scholarly journals Fluid geochemistry of the Jurassic Ahe Formation and implications for reservoir formation in the Dibei area, Tarim Basin, northwest China

2018 ◽  
Vol 36 (4) ◽  
pp. 801-819 ◽  
Author(s):  
Shuangfeng Zhao ◽  
Wen Chen ◽  
Zhenhong Wang ◽  
Ting Li ◽  
Hongxing Wei ◽  
...  
Keyword(s):  
Natural Gas ◽  
Tarim Basin ◽  
Oil And Gas ◽  
Northwest China ◽  
Source Rocks ◽  
Coal Measure ◽  
Hydrocarbon Generation ◽  
Gas Reservoirs ◽  
Isotopic Analyses ◽  
Jurassic Coal

The condensate gas reservoirs of the Jurassic Ahe Formation in the Dibei area of the Tarim Basin, northwest China are typical tight sandstone gas reservoirs and contain abundant resources. However, the hydrocarbon sources and reservoir accumulation mechanism remain debated. Here the distribution and geochemistry of fluids in the Ahe gas reservoirs are used to investigate the formation of the hydrocarbon reservoirs, including the history of hydrocarbon generation, trap development, and reservoir evolution. Carbon isotopic analyses show that the oil and natural gas of the Ahe Formation originated from different sources. The natural gas was derived from Jurassic coal measure source rocks, whereas the oil has mixed sources of Lower Triassic lacustrine source rocks and minor amounts of coal-derived oil from Jurassic coal measure source rocks. The geochemistry of light hydrocarbon components and n-alkanes shows that the early accumulated oil was later altered by infilling gas due to gas washing. Consequently, n-alkanes in the oil are scarce, whereas naphthenic and aromatic hydrocarbons with the same carbon numbers are relatively abundant. The fluids in the Ahe Formation gas reservoirs have an unusual distribution, where oil is distributed above gas and water is locally produced from the middle of some gas reservoirs. The geochemical characteristics of the fluids show that this anomalous distribution was closely related to the dynamic accumulation of oil and gas. The period of reservoir densification occurred between the two stages of oil and gas accumulation, which led to the early accumulated oil and part of the residual formation water being trapped in the tight reservoir. After later gas filling into the reservoir, the fluids could not undergo gravity differentiation, which accounts for the anomalous distribution of fluids in the Ahe Formation.

Jurassic source rocks of hydrocarbon fluids in the Eastern part of the Fukan depression (Junggar oil and gas basin)

2020 ◽  
pp. 55-63
Author(s):  
Yang Houqiang ◽  
E. V. Soboleva
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Research Area ◽  
Molecular Composition ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Gas Reservoirs ◽  
Eastern Side ◽  
Oil And Gas Reservoirs

In recent years, significant successes have been achieved in the search and exploration of oil and gas reservoirs in the Jurassic deposits on the eastern side of the Fukang depression, which is the least studied part of the Junggar oil and gas Basin. In order to find out the source of hydrocarbon generation, we studied source rocks, oil and oil-bearing sandstones (24 samples from 13 wells) from the Badaowan, Sangonghe, Xishanyao, Toutunhe and Qigu production beds of the Fukang depression research area. Based on these studies, the composition of the organic matter of the Jurassic source rocks, the properties and molecular composition of oils, as well as the characteristics of the composition of biomarkers in them are examined in detail. The results of research and interpretation of the data showed that the mudstones of the Badaowan formation were source rocks of oil from the Gumudi zone, the Fukan depression, the Bajiahai ledge and the Shaqi ledge.

Emplacement of intrusions of the Tarim Flood Basalt Province and their impacts on oil and gas reservoirs: A 3D seismic reflection study in Yingmaili fields, Tarim Basin, northwest China

2017 ◽  
Vol 5 (3) ◽  
pp. SK51-SK63 ◽  
Author(s):  
Zhongbo Gao ◽  
Wei Tian ◽  
Lei Wang ◽  
Yongmin Shi ◽  
Mao Pan
Keyword(s):  
Tarim Basin ◽  
Seismic Reflection ◽  
Oil And Gas ◽  
Northwest China ◽  
Lower Permian ◽  
Magmatic Activity ◽  
3D Seismic ◽  
Gas Reservoirs ◽  
Oil And Gas Reservoirs ◽  
Northern Tarim Basin

