Dolomite genesis and reservoir-cap rock assemblage in carbonate-evaporite paragenesis system

Regarding to the problem on the reservoir-cap rock assemblage evaluation in the carbonate-evaporite paragenesis system,this study examined the dolomite and reservoirs genesis and the characteristics of reservoir-cap rock assemblage.Based on the literature research of the global carbonate reservoirs and the case study on four profiles of carbonate-evaporite succession,together with geological and experimental work,three aspects of understandings are achieved.(1)Lithology of carbonate-evaporite paragenesis system is mainly composed of microbial limestone/bioclastic limestone,microbial dolomite,gypsum dolomite and gypsum salt rock deposited sequentially under the climatic conditions from humid to arid,and vice versa,and an abrupt climate change event would lead to the lack of one or more rock types.(2)There developed two kinds of dolomite(precipitation and metasomatism)and three kinds of reservoirs in the carbonate-evaporite system;and the carbon dioxide and organic acid generated during early microorganism degradation and late microbial dolomite pyrolysis process,and early dolomitization are the main factors affecting the development of microbial dolomite reservoirs with good quality.(3)In theory,there are 14 types of reservoir-cap rock assemblages of six categories in the carbonate-evaporite system,but oil and gas discoveries are mainly in four types of reservoir-cap rock assemblages,namely"microbial limestone/bioclastic limestone–microbial dolomite–gypsum dolomite–gypsum salt rock","microbial limestone/bioclastic limestone–gypsum salt rock","microbial dolomite–gypsum dolomite–gypsum salt rock"and"gypsum dolomite–microbial dolomite–tight carbonate or clastic rock".These four kinds of reservoir-cap rock assemblages should be related with the climate change rules in the geologic history,and have good exploration prospects.

Hydrocarbon accumulation in deep ancient carbonate-evaporite assemblages

The Ediacaran–Ordovician strata within three major marine basins(Tarim,Sichuan,and Ordos)in China are analyzed.Based on previous studies focusing on the characteristics of the Neoproterozoic–Cambrian strata within the three major basins(East Siberian,Oman,and Officer in Australia)overseas,the carbonate–evaporite assemblages in the target interval are divided into three types:intercalated carbonate and gypsum salt,interbedded carbonate and gypsum salt,and coexisted carbonate,gypsum salt and clastic rock.Moreover,the concept and definition of the carbonate-evaporite assemblage are clarified.The results indicate that the oil and gas in the carbonate-evaporite assemblage are originated from two types of source rocks:shale and argillaceous carbonate,and confirmed the capability of gypsum salt in the saline environment to drive the source rock hydrocarbon generation.The dolomite reservoirs are classified in two types:gypseous dolomite flat,and grain shoal&microbial mound.This study clarifies that the penecontemporaneous or epigenic leaching of atmospheric fresh water mainly controlled the large-scale development of reservoirs.Afterwards,burial dissolution transformed and reworked the reservoirs.The hydrocarbon accumulation in carbonate-evaporite assemblage can be categorized into eight sub-models under three models(sub-evaporite hydrocarbon accumulation,supra-evaporite hydrocarbon accumulation,and inter-evaporite hydrocarbon accumulation).As a result,the Cambrian strata in the Tazhong Uplift North Slope,Maigaiti Slope and Mazatag Front Uplift Zone of the Tarim Basin,the Cambrian strata in the eastern-southern area of the Sichuan Basin,and the inter-evaporite Ma-4 Member of Ordovician in the Ordos Basin,China,are defined as favorable targets for future exploration.

