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1.
Shale gas has been the exploration focus for future energy supply in South Africa in recent time. Specifically, the Permian black shales of the Prince Albert, Whitehill, Collingham, Ripon and Fort Brown Formations are considered to be most prospective rocks for shale gas exploration. In this study,outcrop and core samples from the Ecca Group were analyzed to assess their total organic carbon(TOC), organic matter type, thermal maturity and hydrocarbon generation potential. These rocks have TOC ranging from 0.11 to 7.35 wt%. The genetic potential values vary from 0.09 to 0.53 mg HC/g,suggesting poor hydrocarbon generative potential. Most of the samples have Hydrogen Index(HI) values of less than 50 mg HC/g TOC, thus suggesting Type-Ⅳ kerogen. Tmax values range from 318℃ to601℃, perhaps indicating immature to over-maturity of the samples. The vitrinite reflectance values range from 2.22% to 3.93%, indicating over-maturity of samples. Binary plots of HI against Oxygen Index(OI), and HI versus Tmax show that the shales are of Type II and mixed Type Ⅱ-Ⅲ kerogen.Based on the geochemical data, the potential source rocks are inferred as immature to over-matured and having present-day potential to produce gas.  相似文献   

2.
珀斯盆地位于澳大利亚西海岸,是西澳大利亚页岩气资源勘探的重点区域。该盆地属于复杂的凹陷裂谷,海相沉积二叠纪的Carynginia组和早三叠世Kockatea页岩层被认为是潜在的含气地层。通过搜集大量外文文献,全面总结了该盆地含气目标层的地物化特征,Carynginia组的总有机碳含量为1%~15%,干酪根为III型,Ro在0.56~1.91;Kockatea页岩层的总有机碳含量为1%~4%,干酪根为II/III混合型,Ro为0.48~1.93。两组共划分了11各岩相段,其中黑色页岩岩相段和含黄铁矿泥岩段是最重要的生烃含气层。综合考虑地层、地化指标和岩石地球物理性质,圈出了可供参考的页岩气甜点区。  相似文献   

3.
The current work investigates the hydrocarbon potentiality of the upper Jurassic–lower Cretaceous rocks in the Marib-Shabwah Basin, Central Yemen, through the Sabatayn-1 well. Therefore, palynological and organic geochemical analyses were carried out on 37 ditch cutting and 12 core samples from the well. Palynofacies analysis of the Madbi (late Oxfordian–early Tithonian) and Nayfa (Berriasian–Valanginian) Formations sediments indicates deposition of their organic-rich shale, calcareous shale and marl in middle to outer shelf environments under dysoxic–anoxic conditions, containing mainly kerogen of types II to III. However, the shales of the lower Sabatayn (Tithonian) Formation were deposited in an inner shelf environment of prevailing dysoxic–suboxic conditions, and show kerogen types III to II. Regional warm and relatively dry palaeoclimate but with local humid conditions developed near the site of the well is thought to have prevailed during deposition of the studied well sediments. The geochemical analyses of the Madbi Formation show higher total organic carbon content (TOC) than the overlying Sabatayn and Nayfa formations: it is varies between 1.2 and 7, and with average 4 wt% TOC, and the obtained S2 values (～3–10, average 7 mg HC/g rock) indicates that the Madbi Formation is mainly good source rock. It shows a good petroleum potential of 4–11 mg HC/g dry rock, and the Rock-Eval pyrolysis indicates mainly kerogen types II to III (oil to gas prone) of hydrogen index values (132–258, and only one sample from Lam Member is of 360 and average 215 mg HC/g TOC). The thermal maturation parameters as T max (425–440 °C), production index (average 0.13 mg HC/g rock) and thermal alteration index (2 to 2+) reflected that this formation is present at margin of maturation to early mature stage oil window. So, the Lam Member (upper part) of the Madbi Formation is considered the main hydrocarbon (oil and gas) source rock in the Marib-Shabwah Basin. Accordingly, we predict that the Meem Member is an active source for gas and oil accumulations in the overlying sandstone reservoir of the Sabatayn Formation in the Sabatayn-1 well.  相似文献   

