Influences of burial process on diagenesis and high-quality reservoir development of deep-ultra-deep clastic rocks:A case study of Lower Cretaceous Qingshuihe Formation in southern margin of Junggar Basin,NW China

Taking the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin as an example,the influences of the burial process in a foreland basin on the diagenesis and the development of high-quality reservoirs of deep and ultra-deep clastic rocks were investigated using thin section,scanning electron microscope,electron probe,stable isotopic composition and fluid inclusion data.The Qingshuihe Formation went through four burial stages of slow shallow burial,tectonic uplift,progressive deep burial and rapid deep burial successively.The stages of slow shallow burial and tectonic uplift not only can alleviate the mechanical compaction of grains,but also can maintain an open diagenetic system in the reservoirs for a long time,which promotes the dissolution of soluble components by meteoric freshwater and inhibits the precipitation of dissolution products in the reservoirs.The late rapid deep burial process contributed to the development of fluid overpressure,which effectively inhibits the destruction of primary pores by compaction and cementation.The fluid overpressure promotes the development of microfractures in the reservoir,which enhances the dissolution effect of organic acids.Based on the quantitative reconstruction of porosity evolution history,it is found that the long-term slow shallow burial and tectonic uplift processes make the greatest contribution to the development of deep-ultra-deep high-quality clastic rock reservoirs,followed by the late rapid deep burial process,and the progressive deep burial process has little contribution.

Lithofacies paleogeography restoration and its significance of Jurassic to Lower Cretaceous in southern margin of Junggar Basin,NW China

In view of the difficulties in the study of lithofacies paleogeography and the low reliability of the distribution range of sedimentary sand bodies in the prototype basin caused by less deep drilling, complex seismic imaging and low degree of exploration in the southern margin of Junggar Basin, NW China. A new method based on the source to sink idea was used to restore lithofacies paleogeography and predict glutenite distribution. In the restoration, apatite fission track age was used to define range and uplift time of macro-provenance;the range of provenance area and the migration process of lake shoreline were restored based on the quantitative relationship between gravel diameter and transportation distance, tectonic shortening and other geological parameters;drilling cores and field outcrop sedimentary structures were analyzed, and a series of maps of lithofacies paleogeographic evolution and distribution range of glutenite bodies were compiled. It is concluded that from Early Jurassic to Early Cretaceous, in the southern margin of Junggar Basin, the provenance area gradually expanded from south to north, the lake basin expanded, shrunk and expanded, and the paleoclimate changed from humid to drought to humid. The western section always had proximal fan delta deposits from the southern ancient Tianshan provenance developed, and in the middle and eastern sections, the provenance areas evolved from far source to near source, mainly river-delta, braided delta, fan delta and other sediments developed. The boundary between provenance areas of the western and middle sections is speculated to be Hongche fault zone. In an angle open to the northwest with the current basin edge line, the restored ancient lake shoreline controlled the heterogeneity of reservoirs in the delta plain belt and delta front belt on its both sides. The ancient lake shoreline, current stratigraphic denudation line and current basin margin line limit the types and scope of favorable reservoirs.This understanding provides an important geological basis for oil and gas exploration in the deep lower source-reservoir assemblage at the southern margin of Junggar Basin.

Investigating the Influence of Parent Rock and Sedimentation on the Diagenesis of Tuffaceous Clastic Rock:An Example from the Lower Cretaceous Junggar Basin,China

This study focuses on tuffaceous clastic rocks of the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin.It aims to explore the influence of sedimentation and parent rock on this kind of reservoir development.The results show that the tuffaceous components formed by the denudation of ultramafic and mafic rocks can transform into chlorite coating or hematite,while those from intermediate rock denudation can be dissolved or transformed into illite.Sedimentary facies and lithofacies are essential in controlling the evolutionary result of tuffaceous components.Matrix-supported medium conglomerate and grain-supported medium-fine conglomerate that developed in the fan delta plain,with a closed original geochemical systems,have been in the oxidizing environment for a long time.The tuffaceous matrices mainly transforms into hematite or illite.These minerals occupy the primary pores and are difficult to dissolve by felsic fluids,which inhibits the development of high-quality reservoirs.The grain-supported sandy fine conglomerate developed in the fan delta front was in the underwater reductive environment with an open original geochemical system.The tuffaceous matrices not only can transform into chlorite coating to strengthen the particle's compaction resistance,but also can be fully dissolved,which promotes the formation of high-quality reservoirs.