Rock Assemblages and Formation Ages of the Baishuijiang Group in the Southwest Qinling Orogenic Belt, Northwest China

The Baishuijiang Group, located in the southwest Qinling orogenic belt, is divided into three belts according to the characteristic of the matrix and rock blocks based on the large scale geological mapping. The north belt and south belt are composed of abyssal mudstone and siltstone, and limestone, chert and basic and ultrabasic rock blocks. The middle belt consists of a few limestone blocks and turbidites, which were formed in the trench environment. At present, in the Baishuijiang Group, many fossils were found in matrix and rock blocks, the fossils contain the Cambrian small shell fossils(Xiao, 1992;Tao et al., 1992), Silurian chitinozoas, scolecodonts and spores, and Ordovician graptolites, and middle Devonian Coral and conodonts in limestone and chert blocks(Wang et al., 2011a), and Permian radiolarians in the matrix(Wang et al., 2007). The volcanic rock blocks have undergone different degree of metamorphism. Their geochemical characteristics indicate that the rocks are similar to oceanic island arc and seamount(Wang et al., 2009), and SHRIMP U-Pb dating yielded ages from Neoproterozoic to early Paleozoic(Yan et al., 2007;Wang et al., 2009, 2011b). Therefore, comprehensive analysis of regional data, the Baishuijiang group is an accretionary complex which was consisted of matrix and blocks, and was finally formed during Permian-Triassic.

The Key Influence of Fluid in Metamorphic Rock Preserves, Mineral Assemblages, Compositions and Structures: Study from High-Pressure Eclogite and Its Amphibolization in the Western Dabie Mountains,Central China

The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should

Accumulation conditions and exploration directions of Ordovician lower assemblage natural gas, Ordos Basin, NW China

Based on drilling cores, well logging and seismic data, source rocks and reservoirs are evaluated;and the natural gas genesis is identified through the analysis of natural gas isotopes, components and fluid inclusions, to study the gas accumulation conditions of the gypsum salt rock related strata of the Ordovician lower assemblage in Ordos Basin.(1) The natural gas from Ordovician lower assemblage is high thermal evolution dry gas from marine source rock, characterized by relatively light δ^(13)C value of methane and heavy δ^(13)C value of ethane. The natural gas is identified as gas cracking from crude oil according to component analysis. Thermochemical sulfate reduction(TSR) reaction has happened between the hydrocarbon fluid and sulfate as sulfur crystals are found in the cores, hydrogen sulfide is found in the natural gas, and hydrocarbon and hydrogen sulfide fluid inclusions are widespread in secondary minerals.(2) Around the gypsum-salt lows, argillaceous rocks are extensive in the Ordovician lower assemblage, reaching a cumulative thickness of 20–80 m. The effective source rocks include argillaceous rock rich in organic laminae, algal clump and algal dolomite. Analysis shows that the source rocks have a dominant TOC of 0.1%–0.5%, 0.31% on average and 3.24% at maximum. The source rocks have an average TOC of 0.58% after recovered through organic acid salt method, indicating the source rocks have high hydrocarbon supply potential.(3) In the sedimentary period, the palaeo-uplift controlled the distribution of reservoirs. The inherited secondary palaeo-uplift in Wushenqi–Jingbian east of the central palaeo-uplift and the low uplift formed by thick salt rocks near Shenmu–Zizhou area controlled the distribution of penecontemporaneous grain shoal dolomite reservoirs. The salinization sedimentary environment of gypsum salt rock can promote the development of reservoir. There are three types of dolomite reservoirs, the one with intercrystalline pore, with dissolution pore, and with fracture;intercrystalline and dissolution pores are main reservoir spaces.(4) There are two types of cap rocks, namely tight carbonate rock and gypsum-salt rock, constituting two types of source-reservoir-cap assemblages respectively. The general accumulation model is characterized by marine source rock supplying hydrocarbon, beach facies limy dolomite reservoir, small fractures acting as migration pathways, and structural-lithologic traps as accumulation zones.(5) The third and fourth members of Majiagou Formation are major target layers in the lower assemblage. The Wushengqi–Jingbian secondary paleo-uplift area and Shenmu–Zizhou low uplift are dolomite and limestone transition zone, there develops tight limestone to the east of the uplift zone, which is conducive to the formation of gas reservoir sealed by lithology in the updip. Two risk exploration wells drilled recently have encouraging results, indicating that the two uplift zones are important prospects.