4.
Thirty-three black shale samples from four locations on the onland Kachchh basin, western India were analyzed to characterize organic carbon (OC), thermal maturity and to determine the hydrocarbon potential of the basin. Upper Jurassic black shales from the Jhuran Formation (Dhonsa and Kodki areas) are characterized by the presence of chlorite, halloysite, high \(T_{\mathrm{max}}\), low OC, low hydrogen index and high oxygen index. These parameters indicate the OC as type IV kerogen, formed in a marine environment. The rocks attained thermal maturity possibly during Deccan volcanism. Early Eocene samples of the Naredi Formation (Naliya-Narayan Sarovar Road (NNSR) and the Matanomadh areas) are rich in TOC, smectite, chlorite and framboidal pyrite, but have low \(T_{\mathrm{max}}\). These indicate deposition of sediments in a reducing condition, probably in a lagoonal/marsh/swamp environment. Organic carbon of the Naredi Formation of NNSR may be considered as immature type III to IV kerogen, prone to generate coal. Core samples from the Naredi Formation of the Matanomadh area show two fold distribution in terms of kerogen. Organic carbon of the upper section is immature type III to IV kerogen, but the lower section has type II to III kerogen having potential to generate oil and gas after attaining appropriate thermal maturity.  相似文献   

5.
The northern Ordos Basin provides a favorable geological environment for the accumulation and development of coal measure gases (CMG). The hydrocarbon generation potential and reservoir systems of the coal measures have been studied based on data from experimental tests and production and exploration wells, respectively. Further, the coupled accumulation characteristics were determined. The results show that the source rocks are characterized by favorable hydrocarbon generation potential, high thermal evolution (Ro%?=?1.3–2.3%), and mainly type III kerogen. Coals, typically aggregated organic matter, with a huge hydrocarbon generation potential (avg. 89.11 mg/g) and total organic content (TOC) (avg. 65.52%), are predominantly involved in gaseous hydrocarbon generation. Shales with good TOC contents (avg. 2.36%) and large cumulative thicknesses have an important role in gaseous hydrocarbon generation. Coal seams, shale layers, and sandstone layers occur as variably interbedded deposits, which form a favorable environment for CMG coupled accumulation. The porosity and permeability are ranked as follows: sandstone?>?coal?>?shale, with significant stress sensitivity and anisotropy. Two continuous gas generation peaks occurred in the Late Jurassic and Late Cretaceous, with an abundant amount of coal-derived and thermogenic gas generation, respectively. Potential gas-bearing sandstone layers can be formed by gas migration via short distances from nearby coal seams and shale layers. Coupled accumulation of CMG occurred in three stages: (1) stacked and interbedded reservoirs formation stage; (2) gas generating and charging stage; and (3) coupled accumulation adjustment stage. Coalbed methane (CBM)–tight sandstone gas (TSG) assemblage is a favorable target for CMG accumulation and development.  相似文献   

6.
河南商城—固始地区石炭系沉积环境及其构造意义   总被引：13，自引：0，他引：13  
赵宗举  杨树锋 《地质论评》2000,46(4):407-416
根据沉积相分析,同时综合分析区域地质资料,笔者提出河南商城－固始地区石炭系及安徽金寨地区梅山群为典型前陆磨拉石含煤建造,其沉积相主要为滨海、潮坪、泻湖、局限台地及砾质辫状河－冲积扇相,代表了统一的石炭纪一二叠纪合肥弧后前陆盆地的南部边缘相,说明大别地块（北大别弧）于早古生代晚期－晚古生代早期即与华北板块碰扪结成一体。  相似文献   

