal complex and heterogeneous dissolution, the platform margin along Ningqiang, Guangyuan, Jiange and Langzhong is the most favorable region for reservoir development. Deep buried Dengying Formation in the guangyuan and langzhong areas should be the most important hydrocarbon target for the future exploration.

Geochemical Characteristics of the Sandstonetype Uranium Deposits in Northern Sichuan Province

Described in detail in this paper are the geochemical charederistics of thesandstone-type urboum deposits in northern Sichuan Province. Favoable and unfavor-able conditions for the enrichment of uranium are explored on the basis of the elementalabundances and ratios of U, Th and K determined by gamma-ray spectroscopy Gamma-ray spectroscopic (U, Th and K) and XRF analyses (As, Ba) are helpful to distinguishU-bearing light-colorea sandstones from U-barren light-colored ones and red sandstones(red claystone) from light-colored sandstones. Therefore, the favorable target area forprospecting the sandstone-type uranium deposits can be defined in northern SichuanProvince.

Mottled dolomite in the lower Cambrian Longwangmiao formation in the Northern Sichuan Basin,South China

At the end of Early Cambrian time,the Sichuan basin(South China)was located in a wide carbonate platform,with hundreds of meters of carbonate deposited.The Longwangmiao Formation carbonate in Sichuan basin is partially to completely dolomitized,displaying a mottled texture in the northern area of the exposure.The mottled dolomitic limestone developed parallel to bedding,with shape irregular boundaries with limestone that has not been dolomitized.The mottled dolomite is composed of powder crystalline and finely crystalline dolomite,while the matrix limestone is composed of micritic calcite.the isotopic composition of mottled dolomite(δ^(13)C=+0.29‰PDB,δ^(18)O=1.15‰PDB)is similar to that of micrite calcite(δ^(13)C=0.49‰PDB,δ^(18)O=1.45‰PDB).Both isotopic values and trace element data indicate that the dolomitized fluid is originated from sea water.Some beds contain gypsum pseudomorphs and mud cracks,indicating a shallow and evaporative environment with local high salinity during deposition.Dolomitization likely took place early,in part as a result of sea water salinity concentration.Trace fossils thalassinoides horizontalis,thalassinoides callianassa and planolites developed in the Longwangmiao Formation,and the sharp edges of mottled dolomite are similar to these trace fossils.The beds are intensely bioturbated.In the burrow network,the sediments and burrow fill were coarse and loose with little clay,and it is interpreted here as being easier to be dolomitized than the surrounding sediments.Partial dolomitization is thus interpreted to have occurred in the burrow system,and the degree of dolomitization was related to the degree of bioturbation,which is controlled by the trace-making creatures.

Evaluation of dolomite reservoirs in the Longwangmiao Formation,Lower Cambrian in Northern Sichuan basin,China

With the extended petroleum exploration of the carbonate reservoir in the Longwangmiao Formation,Lower Cambrian in Sichuan basin,looking for a new favorable exploration area is the primary task in current exploration.This paper focusing on the dolomite reservoir in the Longwangmiao Formation in the Northern Sichuan basin,will evaluate the reservoir conditions,including reservoir lithology,reservoir spaces,physical properties and other basic characteristics.Combined with sedimentary environment study and diagenesis analysis,the genetic mechanism of Longwangmiao reservoir in study area will be discussed.It indicates that the reservoir rocks of Longwangmiao Formation in the study area are composed of dolarenite and crystalline dolomite,and the main reservoir spaces are intergranular dissolved pores,intragranular dissolved pores and intercrystalline dissolved pores.However,most of dissolved pores have been filled with bitumen,which lead to the reservoir properties very poor,both the porosity and permeability are worse than that of central Sichuan basin,so the reservoir in the Longwangmiao Formation in the Northern Sichuan basin is low-porosity and low-permeability reservoir.During the Early Cambrian Longwangmiao period,the study was near the old-land,and the energy of sea water was not enough to deposit many grain shoals,which cause the sediments are small with lots of quartz and muds.Moreover,because lacking of large scale karstification in the late diagenesis,there isn't much dissolved pores and vugs develop in the Longwangmiao Formation.Some Intergranular dissolved pores and intercrystalline dissolved pores formed by the early atmosphere water dissolved exist as some reservoir spaces,but most of them have been filled with bitumen,which was residual when the ancient oil reservoir transformed.Above factors cause the Longwangmiao Formation in the Northern Sichuan basin become not a very favorable reservoir in Sichuan basin.