深层古老碳酸盐岩-膏盐岩组合油气成藏特征

通过分析塔里木、四川和鄂尔多斯三大海相盆地埃迪卡拉系—奥陶系,并对比参考东西伯利亚、阿曼和澳大利亚Officer三大国外盆地新元古界—寒武系的地层特征,将碳酸盐岩-膏盐岩组合划分成碳酸盐岩类和膏盐岩类互为夹层型、碳酸盐岩类和膏盐岩类互层型以及碳酸盐岩类、膏盐岩类和碎屑岩类共生型3种类型,明确了碳酸盐岩-膏盐岩组合的概念及内涵。结果表明:(1)碳酸盐岩-膏盐岩组合的油气通常来源于泥页岩和泥质碳酸盐岩两类烃源岩,咸化环境膏盐岩可促进烃源岩生烃。(2)主要发育膏云坪型、颗粒滩和微生物丘型两大类白云岩储集层,准同生期或表生期的大气淡水淋滤是储集层规模发育的主要控制因素,后期埋藏溶蚀作用对储集层有调整和改造作用。(3)碳酸盐岩-膏盐岩组合油气成藏模式可划分为盐下成藏模式、盐上成藏模式和盐间成藏模式3大类8小类模式。塔里木盆地塔中隆起北坡、麦盖提斜坡和玛扎塔格前缘隆起带寒武系、四川盆地东部—南部地区寒武系和鄂尔多斯盆地奥陶系盐间马家沟组四段等为未来的有利勘探领域。

宽高比对煤柱型冲击地压影响规律的实验研究

我国深部煤炭开采日趋复杂,区段煤柱在采动、构造或坚硬顶底板影响下极易诱发煤柱型冲击地压,煤柱型冲击地压的防治已成为煤矿安全高效开采的难题,研究不同宽高比条件下区段煤柱的力学性能及冲击破坏特性对煤柱型冲击地压防治具有积极意义。采用不同宽高比煤样的“岩-煤-岩”组合体进行了单轴压缩实验,通过分析煤岩组合体的冲击倾向性、动态破坏特征、分形维数和声发射特征参数等,研究了宽高比对煤柱冲击破坏的影响规律。结果发现:①煤柱的宽高比对煤岩组合体的冲击倾向性具有显著影响,宽高比不小于2∶1时,其冲击能量指数K_(E)为1.82~2.65,冲击倾向性无明显变化;小于2∶1时冲击倾向性呈先升高后降低的趋势,1∶1时K_(E)最大,达到了15.43。②随宽高比减小,煤岩组合体破坏特征依次表现为:拉压破坏—压剪破坏—拉剪破坏。煤柱宽高比为5∶1~3∶1时,煤岩组合体破坏较为缓慢;宽高比为2∶1时开始出现片状煤屑弹出,冲击破坏剧烈程度较低;宽高比为1∶1和0.75∶1时,具有明显的冲击破坏特性;宽高比为0.5∶1时,煤岩组合体整体稳定性下降,相对0.75∶1煤岩组合体煤柱破坏的剧烈程度降低。③峰后声发射能量释放率与分形维数D变化规律相似,均随宽高比减小呈先升高后降低的趋势。宽高比不小于2∶1时,煤岩组合体破坏过程中能量持续释放时间较长,煤柱破坏平缓;宽高比为1∶1时,能量释放率和D值明显增大,相较宽高比不小于2∶1煤岩组合体的能量释放率增大了约4倍,D值增大了0.18~0.23,煤柱冲击破坏最为剧烈;宽高比0.75∶1煤岩组合体能量释放率与D值分别降低了约10%和0.01,破坏剧烈程度与1∶1煤岩组合体相近;宽高比减小至0.5∶1时,相关参数的降低幅度约为0.75∶1煤岩组合体的6倍,破坏剧烈程度相对较小。研究表明:宽高比对煤柱的冲击破坏具有显著影响,整体上,煤柱冲击破坏剧烈程度随宽高比减小(5∶1~0.5∶1)呈先升高后逐渐降低的趋势;煤柱宽高比大于3∶1时,煤柱冲击危险性相对较小,煤柱宽高比为1∶1和0.75∶1时冲击危险性较大,0.5∶1次之。