7.
为了弄清柴达木盆地东部石炭系海陆过渡相页岩气特征和成因,选取柴页2井石炭系克鲁克组泥页岩和页岩气样品展开地球化学研究。通过对泥页岩样品热解和镜检实验,页岩气现场解析、室内气体组分测试和碳同位素分析,取得以下认识：柴达木盆地上石炭统海陆过渡相煤系地层发育暗色泥页岩、碳质泥页岩、煤和泥灰岩4类富有机质沉积,TOC含量平均值分别为3.46%、12.34%、77.62%和1.89%,以Ⅲ型和Ⅱ2型干酪根为主,处于高成熟演化阶段,具备生成大量页岩气的物质基础。柴页2井现场解析气中氮气含量较高,含极少量Ar和He,烃类气体以甲烷为主,总体为干气;甲烷稳定碳同位素组成主要分布在-48.6‰～-39.8‰,介于海相和陆相页岩气之间,随深度增大,呈现碳同位素偏重的现象;页岩气以热成因气为主,其次是生物成因气。  相似文献   

8.
《International Geology Review》2012,54(13):1508-1521
Twenty Cretaceous shale samples from two wells in the Orange Basin of South Africa were evaluated for their source rock potential. They were sampled from within a 1400 m-thick sequence in boreholes drilled through Lower to Upper Cretaceous sediments. The samples exhibit total organic carbon (TOC) content of 1.06–2.17%; Rock-Eval S2 values of 0.08–2.27 mg HC/g; and petroleum source potential (SP), which is the sum of S1 and S2, of 0.10–2.61 mg HC/g, all indicating the presence of poor to fair hydrocarbon generative potential. Hydrogen index (HI) values vary from 7 to 128 mg HC/g organic carbon and oxygen index (OI) ranges from 37 to 195 mg CO2/g organic carbon, indicating predominantly Type III kerogen with perhaps minor amounts of Type IV kerogen. The maturity of the samples, as indicated by T max values of 428–446°C, ranges from immature to thermally mature with respect to oil generation. Measured vitrinite reflectance values (%Ro) of representative samples indicate that these samples vary from immature to mature, consistent with the thermal alteration index (TAI) (spore colour) and fluorescence data for these samples. Organic petrographic analysis also shows that amorphous organic matter is dominant in these samples. Framboidal pyrite is abundant and may be indicative of a marine influence during deposition. Although our Rock-Eval pyrolysis data indicate that gas-prone source rocks are prevalent in this part of the Orange Basin, the geochemical characteristics of samples from an Aptian unit at 3318 m in one of the wells suggest that better quality source rocks may exist deeper, in more distal depositional parts of the basin.  相似文献   

9.
为了研究鄂尔多斯盆地西缘羊虎沟组页岩气成藏潜力,根据泥页岩厚度、有机质类型、有机质丰度与成熟度等因素,从暗色泥页岩地层空间展布特征、构造特征与热事件、生烃能力等方面分析页岩气聚集的地质条件。研究表明,羊虎沟组暗色泥页岩单层最大厚度约30m,区内发育的逆冲推覆构造使地层叠置形成厚的泥页岩层段,泥页岩干酪根以III型为主,II—I型也有发育,TOC平均值为3.25%,R0为1%~4%,这些条件均有利于页岩气聚集成藏。综合分析认为呼鲁斯太南部、乌达及石炭井地区为页岩气聚集最有利的区域。  相似文献   

10.
随着我国页岩气勘探的推进,在局部地区已经取得突破并建成一定规模的产能,但天然气资源保障形势依然严峻,亟需加强拓展页岩气新层系沉积环境和富集规律,以进一步扩大页岩气的勘探范围和规模。贵州石炭系黑色页岩作为新发现的页岩气目标层,具有较好的页岩气勘探前景。由于受水城—紫云裂陷槽的控制,贵州石炭系沉积相变复杂,开展该页岩地层的沉积相和沉积模式研究,总结页岩沉积富集特征,有利于推进其页岩气勘探进程。本文通过研究揭示贵州石炭系页岩地层可划分为裂陷槽两侧边缘斜坡相,槽内过渡浅海—半深海相,裂陷槽内槽盆相,水城地区隆起浅海相,威宁地区潮坪—潟湖相沉积,总结具有裂谷边缘—槽盆滞留沉积模式。浅海相、浅海—半深海相、槽盆相、湖盆相是黑色页岩沉积富集的有利区,而具体地层厚度、黑色页岩发育、总有机碳含量（TOC）、干酪根类型受沉积环境和物源区的影响控制明显。  相似文献   