川北地区下侏罗统大安寨段陆相页岩油勘探方向再认识

川北地区下侏罗统大安寨段是四川盆地产油主力层系之一。近年来,随着非常规勘探理论的发展,开始转变思路针对大安寨段页岩储层开展勘探,川北地区陆相页岩油勘探方向的认识得到提高。基于LY1及YY2等页岩油探井的岩心、实验、钻井、压裂等资料,对其油气形成条件、资源潜力、工程地质条件等3个方面进行了再认识。研究表明:(1)阆中大安寨段二亚段页岩具备良好的资源基础和形成条件,勘探潜力巨大。大二亚段主要发育页岩、介壳灰岩、页岩夹介壳灰岩3种岩性,页岩烃源品质较好,整体处于中成熟—高成熟阶段,生烃强度为(20~90)×10^(4)t/km^(2),滞留烃量占总生烃量的66%~78%,页岩油资源量为3.26×10^(8)t;(2)研究区大二亚段页岩样品的裂缝网络不发育,具有渗流条件差、可钻性和可压性条件差的特征,基质型页岩油具有原油黏度大、含蜡量高的特征,页岩样品渗流条件和页岩油流动性之间的耦合配置关系是目的层高产的关键;(3)在目前基质型页岩勘探成效不佳的情况下,建议采用常规—非常规结合的勘探思路,对研究区页岩—灰岩互层型储层成藏体系进行研究,将优质页岩与裂缝—孔隙型灰岩的层段作为有利的勘探目标,通过地质—工程一体化研究方法,对可钻性、可压性及排采等方面的技术难题进行攻关,提升工程工艺水平。

川中北部地区寒武系第二统沧浪铺组一段孔隙特征、成因及演化模式

【目的】近年来,随着川中北部地区寒武系第二统沧浪铺组的不断勘探突破,沧浪铺组呈现出巨大的勘探潜力,而目前孔隙研究的薄弱制约了对储层发育特征的深入认识。【方法】基于岩心、铸体薄片和阴极发光等的观察与鉴定,运用图像识别软件获取岩石组分含量、孔隙参数等定量数据,对川中北部地区寒武系第二统沧浪铺组一段的孔隙特征、成因、不同岩性的孔隙演化模式开展研究。【结果】沧浪铺组一段的孔隙类型主要为粒内溶孔,与总面孔率的正相关性最好,其次是粒间溶孔。较高的鲕粒/陆源砂的含量比例是孔隙发育的重要物质基础,溶解作用是孔隙发育的最有利因素,而高能的陆棚鲕粒滩沉积是原生孔隙发育的关键。因为准同生期大气水的选择性溶解作用是形成沧一段主要鲕粒粒内溶孔的最有利的成岩作用,而准同生期—埋藏期的白云石化作用则增强岩石的抗压性、使固相体积缩小而增加岩石的面孔率,埋藏期的溶解作用则沿着构造破裂形成的裂缝和早期孔隙进行溶解扩大。陆源砂、胶结作用、压实作用和压溶作用等则不利于沧一段孔隙的发育。【结论】因此,有利的碳酸盐组分及后续的成岩—构造作用影响了孔隙的发育和演化,并形成了孔隙面孔率依次降低的岩性排序特征:亮晶鲕粒云岩、含砂鲕粒云岩、砂质鲕粒云岩、细粒岩屑砂岩、石灰岩类。