Restoration of reservoir diagenesis and hydrocarbon accumulation process by calcite in-situ U-Pb dating and fluid inclusion analysis: A case study on Cretaceous Qingshuihe Formation in Gaoquan Structure, southern Junggar Basin, NW China

The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be (122.1±6.4) Ma, (14.4±1.0) Ma - (14.2±0.3) Ma. The hydrocarbon charging events occurred at around 14.2-30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.

Sedimentary filling characteristics and controlling factors of lacustrine microbial carbonates sequence in the Santos Basin,Brazil

Based on comprehensive analysis of seismic,logging,core,thin section data,and stable isotopic compositions of carbon and oxygen,the sedimentary filling characteristics of the Lower Cretaceous Barra Velha Formation sequence in H oil field,Santos Basin,are studied,and the high-frequency sequence stratigraphic framework is established,and the spatial distribution of reef-shoal bodies are predicted and the controlling factors are discussed.During the depositional period of the Barra Velha Formation,the study area is a slope-isolated platform-slope sedimentary pattern from southwest to northeast and the change of climate background from rift to depression periods has resulted in the variation of sedimentary characteristics from the lower third-order sequence SQ1(BVE 300 Member)of low-energy deep water to the upper third-order sequence SQ2(BVE 200 and 100 members)of high-energy shallow water in the Barra Velha Formation.The activities of extensional faults and strike-slip faults in rift period and the sedimentary differentiation from platform margin to intra-platform in depression period made the sedimentary paleogeomorphology in these two periods show features of“three ridges and two depressions”.The reef-shoal bodies mainly developed in the SQ2-LHST period,with vertical development positions restricted by the periodic oscillation of the lake level,and developed on the top of each high-frequency sequence stratigraphic unit in SQ2-LHST in the platform.The strike-slip fault activity controlled the distribution of the reef-shoal bodies on the plane by changing the sedimentary paleogeomorphology.The positive flower-shaped strike-slip faults made the formation of local highlands at the margins of and inside the shallow water platforms and which became high-energy sedimentary zones,creating conditions for the development of reef-shoal bodies.

准噶尔盆地玛湖凹陷二叠系风城组全粒序储层孔喉结构与原油可动性关系

基于铸体薄片、低温氮气吸附、高压压汞、核磁共振T2谱、接触角和油水两相界面张力等实验结果,揭示准噶尔盆地玛湖凹陷下二叠统风城组全粒序储层孔喉结构与原油可动性关系。研究表明:①随玛湖凹陷风城组储层粒级变小,较大喉道所连通孔隙体积和较大孔隙体积均呈减小趋势,喉道半径和孔隙半径分布范围和峰值范围均有序向小尺寸偏移;风城组非常规储层喉道半径、孔隙度和渗透率上限值分别约为0.7μm,8%,0.1×10^(-3)μm^(2);②风城组储层赋存滞留油、可动油的孔隙分布范围和峰值范围均随储层粒级变小而有序向小尺寸偏移;粒级较大储层样品赋存滞留油量、可动油量随驱动压力增大分别呈现更加明显的降低和升高趋势;③风城组各粒级储层中原油驱动压力随喉道半径增大而呈现快速下降、缓慢下降和趋于稳定3个阶段;原油驱动压力和各粒级储层原油驱动压力差异均随温度升高而降低,随喉道半径增大而降低。根据以上实验分析,推断地质条件下玛湖凹陷风城组深部页岩油具有较大的动用潜力。

