Charging history of Paleogene deep gas in the Qibei sag, Bohai Bay Basin, China

Jiang, Fujie; Pang, Xiongqi; Yu, Sa; Hu, Tao; Bai, Jing; Han, Guilin; Li, Boyuan

doi:10.1016/j.marpetgeo.2015.04.022

Cited by 25 publications

(6 citation statements)

References 24 publications

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“…Stable carbon isotope composition can be applied to identify the genetic type of natural gas as it is closely related to the type and maturity of the source OM, and enrichment of 13 C in a source rock typically leads to an enrichment of 13 C in the gas originated from it (Hu et al, ; Jiang et al, ). The 12 C– 12 C bonds generally break earlier than 12 C– 13 C bonds during the thermal degradation, so 12 C gets into the alkane gas earlier, resulting in a progressive reduction in 13 C from C 3 H 8 to CH 4 (James, ; McCarty & Felbeck Jr., ; Schoell, ).…”

Section: Discussionmentioning

confidence: 99%

Genesis and accumulation of natural gas in the Upper Palaeozoic strata of north‐eastern Ordos Basin, China

et al. 2018

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The north‐eastern Ordos Basin in Central China has become an exploration target in recent years due to the potential of natural gas resources in the Upper Palaeozoic strata. In this study, by analysing the geochemical characteristics of the source rocks and the natural gas, the genesis of the Upper Palaeozoic natural gas was identified. In addition, the accumulation process was discussed by combining studies of hydrocarbon generation and burial/thermal history. The results reveal three sets of source rocks developed in the study area—Carboniferous Benxi (C2b), Permian Taiyuan (P1t), and Shanxi (P1s) formations—consisting of mudstones, carbonaceous mudstones, and coals. The source rocks contain abundant Type III organic matter and have entered mature to high‐mature stage, while source rocks in the south‐eastern part of the study area have entered the overmature stage due to the activity of Zijinshan magmatic rocks. The natural gas has a high content of methane (average 93.99%). The stable carbon isotope of methane (δ13C1) value (average −37.05‰) and that of ethane (δ13C2) value (average −26.4‰) and the composition of the light hydrocarbons reflect the idea that the natural gas is organic in origin, thermogenic, and mainly terrigenous‐sourced. The evolution of a transitional to continental depositional environment of the source rocks results in the variation in the geochemical characteristics of the Upper Palaeozoic gas in the study area. Analysis of fluid inclusions indicates a long and continuous period of natural gas charging in the study area from 165 to 65 Ma. Sandstone bodies close to or interbedded with the source rocks made the gas charging from the source rocks to the reservoirs over a short distance with high efficiency, while faults and fractures provided paths for the gas migrating to reservoirs vertically far from the source rocks. The huge gas generation potential of the source rocks and continuous distribution pattern of sandstone bodies provides favourable conditions for the development of a large‐scale natural gas reservoir.

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Section: Discussionmentioning

confidence: 99%

Genesis and accumulation of natural gas in the Upper Palaeozoic strata of north‐eastern Ordos Basin, China

et al. 2018

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“…After the dissolution of the old, cold lithosphere (earlier than ca. 450 Ma) in the middle and late Mesozoic, the thermal convection in the mantle of this area was disturbed and resulted in regional uplifts, while the continental crusts above the new underplating mantle stretched and resulted in rifting depressions [77,78]. On the other hand, the plate tectonic activities and interactions were still ongoing at the same time.…”

Section: Interpretation Of the Tectonic Dynamicsmentioning

confidence: 98%

Determination of Paleocurrent Directions Based on Well Logging Technology Aiming at the Lower Third Member of the Shahejie Formation in the Chezhen Depression and Its Implications

Gao

Shi

et al. 2021

Water

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The Bohai Bay basin, mainly formed in the Cenozoic, is an important storehouse of groundwater in the North China Plain. The sedimentary deposits transported by paleocurrents often provided favorable conditions for the enrichment of modern liquid reservoirs. However, due to limited seismic and well logging data, studies focused on the macroscopic directions of paleocurrents are scarce. In this study, we obtained a series of well logging data for the sedimentary layers of Es3L Formation in the Chezhen depression. The results indicate the sources of paleocurrents from the northeast, northwest, and west to a center of subsidence in the northern Chezhen depression at that time. Based on the well testing data, the physical properties of the layers from Es3L Formation in this region were generally poor, but two abnormal overpressure zones were found at 3700–3800 m and 4100–4300 m deep intervals, suggesting potential high-quality underground liquid reservoirs. By combining with other geological evidence, we suggest that the Pacific Plate was retreating and changing its direction from NE–SE to W–E and the Bohai–Luxi block was suffering an extrusion from NE induced by the Lan–Liao and Tan–Lu strike-slip faults in the early Paleogene.

