Controlling Factor Analysis of Microstructural Property and Storage Capacity of Deep Longmaxi Formation Shale in Sichuan Basin

2021 ◽  
Author(s):  
Jianchao Cai ◽  
Zhenhua Tian ◽  
Shangwen Zhou ◽  
Yihua Xiong ◽  
Chenhao Sun ◽  
...  
Keyword(s):  
Factor Analysis ◽  
Sichuan Basin ◽  
Storage Capacity ◽  
Controlling Factor ◽  
Longmaxi Formation ◽  
Microstructural Property ◽  
And Storage

The molecular and carbon isotopic constrains on origin and storage of Longmaxi Formation shale gas in Changning area, Sichuan Basin, China

2015 ◽  
Vol 3 (2) ◽  
pp. SJ35-SJ47 ◽  
Author(s):  
Qingyan Tang ◽  
Mingjie Zhang ◽  
Chunhui Cao ◽  
Zhe Song ◽  
Zhongping Li ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Mass Spectrometry Analysis ◽  
Hydrocarbon Gases ◽  
Longmaxi Formation ◽  
Isotopic Compositions ◽  
Carbon Isotopic ◽  
Longmaxi Shale ◽  
And Storage

We have developed a vacuum-crushing method for the extraction of gases stored in shale for the determination of gas yield, chemical composition, and carbon isotopic composition by online gas-chromatography and mass spectrometry. Analysis of the evacuation and parallel experiments showed low standard deviation and good reproducibility. This approach significantly improved the detection limits for trace-gas analysis in shale and measured multiple nonhydrocarbon gas components in a single run. We analyzed the chemical and carbon isotopic compositions of the gases released by one-step vacuum crushing from nineteen samples of organic-rich Longmaxi Formation (Fm.) shale in Changning outcrop, Sichuan Basin, China, and we studied the main controls on gas chemistry of retained gas in the Longmaxi Shale. The results showed that the crushed gas is high in [Formula: see text] and [Formula: see text] but low in [Formula: see text]. The crushed gas has obviously lower [Formula: see text] ratios than the gas produced from the Longmaxi Fm. after hydraulic fracturing; it was dominated by [Formula: see text] gas while it is normalized to 100% total gaseous hydrocarbons and similar in chemical composition to hydrocarbon gases in the produced gas. Yields of [Formula: see text], [Formula: see text], and [Formula: see text] in the crushed gas of most samples showed a weak positive correlation with total organic carbon (TOC) contents. The crushed gas had significantly light [Formula: see text] (on average [Formula: see text]) values and similar [Formula: see text] values when compared with the produced gas in the Changning area. The [Formula: see text] values of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] have similar features to the produced gas from the Weiyuan shale-gas play. Isotopically reversed trends ([Formula: see text]) between ethane and methane were observed for some samples. Our findings regarding the similarity in chemical and carbon isotopic compositions between crushed gas and produced gas from the Weiyuan shale-gas play might provide important evidence of the origin and storage of shale gas in the organic-rich Silurian Longmaxi Fm.

scholarly journals Effect of organic maturity on shale gas genesis and pores development: A case study on marine shale in the upper Yangtze region, South China

2020 ◽  
Vol 12 (1) ◽  
pp. 1617-1629
Author(s):  
Kun Zhang ◽  
Jun Peng ◽  
Xin Wang ◽  
Zhenxue Jiang ◽  
Yan Song ◽  
...  
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Storage Capacity ◽  
Thermal Evolution ◽  
Marine Shale ◽  
The Sichuan Basin ◽  
The Impact ◽  
And Storage ◽  
Cracking Gas

AbstractThe marine shale in southern China has undergone complex tectonic evolution with a high thermal evolution degree. Excessive thermal evolution brings certain risks to shale gas exploration and development. With the advancement of experimental methods, the evolution process of shale reservoirs can be better understood from the micro-nanoscale. This work takes the Ordovician-Silurian Wufeng and the first member of Longmaxi Formation in the Sichuan Basin and Lower Cambrian Niutitang Formation in Outer Margin of the Sichuan Basin to study the impact of maturity upon the genesis of shale gas and development features of the reservoir. A series of geochemical research methods, including TOC, gas component and gas isotope, were adopted to study the impact of different thermal evolution stages of organic matter upon the genesis of shale gas. The nanoscale micro-imaging technique, such as FIB-SEM and FIB-HIM, was used to analyze the development of OM-hosted pores. As shown from the results, when Ro = 1.2–3.5%, the marine shale gas is dominated by methane and other hydrocarbon gases, since the mixture of cracking gas from liquid hydrocarbons and kerogen-cracking gas cause the carbon isotope reversal. Besides, the pyrobitumen pores characterized by the strong connectivity and storage capacity were primarily developed. When Ro > 3.5%, the organic matter is at the graphitization stage. The shale gas is mainly composed of nitrogen at this stage. The nitrogen is originated from the atmosphere and the thermal evolution process, and the OM-hosted pores (pyrobitumen and kerogen pores) characterized by the bad connectivity and storage capacity are developed. Finally, the main component of shale gas, the genesis of shale gas and the pattern of OM-hosted pores under different thermal evolution stages of organic matter are summarized, which provide technical support for the exploration and development of shale gas.

scholarly journals Coupling between Source Rock and Reservoir of Shale Gas in Wufeng-Longmaxi Formation in Sichuan Basin, South China

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2679
Author(s):  
Yuying Zhang ◽  
Shu Jiang ◽  
Zhiliang He ◽  
Yuchao Li ◽  
Dianshi Xiao ◽  
...  
Keyword(s):  
Source Rock ◽  
Shale Gas ◽  
Sichuan Basin ◽  
Gas Content ◽  
Potential Zone ◽  
Hydrocarbon Generation ◽  
Gas Generation ◽  
Longmaxi Formation ◽  
Siliceous Shale ◽  
Organic Pores

In order to analyze the main factors controlling shale gas accumulation and to predict the potential zone for shale gas exploration, the heterogeneous characteristics of the source rock and reservoir of the Wufeng-Longmaxi Formation in Sichuan Basin were discussed in detail, based on the data of petrology, sedimentology, reservoir physical properties and gas content. On this basis, the effect of coupling between source rock and reservoir on shale gas generation and reservation has been analyzed. The Wufeng-Longmaxi Formation black shale in the Sichuan Basin has been divided into 5 types of lithofacies, i.e., carbonaceous siliceous shale, carbonaceous argillaceous shale, composite shale, silty shale, and argillaceous shale, and 4 types of sedimentary microfacies, i.e., carbonaceous siliceous deep shelf, carbonaceous argillaceous deep shelf, silty argillaceous shallow shelf, and argillaceous shallow shelf. The total organic carbon (TOC) content ranged from 0.5% to 6.0% (mean 2.54%), which gradually decreased vertically from the bottom to the top and was controlled by the oxygen content of the bottom water. Most of the organic matter was sapropel in a high-over thermal maturity. The shale reservoir of Wufeng-Longmaxi Formation was characterized by low porosity and low permeability. Pore types were mainly <10 nm organic pores, especially in the lower member of the Longmaxi Formation. The size of organic pores increased sharply in the upper member of the Longmaxi Formation. The volumes of methane adsorption were between 1.431 m3/t and 3.719 m3/t, and the total gas contents were between 0.44 m3/t and 5.19 m3/t, both of which gradually decreased from the bottom upwards. Shale with a high TOC content in the carbonaceous siliceous/argillaceous deep shelf is considered to have significant potential for hydrocarbon generation and storage capacity for gas preservation, providing favorable conditions of the source rock and reservoir for shale gas.

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