埋藏过程对深层-超深层碎屑岩成岩作用及优质储层发育的影响——以准噶尔盆地南缘下白垩统清水河组为例

以准噶尔盆地南缘下白垩统清水河组为例,综合利用岩石薄片、扫描电镜、电子探针、稳定同位素组成及流体包裹体等技术手段,开展前陆盆地埋藏过程对深层—超深层碎屑岩成岩作用及优质储层发育影响的研究。研究表明,清水河组依次经历了“缓慢浅埋”、“构造抬升”、“渐进深埋”与“快速深埋”4个埋藏阶段。“缓慢浅埋”与“构造抬升”不仅能够缓解储层颗粒间的机械压实作用,还有利于长期保持开放型的成岩体系;既能够促进大气淡水对储层易溶组分的充分溶解,还能够抑制溶蚀产物的沉淀。晚期“快速深埋”过程促成流体超压的发育,一方面有效地抑制压实、胶结作用对原生孔隙的破坏,另一方面也促进储层微裂缝的大量发育,提高了晚期有机酸充注产生的溶蚀效果。基于孔隙度演化史的定量恢复,证实长期“缓慢浅埋”与“构造抬升”过程对深层—超深层优质碎屑岩储层发育的贡献最大,其次为晚期“快速深埋”过程,“渐进深埋”过程则几乎没有贡献。

准噶尔盆地西北缘下白垩统吐谷鲁群沉积特征及铀矿找矿方向

笔者等通过对准噶尔盆地西北缘乌尔禾—黄花沟地区的露头和钻孔岩芯、钻测井综合分析,结合镜下观察,对下白垩统吐谷鲁群主要岩石学特征、地层结构、沉积相类型及其展布特征进行了综合分析。以砂岩型铀矿成矿理论为指导,从沉积学角度,探讨了研究区下白垩统吐谷鲁群有利成矿砂体的类型及分布情况。结果表明:(1)下白垩统吐谷鲁a亚群岩石类型主要为长石岩屑砂岩和岩屑长石砂岩,吐谷鲁b、c和d亚群则以长石砂岩和长石岩屑砂岩为主;(2)下白垩统吐谷鲁群发育冲积扇、辫状河、三角洲和湖泊等4种沉积相类型,以德伦山为界,乌尔禾—夏子街一带发育远源弱流的浅水三角洲相,物源来自北西的雪米斯坦,而德伦山—黄花沟一带以发育高能量的辫状河沉积为主,物源应来自盆地北部;(3)下白垩统有利找矿层位为吐谷鲁a+b亚群的原生灰—灰绿色粗碎屑建造。乌尔禾—油砂山一带的三角洲平原亚相分支河道是重要的找矿方向;夏子街一带广泛发育的三角洲前缘水下分流河道和席状砂厚大砂体具备形成一定规模砂岩型铀矿的能力;黄花沟一带在吐谷鲁a+b时期发育宽广且具有较大规模的辫状河砂体是寻找层间氧化和潜水氧化的有利区域。

北黄海盆地东部坳陷下白垩统层序地层及沉积演化

北黄海盆地东部坳陷下白垩统是一套有利的油气勘探储集层,对其精细的地层划分及沉积演化的研究薄弱,制约了对东部坳陷油气勘探前景的深入认识。本文通过对东部坳陷钻井的岩芯观察,测井、录井分析及地震层序的井震标定,认为北黄海盆地东部坳陷下白垩统发育典型的陆相层序,可划分为3个三级层序,从底部向上依次为K_(1)SQ_(1)、K_(1)SQ_(2)和K_(1)SQ_(3)。在钻井上仅可见K_(1)SQ_(1)和K_(1)SQ_(2)两个三级层序,且K_(1)SQ_(2)层序的下降半旋回不完整,只残留该层序的上升半旋回。K_(1)SQ_(1)时期为湖盆断陷伸展期,发育一个完整的湖进—湖退旋回。早期盆地边缘发育河流相,南部主控断裂带发育扇三角洲相,北部缓坡带发育辫状河三角洲相;中后期由于湖平面上升,发育泥岩为主的湖泊沉积;晚期北部缓坡带见小规模辫状河三角洲沉积。K_(1)SQ_(2)时期为湖盆稳定裂陷期,继承了K_(1)SQ_(1)时期的沉积特征并略有收缩。K_(1)SQ_(3)时期为湖盆断陷萎缩期,以发育大范围的河流相沉积为特征。