川北山前带寒武系筇竹寺组富有机质页岩发育模式

研究川北山前寒武系筇竹寺组富有机质页岩分布、主控因素及沉积模式,对该地区页岩气勘探具有重要意义。利用野外地质调查、钻井和岩心资料,结合岩石薄片鉴定、全岩X射线衍射分析、总有机碳含量(TOC)测定等分析测试资料,研究川北山前带筇竹寺组富有机质页岩的沉积模式、分布及主控因素。研究表明:①筇竹寺组页岩主要为强脆性硅质页岩和中等脆性硅/黏土混合质页岩,根据总有机碳含量(TOC)—沉积构造—矿物组分将其划分为16种岩相类型川北山前带寒武系筇竹寺组页岩主要为富有机质纹层状强脆性硅质页岩相、富有机质层状强脆性硅质页岩相和含有机质层状强脆性硅质页岩相。其中前两类岩相为页岩气主要勘探开发岩相;②富有机质页岩TOC普遍高于2%,富有机质页岩具南厚北薄、西厚东薄分布的特征,有机质丰度具南高北低、西高东低的特点;③拉张槽及区域内隆-凹相间的古地理格局是筇竹寺组富有机质页岩差异分布的主要原因,区内不均衡构造演化加剧了页岩的非均质性展布;繁盛发育的低等浮游生物及细菌等提供了丰富的有机质来源,早期快速海侵下缺氧的深水环境利于有机质的保存,晚期摩天岭古陆和汉南古陆的持续隆升对有机质富集起抑制作用;④海平面升降和古气候演变控制了富有机质页岩在纵向上呈旋回性分布。

四川盆地北部二叠系栖霞组陆源碎屑岩的发现及其指示意义

在四川盆地北部旺苍双汇剖面二叠系栖霞组碳酸盐地层中发现了陆源碎屑岩沉积,其区内对二叠纪瓜德鲁普世早期古地理演化及二叠系油气勘探具有重要的指示意义。笔者等通过沉积学和锆石U-Pb年代学的方法,对碎屑岩的沉积环境和物源条件进行了分析。栖霞组陆源碎屑岩的沉积特征表明其形成于滨岸沉积环境,指示区内经历过短暂的海平面下降。岩石学及锆石形态特征表明其具有较高的成分成熟度和结构成熟度,碎屑锆石UPb测年结果显示年龄主要集中在2600~2400 Ma、1800~1200 Ma、1000~700 Ma和500~400 Ma 4个峰值区间,反映物源成分较为复杂,指示碎屑颗粒经历了较长距离搬运或再旋回。通过对比锆石年龄频谱发现,栖霞组碎屑岩与扬子地块志留系—二叠系碎屑岩及前寒武系结晶基底均具有相似的锆石年龄分布特征。结合区域构造演化,认为扬子地块前寒武系结晶基底是碎屑锆石的初始来源,上扬子北缘志留系—石炭系可能为栖霞组碎屑岩的形成提供了直接的物源供给。栖霞组碎屑岩的出现指示研究区在瓜德鲁普世早期由于海平面的下降,局部水下隆起短暂暴露形成了海岛或古陆并遭受剥蚀,为碎屑岩形成提供物源。基于栖霞组碎屑岩所指示的沉积环境和物源条件,恢复了研究区瓜德鲁普世早期的古地理格局。栖霞组陆源碎屑岩的发现对揭示四川盆地北部瓜德鲁普世早期地貌分异及古地理格局转换提供了新的证据,为区内下一步油气勘探提供重要指示。

川东—川北地区二叠系茅口组沉积演化及其油气地质意义

近年来,四川盆地二叠系茅口组的勘探思路和布井原则由原来的“占高点、沿长轴”转变为以寻找滩相孔隙型规模储层为目标,并取得了新突破,使其成为了勘探热点层系,这就需要详细的沉积演化研究来支撑。川东—川北地区是茅口组构造—沉积分异最为明显,也是勘探潜力较大的区域。对茅口组386口钻井的测井资料进行系统梳理,并利用野外剖面和钻井取心进行沉积相分析,结合测井曲线与沉积相,分析研究区茅口组的沉积演化。研究认为,川东—川北地区茅口组一段到茅口组二下亚段总体为碳酸盐缓坡,地层厚度和沉积相总体受川中古隆起的影响,局部发育低能滩;茅二上亚段到茅三段转变为具有镶边性质的碳酸盐台地,地层厚度和沉积相带展布转变为北西—南东向,自西向东依次发育台地相、台缘带、斜坡和陆棚相,台缘带发育高能滩相。研究区茅口组沉积期相对海平面总体经历了两次升降过程,对应地层分别为茅一段到茅二下亚段和茅二上亚段到茅三段。受区域海平面升降、区域构造活动以及碳酸盐台地类型的控制,茅一段到茅二下亚段缓坡发育具有岩溶和云化的滩相储层;茅二上亚段到茅三段海槽内发育潜在烃源岩,是非常规油气勘探潜在有利区,而海槽西侧则发育具重要勘探价值的规模性台缘带高能滩。

