The Mianlue Ocean between the South China and South Qinling (SQB) blocks records the separation, accretion, and unification of the eastern Palaeo-Tethys during the Palaeozoic. However, the timing of its opening and closing have not been well constrained. In this study, we integrate petrology, heavy minerals, detrital zircon U-Pb geochronology, and zircon double-dating (U-Pb and fission-track) of Silurian–Devonian clastic deposits from the Longmenshan Range on the northwesten margin of South China Block to constrain the evolution of the Mianlue Ocean from a source–sink perspective. Results show that the Silurian and Lower–Middle Devonian samples are dominated by Neoproterozoic (1100–700 Ma) detrital zircons that were sourced southwesterly from the Jiangnan Orogenic Belt and Kangdian Palaeoland. In constrast, Lower–Middle Devonian samples have an additional Early Palaeozoic peak (520–592 Ma), which is interpreted to be recycled from the ancient strata of the Kangdian Palaeoland as evidenced by the increase in RuZi and rutile contents and the inherited characteristics of zircon age assemblages. Detrital zircon age comparision between the Silurian-Devonian deposits from the Longmenshan and southern SQB indicates a transition from shared to independent provenance systems during the Middle Silurian to Middle Devonian, resulting from the opening of Mianlue Ocean. Zircon double-dating constrain the rift initiation, subduction initiation and collisional closure of the Mianlue Ocean at 425 ± 10 Ma, 308 ± 19 Ma and 232 ± 35 Ma, respectively. These data provide new geochronological evidence constraining the evolution of the ocean–continent palaeo-geographic pattern in the eastern Palaeo-Tethys Ocean.

The Palaeozoic carbonate basement of the Offshore Bohai Bay Basin (OBBB) presents considerable potential for hydrocarbon exploration. However, the multistage tectonism and complex superimposed palaeo-karstification in the area are unclear, which leads to a lack of understanding on the formation mechanism and distribution of the deep carbonate basement reservoirs. In this study, the occurrence of a fracture-vug network and its fillings in carbonate reservoirs were investigated based on borehole cores, thin sections, and image logs from the southwestern slope of the OBBB's Bozhong Sag. Then the diagenetic fluid properties of the carbonate matrix and fillings were analysed via the data of carbon, oxygen, and strontium isotopes, and major, rare elements from coring intervals. The results revealed that fracture-related karst reservoirs have lithologic selectivity inclined toward dolomite strata. The intersecting relationships, widths, and strikes of the fractures and the regional tectonic background indicate three structural fracture families: NW-, NNE-, and NNW- trending, related to the Indosinian, middle Yanshanian, and late Yanshanian orogeny, respectively. The Indosinian NW- and end-Mesozoic NNE-trending fractures produced by compressional tectonic stress mainly contributed to the formation of the basement reservoirs. The geochemistry of the calcite veins filling these fractures suggests two main types of diagenetic fluids. The fluid of autogenic recharge related to the earlier fills is karstification diffuse flow dominated by internal runoff from rainfall in the highland setting of the Indosinian thrusting orogenic belt. The other fluid of allogenic recharge related to the later fills is the main lateral freshwater flow dominated by external runoff from the catchment in the setting of the horst-lowland within the rifting basin, induced by the Yanshanian destruction of the North China Craton. Finally, the relationship between the three fracture families and two kinds of related fluids is revealed. This allows us to propose a model to understand the polyphase-superimposed fracture-related karst reservoir complexes within the deep carbonate basement of tilting fault blocks that neighbour the Bozhong hydrocarbon kitchen and predict the formation of potential plays with high accuracy.