层状复合夹煤岩石组合体试样强度试验与破坏特征研究

针对巷道复合夹煤组合结构顶板易冒落问题,以某矿取芯和钻孔窥视探测获得的巷道层状复合夹煤顶板结构组合类型为实验背景,对砂质泥岩、中砂岩以及煤厚度为20、30、40 mm不同结构组合类型的复合试件进行了单轴压缩试验,研究了复合夹煤岩石组合体的力学特性与破坏特征。试验结果表明:复合夹煤岩石组合体的抗压强度均小于单一岩石,中砂岩夹煤厚度为30mm时抗压强度达到单一中砂岩抗压强度的85.95%,抗压强度随着煤厚变薄而下降;砂质泥岩夹煤厚度为20 mm时仅为单一砂质泥岩抗压强度的32.5%,随着夹煤厚度增加抗压强度也增大,夹煤厚度超过30mm后抗压强度增大不明显。复合夹煤岩石组合体整体呈X状共轭斜面剪切破坏、单斜面剪切破坏、部分拉伸破坏,随着复合夹煤岩石组合类型不同呈现不同的破坏特征等。

陆相细粒沉积岩岩相组合类型划分研究现状及其油气地质意义

细粒沉积岩是陆相页岩油气重要的烃源岩和储集层。然而该类岩石具有岩相类型多样、垂向叠置复杂的特征,已知大部分获得高产油气井对应的甜点层通常为多种岩相类型的组合。当前,细粒沉积岩岩相分类方案仍存在分歧,岩相组合相关研究尚处于初步阶段。通过对比近年来国内学者关于陆相细粒沉积岩岩相类型划分方案的差异性,梳理了岩相组合的划分依据,探寻岩相组合划分新方法及其研究的油气地质意义。认为在岩相类型识别基础上,开展天文旋回理论指导下的岩相组合类型划分、展布特征刻画,对于陆相页岩油甜点精细预测具有重要意义;分析不同岩相组合源-储耦合特征、油气分布特征,注重微运移的相关研究有助于提升对页岩油气差异性富集的认识。

蒙古—鄂霍次克洋俯冲的火成岩记录:来自大兴安岭花岗岩类的证据

大兴安岭地区出露大规模的中生代花岗岩类岩石,它们的形成与蒙古—鄂霍次克洋或古太平洋的关系仍具有争论(杨华本等,2020;王亚东等,2023)。本研究通过野外调查采样,对大兴安岭北部黑河—白石砬子一带附近出露的18个花岗岩类岩石样品进行了岩石学、地质年代学和地球化学研究。

加载速率对煤岩组合体强度特征的影响

为研究加载速率对煤岩组合体强度特征的影响,采用离散元方法分析了不同加载速率下,煤岩组合体强度参数、裂纹数演化和AE计数的变化规律。结果表明:煤岩组合体的起裂应力和峰值应力随加载速率增加而增加,除加载速率为10 mm/s的情况,其他加载速率下试样峰值应变随加载速率的增加而增加,弾性模量随加载速率的增加而减小。不论加载速率量级如何变化,裂纹均以拉伸为主。加载速率较低时,裂纹在加载前期为平静阶段,在接近破坏时出现陡增;加载速率较高时,平静期缩短,表现为加载前期或中期的指数型增加。在高加载速率下,峰值应力后,AE计数仍有较长时期的波动区间。高加载速率条件下,应力-应变曲线存在大范围波动,表明随着加载速率增加,煤岩组合体整体失稳更严重。

Geochemical Features and Tectonic Settings of Upper Ordovician Marine Volcanic Rocks on North Margin of Qaidam

