Testing Utility of Organogeochemical Proxies to Assess Sources of Organic Matter, Paleoredox Conditions, and Thermal Maturity in Mature Marcellus Shale

Agrawal, Vikas

doi:10.3389/fenrg.2018.00042

Cited by 15 publications

(4 citation statements)

References 37 publications

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“…In these parameters, S 1 represents the volatile free liquid hydrocarbons per unit mass of rock measured at 300 °C, which can quickly and intuitively characterize the amount of free oil in shales. 45,46 The study shale (Chang 7 Formation) is in the low-to mid-mature stage of hydrocarbon generation, as observed in the rock eval pyrolysis data. The value of S 1 here ranges between 2.39 and 9.34 mg/g while the T max values range between 439 and °C (average 447.2 °C) (Table 3).…”

Section: Materials and Methodologymentioning

confidence: 85%

“…Rock pyrolysis parameters include free hydrocarbons, hydrocarbon generation potential, total organic carbon (TOC), oil generative potential ( S 2 ), thermal maturity ( T max ), and other parameters, which can effectively evaluate reservoir fluid properties. In these parameters, S 1 represents the volatile free liquid hydrocarbons per unit mass of rock measured at 300 °C, which can quickly and intuitively characterize the amount of free oil in shales. , …”

Section: Materials and Methodologymentioning

confidence: 99%

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A New Approach To Calculate Gas Saturation in Shale Reservoirs

Chen

et al. 2022

Energy Fuels

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In recent years, China's shale gas exploration and development has achieved immense development, but the evaluation of fluid saturation in shale gas reservoirs is still not well documented. The Mesozoic Chang 7 Formation is one of the main source rocks in the Ordos Basin and has also proven to have good shale gas accumulation conditions. At present, there are a few methods to directly obtain gas saturation in shale reservoirs, and the conventional method using Archie's equation (which is mainly designed for pure sandstone reservoirs) is still accepted by most researchers. However, because shales usually contain some amount of clay minerals, the accuracy of the calculated gas saturation is reduced. To compensate for the presence of clay minerals, the Waxman-Smits (W-S) model was proposed, with high applicability in the quantitative calculation of water saturation. In this study, we calculated the oil saturation values of the Chang 7 Formation and compared the results with laboratory-measured values. Furthermore, we complimented our results with the support vector machine (SVM) machine-learning algorithm to make up for sparse data from the laboratory measurements. Our results suggest that gas saturation in shale reservoirs can be obtained by the calculation of oil saturation first, using laboratory-measured litho-electric and pyrolysis data, as well as using the W-S model. When the results were applied to other locations in the study area, the results were consistent with the calculated gas saturation values using previously proposed (laborious) methodologies. This suggests that the methods described here can be applied to calculate gas saturation in unconventional reservoirs.

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Section: Materials and Methodologymentioning

confidence: 85%

Section: Materials and Methodologymentioning

confidence: 99%

A New Approach To Calculate Gas Saturation in Shale Reservoirs

Chen

et al. 2022

Energy Fuels

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“…Exploring the enrichment pattern of sedimentary organic matter is becoming increasingly significant as the total organic carbon (TOC) content in shale is influenced by thermal evolution degrees and abundance of this matter. Many studies using different approaches have been conducted to analyze the mechanism [5][6][7][8][9]. Xia et al utilized trace and rare Earth elements to prove that ascending currents facilitated organic matter enrichment.…”

Section: Introductionmentioning

confidence: 99%

Influence of Organic Matter on Gas-Bearing Properties and Analysis of Sedimentary Mechanism of Organic Matter Enrichment: A Case Study on the Yangtze Region of Southern China during the Early Cambrian

Zhang

Wei

et al. 2022

Geofluids

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Shale gas exploration requires studies on the enrichment mechanism of sedimentary organic matter. The Lower Cambrian shale is taken as a study object to analyze the effect of organic matter on gas content using TOC content and porosity analyses, isothermal adsorption experiments, and FIB-HIM scanning electron microscopy observations. Then, we selected typical wells to determine the presence of excessive silica in the siliceous minerals by quantitative calculations. Besides, we analyzed the genesis of excessive siliceous minerals using elements including Al, Fe, and Mn, thus speculating the controlling factors of the redox environment and biological productivity. Results show that total organic carbon content controls the content of free and adsorbed gas, while shale gas mainly exists in organic pores and is developed in large numbers and with high roundness, showing the characteristics of “small pores inside big pores.” In the Lower Yangtze region during the Early Cambrian, the excessive siliceous minerals were of hydrothermal origin, and there were frequent hydrothermal activities due to its closeness to plate boundaries. These activities can intensify the reducibility of the waterbody’s bottom and improve the biological productivity on its surface, resulting in the enrichment of this matter. Most excessive silicon in this region is biogenic, while only a small part is of hydrothermal and biogenic mixed origin. The enclosed waterbody of the Upper Yangtze region was far from plate boundaries and close to the semiclosed “gulf,” resulting in its delamination. The waterbody’s surface was abundant with oxygen, thus increasing the biological productivity, while the high reducibility at the waterbody’s bottom was conducive to preserving sedimentary organic matter.

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“…The Marcellus Shale is the most productive shale formation for dry gas in the United States (EIA, 2016) and is economically vital to the Appalachian region. However, within the Marcellus shale Formation, there can be significant variations in total organic carbon, organic matter type, thermal maturity, and mineralogy (U.S. EIA, 2017;Agrawal and Sharma, 2018a, 2018cPilewski et al, 2019;Sharma et al, 2020a;Sharma et al, 2020b). Due to these variations in physicochemical properties, the chemical reactions that occur within hydraulically fractured unconventional formations can vary significantly, and influence the selection of hydraulic fracturing fluid (HFF) components used at any given well site (Abualfaraj et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

et al. 2021

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Natural gas extracted from tight shale formations, such as the Marcellus Shale, represents a significant and developing front in energy exploration. By fracturing these formations using pressurized fracturing fluid, previously unobtainable hydrocarbon reserves may be tapped. While pursuing this resource, hydraulic fracturing operations leave chemically complex fluids in the shale formation for at least two weeks. This provides a substantial opportunity for the hydraulic fracturing fluid (HFF) to react with the shale formation at reservoir temperature and pressure. In this study, we investigated the effects of the carbonates on shale-HFF reactions with a focus on the Marcellus Shale. We performed autoclave experiments at high temperature and pressure reservoir conditions using a carbonate-rich and a decarbonated or carbonate-free version of the same shale sample. We observed that carbonate minerals buffer the pH of the solution, which in turn prevents clay dissolution. Carbonate and bicarbonate ions also scavenge reactive oxidizing species (ROS), which prevents oxidation of shale organic matter and volatile organic compounds (VOCs). Carbonate-free samples also show higher pyrite dissolution compared to the carbonate-rich sample due to chelation reactions. This study demonstrates how carbonate minerals (keeping all other variables constant) affect shale-HFF reactions that can potentially impact porosity, microfracture integrity, and the release of heavy metals and volatile organic contaminants in the produced water.

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Testing Utility of Organogeochemical Proxies to Assess Sources of Organic Matter, Paleoredox Conditions, and Thermal Maturity in Mature Marcellus Shale

Cited by 15 publications

References 37 publications

A New Approach To Calculate Gas Saturation in Shale Reservoirs

A New Approach To Calculate Gas Saturation in Shale Reservoirs

Influence of Organic Matter on Gas-Bearing Properties and Analysis of Sedimentary Mechanism of Organic Matter Enrichment: A Case Study on the Yangtze Region of Southern China during the Early Cambrian

Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

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