A basaltic dike-sill network is emplaced into the shallow subsurface of the Yingmai-2 dome, northern Tarim Basin, northwest China. The 3D seismic reflection imaging suggests that these dikes and sills are fed from an intrusion at the focal area of the dome. This basaltic intrusion has a width of approximately 3000 m and thickness of approximately 1000 m, and it is connected with a much larger Early Permian igneous body in the northern Tarim Basin. An unconformity between the Permian basalt lava flows and the base Triassic conglomerates truncates the dome, meaning that the dome must have developed prior to the Triassic. The basaltic intrusion that emplaced beneath the dome likely pushed the surrounding middle Cambrian salts away and instigated uplift of the overlying upper Cambrian to the lower Permian strata. In most cases, igneous activity plays a negative role on formation of oil and gas reservoirs. However, in the Yingmai-2 case, intrusive magmatic activity has caused “forced folding” of the overburdened strata and controlled the formation of a large commercial oil trap. We suggest that the magmatic activity thus also acts as a positive role on the local formation of a producing petroleum system.

scholarly journals Fracture, Dissolution, and Cementation Events in Ordovician Carbonate Reservoirs, Tarim Basin, NW China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-28 ◽  
Author(s):  
Vinyet Baqués ◽  
Estibalitz Ukar ◽  
Stephen E. Laubach ◽  
Stephanie R. Forstner ◽  
András Fall
Keyword(s):  
Tarim Basin ◽  
Oil And Gas ◽  
Hydrocarbon Generation ◽  
High Porosity ◽  
Late Permian ◽  
Gas Reservoirs ◽  
Near Surface ◽  
Principal Source ◽  
Igneous Activity ◽  
Karstic Features

Ordovician carbonate rocks of the Yijianfang Formation in the Tabei Uplift, Tarim Basin, contain deeply buried (>6000 m), highly productive oil and gas reservoirs associated with large cavities (>10 m). Previous workers inferred that large cavities are paleocaves (paleokarst) formed near the surface and subsequently buried. Alternately, caves may have formed by dissolution at depth along faults. Using 227 samples from 16 cores, we document textures and cement compositions bearing on cavity histories with petrographic, high-resolution scanning electron microscopy (SEM), isotopic, and fluid inclusion microthermometric observations. Results show that dissolution occurred at depth and was caused by (1) acidic fluids derived from Middle-Late Silurian and/or Devonian-Permian hydrocarbon generation and maturation, (2) high-temperature fluids, of which some were associated with Late Permian igneous activity, and (3) Mg-rich fluids that accompanied Jurassic-Cretaceous deformation and the formation of partially open fractures and stylobreccias (fault breccias). The relative paragenetic sequence of the structure-related diagenesis suggests seven stages of fracturing, dissolution, and cementation. Mottle fabrics in the Yijianfang Formation contain argillaceous carbonate-rich silt and are bioturbation features formed within the marine environment. Those mottled fabrics differ from clearly karstic features in the overlying Lianglitage Formation, which formed by near-surface dissolution and subsequent infilling of cavities by allochthonous sediment. Mottle fabrics are crosscut by compacted fractures filled with phreatic-vadose marine cements and followed by subsequent generations of cement-filled fractures and vugs indicating that some fractures and vugs became cement filled prior to later dissolution events. Calcite cements in fractures and vugs show progressively depleted values of δ18O documenting cement precipitation within the shallow (~220 m), intermediate (~625 m), and deep (~2000 m) diagenetic environments. Deep (mesogenetic) dissolution associated with fractures is therefore the principal source of the high porosity-permeability in the reservoir, consistent with other pieces of evidence for cavities localized near faults.

scholarly journals Factors Controlling Natural Gas Accumulation in the Southern Margin of Junggar Basin and Potential Exploration Targets

2021 ◽  
Vol 9 ◽  
Author(s):  
Jianping Chen ◽  
Xulong Wang ◽  
Yongge Sun ◽  
Yunyan Ni ◽  
Baoli Xiang ◽  
...  
Keyword(s):  
Natural Gas ◽  
Tarim Basin ◽  
Oil And Gas ◽  
Junggar Basin ◽  
Petroleum System ◽  
Source Rocks ◽  
Gas Generation ◽  
Kuqa Depression ◽  
Gas Accumulation ◽  
Southern Margin