Ultra-deeply buried (>5000 m) marine carbonate reservoirs have gradually become important exploration tar-gets. This research focuses on providing an understanding of the basic elements of the ultra-deeply buried Middle Triassic Leikoupo marine carbonate petroleum system within the Western Sichuan Depression, China. Comprehensive analyses of organic geochemistry, natural gas, and C-H-He-Ne-Ar isotope compositions suggest that the reservoir is charged with compound gases from four source rock units including the Permian Longtan, Middle Triassic Leikoupo, Late Triassic Maantang and Xiaotangzi formations. Approximately a 50-m thick outcrop and 100-m length of drilling cores were examined in detail, and 108 samples were collected from six different exploration wells in order to conduct petrographic and petrophysical analyses. Thin-section and scanning electron microscope (SEM) observations, helium porosity and permeability measurements, mercury injection capillary pressure (MICP) analysis, and wire-line logging (5500-6900 m) indicate that the reservoir lithologies include argillaceous algal limestones, dolograinstones, crystalline dolostones, and microbially-derived stromatolitic and thrombolitic dolostones. Reservoir properties exhibit extreme heterogeneity due to different paleogeographic environmental controls and mutual interactions between constructive (e.g., epigenetic paleo-karstification, burial dissolution, structural movement, pressure-solution and dolomitization) and destructive (e.g., physical/chemical compaction, cementation, infilling, recrystallization, and replacement) diagenetic pro-cesses. An unconformity-related epigenetic karstification zone was identified in the uppermost fourth member of the Leikoupo Formation, which has developed secondary solution-enhanced pores, vugs, and holes that resulted in higher porosity (1.8-14.2%) and permeability (0.2-7.7 mD). The homogeneity and tightness of the reservoir increases with depth below the unconformity, and it is characterized by primary intergranular and intra-crystalline pores, solution pores, fractures, stylolites, and micropores with a lower helium porosity (0.6-4.1%) and permeability (0.003-125.2 mD). Regional seals consist of the Late Triassic Xujiahe Formation, comprised of-300 m of mudstones that are overlain by-5000-m thick of Jurassic to Quaternary continental argillaceous overburden rocks. Effective traps are dominated by a combination of structural-stratigraphic types. Paleo-reservoir crude oil cracking, wet-gases, and dry-gases from three successive hydrocarbon generation processes supplied the sufficient hydrocarbon resources. The homogenization temperatures of the hydrocarbon-associated aqueous fluid inclusions range from 98 to 130 degrees C and 130-171 degrees C, which suggests hydrocarbon charging occurred between 220-170 Ma and 130-90 Ma, respectively. One-dimensional basin evolution models combined with structural geologic and seismic profiles across wells PZ1-XQS1-CK1-XCS1-TS1 show that hydrocarbon migration and entrapment mainly occurred via the unconformity and interconnected fault-fracture networks with migration and charging driven by formation overpressure, abnormal fluid flow pressure, and buoyancy forces during the Indosinian and Yanshanian orogenies, with experiencing additional transformation occurring during the Himalayan orogeny. The predicted estimated reserves reached-300 x 109 m3. The results provide excellent scientific implications for similar sedimentary basin studies, it is believed that abundant analogous deeply buried marine carbonate hydrocarbon resources yet to be discovered in China and elsewhere worldwide in the near future.

攀枝花市地处金沙江干热河谷,地下水及地热资源丰富,但目前对地下水的化学特征和分布特征,地热资源的形成机理和分布特征尚未有较为深入的研究.本次研究通过野外剖面实测、室内化学分析(离子浓度、水样的矿化度和硬度)等方法,结合区域构造背景和热红外遥感数据,对攀枝花市西区的地下水分布情况和地热分布条件开展了分析,并预测了地下水和地热资源的有利分布区.结果表明,攀枝花市西区主要有三种类型的地下水,其中震旦系灯影组顶部岩溶水为Ca(HCO3)2型,水体硬度平均值为170.42 mg/L,Ca2+,Mg2+含量较高;前震旦系基岩顶部风化壳—裂缝型地下水为NaHCO3型,水体硬度为272.8 mg/L,K+,Na+含量较高;上三叠统丙南组砂岩裂缝—孔隙型地下水为NaHCO3型,水体硬度为91 mg/L,可以作为饮用水,且Na+含量高;三种类型的地下水中,灯影组碳酸盐岩岩溶水与前震旦系基岩风化壳裂隙—孔隙水分布最广.研究区地热资源地质条件良好,区域内广泛分布的深大断裂提供热流通道、多期次的岩浆活动所提供的余热与广泛分布的岩浆岩中富含放射性元素的衰变释放能量是研究区热富集的主要原因.根据本次研究预测了 4个地下水有利富集带和6个地热资源有利区,为该地区未来地下水和地热资源勘探提供了参考.

