Gas generation of shale organic matter with different contents of residual oil based on a pyrolysis experiment

Gai, Haifeng; Xiao, Xianming; Cheng, Peng; Tian, Hui; Fu, Jiamo

doi:10.1016/j.orggeochem.2014.11.001

Cited by 43 publications

(35 citation statements)

References 50 publications

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“…Kaolinite begins to convert to illite rapidly and generate illite/smectite (I/S) as an intermediate product [53], leading to the decrease in kaolinite and increase in illite and I/S, while smectite in I/S converts to illite during the period. Kerogen pyrolysis, liquid hydrocarbon and bitumen cracking, and volatile matter release generate nearly circular or bubble-like pores in OM [54,55] and gaseous hydrocarbon generation forms high pore pressure resisting further compaction [56,57], while OM shrinkage forms fissures [58]. Organic acids originating from kerogen decarboxylation, hydrocarbon cracking, and minerals oxidation dissolve feldspar and clay mineral to form secondary pores [59,60].…”

Section: Pore Evolutionmentioning

confidence: 99%

Upper Paleozoic Transitional Shale Gas Enrichment Factors: A Case Study of Typical Areas in China

Wang

Guo

2020

Minerals

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Based on the shale gas research experience in North America, large-scale geological evaluations have been conducted in China to determine the enrichment characteristics of deep marine shale gas, leading to the discovery of the Fuling, Changning and Weiyuan shale gas fields. However, research on Upper Paleozoic transitional shale gas remains limited, restricting the subsequent exploration and development. Therefore, taking the Lower Permian Shanxi and Pennsylvanian Taiyuan Formations in the northeastern Ordos Basin and the Upper Permian Longtan Formation in southwestern Guizhou as examples, gas logging, gas desorption, thermal simulation, maximum vitrinite reflectance (Rmax), and X-ray diffraction (XRD) were used to study the influence of lithological associations, sedimentary facies, gas generation thresholds, and pore evolution on transitional shale gas, and then Upper Paleozoic transitional shale gas enrichment factors of the northeastern Ordos Basin and southwestern Guizhou were analysed. The results show that carbonaceous mudstone adjacent to coal seams presents a high gas content level, and is primarily developed in swamps in the delta plain environment, and swamps and lagoons in the barrier coastal environment. The gas generation threshold maturity (Rmax) of transitional shale is 1.6% and the corresponding threshold depths of the northeastern Ordos Basin and southwestern Guizhou are estimated to be 2265 m and 1050 m. Transitional shale pore evolution is jointly controlled by hydrocarbon generation, clay minerals transformation, and compaction, and may have the tendency to decrease when Rmax < 1.6% or Rmax > 3.0%, but increase when Rmax ranges between 1.6% and 3.0%, while the main influential factors of pore evolution differ in each period. Continuous distribution of transitional shale gas enrichment areas can be formed along the slope adjacent to coal seams with a moderate maturity range (1.6%–3.0%) in the northeastern Ordos Basin, and transitional shale gas can be enriched in the areas adjacent to coal seams with a moderate maturity range (1.6%–3.0%), abundant fractures, and favorable sealing faults in southwestern Guizhou.

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Section: Pore Evolutionmentioning

confidence: 99%

Upper Paleozoic Transitional Shale Gas Enrichment Factors: A Case Study of Typical Areas in China

Wang

Guo

2020

Minerals

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“…Some studies report that hydrocarbon expulsion efficiency plays an important role on resource abundance in a shale oil/gas layer (Jarvie et al 2007;Jia et al 2014;Li et al 2015). Petroleum geologists have found that retained oil in shales influences not only the gas generation potential at high maturities, but also the chemical compositions of gaseous products (Gai et al 2015;Pan et al 2012). In addition, researchers have stated that oil and gas released during hydrocarbon generation may attach to kerogens (Erdmann and Horsfield 2006;Mahlstedt et al 2008;Vu et al 2008).…”

Section: Introductionmentioning

confidence: 99%

“…This recombination between hydrocarbon and kerogen structures at low thermal maturity can affect hydrocarbon generation at high maturity in different ways, depending on the types and thermal maturities of organic matters. Gai et al (2015) used mixtures of immature kerogens and artificially matured oils in their pyrolysis experiments. The results suggested that interactions between kerogens and residual oils during hydrocarbon generation do not change total gas generation potential.…”

Section: Introductionmentioning

confidence: 99%

Hydrocarbon generation from lacustrine shales with retained oil during thermal maturation

Shao

Pang

et al. 2020

Pet. Sci.

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Thermal maturation in the shale oil/gas system is inherently complex due to the competitive interplays between hydrocarbon generation and retention processes. To study hydrocarbon generation characteristics from shales within different stages of thermal maturation under the influence of retained oil, we performed Micro-Scale Sealed Vessels (MSSV) pyrolysis on a set of artificially matured lacustrine shale samples from the Shahejie Formation in the Dongpu Depression in Bohai Bay Basin, China. Experimental results show that hydrocarbon yields of shale samples with or without retained oil at various thermal maturities follow different evolution paths. Heavy components (C 15+) in samples crack at high temperatures and generally follow a sequence, where they first transform into C 6-14 then to C 2-5 and C 1. Methane accounts for most of the gaseous products at high temperatures in all samples, with different origins. The cracking of C 2-5 is the main methane-generating process in samples with retained oil, whereas the source of methane in samples without retained oil is kerogen. In the studied shales, retained oils at early-mature stage retard the transformation of liquid to gaseous hydrocarbon and prompt the cracking of C 2-5 to C 1 to some extent. TSR reaction related to gypsum in the studied samples is the primary reason that can explain the loss of hydrocarbon yields, especially at high temperatures. In addition, transformation of volatile hydrocarbons to gas and coke also accounts for the loss of generated hydrocarbon, as a secondary factor.

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“…The simulation of hydrocarbon expulsion under actual geological conditions is also difficult. Gai et al (2015) used an artificial mix of kerogen and its extracts to design a suite of samples with variable oil expulsion efficiencies, and performed pyrolysis experiments to analyze the effect of oil expulsion efficiency on shale gas generation in a closed system. During shale maturation, however, bitumen is an intermediate product with an evolving concentration, composition, and gas generation potential.…”

Section: Introductionmentioning

confidence: 99%

The origin and evolution of thermogenic gases in organic-rich marine shales

Xiong

Zhang

Chen

et al. 2016

Journal of Petroleum Science and Engineering

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Gas generation of shale organic matter with different contents of residual oil based on a pyrolysis experiment

Cited by 43 publications

References 50 publications

Upper Paleozoic Transitional Shale Gas Enrichment Factors: A Case Study of Typical Areas in China

Upper Paleozoic Transitional Shale Gas Enrichment Factors: A Case Study of Typical Areas in China

Hydrocarbon generation from lacustrine shales with retained oil during thermal maturation

The origin and evolution of thermogenic gases in organic-rich marine shales

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