In this paper, factors controlling natural gas accumulation in the southern margin of Junggar Basin were mainly discussed by a comparison with natural gas generation and accumulation in the Kuqa Depression of Tarim Basin. The southern margin of Junggar Basin and the Kuqa Depression of Tarim Basin are located on the north and south sides of the Tianshan Mountains respectively, and they share the similar sedimentary stratigraphy and tectonic evolution history. In recent several decades, many large gas fields have been found in the Kuqa Depression of Tarim Basin, but no great breakthrough in the southern margin of Junggar Basin. Our results suggest that natural gas in the southern margin of Junggar Basin is mainly thermogenic wet gas, and can be divided into three types as coal-derived gas, mixed gas and oil-associated gas, of which the former two types are dominated. The Jurassic coal measures are the main source rocks of natural gas, and the main gas generation time from this set of source rocks matched well with the formation time of the anticline structures, resulting in favorable conditions for natural gas accumulation. In the western part of the southern margin in the Junggar Basin, the Permian lacustrine and the Upper Triassic lacustrine-swamp source rocks could be important sources of natural gas, and the main gas generation time also matched well with the formation time of traps. Compared with the Kuqa Depression of Tarim Basin, natural gas sources are better in the southern margin of Junggar Basin, and the geologic conditions are favorable for the formation of large oil and gas fields in the southern margin of Junggar Basin. The deep Permian-Jurassic-Cretaceous petroleum system is the most favorable petroleum system for natural gas exploration in the southern margin of Junggar Basin. The western part and the central part of the southern margin in the Junggar Basin could be the first targets for the discovery of the Jurassic coal-derived oil and gas reservoirs. The shallow Cretaceous-Neogene petroleum system is the second target for natural gas exploration.

scholarly journals Chemometric differentiation of natural gas types in the northwestern Junggar Basin, NW China

2020 ◽  
Vol 38 (6) ◽  
pp. 2128-2142
Author(s):  
Yao-Ping Wang ◽  
Xin Zhan ◽  
Yuan Gao ◽  
Sibo Wang ◽  
Jia Xia ◽  
...  
Keyword(s):  
Natural Gas ◽  
Oil And Gas ◽  
Junggar Basin ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Geological Evidence ◽  
Oil And Gas Exploration ◽  
Natural Gases ◽  
Group A ◽  
Group B

In recent years, the natural gas has displayed a growing significance in oil and gas exploration in the northwestern Junggar Basin (NWJB), although oil has been the main focus of exploration in the basin. Here, we systematically discuss the classification and origin of the natural gases from the NWJB based on the natural gas geochemistry and chemometric methods. The natural gases collected from the NWJB were chemometrically classified into three groups. Group A gases, defined as coal-derived gases, were likely generated from the mixing of the Jiamuhe Formation and Carboniferous strata. Group B gases, defined as the mixing of coal-derived and oil-associated gases, were restricted to the source rocks of group A and C gases. Group C gases, defined as oil-associated gases, were likely derived from both the Fengcheng and Wuerhe Formations, with a higher contribution from the latter strata. The result of this study suggests that the potential of oil generation in the Wuerhe Formation has been underestimated in the past. This is in accordance with geochemical and geological evidence. This study provides an effective chemometric method of natural gas classification and evaluation of hydrocarbon generation potential. This contributes to a better understanding of the origin of gases and distribution of oil and gas, assisting in exploration deployment in the basin.

scholarly journals Geochemistry and Origins of Natural Gases in the Southwestern Junggar Basin, Northwest China

2012 ◽  
Vol 30 (5) ◽  
pp. 707-725 ◽  
Author(s):  
Ping'an Sun ◽  
Jian Cao ◽  
Xulong Wang ◽  
Yueqian Zhang ◽  
Yong Tang ◽  
...  
Keyword(s):  
Natural Gas ◽  
Junggar Basin ◽  
Northwest China ◽  
Hydrocarbon Exploration ◽  
Source Rocks ◽  
Southern Basin ◽  
Genetic Types ◽  
Western Area ◽  
Jurassic Coal ◽  
Coal Type