渤海湾盆地渤南低凸起潜山具有极好的勘探前景,但目前与其相关的研究尚不系统.文中运用测井、录井资料及实际生产数据,通过岩石薄片镜下观察及实测储层孔渗等实验测试手段,对渤南低凸起BZ28-1构造带碳酸盐岩潜山储层岩石学特征、储集空间类型及储集物性特征进行了分析,并探讨了潜山有利储层形成的主控因素.结果 表明:渤南低凸起潜山岩性主要为晶粒云岩,其次为晶粒灰岩、颗粒灰岩和颗粒云岩;储层储集空间以溶蚀孔洞为主,其次为裂缝,储层类型以裂缝-孔隙复合型为主;储层整体以低孔、低渗储层为主;潜山有利储层的形成主要受区域沉积相、古岩溶作用、构造破裂作用、白云石化作用等控制,其中沉积相是有利储层形成的基础.

Based on the field outcrops surveyed, combined with recent published the regional tectonic evolution and geochronology data, we analyzed the lithologies and rock associations of strata, identified the sedimentary facies types, and discussed the distribution sedimentary facies and the hydrocarbon accumulation in the eastern Qiangtang basin during the Late Triassic – Jurassic. Marked by regional unconformities, there are two tectono‐stratigraphic units (from the Carnian to the Norian and from the Rhaetian to the Kimmeridgian, respectively) in the eastern part of Qiangtang basin. We systematically described the distribution range, thickness variation and lithological characteristics of different formations in the tectono‐stratigraphic units. The Late Triassic‐Jurassic is dominated by marine facies and marine ‐ continental transitional facies. The marine ‐ continental transitional facies include deltaic and tidal‐lagoon facies. Marine facies including gentle carbonate slope, evaporative platform, restricted platform, littoral, neritic, bathyal and abysmal facies. The Carnian stage is dominated by littoral–neritic–bathyal–abysmal facies in the north Qiangtang depression otherwise the littoral–neritic facies in the south Qiangtang depression. The early Norian stage is dominated by carbonate gentle slope‐mixed continental shelf facies. The late Norian, Bajocian, Callovian and Kimmeridgian stage are dominated by tidal flat‐delta facies in the north Qiangtang depression and littoral‐neritic facies in the south Qiangtang depression. The Bathonian and Oxfordian stage are dominated by evaporative platform‐ restricted platform‐ mixed continental shelf facies. The sedimentary facies formed zones from north to south and extended in an E–W direction. The Eastern Lower Uplift (ELU) played an important role in the division zones of sedimentary facies from north to south. During the Bathonian and Oxfordian, the ELU developed below the sea level and controlled the distribution of restricted platform, evaporative platform and platform margin. We analyzed 20 source rock samples from the upper Triassic‐Jurassic. The total organic carbon (TOC) value from Qoimaco, Buqu and Adula Formations. of late Triassic‐Jurassic in the eastern Qiangtang basin are ranges from 0.17∼0.33% (average 0.28%), 0.05∼0.25% (average 0.15%) and 10.32∼28.78% (average 19.33%), respectively. Obviously, the Adula Fm. developed good source rocks. The values of Tmax and S 1 +S 2 in the Adula formation are 459–461°C (average 460°C) and 6.75‐28.55 mg/g (average 18.18mg/g), indicating that the Adula source rock has reached high‐over‐maturity stage. The bathyal, gentle slop and platform facie belts of the Upper Triassic can configurate the good hydrocarbon prospects in the northeastern area of the Qiangtang basin.

