scholarly journals Petrographic evidence for hydrocarbon migration in Lower Cambrian sandstones, Bornholm, Denmark

1999 ◽  
Vol 45 ◽  
pp. 117-127 ◽  
Author(s):  
Lars Nicolai Nebel Møller ◽  
Henrik Friis
Keyword(s):  
Source Rock ◽  
Lower Cambrian ◽  
Hydrocarbon Generation ◽  
Reservoir Properties ◽  
Hydrocarbon Migration ◽  
Middle Cambrian ◽  
Alum Shale ◽  
Dark Colour ◽  
Quartz Cement ◽  
And Migration

The Lower Cambrian sandstones from Bornholm, and in particular the Hardeberga Sandstone, contain a substance that has been interpreted to be pyrobitumen which causes the dark colour seen at many outcrop localities. The presence of pyrobitumen indicates the former presence of hydrocarbons that migrated through the sandstones during the Mid Palaeozoic subsidence. In contrast to previous assumptions it is shown that even though the sandstones were extensively com-pacted, it had only very little cement, and consequently excellent reservoir quali-ties at the time of hydrocarbon generation and migration. The only known source rock is the Middle Cambrian Alum Shale that must have been down-faulted rela-tive to the lower Cambrian sandstones at the time of hydrocarbon generation. Quartz cement did not form until deep burial, and similar sandstones at locations outside the onshore Bornholm area that have not been so deeply buried may not have quartz cement and therefore still posses good reservoir properties.

The coupled generation of organic acids and hydrocarbons during source rock maturation

2020 ◽  
Author(s):  
Jian Chen ◽  
Jie Xu ◽  
Zhenyu Sun ◽  
Susu Wang ◽  
Wanglu Jia ◽  
...  
Keyword(s):  
Organic Acids ◽  
Source Rock ◽  
Maximum Yield ◽  
Source Rocks ◽  
Type I ◽  
Hydrocarbon Generation ◽  
Pore Waters ◽  
Reservoir Properties ◽  
Type Iii ◽  
Short Period

<p><strong>Introduction: </strong>Organic acids which are commonly detected in oilfield waters, can partially enhance reservoir properties. Previous studies have suggested that cleavage of the oxygen-containing functional group in kerogen is a major source of organic acids. However, this cleavage is assumed to occur before the source rock enters the oil window. If this is correct, then these acids can dissolve only minerals in the source rocks. Presently, no detailed study of the generation of organic acids during the whole thermal maturation of source rocks has been conducted. It is unclear whether organic acids could migrate into reservoirs.</p><p><strong>Aim: </strong>This research simulated the thermal evolution of source rocks in order to build a coupled model of organic acid and hydrocarbon generation, and investigate if organic acids generated in source rocks can migrate into reservoirs.</p><p><strong>Methods: </strong>Three immature source rocks containing type I, II, and III kerogens were crushed to 200 mesh. These powders, along with deionized water, were sealed in Au tubes and heated to 220–360°C for 72 h (EasyRo 0.37-1.16%). All the run products, including organic acids, gas, and bitumen, were analyzed.</p><p><strong>Results: </strong>At all temperatures, the organic acids dissolved in the waters are composed of formate, acetate, propionate, and oxalate. Acetate is the major compound with a modal proportion of >83%. The maximum yield of total organic acids was from source rocks containing type I kerogen (31.0 mg/g TOC), which was twice that from source rocks containing type II and III kerogens (13.3–15.4 mg/g TOC). However, for the type I and II kerogen-bearing source rocks, the organic acids reached a maximum yield (EasyRo = 1.16%) following the bitumen generation peak (EasyRo = 0.95%). Organic acids from type III kerogen-bearing source rocks reached their maximum yield (EasyRo = 0.95%) before the source rock entered the gas window (EasyRo > 1.16%).</p><p><strong>Conclusions: </strong>Our data suggest that the generation of organic acids is coupled with the generation of oil from type I and II kerogen-bearing source rocks, but form earlier than gas from type III kerogen-bearing source rocks. As such, some organic acids dissolved in pore waters are possibly expelled from source rocks containing type I and II kerogen with oils, which can then migrate into reservoirs. Migration of organic acids into reservoirs from source rocks containing type III kerogen is also possible in some situations. For example, when a source rock is rapidly buried for a short period, such as in the Kuqa Depression, Tarim Basin, China, the generation interval of organic acids and gas is short. Both could be expelled outside and migrate upwards into reservoirs. In conclusion, organic acids derived from source rocks can contribute to reservoir alteration.</p>