The geochemical and petrological features show that the Upper Ordovician marine volcanic rocks on north margin of Qaidam can be classified into three main kinds of petrotectonic assemblages. The three assemblages exhibit features of tectonic melange. And they indicate that there exists an ancient ocean basin on north margin of Qaidam during Late Ordovician period. At the last stage of Ordovician period, the ocean basin on north margin of Qaidam closed gradually, then Qaidam continental block subducted continually and Qilian continental block thrusted onto Qaidam continental block in the direction from north to south, formed the orogenic belt of continent to continent collision type. As a result, a three unit tectonic model is proposed. The three units are: the overlying Qilian crustal wedge, the collision tectonic melange belt on the north margin of Qaidam and the Qaidam underthrusted wedge.

甘肃北山地区“牛圈子蛇绿岩”属性再研究

牛圈子蛇绿岩被认为是甘肃北山构造单元划分的重要依据,但是其蛇绿岩属性的真实性一直没有得到有效的验证。本次研究工作通过1∶5万地质调查和剖面研究,查明其岩石组合、接触关系及野外产出特征;通过对辉长岩岩石地球化学测试与分析,讨论其形成的大地构造背景。研究认为原划牛圈子蛇绿岩岩石组合缺失严重、火山熔岩极不发育、缺失超基性岩、没有混杂堆积特征,没有“岩块+基质”的物质组成样式,也没有深海沉积的记录;同时,辉长岩具有明显壳幔混源的岩石地球化学特征,与N-MORB和OIB的微量元素特征差异较大。综合研究认为前人划分的牛圈子蛇绿岩可能不是典型的蛇绿岩。

煤岩组合体变形破裂声发射特征及损伤演化规律研究

为研究煤岩组合体变形破裂过程中煤厚对其声发射特征和峰前损伤特性的影响,对煤厚分别为20mm、33.33mm和60mm的三种煤岩组合体进行室内单轴压缩声发射试验。研究表明:随着煤厚的增加,煤岩组合体的单轴抗压强度和声发射峰值计数均下降,且煤厚与声发射峰值计数满足指数函数关系;组合体的破坏持续时间随煤厚的增加而变长;声发射累计数的变化情况可分为缓慢增长阶段、快速增长阶段和声发射峰值及破坏后阶段,前两个阶段,累计数增长的速度与煤厚呈正相关,最后一个阶段,呈负相关。组合体峰前损伤演化可分为初始损伤、损伤稳定发展和损伤突增不稳定发展三个阶段;损伤变量与应变满足幂指数函数关系,且随着煤厚的增加,组合体D=1时对应的峰值应变也增加。

四川盆地东部中二叠统茅口组孤峰段展布特征及其油气地质意义

基于钻井岩-电特征和野外露头特征,结合区域沉积-构造格局,利用宏观及微观观察、主微量及稀土元素测试、总有机碳含量和镜质体反射率测定等手段对四川盆地东部中二叠统茅口组孤峰段展布特征、沉积环境和成藏条件进行研究。结果表明:①川东地区茅口组孤峰段的存在,证实茅口中、晚期受构造-沉积分异的影响,出现槽台格局。在茅口组二段B亚段沉积期(茅二B沉积期),川东地区孤峰段主要分布在盆地东北角。在茅口组二段A亚段沉积期(茅二A沉积期),孤峰段向南扩大到渠县—大竹—梁平,呈北西-南东向带状展布,厚度在0.8~26.6 m,川西北-川北则对应茅口组三段(茅三段)或茅口组四段(茅四段)。②孤峰段硅质页岩富含硅质放射虫,有机质含量高,具有典型的深水海槽相沉积特征。地球化学测试数据反映硅质页岩为深水缺氧还原环境且盐度较高,硅质来源以生物硅为主。③孤峰段烃源岩为一套富有机质的优质烃源岩,总有机碳含量整体较高、变化范围大,分布在1.69%~38.27%,平均值为11.51%,处于成熟-过成熟阶段。④川东地区孤峰段优质烃源岩可通过断裂与开江-梁平海槽礁滩相储层沟通,构成“下生上储”的源-储关系;此外,也可与茅口组优势滩相储层形成“旁生侧储”的成藏组合。川东地区孤峰段有望作为区域内优质烃源岩的接力勘探层系,对研究区内下一步油气勘探开发具有重要意义。