探讨川南-黔北地区下寒武统筇竹寺组(牛蹄塘组)海相泥质烃源岩发育特征及控制因素.在钻井资料及野外剖面调查、对筇竹寺组(牛蹄塘组)沉积相特征分析的基础上,利用烃源岩地球化学分析资料对有机质丰度、类型和成熟度等参数进行评价.结果 表明,川南-黔北地区筇竹寺组(牛蹄塘组)发育了一套黑色碳质页岩、黑色-深灰色泥页岩、灰色砂质泥岩与灰质泥岩;沉积相类型为陆棚相,有深水泥质陆棚、深水含磷硅质陆棚及浅水砂质或灰质陆棚3种亚相,其中深水陆棚相发育的碳质页岩、黑色-深灰色泥页岩与深水含磷硅质陆棚相发育的磷块岩、黑色-深灰色碳质含磷页岩及黑色硅质页岩为富烃源岩,浅水陆棚相发育的灰色泥页岩或砂质泥岩、灰质泥岩为一般烃源岩.烃源岩地球化学特征显示,绵阳-长宁拉张槽内及黔北地区一般为好-极好烃源岩,槽外浅水陆棚区为中等-差的烃源岩;以腐泥型(Ⅰ型)为主,生烃能力强,为油型有机质;烃源岩成熟度高,整体达到过成熟阶段(Ro>2.0％).川南-黔北地区下寒武统烃源岩分布明显受绵阳-长宁拉张槽控制,拉张槽内与黔北地区为烃源岩发育的中心,富烃源岩厚度大;拉张槽外富烃的烃源岩厚度小或没有富烃的烃源岩分布;拉张槽内发育的强生烃区控制了川中—川南海相"下组合"天然气藏的分布,预测宜宾—长宁—筠连—威信一带和内江—资中一带有较好的勘探潜力.

The physical properties, group composition, stable carbon isotope, and biomarker compound distribution characteristics of crude oil in the Archean buried hill were studied and compared with the geochemical characteristics of Paleogene crude oil, in order to discuss the geochemical characteristics and sources of crude oil from the Archean buried hill JZ25-1S in the Liaoxi Low Uplift. The crude oil from the second member of the Paleogene Shahejie Formation and the Archean buried hill in this area are mainly light and medium crude oil. The oil has medium saturated hydrocarbon, high aromatic hydrocarbon, high non-hydrocarbon and asphaltene contents. The carbon isotopes of the crude oil are distributed between -26.2‰ and -24.4‰, and the isotopic fractionation among group components is small. The chromatographic curve clearly shows the "bulge" formed by biodegradation, the single peak and post-kurtosis state is dominant, the Pr/Ph value is generally around 1.3, and the Pr/nC17, Ph/nC18 values are both high. The sterane characteristics of crude oil show a high gammacerane abundance, the C27 rearranged sterane and 4-methyl sterane contents are medium, the dinostane content is low, and the regular sterane C27, C28, C29 fingerprints are partial"V" or "L" shaped. However, the characteristics of Archean crude oil from wells JZ25-1S-4D and JZ25-1-10D are quite different from the above-mentioned crude oil. Comprehensive analysis suggests that the main body of crude oil from the Paleogene and Archean buried hills in the JZ25-1S area is a mixture from the Es3 member of the Liaoxi Sag and the Es1 member of the Liaozhong Sag. Its parent material comes from a weakly reducing environment with moderate salinity and is mainly derived from algae and other phytoplankton. The crude oil has a high degree of maturity and is severely biodegraded. The Archean buried hill crude oil from wells JZ25-1S-4D and JZ25-1-10D is derived from the Es3 member source rock in the Liaoxi Sag, which was deposited in a weakly reducing freshwater environment with high maturity and weak biodegradation.

