Hydrocarbon generation and expulsion characteristics of the Lower Cambrian Qiongzhusi shale in the Sichuan Basin, Central China: Implications for conventional and unconventional natural gas resource potential

A center in the present paper is referred to as an area or region which may include one or more hydrocarbon accumulations. A hydrocarbon generation center is referred to as an area containing high quality source rock which was subjected to thermal maturation. A gas generation center is an area in which an oil pool or accumulation was present, and oil was thermally cracked to generate gas. A gas accumulation center is referred to as an area in which natural gas generated from cracked oil accumulated. A gas preservation center is referred to as an area or region where the present natural gas pool/pools is/are located. As one of the oldest petroleum reservoir rocks in the world, the upper Sinian Dengying Formation (Upper Proterozoic) in the Sichuan basin was deeply buried, and its paleo-oil pools (gas generation centers) underwent complex transformation into paleo-gas pools (gas accumulation centers) and the present gas pools (gas preservation centers) as a result of multiphase tectonic activities. The paleo oil pools (gas generation centers) were the main hydrocarbon sources of the paleo gas pools (gas accumulation centers), which were in turn the main sources of hydrocarbons for today's (remaining) gas pools (gas preservation centers). The key factor in the oil accumulation was the presence of rich hydrocarbon source rocks (hydrocarbon generation centers) in the Early Cambrian strata and a good seal development. Being controlled by the early tectonics and sedimentary development of the basin, the hydrocarbon generation centers appeared to have been stationary in space, while in time the other three centers (gas generation centers, gas accumulation centers and gas preservation centers) migrated as result of tectonic events in the basin. Therefore, the time-spatial relationships between these “three centers” (gas generation centers, gas accumulation centers and gas preservation centers) decides the final distribution of natural gas in the Sichuan basin. Relationship between generation, accumulation and preservation of hydrocarbons in the marine carbonates buried deeper than 4500 m in the Sichuan basin, can be separated into: (1) an accumulation mode with the “three centers” being superimposed; (2) an accumulation mode with “the preservation center” disintegrated; (3) an accumulation mode with the “three centers” migrated for a short distance; (4) a destruction mode with the preservation center lost. The natural gas exploration of the upper Sinian carbonate rocks in the Sichuan basin can be most successful where the “three centers” overlap, such as at the front area of the Micang Mountains, which could be the most promising area for the future gas exploration.

Download Full-text

Quantitative prediction of oil and gas prospects of the Sinian-Lower Paleozoic in the Sichuan Basin in central China

Energy ◽

10.1016/j.energy.2019.03.018 ◽

2019 ◽

Vol 174 ◽

pp. 861-872 ◽

Cited By ~ 8

Author(s):

Wenyang Wang ◽

Xiongqi Pang ◽

Zhangxin Chen ◽

Dongxia Chen ◽

Tianyu Zheng ◽

...

Keyword(s):

Sichuan Basin ◽

Oil And Gas ◽

Central China ◽

Quantitative Prediction ◽

Lower Paleozoic ◽

The Sichuan Basin

Download Full-text

Geochemical characteristics of ultra-deep natural gas in the Sichuan Basin, SW China

Petroleum Exploration and Development ◽

10.1016/s1876-3804(18)30067-3 ◽

2018 ◽

Vol 45 (4) ◽

pp. 619-628 ◽

Cited By ~ 13

Author(s):

Jinxing DAI ◽

Yunyan NI ◽

Shengfei QIN ◽

Shipeng HUANG ◽

Weilong PENG ◽

...

Keyword(s):

Natural Gas ◽

Sichuan Basin ◽

Geochemical Characteristics ◽

Sw China ◽

The Sichuan Basin

Download Full-text

Maturity evolution of Lower Cambrian Qiongzhusi Formation shale of the Sichuan Basin

Marine and Petroleum Geology ◽

10.1016/j.marpetgeo.2021.105061 ◽

2021 ◽

pp. 105061

Author(s):

Qiu Nansheng ◽

Liu Wen ◽

Fu Xiaodong ◽

Li Wenzheng ◽

Xu Qiuchen ◽

...

Keyword(s):

Lower Cambrian ◽

Sichuan Basin ◽

The Sichuan Basin

Download Full-text

Analysis of Developmental Characteristics and Dominant Factors of Pore-Fracture Systems in Lower Cambrian Marine Shale Reservoirs: A Case Study of the Niutitang Formation, Fenggang Block, Southern China

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.18461 ◽

2021 ◽

Vol 21 (1) ◽

pp. 57-71

Author(s):

Fu-Hua Shang ◽

Yan-Ming Zhu ◽

Hai-Tao Gao ◽

Yang Wang ◽

Rui-Yin Liu ◽

...