11.
In Egypt, organic-rich sediments in the Duwi and Dakhla Formations of the Campanian-Danian age are customarily assigned as “oil shale” that occupies the middle latitudes of the country but may extend southward to Kurkur Oases. This oil shale belt has a vast worldwide extension, and it is considered as major oil- and gas-prone source rock in many places, especially in the Middle East. The sedimentation of the oil shale was triggered by the major transgression event that occurred during the Late Cretaceous. The lithology, type of kerogen, organic richness, and thickness of these organic-rich sediments vary markedly both on lateral and vertical scales. In Quseir area, the in-place geological reserves, of oil shale of the 800-kcal/kg quality, is estimated to be more than 9 billion tons that can produce 5.48 bbls equivalent upon retorting. Very optimistic resources are expected in the unexplored Nile Valley region. The factor analysis of data rank representing 1176 core samples and analysis of 58 major and trace elements besides Rock-Eval analyses point to five main controlling factors that control deposition of oil shale. The terrestrial indicators Al2O3, TiO2, Fe2O3, and K2O and the marine indicators Ca and Sr are oppositely loaded in the first factor. The second factor expresses the reducing conditions that prevailed during the deposition of the organic-rich marine environments. The euxinity of the basin is recognized by the third factor where sulfide and vanadium seem to be mutual. The fourth factor expresses the role of dolomitization while the fifth factor points to the humble role of oxidation. Considering the metric core samples, the highest TOC content recorded in the borehole drilled in Abu Tartur plateau is 3.6%, but it is about 14% for Quseir area. Regarding the spot samples in Quseir area, the highest TOC measured about 24%. It is not only the low TOC in Abu Tartur but also the kerogen type that is of type II + III, mostly of terrestrial origin (gas-prone) and lithology dominated by argillites. Organic richness is remarkable in Quseir-Safaga area, where the average TOC of 160-m-thick sequence is about 5%, with kerogen of type I or mixed I + II, mostly of marine origin (oil prone). The Dakhla Formation (Maastrichtian-Danian) is the richest in organic matter while Quseir Formation (Campanian) has the least organic richness and lowest kerogen quality. Detailed investigation on biomarkers confirms the relations among transgression, organic richness, kerogen type, and anoxic conditions. The organic matter is immature as witnessed by the low S1 values (<5%, in average), the low T max (<430 °C), the low vitrinite reflectance (<0.4%), and biomarker signature. The variation in the S1 values between 1 and 9% is attributed to the influence of tectonics associating the Red Sea rift. In Quseir-Safaga area, there are particular prolific horizons of oil shale that seem to be visible for utilization by different technologies of combustion and retorting. The content of the heavy metals and uranium, as well as the spent, is a significant benefit. The faulting, dragging, and steep tilting of beds in the Quseir-Safaga area shall remain a serious challenge for extensive utilization of the estimated in-place geological reserves.  相似文献   

12.
为了揭示湘中与湘东南坳陷海陆过渡相页岩含气潜力及勘探方向,对该区下石炭统岩关阶组和上二叠统龙潭组泥页岩进行总有机碳含量TOC、镜质体反射率Rran、干酪根碳同位素、有机质显微组成、X衍射、扫描电镜、孔渗特征和等温吸附等测试。结果表明岩关阶组和龙潭组处于成熟-高成熟期、类型以Ⅲ型为主;龙潭组泥页岩TOC含量普遍较高、而岩关阶组泥页岩TOC含量较低。龙潭组和岩关阶关组泥页岩矿物主要为黏土矿物和石英,部分含有较高的方解石。这两套页岩的孔隙发育较差,主要孔隙类型为有机孔、溶蚀孔和层间裂缝。孔隙度为0.41%~2.76%、渗透率为（0.08~0.98）×10-3 μm2。孔隙度主要受TOC控制,不稳定矿物如长石和碳酸盐岩虽然能提供一定孔隙,但对页岩物性的影响有限。泥页岩的甲烷吸附量普遍在1.67~2.5 cm3/g,2015H-D3井龙潭组泥页岩现场解吸气量普遍大于0.5 cm3/g,最高为2.35 cm3/g,表明湘中和湘东南地区龙潭组具有一定的页岩气潜力,但岩关阶组勘探前景相对较差。   相似文献   