A scientific exploration well (CK1) was drilled to expand the oil/gas production in the western Sichuan depression, SW, China. Seventy‐three core samples and four natural gas samples from the Middle–Late Triassic strata were analyzed to determine the paleo‐depositional setting and the abundance of organic matter (OM) and to evaluate the hydrocarbon‐generation process and potential. This information was then used to identify the origin of the natural gas. The OM is characterized by medium n‐alkanes (nC 15 –nC 19 ), low pristane/phytane and terrigenous aquatic ratios (TAR), a carbon preference index (CPI) of ∼1, regular steranes with C 29 > C 27 > C 28 , gammacerane/C 30 hopane ratios of 0.15–0.32, and δ D org of −132‰ to −58‰, suggesting a marine algal/phytoplankton source with terrestrial input deposited in a reducing–transitional saline/marine sedimentary environment. Based on the TOC, HI index, and chloroform bitumen “A,” the algal‐rich dolomites of the Leikoupo Formation are fair–good source rocks; the grey limestones of the Maantang Formation are fair source rocks; and the shales of the Xiaotangzi Formation are moderately good source rocks. In addition, maceral and carbon isotopes indicate that the kerogen of the Leikoupo and Maantang formations is type II and that of the Xiaotangzi Formation is type II–III. The maturity parameters and the hopane and sterane isomerization suggest that the OM was advanced mature and produced wet–dry gases. One‐dimensional modeling of the thermal‐burial history suggests that hydrocarbon‐generation occurred at 220–60 Ma. The gas components and C–H–He–Ar–Ne isotopes indicate that the oil‐associated gases were generated in the Leikoupo and Maantang formations, and then, they mixed with gases from the Xiaotangzi Formation, which were probably contributed by the underlying Permian marine source rocks. Therefore, the deeply‐buried Middle–Late Triassic marine source rocks in the western Sichuan depression and in similar basins have a great significant hydrocarbon potential.

渤海湾盆地渤海海域渤中19-6深层潜山构造带周缘发育多个富烃深次洼,油气聚集条件复杂,对其油气的有机地球化学特征及主要来源认识尚不明确.为此,利用饱和烃及轻烃色谱、色谱—质谱、天然气组分及碳同位素组分检测等地球化学测试技术对该潜山构造带的原油、天然气与其周缘富烃深次洼烃源岩的地球化学特征进行对比分析,运用油—源生物标志化合物分析技术,系统研究了渤中19-6潜山构造带油气的来源与特征.结果表明:①渤中19-6深层潜山构造带周缘凹陷主要发育古近系东营组二段下亚段、东营组三段、沙河街组一段及沙河街组三段上亚段等4套烃源岩,其中东三段和沙三上亚段烃源岩为其主力烃源灶,有机质丰度较高,为偏腐泥混合型有机质类型,已进入生烃高峰期;②深层太古界潜山及上覆古近系孔店组天然气为典型的油型气,具有不同成熟度天然气混合特征,成藏过程具有多阶段性;③浅层与深层油气来源都具有3套烃源岩混源输入的特征,但仍存在着差异性,其中浅层油气来源以东三段烃源岩的输入为主,并且可能存在着东二下亚段烃源岩的输入,而深层油气来源则以沙三上亚段烃源岩的输入为主.结论认为,该区油气源条件复杂,油气源主要以周缘富烃深次洼内沙三上亚段烃源岩为主,其深层凝析气藏表现出多期次油型气输入的特征.