Clay diagenesis in the Kimmeridge Clay Formation, onshore UK, and its relation to organic maturation

1987 ◽  
Vol 51 (362) ◽  
pp. 535-551 ◽  
Author(s):  
Iain C. Scotchman
Keyword(s):  
Source Rock ◽  
Fine Fraction ◽  
Upper Jurassic ◽  
Hydrocarbon Generation ◽  
The North ◽  
And Migration ◽  
Oil Source ◽  
Hydrocarbon Expulsion ◽  
The Uk ◽  
Clay Formation

AbstractConversion of randomly ordered illite-smectite to ordered illite-smectite in the Upper Jurassic Kimmeridge Clay Formation from the North Sea has been recorded in the literature as occurring within the ‘oil window’ and has been suggested as an indicator of oil source rock maturity. Studies of authigenic clay minerals in the fine fraction (>0.5 µm) of the Kimmeridge Clay Formation mudstones from fourteen locations along the UK onshore outcrop between Dorset and North Yorkshire show that they comprise mainly ordered illite-smectites. The onshore Kimmeridge Clay section is organically immature, suggesting that the illite-smectite ordering reaction cannot be extrapolated between basins as an inorganic indicator of ‘oil window’ levels of maturity. These results also have important implications in source rock hydrocarbon expulsion and migration models which involve shale dewatering as a flushing agent. However, dewatering of shales may aid migration as it could cause fracturing of the shale bands separating the organic-rich layers within the source rock, prior to hydrocarbon generation.

Hydrocarbon Origin and Accumulation Model of Putaohua Reservoir in Southern Daqing Placanticline Area

2012 ◽  
Vol 616-618 ◽  
pp. 64-68
Author(s):  
Na Wang ◽  
Shuang Fang Lu ◽  
Dian Shi Xiao
Keyword(s):  
Source Rock ◽  
Oil And Gas ◽  
Source Area ◽  
Analysis Data ◽  
Research Area ◽  
Hydrocarbon Generation ◽  
Small Contribution ◽  
Hydrocarbon Migration ◽  
Oil And Gas Exploration ◽  
Accumulation Model

There are great oil and gas exploration prospect in south of Daqing Placanticline, with unclear understanding of source rock and accumulation model, the progress of oil exploration is restricted. To definite the source of oil and gas, according to chromatography data and analysis data, combined with potential of hydrocarbon generation and expulsion, oil-gas migration pathway, the hydrocarbon migration and accumulation model is proposed. It can be concluded that the oil from Putaohua reservoir in the south of Daqing Placanticline area mainly come from K2qn1 source rock locally, while the hydrocarbon sources of K2qn1 in the east and west of the depression makes small contribution to the research area. Migrate in source area is the main hydrocarbon migration and accumulation mode. Re-define the oil source of Putaohua reservoir can help enhance the cognition of the hydrocarbon accumulation condition and accumulation model, in order to direct the research for the accumulation and distribution principle of oil and gas exploration and favorable area prediction in the future.

scholarly journals Further contributions to the knowledge of the Palaeozoic of Slagelse no. 1, Western Sealand

1974 ◽  
Vol 101 ◽  
pp. 1-42
Author(s):  
Chr. Poulsen
Keyword(s):  
New Species ◽  
Lower Cambrian ◽  
Upper Permian ◽  
Deep Borehole ◽  
Middle Cambrian ◽  
Lower Silurian ◽  
Alum Shale ◽  
Framboidal Pyrite ◽  
Lowermost Part ◽  
A New Species