中国西南地区寒潮避风港现象与气候康养资源分析

近年来,受全球气候变化大背景的影响,寒潮等极端天气气候事件的发生频次或强度不断增加,加之国家应对人口老龄化各项政策的逐步落实,越来越多的北方老年候鸟人群冬季到我国华南和西南地区进行避寒旅居康养;随着国家全民大健康战略实施力度的加大,此热潮方兴未艾。因此,有针对性地探究我国境内的寒潮避风港现象,既是大气科学的重要科学问题,又是避寒康养的现实需求,具有重要科学价值和民生意义。基于此,本文初步梳理了2022年11月至2023年12月中旬期间,影响我国大范围地区的数次寒潮或强冷空气活动天气过程,东西部比较后,率先发现我国西南地区、特别是川南滇北交汇区具有“寒潮避风港”现象,尤其是攀枝花地区在寒潮天气过程中能够保持气温相对稳定,日均气温变化幅度较小;与周边其他城市相比较,大部分情况下攀枝花地区的气温波动最小,变化幅度也最小。据此本文做了一点成因方面的粗浅探究,初步分析了其避寒康养气候等资源优势与挖掘潜力,其深层次的成因及其避寒康养效应与价值更值得后续深入研究。

川东地区二叠系火山岩石油地质特征及天然气勘探有利区

为了研究四川盆地东部地区火山岩的岩相展布规律、储层发育主控因素、油气成藏富集模式等问题,以野外露头、钻井、测井、分析化验等资料为基础,分析了该区二叠系火山岩成储成藏模式,指出了天然气勘探有利区。研究结果表明:(1)受峨眉地裂运动影响,川东地区中二叠统茅口组—上二叠统吴家坪组发育两类火山岩相关的有利储层,一类是近火山口的火山碎屑熔岩储层,发育于茅三段中部及上部,主要分布在涪陵北部大竹—梁平—兴隆场喷溢相区,储层厚10~35 m,测井解释孔隙度介于3.4%~8.0%;另一类是远离火山口的火山—沉积碎屑岩储层,为火山灰与正常沉积物的混合沉积,发育于茅三段底部及吴家坪组,平面上分布于普光—涪陵北—建南地区,储层厚16~35 m。(2)茅三段底部和吴家坪组火山—沉积碎屑岩作为储层的同时,也是优质的烃源岩,自身具有高孔隙度、高有机碳含量、自生自储、大面积连片分布的特点,能够源内成藏。茅三段火山碎屑熔岩储层被下伏茅三段底部和上覆吴家坪组烃源岩所包裹,形成“夹心”式的源储配置关系,具有“近源成藏”的有利条件。结论认为:(1)涪陵北部为火山碎屑熔岩气藏勘探有利区,可进行老井复查、复试或优选有利构造位置部署探井;(2)围绕开江—梁平陆棚及其边缘的涪陵北、建南、普光地区是火山—沉积碎屑岩气藏勘探有利区,对于此类储层可采用非常规油气勘探思路,避开高陡构造区,优选保存条件好、埋深小于6 000 m的甜点区进行天然气勘探开发。

川西北部梓潼区块中侏罗统沙一段气藏勘探开发初步研究与实践

为了推进四川盆地致密气上产,以川西北部梓潼区块中侏罗统沙溪庙组一段气藏为研究对象,分析了该气藏的地质特征及主要开发特征,指出了梓潼区块沙一段气藏地质条件复杂,与邻区简阳区块沙一段、金秋区块沙二段气藏存在较大的差异,需要通过开发先导试验建立适宜的开发技术对策。研究结果表明:①梓潼区块沙一段气藏多期河道砂体纵向叠置发育,储层具有物性差、厚度小、非均质性强等特点;②气藏存在多套压力系统,并且含水饱和度高,产水可能性大。结论认为:①梓潼区块天然气勘探开发潜力较大,是下一步增储上产的重要新领域,但由于目前缺乏静动态资料,对气藏地质认识不足,因此有必要开展先导试验;②梓潼区块沙一段1、4号砂组储层大面积叠置发育,测试获工业气流,优选1、4号砂组为先导试验区目的砂组以探索两套砂组的含气性;③根据邻区开发经验,采用大夹角、水平井模式部署8口水平井,优选高效改造工艺技术,建立地质工程一体化模型,设计单井配产介于(6~9)×10^(4)m^(3)/d,预测单井累计产气量介于(1.06~1.30)×10^(8)m^(3)。