探讨渤海湾盆地石臼坨凸起潜山储层的成藏过程与成藏机理.运用流体包裹体技术,结合油-源抽提物及生物标志化合物等有机地球化学特征,对油气来源、成藏过程及成藏机理进行研究.石臼坨凸起主体原油表现为混源油特征,为渤中凹陷供油,存在一定的生物降解;428构造带北侧原油主要来自秦南凹陷沙三段及沙一段烃源岩;427构造带及428构造带南侧原油主要来自渤中凹陷沙三段及沙一段烃源岩.包裹体镜下特征、均一温度及盐度表明,428E/W构造带潜山储层在前古近系存在油气充注过程,而在古近系烃源岩成熟以后,潜山储层又经历了油气充注过程,对应充注时间为3 MaB.P..该区油气来源丰富,晚期大量油气快速充注潜山储层,具有较高的勘探开发价值.但成藏过程复杂,基于潜山结构特征、供烃模式及输导体系划分为“三层侵蚀双源复式输导晚期型”和“双层单源复式输导晚期型”2种成藏模式.

锦州南潜山油田和渤中19-6潜山大气田的发现揭示出渤海海域深层潜山具有巨大的油气勘探潜力.但是,该区复杂多样的潜山结构导致潜山分类方案繁多,制约了对渤海海域潜山类型及油气成藏规律的认识.为此,基于该区已钻井和三维地震资料,在区域地质背景分析的基础上,研究渤海海域潜山地层结构和断裂分布特征,明确潜山构造特征和潜山演化动力力学机制,讨论潜山分类方案,进而评价潜山带的油气勘探潜力.研究结果表明:①中生代以来的历次构造运动奠定了渤海海域潜山构造的发育基础,侏罗纪—白垩纪的燕山运动主导了潜山内幕构造样式和外部形态的形成,新生代以来的晚期断陷走滑活动对潜山具有加强及定型作用;②渤海海域前古近系构造层自下而上可划分为太古界—元古界构造层、古生界构造层和中生界构造层;③潜山构造样式可划分为挤压褶皱、伸展断裂、走滑、反转、底辟等5种类型;④渤海海域潜山具有多成因、多结构、多岩性、多形态的复杂特征,依据潜山的“成因—结构”分类原则将其划分为2大类7小类,其中侵蚀残丘型潜山和拉张断垒型潜山具有较好的油气勘探前景.结论认为,渤中低凸起PL7-1中生界潜山与辽西凸起SZ36-1潜山具有较好的油气勘探前景,辽西凸起南端、渤海海域西部的沙垒田凸起西侧—歧口凹陷和渤中凹陷西南缓坡带是有利的潜山油气成藏区.

There are abundant hydrocarbon resources in the western subsag of Bozhong sag in the Bohai Bay Basin, where oil–gas discoveries have been made in those shallow Neogene and Paleogene reservoirs and deep Mesozoic buried hill reservoirs, but no better understandings have yet been achieved in terms of the process of hydrocarbon accumulation and the relationship between deep buried hill reservoirs and the allocation of shallow reservoirs. Based on the organic geochemical analysis of source rocks and basin modeling of hydrocarbon generation evolution, distribution characteristics of fluid inclusion and homogeneous temperature measurement, combined with the characteristics of oil-source biomarkers, the process of hydrocarbon accumulation in this study area was resumed based upon the regional tectonic background. The following findings were obtained. (1) There are 3 sets of source rocks in the third and first members of Paleogene Shahejie Fm, and the second lower member of Paleogene Dongying Fm; the reservoirs in the peripheral uplift zones include Mesozoic volcanic rocks, Archean metamorphic rocks, and Paleogene–Neogene delta–fluvial porous sandstones. Hydrocarbon generated in this sag migrated along the fault and the unconformity surface to the slope before accumulated in the peripheral tectonic zones, resulting in 3 sets of source–reservoir–caprock assemblages formed with the characteristics of reservoir formation in compound oil and gas accumulation zones. (2) The stratum in the third member of Shahejie Fm is the main source rock. (3) The above three assemblages went through four periods of generating process during the geological time of 11–1 Ma. Vertically hydrocarbon sources first filled in the deep Mesozoic and Archean reservoirs, then migrated and accumulated in the shallow Neogene and Paleogene reservoirs, where multiple shore-term rapid filling of high-temperature fluids led to this typical oil and gas pooling mode.