The material described and discussed in the present paper originates from a deep borehole near Slagelse on western Sealand. The lowermost strata have been referred to the Lower Cambrian (Sorgenfrei & Buch 1964 and C. Poulsen 1969). The present paper deals with the succession of strata between the Lower Cambrian and the Upper Permian evaporite series. The sediments in question are: Alum shale (lowermost part possibly Middle Cambrian and uppermost part possibly basal Ordovician), shales and siltstones with Lower Silurian graptolites (Table 2, p. 11), red, silty claystone (Rotliegendes?), and finally grey dolomite and dark grey, thinly laminated shale with Upper Permian gymnosperm pollen and numerous remains of a vigorous vegetation of hepatics.The description and discussion of the Silurian fossils embrace trace fossils, brachiopods, eurypterids, asteroids, graptolites (e.g. two new species of Dictyonema and a new species of Monograptus), and finally a few vertebrate scales. A study of numerous Silurian specimens of framboidal pyrite resulted in several new observations; the framboids may be explained as primitive pyritized algae.The Upper Permian microflora contains a very predominant new species of Lueckisporites; the macroflora consists exclusively of new species of hepatics referable to Jungermannites and Gessella n.g.The Palaeozoic palaeogeography and geological development of the Slagelse region is discussed in connection with a comparison with sections of some other localities.

scholarly journals Fluid inclusions in buried quartz of the Yanchang sandstone in the Jiyuan area, Ordos Basin, China: Implications for basin evolution and petroleum accumulation

2020 ◽  
pp. 014459872097451
Author(s):  
Wenqi Jiang ◽  
Yunlong Zhang ◽  
Li Jiang
Keyword(s):  
Fluid Inclusions ◽  
Ordos Basin ◽  
Homogenization Temperature ◽  
Burial Depth ◽  
Hydrocarbon Generation ◽  
Rock Interaction ◽  
Yanchang Formation ◽  
Reflection Data ◽  
And Migration ◽  
Vitrinite Reflection

A fluid inclusion petrographic and microthermometric study was performed on the sandstones gathered from the Yanchang Formation, Jiyuan area of the Ordos Basin. Four types of fluid inclusions in quartz can be recognized based on the location they entrapped. The petrographic characteristics indicate that fluid inclusions in quartz overgrowth and quartz fissuring-I were trapped earlier than that in quartz fissuring-IIa and fissuring-IIb. The homogenization temperature values of the earlier fluid inclusions aggregate around 80 to 90°C; exclusively, it is slightly higher in Chang 6 member, which approaches 95°C. The later fluid inclusions demonstrate high homogenization temperatures, which range from 100 to 115°C, and the temperatures are slightly higher in Chang 9 member. The calculated salinities show differences between each member, including their regression characteristics with burial depth. Combining with the vitrinite reflection data, the sequence and parameters of fluid inclusions indicate that the thermal history of the Yanchang formation mostly relied on burial. Salinity changes were associated with fluid-rock interaction or fluid interruption. Hydrocarbon contained fluid inclusions imply that hydrocarbon generation and migration occurred in the Early Cretaceous. The occurrence of late fluid inclusions implied that quartz cement is a reservoir porosity-loose factor.

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.

Deep fluids and their role in hydrocarbon migration and oil deposit formation exemplified by supercritical СO2

2021 ◽  
pp. 1-11
Author(s):  
Sara LIFSHITS
Keyword(s):  
Supercritical Fluid ◽  
Oil And Gas ◽  
Gas Permeability ◽  
Sedimentary Rocks ◽  
Source Rocks ◽  
Reservoir Properties ◽  
Hydrocarbon Migration ◽  
Geological Processes ◽  
Before And After ◽  
Oil Source

ABSTRACT Hydrocarbon migration mechanism into a reservoir is one of the most controversial in oil and gas geology. The research aimed to study the effect of supercritical carbon dioxide (СО2) on the permeability of sedimentary rocks (carbonates, argillite, oil shale), which was assessed by the yield of chloroform extracts and gas permeability (carbonate, argillite) before and after the treatment of rocks with supercritical СО2. An increase in the permeability of dense potentially oil-source rocks has been noted, which is explained by the dissolution of carbonates to bicarbonates due to the high chemical activity of supercritical СО2 and water dissolved in it. Similarly, in geological processes, the introduction of deep supercritical fluid into sedimentary rocks can increase the permeability and, possibly, the porosity of rocks, which will facilitate the primary migration of hydrocarbons and improve the reservoir properties of the rocks. The considered mechanism of hydrocarbon migration in the flow of deep supercritical fluid makes it possible to revise the time and duration of the formation of gas–oil deposits decreasingly, as well as to explain features in the formation of various sources of hydrocarbons and observed inflow of oil into operating and exhausted wells.

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