Calculation of petroleum masses generated and expelled from source rocks

Cooles, G. P.; Mackenzie, A. S.; Quigley, Thomas M.

doi:10.1016/0146-6380(86)90026-4

Cited by 314 publications

(115 citation statements)

References 9 publications

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“…The carboxylic acid dominance with respect to alkalinity is particularly pronounced in the 80-120~ range. This suggests that major VFA production from organic-rich rocks in the subsurface starts at a temperature of around 80 ~ 20-40 ~ lower than that at which most petroleum source rocks start to generate significant volumes of oil and gas (Cooles et al, 1986). Once liberated inside the source rock, the aliphatic VFA species, being highly water soluble, partition into in situ pore waters where they may be expelled from the source rock.…”

Section: Discussionmentioning

confidence: 99%

Non-hydrocarbons of significance in petroleum exploration: volatile fatty acids and non-hydrocarbon gases

Cooles¹

1987

Mineral. mag.

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Non-hydrocarbon gas species (COz, N2, 1-I2) are locally important in exploration for gas, and there is a growing body of evidence that acid water originating in shales materially affects the diagenesis of nearby sandstones. These gases have been studied by analysing the products of closed-vessel hydrous pyrolysis of known petroleum source rocks, and comparing the results with field observations. Alteration of petroleum source rocks at temperatures >250 ~ yields a significant amount of non-hydrocarbon components. Ethanoate and higher acid anions are liberated in substantial quantities; the yield appears to be related to the oxygen content of the sedimentary organic matter present.The non-hydrocarbon gases CO2, H2 and N 2 are frequently the dominant gaseous products from hydrous pyrolysis: in the natural environment the same rock sequences at a higher maturity preferentially generate hydrocarbon gases--mainly methane. This discrepancy may be attributed to reaction and phase thermodynamic effects between laboratory and natural systems, behaviour that has important implications in the prediction of gas generation and composition in nature by source rock pyrolysis in the laboratory.

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Section: Discussionmentioning

confidence: 99%

Non-hydrocarbons of significance in petroleum exploration: volatile fatty acids and non-hydrocarbon gases

Cooles¹

1987

Mineral. mag.

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“…In the upper part of the Longmaxi Formation the TOC is much lower and ranges from 0.08% to 0.8%. Total organic carbon in a source rock includes three basic components: 1/ organic carbon in retained hydrocarbons, 2/ organic carbon that can be converted to hydrocarbons (called convertible, reactive or labile carbon) (Cooles et al, 1986) and 3/ carbonaceous residue that will not yield hydrocarbons, because of insufficient hydrogen, commonly referred to as inert, dead, or residual organic carbon (Jarvie, 1991). Petrographic study of the macerals from the Longmaxi Formation in Dingshan 1, Lin 1, Jianshen 1, Sanxing 1 wells and Shizhu profile show that the organic matter on average is comprised by 60 % sapropelic matter and 40 % by vitrinite-type organic matter.…”

Section: Total Organic Carbonmentioning

confidence: 99%

Characteristics of the Shale Gas Reservoir Rocks in the Lower Silurian Longmaxi Formation, East Sichuan Basin, China