探讨辽东湾拗陷勘探程度较低的次级构造单元——辽东凸起锦州23构造带的勘探潜力,从烃源特征、储集条件、圈闭类型以及输导体系等分析其成藏条件,恢复其成藏过程.研究结果表明:锦州23构造带具有2套时空匹配关系良好的生储盖组合,储集层为展布范围广、储集性能优越的扇三角洲和辫状河砂体,其与辽中凹陷优质且供烃充足的深湖相烃源岩直接接触,具备有效的油气输导通道;盖层为封闭能力强的深水湖泊相泥岩或较强的河流相泥岩;以规模较大的断块和断背斜为主要类型的圈闭,其形成均早于油气主运移期.锦州23构造带优越的成藏条件以及成藏各要素之间良好的动态耦合关系,具备广阔的油气勘探潜力.辽东凸起上类似于锦州23构造带的一系列圈闭应为今后的勘探新区域.

The multi-stage minerals filled in pore space were sequenced, and the charging stages of fluid and hydrocarbon were reconstructed based on the observation of drilling cores and thin sections, homogeneous temperature testing of fluid inclusions, Laser Raman composition analysis and isotope geochemical analysis. The Cambrian Longwangmiao Formation in the study area went through 5 stages of fluid charging, in which 3 stages, mid-late Triassic, early-mid Jurassic and early-mid Cretaceous, were related to oil and gas charging. Especially the oil and gas charging event in early-mid Cretaceous was the critical period of gas accumulation in the study area, and was recorded by methane gas inclusions in the late stage quartz fillings. The 40Ar-39Ar dating of the 3rd stage methane inclusions shows that the natural gas charging of this stage was from 125.8±8.2 Ma. Analysis of Si, O isotopes and 87Sr/86Sr of the late stage quartz indicates that the fluid source of the quartz was formation water coming from long term evolution and concentration of meteoric water, but not from deep part or other sources, this also reflects that, in the critical charging period of natural gas, the Cambrian Longwangmiao Formation in Moxi structure had favorable conservation conditions for hydrocarbon accumulation, which was favorable for the formation of the Longwangmiao large natural gas pool.

The Laizhou Bay Sag, one of the oil-bearing sags with large exploration potential in the South Bohai Sea of China, contains two sets of high-quality hydrocarbon source rocks, i.e. Member 3 and Member 4 of Shahejie Fm (E(2)s(3) and E(2)s(4)). As an important hydrocarbon accumulation zone in the sag, the KL16-1 low bulge is found to have oil reservoirs in the Neogene Guantao Fm (N(1)g), the Paleogene Dongying Fm (E(3)d), the Paleogene Shahejie Fm (E(2)s), and the Mesozoic buried hill formation. It is characterized by distinct features of composite reservoirs. Nonetheless, its hydrocarbon accumulation process and mechanism are unknown yet. In this paper, the hydrocarbon generation modelling of source rocks, combined with the characteristics of oil-source rock biomarker compounds and fluid inclusions, is used to restore the hydrocarbon accumulation process in the KL16-1 low bulge. Crude oil in all three KL16-1 plays is characterized by low Pr/Ph, low gammacerane, high 4-methyl sterane and high dinosterane. In other words, it is oil of low maturity to maturity. As the biomarker index of the oil is very similar to that of the E(2)s(3) source rocks, it is thought that E(2)s(3) is the primary source rock layer, while E(2)s(4) is the secondary source rock layer. In addition, episodic oil and gas charging happened in two phases under high pressure in the late period (from 5.0 Ma till now).

