Variation in the carbon isotopic composition of alkanes during shale gas desorption process and its geological significance

Meng, Qiang; Wang, Xiangzeng; Zhang, Lixia; Jiang, Chengfu; Li, Xiaofu; Shi, Baoguang

doi:10.1016/j.jnggs.2016.05.004

Cited by 16 publications

(23 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The isotope enrichment determined for ethane release ε = −2.7 to −3.7% was larger than that measured for rock experiments (−0.8 to −1.6% ) [9]. Although quite different isotope fractionation values for both methane (−9.2% ) and ethane (−2.8% ) were reported in the experimental study in Reference [28], it is generally accepted that carbon isotope fractionation should decrease with increasing carbon number [9,29]. Results from diffusion modeling in Reference [11] were also similar.…”

Section: Carbon Isotope Fractionation During the Sample Degassingcontrasting

confidence: 53%

Evaluation of the Gas Content in Archived Shale Samples: A Carbon Isotope Study

et al. 2019

View full text Add to dashboard Cite

We examined 14 archived samples of shale for the chemical and 13C isotopic composition of residual gases produced as part of rock-crushing operations at a hammer mill. Results were compared with data on maturity from Rock-Eval pyrolysis and vitrinite reflectance measurements. The samples originated from three different formations (Mikulov Marls, Ostrava Formation, and Liteň Formation) located in the Czech Republic. For comparison, we examined a gas-prone shale sample from the Polish Silurian. We used changes in the chemical and isotopic composition of released gases to evaluate the isotope fractionation during gas loss and retroactively calculated the initial content of gas in the shale samples. The gas content estimates (in L of gas per ton of rock) correspond with the maturity parameters of the shales. Calculated isotope fractionation for the gas release was −3‰ for both methane and ethane. The archived samples primarily lost methane (up to 90%), with subsequent changes in the content of ethane and higher hydrocarbon levels.

show abstract

Section: Carbon Isotope Fractionation During the Sample Degassingcontrasting

confidence: 53%

Evaluation of the Gas Content in Archived Shale Samples: A Carbon Isotope Study

et al. 2019

View full text Add to dashboard Cite

show abstract

“…10−12 The adsorption/desorption effect can result in a partitioning of the methane isotopologues because a methane molecule with a 13 C atom ( 13 CH 4 ) has higher adsorption energy compared with a methane molecule with a 12 C atom ( 12 CH 4 ). 13 Generally, the fraction of 12 CH 4 is higher than that of 13 CH 4 in shale gas stored in nanopores since 13 CH 4 is in trace amounts. The proportion of adsorbed isotope gas on the surface of organic (OP) and inorganic pores (IP) commonly accounts for 20−85% of the total gas content.…”

Section: Introductionmentioning

confidence: 99%

Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Wang

Zhao

et al. 2021

Energy Fuels

View full text Add to dashboard Cite

Carbon isotope fractionation is a promising method to predict gas-in-place content and evaluate the shale gas production stage. In this study, molecular simulations are conducted to investigate fractionation characteristics of 12CH4 and 13CH4 in high-Kn (Knudsen number) flows (Kn > 0.1) within organic and inorganic pores under shale reservoir conditions (353 K, 5–25 MPa). The results show that isotope fractionation is more obvious (i.e., the difference in transport capacities between 12CH4 and 13CH4 is larger) in organic pores than in inorganic pores. Methane adsorption capacity and surface roughness of pore walls are two major reasons. High-coverage adsorption in organic pores reduces the effective pore size, and the Knudsen diffusion becomes significant. Moreover, the specular reflection of molecules occurs frequently on the smooth surfaces of organic pores, which enlarges the difference in isotope diffusion capacity. Indeed, the difference in energy (specific enthalpy) transport of methane isotopes in organic and inorganic pores is the intrinsic reason for fractionation. Furthermore, the fractionation level is positively correlated with Kn due to the enhanced contribution of Knudsen diffusion and surface diffusion in high-Kn flows. In addition, the isotope fractionation level decreases as pore size increases because Kn and the contribution of the adsorbed phase to the total molar flux reduce in a large pore. Our findings and related analyses may help us to understand isotope fractionation in different pore types and sizes from the atomic level and assist future applications in engineering.

show abstract

“…Meanwhile, stable carbon isotope analysis have been carried out on coal [9][10][11][12] and shale cuttings and core chips sealed in headspace or bags [13][14][15][16][17][18][19], and these results reported isotopic shifts which are both large and changing over the time after collection, as a typical example depicted in Figure 1 here. Figure 1.…”

mentioning

confidence: 99%

“…Depicts the headspace isotope composition analysis (HICA) of cuttings from shale or coal chips. Previous results [9][10][11][12][13][14][15][16][17][18][19][20] strived to retrieve the permeability information through simple diffusion and adsorption models, while this paper describes the model to extract the pore throat and pore pressure information based on HICA.…”

mentioning

confidence: 99%

“…Geomark [19] related the heavy fractionation to permeability and sweetspots, because adsorption favors heavy 13 CH4 methane and better permeability will release the lighter 12 CH4 faster, and this seemingly intuitive model has been adopted by some [18] in the shale drilling community. While some argue that adsorption fractionation is a minor factor even when adsorption favors 13 CH4 [11,20] and therefore diffusion process should dominate the heavy fractionation.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Headspace Isotope & Compositional Analysis for Unconventional Resources: Gas in Place, Permeability and Porosity Prediction and Completions Planning

Tang

Lin

et al. 2020

Geosciences

View full text Add to dashboard Cite

Cuttings/cores’ Headspace Isotope and Composition Analysis (HICA) provides an effective way to calculate the nano pore throat size and distributions much like nitrogen and CO2 adsorption BET/BJH analysis, and it could also provide information about the original pore pressure or gas in place. Tight gas and oil storage is different from conventional where a majority of oil and gas are stored in nanometer sized pores (nanopores). Therefore the nanofludics, i.e., nanometer scale capillary sealing and opening in nanopores of tight rocks, plays a key role in overpressure conservation and storage of oil and gas, and also the fracing process involves the opening of the nano pore capillary seals through rock-fluid interactions. The rock-fluid nanofluidics interactions during fracing could also be studied through HICA and the results could help the optimization of fracing designs.

show abstract

Variation in the carbon isotopic composition of alkanes during shale gas desorption process and its geological significance

Cited by 16 publications

References 6 publications

Evaluation of the Gas Content in Archived Shale Samples: A Carbon Isotope Study

Evaluation of the Gas Content in Archived Shale Samples: A Carbon Isotope Study

Carbon Isotope Fractionation during Shale Gas Transport through Organic and Inorganic Nanopores from Molecular Simulations

Headspace Isotope & Compositional Analysis for Unconventional Resources: Gas in Place, Permeability and Porosity Prediction and Completions Planning

Contact Info

Product

Resources

About