准噶尔盆地南缘下白垩统层序界面的识别

准噶尔盆地南缘下白垩统内部的层序及界面单纯在地震剖面或电测曲线上都较难识别,但它们在岩石地球化学等特征上有较明显的反映。研究发现,层序边界处具有Ro值的突变,有机质含量(TOC)的低谷,ΔlogR曲线处于基线,粘土矿物组合突变,坡缕石、伊/蒙混层的含量明显增加;Cu、Li、Zn、Cr、V、Ba等微量元素的含量处于低谷;锆石等稳定重矿物含量以及黄铁矿含量较低,褐铁矿含量高等特征。结合地震剖面、测井曲线等特征,将准噶尔盆地南缘下白垩统划分出2个三级层序,每个层序又分别由低位体系域、湖侵体系域和高位体系域组成。

准噶尔盆地车排子地区下白垩统层序地层格架及主控因素分析

基于准噶尔盆地车排子地区下白垩统地震、钻井、录井和古生物资料分析,运用高精度层序地层分析方法,结合下白垩统沉积序列和构造演化特征、气候周期性变化特征等,将下白垩统吐谷鲁群划分为4个三级层序,并指出各层序边界在地震、岩性和电性资料上的响应特征。根据车排子地区特定的缓坡斜坡构造背景,建立起无坡折缓坡型层序地层模型,将三级层序划分为湖侵体系域和湖退体系域。湖侵体系域以粗粒扇三角洲前缘和细粒滨浅湖沉积为主,湖退体系域则发育粒度相对较粗的滨浅湖滩坝沉积。研究区沉积演化旋回性特征明显,幕式构造运动和古气候旋回变化对层序的发育起重要的控制作用。

松辽盆地北部白垩纪超层序特征

松辽盆地北部白垩系由3个超层序组、8个超层序、28个沉积层序组成。断陷湖盆期发育3个超层序和6个沉积层序,以火山岩与粗碎屑岩组合为特征。断拗转化期形成1个超层序和4个沉积层序,以中粗碎屑岩为特征。典型的大型拗陷湖盆期,可识别出3个超层序和15个沉积层序,以湖泊、三角洲相中细碎屑岩沉积为主,水进体系域和高水位体系域沉积时期半深湖—深湖相暗色泥岩广为发育。湖盆萎缩期,可识别出1个超层序和3个沉积层序,以湖泊、三角洲相中粗碎屑岩沉积为主。超层序组界面包括白垩系基岩顶面、营城组顶界面和嫩江组顶界面,与燕山运动各主要幕次形成的区域不整合面相对应,区域构造运动对其起着重要的控制作用。超层序界面可以是上述超层序组界面,也可由平行不整合面和剥蚀界面构成。超层序界面处沉积间断的时间较长,河道下切、地层缺失、暴露等沉积现象发育,与岩石地层单位界面一致。沉积层序界面处沉积间断的时间相对超层序界面要短,与岩石地层单位界面往往不一致。超层序界面在地震剖面上最明显的特征是出现削截、上超和顶超等反射终止现象,岩性、测井曲线也发生剧烈变化。

新疆准噶尔盆地中、晚侏罗世多重地层研究

对新疆维吾尔自治区沙湾县玛纳斯河红沟侏罗系剖面开展了生物地层学、同位素年代地层学、旋回地层学和磁性地层学等的综合研究。研究结果表明,头屯河组的时代为中侏罗世中晚期到晚侏罗世早期,包括巴通阶的最顶部、卡洛维阶和牛津阶的中下部;其底界年龄约为166.2 Ma,顶界线年龄约为160.8 Ma,沉积时间约5.4 Ma。齐古组顶部年龄值为155.3 Ma,沉积时间约5.5 Ma,包括了牛津阶的上部和基默里奇阶的中下部,其顶部与东部冀北、辽西地区髫髻山组顶部大体相当,比土城子组层位低。喀拉扎组的时代为晚侏罗世基默里奇期晚期,而其上覆地层吐谷鲁群的时代为早白垩世早期,两者之间存在一个相当大的不整合,缺失了晚侏罗世提塘期以及可能包括早白垩世最早期的地层,有超过了7 Ma的地层缺失量。侏罗系与白垩系的界线为此不整合面,侏罗纪/白垩纪之交的地层未保存。