The southwestern Junggar Basin in northwest China is a significant target of basin's hydrocarbon exploration and exploitation at present. It is petroliferous mainly in oil production. However, natural gas should have good prospects because multiple sets of gas-prone source rocks are developed. Thus, in order to expand the field of hydrocarbon exploration (natural gas in particular), origins of the gases were discussed in this paper based on relatively comprehensive analyses of gas geochemistry, which include components, carbon isotopes and light hydrocarbons of gas and biomarkers of associated condensates. The results indicate two typical genetic types of gases. The first type is the coal-type and oil-type gases sourced from Permian lacustrine mudstones in the Shawan sag. It is distributed mainly in the Chepaizi area, whose most distinctive geochemical feature is the θ13C2 value (ranging from −30.29‰ to −25.09‰ with an average of −27.03‰.) The gas exploration potential is good. By contrast, the second type of gas is the coal-type gas sourced from Jurassic coal-bearing rocks in the southern basin. It is distributed mainly in the western area of the southern basin, with a few in the southern part of the Chepaizi area. θ13C2 value of the gases ranges from −27.14‰ to −21.74‰ with an average of −24.81‰, sharply heavier than that of the first type of gas. Gas exploration potential is fairly good, mainly being controlled by source-rock maturity.

Distribution and source significance of 2-methylalkanes in coal-measure source rocks, northwest China

2019 ◽  
Vol 174 ◽  
pp. 257-267 ◽  
Author(s):  
Qingsong Cheng ◽  
Huang Guanghui ◽  
Min Zhang ◽  
Zhang Wenjun ◽  
Liu Xi
Keyword(s):  
Northwest China ◽  
Source Rocks ◽  
Coal Measure

scholarly journals Evaluation of hydrocarbons generated from the Permo-Carboniferous source rocks in Huanghua Depression of the Bohai Bay Basin, China

2018 ◽  
Vol 36 (5) ◽  
pp. 1229-1244
Author(s):  
Xiao-Rong Qu ◽  
Yan-Ming Zhu ◽  
Wu Li ◽  
Xin Tang ◽  
Han Zhang
Keyword(s):  
Oil And Gas ◽  
Source Rocks ◽  
Bohai Bay ◽  
Hydrocarbon Generation ◽  
Burial History ◽  
Bohai Bay Basin ◽  
Important Conclusion ◽  
The North ◽  
Huanghua Depression ◽  
History Of

The Huanghua Depression is located in the north-centre of Bohai Bay Basin, which is a rift basin developed in the Mesozoic over the basement of the Huabei Platform, China. Permo-Carboniferous source rocks were formed in the Huanghua Depression, which has experienced multiple complicated tectonic alterations with inhomogeneous uplift, deformation, buried depth and magma effect. As a result, the hydrocarbon generation evolution of Permo-Carboniferous source rocks was characterized by discontinuity and grading. On the basis of a detailed study on tectonic-burial history, the paper worked on the burial history, heating history and hydrocarbon generation history of Permo-Carboniferous source rocks in the Huanghua Depression combined with apatite fission track testing and fluid inclusion analyses using the EASY% Ro numerical simulation. The results revealed that their maturity evolved in stages with multiple hydrocarbon generations. In this paper, we clarified the tectonic episode, the strength of hydrocarbon generation and the time–spatial distribution of hydrocarbon regeneration. Finally, an important conclusion was made that the hydrocarbon regeneration of Permo-Carboniferous source rocks occurred in the Late Cenozoic and the subordinate depressions were brought forward as advantage zones for the depth exploration of Permo-Carboniferous oil and gas in the middle-northern part of the Huanghua Depression, Bohai Bay Basin, China.

scholarly journals New exploration strategy in igneous petroliferous basins – Enlightenment from simulation experiments

2018 ◽  
Vol 36 (4) ◽  
pp. 971-985
Author(s):  
Qingqiang Meng ◽  
Jiajun Jing ◽  
Jingzhou Li ◽  
Dongya Zhu ◽  
Ande Zou ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Liquid Hydrocarbon ◽  
Hydrogen Gas ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Simulation Experiments ◽  
Gaseous Hydrocarbon ◽  
Oil And Gas Fields ◽  
Gaseous Hydrocarbons ◽  
Hydrocarbon Productivity