柴达木盆地英雄岭页岩纹层结构特征及石油地质意义

柴达木盆地英雄岭构造带干柴沟地区下干柴沟组上段(E32)Ⅳ—Ⅵ油组发育一套咸化湖相页岩,碳酸盐矿物含量高,纹层发育。该层系页岩油勘探取得了重大进展,纹层结构特征、沉积机理、有利岩相组合等急需深入研究。岩心描述、薄片鉴定、扫描电镜、X—射线衍射等分析结果表明:干柴沟地区页岩纹层结构可分为水体分层型纹层结构(Ⅰ型)、季节型纹层结构(Ⅱ型)、洪水阵发型纹层结构(Ⅲ型)3类,其中Ⅰ型纹层结构为典型纹层结构,相对占比为70%,由黏土质纹层与方解石纹层构成偶纹层,单纹层厚度为0.1~0.5mm,为咸水湖水体季节性分层条件下沉积的纹层结构。夏秋季水体分层,上层水体有利于微生物繁衍;冬春季水体分层消失,有利于有机质沉积和保存,同时,Ⅰ型纹层结构沉积速率慢,有利于有机质富集,TOC平均为1.33%。Ⅱ型纹层结构相对占比为20%,由黏土质纹层与粉砂质纹层组成,单纹层厚度为0.5~1mm,沉积与陆源输入物的季节性变化有关,沉积速率快,TOC平均为0.47%。Ⅲ型纹层结构相对占比为10%,由黏土质纹层与粉砂质纹层组成,单纹层厚度为0.5~2mm,发育微冲刷面、透镜状粉砂脉等,反映沉积时具有一定水动力条件,非静水沉积,与重力流、湖流相关,沉积速率快,TOC平均为0.27%。干柴沟地区页岩主要分布于半深湖区,沉积单旋回自下而上为泥岩→页岩→泥质白云岩→白云岩,期间偶发砂质重力流沉积。Ⅰ型纹层结构页岩沉积序列上与白云岩叠置分布,白云岩孔隙度平均为9.8%,微观尺度上形成良好的源储组合,有利于页岩油成藏,为干柴沟地区页岩油有利岩相组合;宏观尺度上该套页岩层系TOC高,物性好,脆性矿物含量高,是柴达木盆地页岩油勘探开发的理想层系。Ⅱ型纹层结构页岩、Ⅲ型纹层结构页岩生烃能力差,对油气成藏贡献小。

土岩组合深基坑围护结构受力与变形特性分析——以青岛海天中心深基坑为例

为了研究土岩组合二元地层超深基坑受力、变形和邻近建筑沉降随基坑开挖的演化规律,依托于青岛海天中心城市综合体桩锚支护结构体系超深基坑工程,对预应力锚索轴力、基坑水平和竖向位移以及周边建筑物沉降进行了实时监测。结果表明,基坑开挖期间内,预应力锚索轴力随时间的变化规律主要分快速下降、稳定变化和基本稳定3个阶段,锚索轴力平均损失率约为15.08%;基坑最大水平位移为12.30 mm,最大竖向位移为11.01 mm,基坑临近建筑物最大沉降量为1.2 mm,远小于设计和现行《建筑基坑工程监测技术标准》的容许变形值,说明桩锚支护结构体系可以有效控制基坑变形,确保毗邻建筑物安全;同时表明该基坑的支护设计方案有较大的优化空间,从而节约工程成本。研究成果对相似地质条件的超深基坑围护结构设计具有重要参考价值。