13.
The paper presents data on the composition of biomarkers from bitumen extracts and the chemical structure of kerogen from Corg-rich sedimentary rocks before and after hydrothermal treatment in an autoclave at 300°C. Samples selected for this study are kukersite and Ordovician Dictyonema shale from the Baltics, Domanik oil shale from the Ukhta region, Upper Permian brown coal from the Pre-Ural foredeep, carbonaceous shale from the Oxfordian horizon of the Russian plate, and Upper Jurassic oil shales from the Sysola oil shale bearing region. The rocks contain type I, II, III, and II-S kerogens. The highest yield of extractable bitumen is achieved for Type II-S kerogen, whereas Type III kerogen produces the lowest amount of bitumen. The stages of organic matter thermal maturation achieved during the experiments correspond to a transition from PC2–3 to MC1–2. The 13C NMR data on kerogen indicate that the aromatic structures of geopolymers underwent significant changes.  相似文献   

14.
The Alum Shale Formation is a metal-rich black shale, deposited on the Baltoscandian platform between Middle Cambrian and Early Ordovician. These black shales may be of particular economic interest for their relatively high uranium content (100–300 ppm) and their wide distribution from Norway to Estonia. Scandinavian Alum Shale may thus constitute a great potential resource of uranium, as a low grade ore. The Alum Shale Formation is particularly interesting to study the mineralogical expression and content of uranium in series submitted to progressive burial and metamorphism. For this purpose, the behavior of U, P, Ti and organic matter was studied on a series of representative samples from most Alum Shale prospection zones. In southern Sweden, where Alum Shale underwent fairly shallow burial, uranium concentrations have no mineralogical expression except a rather high U content of biogenic phosphates. Calcite concretions (beefs) and fractures recorded the migration of hot overpressured hydrocarbons and brines from thermally mature areas to immature Alum Shale. However, thermal maturation and fluid migration did not allow remobilization of uranium and metals. At the opposite, in northern Sweden, where the series were folded, duplicated and submitted to low grade Greenschist metamorphism during Caledonian orogeny, phospho-silicates U-Si-Ca-P (±Ti ±Zr ±Y) and minor amounts of uraninite are identified and indicate that U, P, and Ti were mobile and precipitated as new phases. The effect of metamorphism is therefore important to consider as the leachability of U, especially during (bio)-hydrometallurgical processes, which will be by far different between the two considered areas.  相似文献   

15.
India recognizes the strategic importance for developing shale gas resources like other countries in the world. Shale gas reservoirs are known to be difficult for extracting gas in comparison to conventional reservoirs. Recently, due to high prices of gas, rising demand and enhancement in recovery technologies has attracted the Indian energy industries to explore the shale gas resource. Coal and lignite are the prime source of energy in India and these resources are well explored, while shale is ignored, despite it being associated with coal and lignite bearing formations. The paper presents reservoir characteristics of shale horizons in Barren Measures and Barakar formations of north and south Karanpura coalfields. Shale core samples were collected from exploratory boreholes in air tight canisters. In-situ gas content and adsorption capacities ascertained to be 0.51–1.69 m3/t and 3.90–5.82 m3/trespectively. Desorbed gas derived from canisters contains CH4, C2H6, C3H8, CO2, N2 and O2 and varies from 76.19–82.63, 0.38–0.76, 0.10–0.50, 8.65–12.34, 9.89–19.34 and 0.56–2.24 vol. % respectively. The permeability and porosity determined under reservoir simulated confining pressure is varying from 0.41–0.75 mD and 0.89–2.28 % respectively. The plots of Rock Eval S2vs TOC and HI against Calc. VRo% indicates that all shale samples belong to Type III kerogen, which is prone to generate gas. It is evaluated that insitu gas content, sorption capacity, saturation level and low permeability of shale beds are critical parameters for development of shale gas resource in the studied area.  相似文献   