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“…values of 16 samples from the SE range from 0.31 to 38.53 mg/g (mean value: 7.86 mg/g), those of 13 samples from the BE range from 0.42 to 26.84 mg/g (mean value: 3.66 mg/g) and those of 12 samples from the FE range from 0.06 to 4.31 mg/g (mean value: 1.43 mg/g). According to the evaluation standard of organic matter abundance in lacustrine source rocks, which has been used in many lacustrine depressions (Jiang et al, 2015 and, most samples from the SE represent fair or good source rock; about half of the samples from the BE represent poor source rock, the rest being fair; about half the samples from the FE were not source rocks; the rest were fair or good source rock (Table 1; Fig. 6a).…”

Section: Organic Matter Abundance Type and Thermal Maturitymentioning

confidence: 99%

Hydrocarbon Generation Characteristics of Source Rocks from Different Saline Environments in the Dongpu Depression, Bohai Bay Basin, China

Zhang

Jiang

et al. 2021

Acta Geologica Sinica (Eng)

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The Dongpu Depression is a secondary salt‐bearing tectonic unit in the Bohai Bay Basin, eastern China. The depositional environment of this depression regarding its Paleogene strata is clearly different in plane, including the saltwater environment (SE) in the north, the freshwater environment (FE) in the south and the brackish water environment (BE) in the middle. The result of oil and gas exploration in the Dongpu Depression shows that more than 90% of the proven oil reserves are distributed in the northern saltwater environment. Previous studies indicate that the organic geochemistry characteristics and the hydrocarbon generation capacity of the source rocks are very clearly diverse under different environments, which results in the significant differences in the proved reserves between the north and the south. In order to further explore the differences in the hydrocarbon generation capacity of the source rocks under distinct depositional environments and the mechanism of their occurrence, three samples from different depositional environments (W18‐5 for SE, H7‐18 for BE, CH9 for FE) were used for confined gold tube pyrolysis experiments. The results show that the CH4 yields of W18‐5, H7‐18 and CH9 increase with increasing temperature, the maximum yields being 405.62 mg/g TOC, 388.56 mg/g TOC and 367.89 mg/g TOC, respectively. The liquid hydrocarbon yields of W18‐5, H7‐18 and CH9 firstly increase with increasing temperature and then decrease after the critical temperatures. The maximum yields of C6–14 are 149.54 mg/g TOC, 140.18 mg/g TOC and 116.94 mg/g TOC, the maximum yields of C14+ being 852.4 mg/g TOC, 652.6 mg/g TOC and 596.41mg/g TOC, respectively for W18‐5, H7‐18 and CH9. To summarize, the order of hydrocarbon potential from high to low is W18‐5, H7‐18 and CH9. On this basis, through analyzing the influencing factors of hydrocarbon differences, this paper reveals that the saltwater environment is characterized by 4 factors: higher salinity, halophilic algae, high paleo‐productivity and a strongly reducing environment, which are beneficial to the enrichment of organic matter and lead to the formation of high levels of sapropelite and exinite. According to the variation of oil and gas components in the pyrolysis experiments, the hydrocarbon generation process is divided into three stages: kerogen cracking, oil cracking and C2–5 cracking. Combined with hydrocarbon generation characteristics and stages, the evolutionary model of hydrocarbon generation for source rocks under different environments is established.

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Charging history of Paleogene deep gas in the Qibei sag, Bohai Bay Basin, China

Cited by 25 publications

References 24 publications

Genesis and accumulation of natural gas in the Upper Palaeozoic strata of north‐eastern Ordos Basin, China

Genesis and accumulation of natural gas in the Upper Palaeozoic strata of north‐eastern Ordos Basin, China

Determination of Paleocurrent Directions Based on Well Logging Technology Aiming at the Lower Third Member of the Shahejie Formation in the Chezhen Depression and Its Implications

Hydrocarbon Generation Characteristics of Source Rocks from Different Saline Environments in the Dongpu Depression, Bohai Bay Basin, China

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