中非走滑裂谷盆地群石油地质特征与勘探方向

中非走滑裂谷盆地群是在中非剪切带影响下形成的中、新生代陆相裂谷盆地,构造复杂多样且勘探程度较低,成藏规律认识不清制约了该区的油气勘探发现。基于盆地构造、沉积、成藏组合特征和已发现油气田解剖,总结盆地油气富集规律和主控因素,并分析了勘探潜力和方向。研究认为,中非走滑裂谷盆地群在早白垩世以来经历了多期伸展、走滑和反转等构造活动,对沉积地层、构造特征和油气成藏具有较强的控制作用;受储盖组合和构造演化的影响,中非走滑裂谷盆地群不同盆地的油气发现和成藏组合有较大差异,总体表现为“西富东贫、下稀上稠”的特点;油气富集的主控因素是有效生烃灶、构造活动和断层;西部Doba盆地油气最为富集,发育多套成藏组合,上、下白垩统均已经获得规模发现,未来主要勘探方向包括下白垩统岩性圈闭和基岩圈闭;中部Doseo盆地上白垩统缺乏有效盖层,主要勘探目标为下白垩统砂泥岩组合,圈闭类型为走滑形成的断背斜、断块圈闭,基岩潜山是潜在的勘探目的层;东部的Salamat盆地尚未证实有效的成藏组合,勘探潜力有限。

中国东南部晚中生代盆岭格局及其构造—岩浆作用

晚中生代时期,中国东南部位于日本—中国台湾火山岛弧的后缘。中侏罗世—晚白垩世期间,受太平洋板块朝东亚陆缘俯冲以及弧后扩张作用的影响,中国东南部广泛发育了伸展断陷盆地和火山—侵入岩岩系。盆地类型包括中侏罗世的裂谷盆地、晚侏罗世—早白垩世的火山碎屑—熔岩断陷盆地、晚白垩世—古近纪的红色碎屑断陷盆地等3种,火成岩岩系则主要由花岗岩类、双峰式火成岩、碱性花岗岩、变质核杂岩与穹隆状花岗岩等组成。盆地形成时代和岩浆岩侵位结晶时代相近,年龄峰期140~110 Ma(早白垩世),两者紧密分布在一起,构成早白垩世中国东南部盆岭构造。文章对中国东南部晚中生代盆地和岩浆岩山岭的基本地质特征进行了归纳,对火成岩系列的岩石学和构造地质等特征以及形成中国东南部盆岭格局的制约因素进行了分析。最后,对中国东南部晚中生代地球动力学演化过程进行了探讨。

塔里木盆地沙井子断裂带油气地质条件及勘探潜力

通过钻井、地震和野外露头等资料的综合分析,根据构造特征及派生断层的差异性,将塔里木盆地沙井子断裂带划分为东段、西段、中段及阿恰段等4段。沙井子断裂带具有加里东晚期开始发育、海西期—印支期—燕山期多期活动、喜马拉雅期定型的演化特征,发育构造、地层、潜山等多种类型的圈闭,是油气运聚的有利区。研究表明:①下寒武统玉尔吐斯组和中奥陶统萨尔干组2套优质烃源岩为研究区油气的主要来源;②寒武系盐下丘滩相白云岩、志留系柯坪塔格组潮坪-滨岸复合沉积相的潮汐水道砂岩及滨岸砂坝、三叠系俄霍布拉克组扇三角洲及克拉玛依组辫状河三角洲砂岩为研究区的3套主要储层;③中寒武统厚层膏盐岩、志留系塔塔埃尔塔组泥岩夹层及依木干他乌组厚层泥岩、三叠系俄霍布拉克组及克拉玛依组泥岩夹层为研究区的3套主要盖层;④油气充注呈现多期性、以晚期为主的特点。建立了志留系、三叠系“构造主控、多期充注、晚期成藏”和寒武系盐下“构造主控、连续充注”2种油气成藏模式,指出沙井子断裂带下盘的志留系和三叠系、上盘阿恰段的寒武系盐下为有利勘探区。