Liu

Jansa

et al. 2013

Energy Exploration & Exploitation

104

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The Sichuan basin is an oil-bearing and gas-rich basin with extensive development of the Lower Silurian Longmaxi Formation shale in southwestern China. The gas shows in the shale were identified in exploration wells mainly located between southeastern Sichuan basin and Western Hubei-Eastern Chongqing. The thickness of the Lower Silurian Longmaxi Formation shale ranges from 65 to 516 m. The base of the Longmaxi Formation shale is graptolite-rich transgressive black shale. Its thickness increases eastward in the study area, similarly as the sand content in the formation, with the latter also increasing stratigraphically upward. The Longmaxi Formation is comprised by eight lithofacies, including laminated and nonlaminated mudstone/shale, dolomitic siltstone, laminated lime mudstone/shale, argillaceous siltstone, laminated and nonlaminated silty mudstone/shale, fine grained silty sandstone, calcareous concretions and nonlaminated shale enriched organic matter. The biota in the formation is dominated by graptolites, ostracods, echinoderms, brachiopods, trilobites and radiolarian. Longmaxi Formation contains 0.2% to 6.7% of organic carbon (TOC). The organic matter is overmature, with Ro 2.4%-3.6% and dominated by Type II-kerogen. Quartz silt, which is the second important component of the shale gas reservoir quality, occurs as laminae and/or disseminated and varies from 2% -93% in the shale. The size of quartz silt ranges from 0.03 to 0.05mm, with terrigenous origin. Porosity measured on the core samples of the shale from the Longmaxi Formation in exploratory wells ranges from 0.58% to 0.67%. The microporosity observed in the thin sections of the shale is about 2%, and dominated by the intercrystal and intragranular pores, with the pore size ranging from 100nm to 50µm. The other pore types are related to fractures, with the width of ranging from 2 to 5µm. The formation mechanism of the shale reservoir rocks includes favorable mineral composition, diagenesis and thermal cracking of organic component. There are some differences between Longmaxi Formation shale and Barnett shale in USA. The former is buried deeper, higher degree of thermal evolution, lower gas content, denser, more quartz of terrigenous origin. The prevailing low content of organic matter and highly variable quartz content in the Longmaxi Formation shale suggests there are only marginal conditions for exploration of shale gas resource. However, the high variability in both the content of TOC and quartz in the shale indicates that locally, particularly in the southeastern part of the basin, favorable conditions for shale gas may have developed. More detailed paleogeographic, burial history, gas content and quartz origin studies are needed to better access shale-gas potential of the Lower Silurian Longmaxi Formation shale.

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“…Based on studying many source rocks Cooles et al (1985) noted that "… most oil and gas generation occurs within the temperature range 120-150 ℃, with some limited generation occurring in some source rocks between 100-120 ℃. Most generation beyond 180 ℃ is thought to be of gas."…”

Section: Thermal Conditions and Maturity Of Om/hcsmentioning

confidence: 99%

On the Origin of Hydrocarbons in the Main Lower Pliocene Reservoirs of the South Caspian Basin, Azerbaijan

Feyzullayev

Tagiyev

Lerche

2015

Energy Exploration & Exploitation

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Two opposing points of view concerning the sources of hydrocarbons (HC) in the main reservoirs of the South Caspian Basin (SCB) Productive Series (PSLower Pliocene) reflect syngenetic or epigenetic genesis. Based on recent research results the nature of HCs in the PS is shown to be epigenetic. In the elevated onshore parts of the SCB PS Oligocene-Lower Miocene (Maikop series) rocks play a prevailing role in the formation of oil fields but in the central buried part of the SCB Middle-Upper Miocene rocks (Diatom suite) play a more dominant generation role. Нydrocarbon generation induces overpressure as shown by direct measurements in wells. The formation of HC pools in the PS occurred as a consequence of subvertical migration from underlying OligoceneMiocene deposits, characterized by impulsive injection. Two main phases of oil migration occurred during the development of commercial accumulations in the PS. The distance of subvertical migration of HCs in the SCB is estimated to be about 4 km for oils and 10-11 km for gases.

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Calculation of petroleum masses generated and expelled from source rocks

Cited by 314 publications

References 9 publications

Non-hydrocarbons of significance in petroleum exploration: volatile fatty acids and non-hydrocarbon gases

Non-hydrocarbons of significance in petroleum exploration: volatile fatty acids and non-hydrocarbon gases

Characteristics of the Shale Gas Reservoir Rocks in the Lower Silurian Longmaxi Formation, East Sichuan Basin, China

On the Origin of Hydrocarbons in the Main Lower Pliocene Reservoirs of the South Caspian Basin, Azerbaijan

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