Keyword(s):

Lower Cambrian ◽

Sichuan Basin ◽

Distribution Area ◽

Strong Positive Correlation ◽

Longmaxi Formation ◽

Positive Correlation ◽

Fracture Systems ◽

Fracture Development ◽

The Sichuan Basin ◽

Niutitang Formation

Due to breakthroughs in the Lower Silurian Longmaxi Formation in the Sichuan Basin and multiple strata around the basin, the northern part of Guizhou adjacent to the Sichuan Basin has become a key area for shale gas exploration. Compared with the Longmaxi Formation, the Niutitang Formation displays greater TOC (total organic carbon) content, depositional thickness and distribution area, but the details remain undetermined. In the study area, the Lower Cambrian Niutitang Formation typically has high TOC content, maturity and brittle mineral content. The study area has experienced multiple periods of tectonic movement, which have great influence on the fracture and pore characteristics. The fractures are mainly structural fractures and have obvious zoning. The primary types of pores are intraparticle pores, organic matter pores, and interparticle pores. Further, macropores and mesopores less than 50 nm contribute most of the pore volume, while pores less than 2 nm contribute most of the specific surface area. Many factors affect the pore-fracture system, such as tectonism, TOC content, mineral composition, and sedimentary environment. Tectonic movements produce fractures based on the changing stress field, but the degree of fracture development does not agree well with the degree of pore development. The TOC content has good positive correlations with the development of fractures and micropores, especially for nanoporosity, while clay minerals show a negative correlation with the development of fractures but a strong positive correlation with the growth of micropores. Quartz displays a positive correlation with the development of fractures but no good correlation with pore development. Finally, the lithofacies, lithologies and mineral compositions under the control of sedimentary environments are internal factors that can impact the development of pore-fracture systems.

Download Full-text

Carbon isotopic composition and genetic types of natural gas in the Sichuan Basin, China

Acta Geochimica ◽

10.1007/s11631-016-0134-2 ◽

2016 ◽

Vol 36 (1) ◽

pp. 102-111

Author(s):

Jin-ning Peng ◽

Dong-yan Wang ◽

Guang-xiang Liu ◽

Min Zhang ◽

Feng-li Li

Keyword(s):

Natural Gas ◽

Isotopic Composition ◽

Sichuan Basin ◽

Carbon Isotopic Composition ◽

Carbon Isotopic ◽

Genetic Types ◽

The Sichuan Basin

Download Full-text

Slope Belts of Paleouplifts Control the Pore Structure of Organic Matter of Marine Shale: A Comparative Study of Lower Cambrian Rocks in the Sichuan Basin

Geofluids ◽

10.1155/2021/5517655 ◽

2021 ◽

Vol 2021 ◽

pp. 1-18

Author(s):

Pengfei Wang ◽

Chen Zhang ◽

Aorao Liu ◽

Pengfei Zhang ◽

Yibo Qiu ◽

...

Keyword(s):

Organic Matter ◽

Sichuan Basin ◽

Thermal Evolution ◽

Hydrocarbon Generation ◽

Thermal Maturity ◽

Marine Shale ◽

Chongqing City ◽

Stable Production ◽

The Sichuan Basin ◽

Niutitang Formation

Extensive exploration of the marine shale of the Niutitang Formation in south China has been conducted. However, exploration and development results have varied considerably in different areas. For example, the Niutitang shale in Jingyan City (Southwestern Sichuan Basin) produces a large amount of gas with a long period of stable production. In contrast, most development wells in the Niutitang shale in Chongqing City do not produce gas. Scanning electron microscopy images showed that the organic matter (OM) pore development in the Niutitang shale in Jingyan is abundant, large in size, and are well connected. In contrast, OM pores in the Niutitang shale in Chongqing are rarely observed. OM pore development of the Jingyan and Chongqing shales is mainly controlled by thermal maturity as shown by equivalent vitrine reflectance determinations. The moderate thermal maturity has resulted in the development of a large number of OM pores in the Niutitang shale in Jingyan, whereas the high thermal maturity of the Niutitang shale in Chongqing has led to the destruction of most of the OM pores. Due to the existence of ancient uplift, the shale was buried shallowly in the process of hydrocarbon generation evolution, and the shale avoided excessive thermal evolution and retained appropriate thermal maturity. In the Jingyan area, due to its location near the central uplift in the Sichuan Basin, the Niutitang shale deposited nearby avoided excessive evolution, and a large number of OM pores were retained in the reservoir.

Download Full-text