优化的AI断裂识别技术在川中北斜坡的应用

最新研究表明四川盆地川中北斜坡地区走滑断裂发育,具有断面陡直、断距小、断裂不明显的特征,由于目的层下古生界埋藏较深,地震资料信噪比低,难以对走滑断裂进行快速精确地识别。为此,采用了优化后的AI断裂识别技术:(1)对地震数据进行背景建模,求取局部背景能量数据与原始地震数据残差,增强地层背景反射之下微小断裂地震信息的显现;(2)进行构造导向滤波,提高地震数据的信噪比,使地震数据同相轴的连续性和断裂特征更加明显;(3)进行AI断裂识别。应用结果表明:不仅大大节省了人工解释的时间,还具有较强抗噪性,能较好地压制地震数据的冗余信息,提高信噪比,识别出常规地震属性难以识别的微小断裂,更好地预测走滑断裂的展布特征及交割关系。

四川盆地北部地区寒武系沧浪铺组沉积演化

四川盆地下古生界寒武系沧浪铺组勘探潜力巨大。文中结合钻井和野外地质剖面实测成果等最新资料,研究了四川盆地北部地区沧浪铺组沉积演化规律。结果表明:1)沧浪铺组沉积期,研究区内可识别出开阔台地相、局限台地相和潮坪相3种沉积相类型,纵向上具有明显的分异特征,横向上沉积厚度西薄东厚。沧一段沉积期,开阔台地相发育以鲕粒石灰岩、砂屑石灰岩为主要岩性并可见小型槽状交错层理的台内滩亚相,和以泥晶石灰岩为主要岩性的滩间海亚相;局限台地相发育以具有残余结构的砂屑白云岩和鲕粒白云岩为岩性并可见重结晶作用的台内滩亚相,和以灰质泥晶白云岩、砂质白云岩为主要岩性的滩间海亚相;在裂陷槽和古隆起之间区域,发育以泥质白云岩、泥灰岩和砂质白云岩为主要岩性的混积潮坪相。沧二段沉积期,发育以紫红色泥岩、砂岩等为主要岩性的碎屑潮坪相,见小型水平层理、羽状交错层理和砂岩透镜体。2)沧浪铺组沉积期,以大规模海退为主,水体总体逐渐变浅。沧一段沉积期,碎屑物质输入受到裂陷槽隔档作用影响,发育碳酸盐岩沉积,在构造高部位发育以颗粒岩为主的台内滩亚相。至沧一段沉积末期,裂陷槽逐渐被填平,碎屑物质得以向东持续迁移。沧二段沉积期,发生了小规模的海侵—海退过程,水体由深变浅,最终形成以砂泥岩互层沉积为主要特征的碎屑潮坪沉积环境。

四川盆地北部二叠系茅口组沉积特征及油气意义

基于地震资料精细解释成果,结合野外剖面及室内薄片观察,通过分析主要岩石类型及古生物、地球化学和地震相特征,对四川盆地北部二叠系茅口组沉积相展布特征进行研究,依据生物(屑)灰岩、礁灰岩和硅质岩等岩相发育规律以及地震地层结构和地层厚度变化特征,认为茅口组发育了开阔台地、台地边缘及斜坡—盆地等沉积亚相,总结出了开阔海夹点礁、开阔海夹点滩、台地边缘滩和灰质—硅质盆地等4种沉积微相组合,明确了沉积相纵向演化和平面展布规律。结果表明,台地边缘高能生物滩平面上呈条带状在剑阁—元坝—龙岗一带规模发育,生物(屑)灰岩的晶间溶孔、粒间溶孔和生物体腔孔发育,物性好,是优质储集层发育带;川西海槽和广元—旺苍海槽茅四段的硅质岩和泥岩有机碳含量高,则是优质生油岩,优越的沉积环境为该区油气成藏提供了有利的生油和储集条件。

川北典型陆相页岩-砂岩油气潜力表征与评价

四川盆地北部中侏罗统千佛崖组陆相地层颇具油气资源潜力,亟待实现突破。在岩芯描述,沉积微相分析和储集体识别基础上,解析了研究区千佛崖组典型陆相页岩-砂岩储集体纵横向叠合类型和平面组合类型,发现了多层致密砂岩油(气)藏、上页下砂油(气)藏、砂页互层油(气)藏、页包砂油(气)藏和孤立油(气)藏等5类油气混合储集类型,分层段、分类型评价了研究区各个层段发现的44个油气藏,从中优选出A、B和C等3个典型陆相页岩砂岩油气混合储集有利区。上述成果有利于中国陆相页岩油气成储理论的深入发展。