16.
南盘江坳陷是四川盆地外围海相页岩气勘探战略突破区,具有巨大的勘探潜力,但其页岩气勘探起步晚、勘探方向不明确,严重制约了该区页岩气勘探开发.本次研究以南盘江坳陷东北缘东兰地区野外考察为基础,结合有机地球化学、全岩X衍射、扫描电镜等分析手段,分析了下石炭统鹿寨组泥页岩分布特征、源岩地球化学、储层物性特征、页岩气保存等成藏条件.研究表明:南盘江坳陷东北缘下石炭统鹿寨组泥页岩沉积厚度主要为250~350 m,埋深主要介于1 000~3 000 m;页岩有机碳含量多数大于2.0%,有机质主要为Ⅱ1~Ⅱ2型干酪根,处于高成熟-过成熟阶段,具备良好的供烃能力;页岩储层中脆性矿物含量高,孔隙空间发育良好,吸附性好,页岩气储集能力良好;页岩粘土矿物相对较高,成岩期压实、胶结作用较强,使页岩层自封闭性增强,保存条件较好;多期构造运动对后期页岩气保存与否具有决定性作用.对比国内外典型页岩气田成藏条件特征,认为南盘江坳陷东北缘下石炭统鹿寨组具备有利的页岩气成藏条件,提出南盘江坳陷东兰地区东北部为页岩气有利勘探区.   相似文献   

17.
松辽盆地南部青山口组一段页岩油资源丰富,多口井试油获得工业及高产油流,具有较大的勘探开发潜力。本文以青山口组一段下段为研究对象,以页岩油赋存状态为切入点,重点针对研究区页岩油富集优质岩相,即高有机质薄片状页岩和中有机质纹层状页岩中溶胀油、吸附油以及游离油量进行定量评价,揭示页岩油在地下页岩层系储层中的赋存特征。青山口组一段页岩油主要以干酪根溶胀态、干酪根吸附态、有机质孔隙游离态、无机矿物吸附态及无机孔隙游离态等5种赋存形式存在于页岩层系储层中。其中：高有机质薄片状页岩中页岩油赋存状态以干酪根溶胀油、干酪根吸附油和有机质孔隙游离油等有机赋存油为主,有机赋存油量可高达253.0 mg/g TOC,以TY1井页岩油赋存量最大,其次为CY8井,H238井页岩油量最低;中有机质纹层状页岩中页岩油赋存状态以无机矿物吸附油、无机孔隙游离油等无机赋存油为主,可达167.0 mg/g TOC,CY8井页岩油赋存量最大,H258井次之,H238井页岩油量最低。TY1井、CY8井位于半深湖—深湖区,发育大套泥页岩;H238井位于三角洲外前缘,离物源区较近,导致其页岩油赋存量明显低于半深湖—深湖区。因此,沉积环境是导致不同工区页岩油赋存量差异的主要原因。  相似文献   

18.
Abstract

Small- and medium-sized basins are widely distributed, and some contain commercial gas reservoirs demonstrating their gas-generation potential. The Xuanhua Basin, which is a small-sized coal-bearing basin in north China, includes a promising target for shale-gas exploration in the Xiahuayuan Formation. In this study, we used this basin as a case study to assess the critical geochemical features for small or medium-sized basins to form commercial gas reservoirs. Total organic carbon (TOC) analysis, Rock-Eval pyrolysis, microscopic observation of macerals, vitrinite reflectance measurement and kerogen stable carbon isotope analysis were performed to characterise the organic geochemistry of the Xiahuayuan shales. The original total organic carbon (TOCo) content and hydrocarbon-generative potential (S2o) were reconstructed to further evaluate the gas-generation potential of these shales. In addition, geochemical data of shales from other similar-sized basins with gas discoveries were compared. The results showed that the kerogen from the Xiahuayuan Formation is Type III (gas-prone), and macerals are dominated by vitrinite. TOC values showed a strong heterogeneity in the vertical profiles, with most higher than 1.5?wt%. The measured Ro values ranged from 1.4 to 2.0%. However, thermal maturity was not correlated with the present-day burial depth with higher maturity in the wells closest to the diabase intrusion centre. The remaining generation potential (S2) averaged 0.91?mg HC/g rock, equal to 1.4?cm3 CH4/g rock, and the average amount of hydrocarbon generated was 4.33?cm3 CH4/g rock. In small and medium-sized basins, the TOC content of commercially developed gas shales ranged from 0.5 to 2.5?wt%, organic matter was mainly humic (gas-prone), and the burial depth was generally shallow. Biogenic gas reservoirs for commercial exploitation tend to have larger shale thicknesses (120–800?m) than thermogenic gas reservoirs (60–90?m).