The features of the biomarkers of the pore hydrocarbon and inclusion hydrocarbon were comparatively studied in order to determine the hydrocarbon sources of the reservoir in Dongdaohaizi area.The pore hydrocarbon and inclusion hydrocarbon are separated from 12 sandstone samples of 6 wells in the study area,and the features of their biomarkers and the distribution characteristics of the biomarkers of three sets of hydrocarbon source rocks in the study area are compared and analyzed by GC analysis and GC-MS analysis.The results show that,there is significant difference between the biomarkers of pore hydrocarbon and inclusion hydrocarbon:the hydrocarbon in inclusions has better consistency than that in pores,the distribution of its n-alkanes is more complete,its Pr / Ph ratio is lower,and its steranes and terpanes is more mature.It is held that the inclusion hydrocarbon may be related to Permian hydrocarbon source rocks;the pore hydrocarbon may be related to Jurassic and Permian source rocks.The analysis of reservoir hydrocarbon sources can provide certain geological basis for the further exploration of the study area.

The geochemical characteristics of crude oil and source rocks from the drilling wells of Well Dinan-1,Well Dinan-7,Well Dinan-8 in the Dinan area of Dongdaohaizi Sag in Junggar Basin are analyzed,and the oil-source relationship is also discussed.Focus is put on the research of oil group composition,oil carbon isotope,oil saturated chromatographic feature and parameters analysis of oil steroid terpane compounds,light hydrocarbon,as well as biomarker of the source rock.It shows that the hydrocarbon source rock of Permian Pingdiquan Formation in Dongdaohaizi Sag is in the immature to mature phase,with high tricyclic terpane content,low gammacerane content,Ts/Tm less than 1, and reverse “L”shape in the distribution of C27 ,C28 ,C29 regular sterane fingerprint.The geochemical parameter and steroid terpane characteristics from the crude oil and the reservoir material extracted in the Permian in Dinan area are similar to those of the source rocks in Pingdiquan Formation.The Jurassic crude oil is characterized by the Jurassic source rock.

The Chagan sag has the greatest oil and gas exploration potential among other sags in the Yingen Ejinaqi Basin, Inner Mongolia. The average geothermal gradient in the Chagan sag is 33.6 degrees C/km, whereas the heat flow ranges from 65.9 mW/m(2) to approximately 85.5 mW/m(2), with an average value of 74.5 mW/m(2). Thermal history reveals that the Chagan sag experienced the following 4 stages of thermal evolutions: (1) a rapidly increasing geothermal gradient stage from the Early Cretaceous Bayingebi Formation depositional period to the Early Cretaceous Suhongtu Formation depositional period; (2) a geothermal gradient peak stage during the Early Cretaceous Yingen Formation depositional period; (3) a high geothermal gradient continuation stage during the Late Cretaceous Wulansuhai Formation depositional period; and (4) a thermal subsidence stage during the Cenozoic. Tectonic subsidence analysis reveals that the area experienced an initial synrift subsidence during the Early Cretaceous followed by a subsequent long-term thermal subsidence since Late Cretaceous. Thermal and tectonic subsidence histories of this area are of great significance to petroleum exploration and hydrocarbon resource assessment because they bear directly on issues of source rock maturation. The maturation histories of the 3 sets of source rocks in the sag were modeled on the basis of the present geothermal field, thermal history and tectonic subsidence history. The results reveal that the hydrocarbon generation of the Chagan sag was controlled by the Early Cretaceous geothermal fields, and the source rock maturity reached the maximum at the end of the Yingen Formation depositional period. Moreover, the maturation evolution degree shows a difference for the 3 sets of source rocks. The source rocks of the Bayingebi 1 and 2 Formations reached the middle mature and dry-gas stage. In contrast, the source rocks of the Suhongtu 1 Formation only reached the early mature and middle mature stage. This work may provide new insights for the understanding of the oil and gas exploration potential of the Chagan sag. (C) 2014 Elsevier Ltd. All rights reserved.