厄瓜多尔Oriente盆地东北部区块白垩系层序地层格架及发育模式

白垩系是厄瓜多尔Oriente盆地东北部区块目前油气勘探的主要目的层位,但研究区目前勘探程度不均,对白垩系层序地层划分方案尚未形成系统的认识,极大制约了进一步的油气勘探。因此在研究区白垩系全面开展层序地层学研究具有重要的理论及实践意义。运用经典层序地层学原理与方法,依据岩芯、钻测井、地震等资料,通过识别地震反射终止关系、岩性突变及地层叠置样式变化,对Oriente盆地东北部地区白垩系各级层序边界进行识别,确定了三级层序发育II型层序边界,并建立了全区对比的精细等时地层格架,将白垩系Hollin组和Napo组划分为1个二级层序、6个三级层序、16个四级层序、34个五级层序。各级层序边界识别特征明显。白垩系作为一个较为完整的二级层序,经历了相对海平面的下降—上升—下降完整的沉积旋回,三级层序也具有明显的海进—海退旋回,响应的沉积环境经历了多期潮坪环境过渡到局限台地、内陆棚水下浅滩、外陆棚泥,随后海平面下降,演变为内陆棚灰质滩及局限台地沉积。白垩系精细等时层序地层格架的建立将为下一步有利砂体的分布及预测提供科学依据。

准噶尔盆地中部侏罗系层序地层格架

应用层序地层学地层基准面的原理和方法,综合研究准噶尔盆地中部钻井、测井及地震资料,确定层序界面的识别标志。在盆地中部侏罗系识别出两种层序界面类型(不整合面和沉积作用转换面),在井-震标定的基础上建立了层序地层格架。准噶尔盆地中部侏罗系发育5个具有等时意义的层序界面,将其划分为4个长期基准面旋回,分析侏罗系不同层序基准面上升期与下降期地层叠加样式及沉积相、微相构成,确定三工河组是盆地中部最重要的勘探目的层系,其储集层类型主要为三角洲前缘河口坝和水下分支水道,有利储集相带的展布与所处层序地层位置密切相关,主要分布于基准面上升期。

准噶尔盆地腹部白垩系底界划分

准噶尔盆地腹部白垩系与侏罗系界限存在着不同的划分方案,这给综合研究造成了混乱。白垩系与侏罗系的界线对应于燕山构造运动第Ⅱ幕产生的不整合面,在其这一不整合面上下发育众多地层-岩性圈闭,因此,白垩系底界的划分将直接影响地层-岩性圈闭的识别。基于生物群组合特征、岩性组合特征、地质模型、正演模型、地震反射等多方面资料进行不同方案的对比和论证,确定了合理的分层方案。

塔里木盆地下古生界碳酸盐岩层序界面类型划分及其意义

塔里木盆地海相碳酸盐岩储层是增储上产的重要领域。然而按照经典模式划分的碳酸盐岩层序,在生产中与目标优选及开发方式结合并不紧密,进而影响了实际生产。因此,根据不同的层序界面成因(即构造、暴露剥蚀、成岩强度等),结合塔里木盆地碳酸盐岩野外露头、地震剖面、测井曲线和岩心资料等综合因素,把海相碳酸盐岩层序界面划分为5种类型:即Ⅰ型(晚期强烈隆起喀斯特型)、Ⅱ型(早期强制海退剥蚀微喀斯特型)、Ⅲ型(早期溶蚀-弱剥蚀台地边缘型)、Ⅳ型(准同生间歇暴露浅水礁滩型)和Ⅴ型(同生无暴露碳酸盐岩台地型)。虽然不同界面类型的成因和储层特征迥异,但是依据地震、测井、钻井、岩心等现场资料很容易划分。这套层序划分可操作性强,在有利区带选择、油气高效富集区优选、开发井井型选择等方面均有很现实的生产指导意义。