There are two kinds of relationships between magmatism and the generation of hydrocarbons from source rocks in petroliferous basins, namely: (1) simultaneous magmatism and hydrocarbon generation, and (2) magmatism that occurs after hydrocarbon generation. Although the influence of magmatism on hydrocarbon source rocks has been extensively studied, there has not been a systematic comparison between these two relationships and their influences on hydrocarbon generation. Here, we present an overview of the influence of magmatism on hydrocarbon generation based on the results of simulation experiments. These experiments indicate that the two relationships outlined above have different influences on the generation of hydrocarbons. Magmatism that occurred after hydrocarbon generation contributed deeply sourced hydrogen gas that improved liquid hydrocarbon productivity between the mature and overmature stages of maturation, increasing liquid hydrocarbon productivity to as much as 451.59% in the case of simulation temperatures of up to 450°C during modelling where no hydrogen gas was added. This relationship also increased the gaseous hydrocarbon generation ratio at temperatures up to 450°C, owing to the cracking of initially generated liquid hydrocarbons and the cracking of kerogen. Our simulation experiments suggest that gaseous hydrocarbons dominate total hydrocarbon generation ratios for overmature source rocks, resulting in a change in petroleum accumulation processes. This in turn suggests that different exploration strategies are warranted for the different relationships outlined above. For example, simultaneous magmatism and hydrocarbon generation in an area means that exploration should focus on targets likely to host large oilfields, whereas in areas with magmatism that post-dates hydrocarbon generation the exploration should focus on both oil and gas fields. In addition, exploration strategies in igneous petroliferous basins should focus on identifying high-quality reservoirs as well as determining the relationship between magmatism and initial hydrocarbon generation.

scholarly journals GEOCHEMICAL AND GEOSTATISTICAL ASSESSMENT OF CRETACEOUS COALS AND SHALES IN SOME NIGERAIN SEDIMENTARY BASINS FOR THEIR HYDROCARBON PRONESS AND MATURITY LEVELS

2020 ◽  
Vol 1 (2) ◽  
Keyword(s):  
Source Rock ◽  
Oil And Gas ◽  
Linear Regression Analysis ◽  
Sedimentary Basins ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Good Source ◽  
Type Iii ◽  
Limit Value ◽  
The Impact

The Rock–Eval pyrolysis and LECO analysis for 9 shale and 12 coal samples, as well as, geostatistical analysis have been used to investigate source rock characteristics, correlation between the assessed parameters (QI, BI, S1, S2, S3, HI, S1 + S2, OI, PI, TOC) and the impact of changes in the Tmax on the assessed parameters in the Cretaceous Sokoto, Anambra Basins and Middle Benue Trough of northwestern, southeastern and northcentral Nigeria respectively. The geochemical results point that about 97% of the samples have TOC values greater than the minimum limit value (0.5 wt %) required to induce hydrocarbon generation from source rocks. Meanwhile, the Dukamaje and Taloka shales and Lafia/Obi coal are found to be fair to good source rock for oil generation with slightly higher thermal maturation. The source rocks are generally immature through sub-mature to marginal mature with respect to the oil and gas window, while the potential source rocks from the Anambra Basin are generally sub-mature grading to mature within the oil window. The analyzed data were approached statistically to find some relations such as factors, and clusters concerning the examination of the source rocks. These factors were categorized into type of organic matter and organic richness, thermal maturity and hydrocarbon potency. In addendum, cluster analysis separated the source rocks in the study area into two groups. The source rocks characterized by HI >240 (mg/g), TOC from 58.89 to 66.43 wt %, S1 from 2.01 to 2.54 (mg/g) and S2 from 148.94 to 162.52 (mg/g) indicating good to excellent source rocks with kerogen of type II and type III and are capable of generating oil and gas. Followed by the Source rocks characterized by HI <240 (mg/g), TOC from 0.94 to 36.12 wt%, S1 from 0.14 to 0.72 (mg/g) and S2 from 0.14 to 20.38 (mg/g) indicating poor to good source rocks with kerogen of type III and are capable of generating gas. Howeverr, Pearson’s correlation coefficient and linear regression analysis shows a significant positive correlation between TOC and S1, S2 and HI and no correlation between TOC and Tmax, highly negative correlation between TOC and OI and no correlation between Tmax and HI. Keywords- Cretaceous, Geochemical, Statistical, Cluster; Factor analyses.

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