川北地区上二叠统吴家坪组火山碎屑岩油气藏储层特征及主控因素

受峨眉地裂运动影响,川北地区二叠纪吴家坪期发育一套火山碎屑岩。该类岩性非均质性强,储层孔隙结构复杂。为进一步明确该地区吴家坪组火山碎屑岩油气藏储层发育特征和形成机理,从而落实其勘探潜力,以露头和实钻资料为基础,结合岩心薄片观察、地化分析、氩离子抛光扫描电镜、盖层微孔联合测定等多种手段,分析川北地区吴家坪组火山碎屑岩储层发育特征及成因机理。研究认为,该火山碎屑岩主要岩性为凝灰质泥岩、泥质凝灰岩及沉凝灰岩。储层储集空间主要为纳米级黏土矿物收缩孔和有机质孔,微米级有机酸溶蚀孔和微裂缝。储层物性具有中—高孔特低渗的特征,其中凝灰质泥岩物性最好。储层主控因素分析认为,近火山口斜坡—陆棚环境有利于火山碎屑岩储层发育,火山灰脱玻化作用及次生有机酸溶蚀是储层形成孔隙的主要原因。

川北地区灯四段台内丘滩储层特征及主控因素

台内丘滩是四川盆地上震旦统灯影组天然气勘探的重要后备领域,为了落实灯影组四段(以下简称灯四段)优质储层主控因素与展布特征,以川北地区灯影组台内钻井和野外露头为研究对象,通过岩心观察、薄片鉴定、储层物性等研究,对灯四段储集层基本特征及主控因素进行了综合分析。研究结果表明:(1)川北地区灯四段台内丘滩储集层岩性主要为藻粘结白云岩、藻砂屑白云岩、藻叠层白云岩和藻纹层白云岩,储集空间以晶间(溶)孔、藻格架孔、粒间溶孔以及裂缝为主;(2)台内丘滩优质储层展布主要受沉积相带控制,藻丘和浅滩沉积微相是储集层发育的有利沉积相带;(3)多期溶蚀作用能有效提升储层性能,其中早成岩期岩溶是优质储层形成的基础,埋藏期溶蚀能有效扩大储集空间,第一期埋藏溶蚀作用强度从灯四段顶部向下逐渐减弱,第二期埋藏溶蚀作用造成早期孔洞储集层进一步溶蚀扩大,形成现今储集空间。结论认为,受汉南古陆和宣汉—开江古隆起控制,在坡折带发育近南北向的台内丘滩条带,是灯四段油气勘探的有利地区。

四川盆地北部大隆组页岩气地质条件及勘探潜力

以最新钻井LB1井、7个野外露头剖面及部分老井资料为依托,探讨了四川盆地北部大隆组优质页岩的平面及纵向展布规律,认为优质页岩的展布受沉积相控制,呈NW—SE走向。在广元—旺苍地区发育盆地相,泥页岩厚度较小(10~20 m);盆地相两边发育深水陆棚相,泥页岩厚度较大(20~45 m);外围依次发育浅水陆棚或斜坡相,泥页岩厚度逐渐变小(0~15 m)。从斜坡相到陆棚相,再到盆地相,呈现出灰质逐步减少,硅质含量逐渐增加的特征,泥页岩厚度呈先大(深水陆棚相)后小(盆地)的趋势。另外,对LB1井地化特征、储层微观特征开展研究,并与已突破的焦石坝、丁山、东溪地区志留系页岩对比,分析认为,四川盆地北部大隆组优质页岩具有高有机碳、高含气量、有机质类型好、成熟度适中及可压性好等特点。根据高有机碳的特点,认为无定形体有机质的广泛发育是高有机碳含量的基础,缺氧硫化环境是保存的关键。根据高含气量的特点,认为含气性和比表面积具有较好的相关性,而对比表面积贡献较大的主要是有机质含量。最后评价了中国石化矿权内大隆组勘探潜力,认为资源量较大,值得进一步开展工作。