准噶尔盆地车莫古隆起内物源沉积体系探讨及勘探意义——以白垩系清水河组一段为例

为了探讨车莫古隆起对内物源沉积体系及油气成藏的控制作用,从车莫古隆起形成与演化入手,利用岩心、地震、测井等资料,多种方法结合恢复其剥蚀量、古地貌,提出车莫古隆起从中侏罗世到早白垩世发育,侏罗世末是其鼎盛时期,并提供内物源,控制围绕车莫古隆起周缘沉积体系和砂体展布,从岩心、地震特征、重矿物稳定系数、古水流指向、砂岩厚度等方面给出存在依据,合理解释了古隆起控制范围内已发现油藏的砂体成因。车莫古隆起发育和潜伏埋藏期控制古油气藏的形成与分布,掀斜后内物源砂体展布、断裂体系和现今构造共同控制着油气调整、运移及次生油气藏的分布,围绕车莫古隆起发育的内物源砂体尖灭方向与现今构造高部位指向垂直和斜交区域是岩性地层油气藏有利区。围绕内物源勘探刚开始,在此认识指导下部署的沙门1、莫17、夏盐11、夏盐12等井已获得突破,腹部岩性地层油气藏勘探将进入一个油气发现新阶段。

松辽盆地上、下白垩统界线划分

松辽盆地白垩纪发育有热河生物群、松花江生物群和明水生物群,表现为三大生物群有序演化与更替。白垩纪中期是松花江生物群发育期,松花江生物群具有明显的地域性色彩,泉头组被子植物化石Trapaangulata、Platanus septentrionalis和孢粉化石Crenwellia、Xinjiangpollis、Quantonenpollenites、Lythraites和Gothanipollis显示其时代已进入晚白垩世。火山岩锆石SHRI MP法U-Pb年龄测试结果表明,营城组的年龄为(115.1±1.2)^(111.1±0.9)Ma,说明营城组已属晚Aptian期至早Albian期。磁性地层学研究表明,登娄库组-姚家组以稳定的正极性为主,仅在登娄库组上部和姚家组下部分别出现一次短暂的反极性事件。青山口阶下部具一套广泛分布富含有机碳的黑色页岩、油页岩沉积,其干酪根碳同位素表现为明显的正向偏移特征,为古湖泊缺氧事件的产物。结合生物、同位素年代、磁性地层研究的结果,认为青山口阶底部缺氧事件层对应于白垩纪古海洋Cenomanian-Turonian期界线缺氧事件,由此,给出的松辽盆地上、下白垩统的界线划分在泉头组和登娄库组之间。

内蒙古海拉尔盆地早白垩世含煤岩系层序地层与聚煤规律

利用煤田钻孔资料,对内蒙古海拉尔盆地下白垩统含煤岩系层序地层格架及聚煤规律进行研究。根据区域不整合面、下切谷砂砾岩体底面、古生物组合突变面及沉积相转换面等层序界面,将海拉尔盆地下白垩统含煤岩系划分为6个三级层序。铜钵庙组是盆地初始断陷阶段的产物;南屯组一段、二段是盆地快速沉降阶段,大磨拐河组一段、二段是盆地稳定拉张阶段,伊敏组是断陷萎缩阶段。盆地早白垩世含煤地层的煤层发育表现为东、北部好,中部次之,西南部差的特点;聚煤作用主要发生在伊敏组及南屯组二段,这2个时期构造沉降表现出间歇性、震荡性及多旋回性,保证了可容空间增加速率与泥炭堆积速率之间的平衡关系,从而形成了区域性的厚煤层。