  1. The Xiahuayuan Formation is a good gas-source rock with gas-prone kerogen type, relatively high TOC values and moderate thermal maturity.

  2. The average amount of hydrocarbon generated from the Xiahuayuan shales is about 4.33?cm3 CH4/g rock, indicating a potential to form a shale gas reservoir.

  3. Owing to the influence of diabase intrusions, the Xiahuayuan shales have entered the dry gas window at relatively shallow-buried depths.

  4. Small- and medium-sized basins have the potential to generate commercial gas reservoirs with the generated volume mainly a product of the thickness and maturity of black shales.

  相似文献   

19.
Frontier exploration in the Kuqa Depression, western China, has identified the continuous tight-sand gas accumulation in the Lower Cretaceous and Lower Jurassic as a major unconventional gas pool. However, assessment of the shale gas resource in the Kuqa Depression is new. The shale succession in the Middle–Upper Triassic comprises the Taliqike Formation (T3t), the Huangshanjie Formation (T3h) and the middle–upper Karamay Formation (T2–3k), with an average accumulated thickness of 260 m. The high-quality shale is dominated by type III kerogen with high maturity and an average original total organic carbon (TOC) of about 2.68 wt%. An improved hydrocarbon generation and expulsion model was applied to this self-contained source–reservoir system to reveal the gas generation and expulsion (intensity, efficiency and volume) characteristics of Middle–Upper Triassic source rocks. The maximum volume of shale gas in the source rocks was obtained by determining the difference between generation and expulsion volumes. The results indicate that source rocks reached the hydrocarbon expulsion threshold of 1.1% VR and the hydrocarbon generation and expulsion reached their peak at 1.0% VR and 1.28% VR, with the maximum rate of 56 mg HC/0.1% TOC and 62.8 mg HC/0.1% TOC, respectively. The volumes of gas generation and expulsion from Middle–Upper Triassic source rocks were 12.02 × 1012 m3 and 5.98 × 1012 m3, respectively, with the residual volume of 6.04 × 1012 m3, giving an average gas expulsion efficiency of 44.38% and retention efficiency of 55.62%. Based on the gas generation and expulsion characteristics, the predicted shale gas potential volume is 6.04 × 1012 m3, indicating a significant shale gas resource in the Middle–Upper Triassic in the eastern Kuqa Depression.  相似文献   

20.
目前针对桂中坳陷早石炭世富有机质泥页岩的生烃潜力方面研究很少,严重制约了该区以页岩气为主的非常规油气勘探.本研究对鹿寨县城西石炭系鹿寨组泥页岩系统取样分析,从有机碳含量、岩石热解、有机碳同位素组成、抽提物正构烷烃组成特征及泥岩镜质体反射率多个方面讨论了该套泥页岩的生烃潜力;结合区域构造演化史总结了与下石炭统岩关阶泥页岩密切相关的3种近源气藏赋存模式.研究结果表明:泥页岩的TOC值分布于0.25%~15.67%,其中强制海退前沉积的泥页岩富含有机质,TOC值均大于2%,TOC值与氯仿沥青"A"、生烃潜量及总烃呈弱正相关关系.泥页岩的有机质类型主体为Ⅱ型;泥页岩的Ro值分布于1.72%~2.78%,处于过成熟阶段.泥页岩上下岩性组合特征及桂中坳陷现今所处的构造位置表明,坳陷中部对冲构造区为有利的近源气藏形成区,背冲构造区为较差区;坳陷边缘逆冲推覆构造区为存在岩性圈闭的近源气藏形成区.   相似文献   

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