THE USE OF COALS AS INDICATORS OF THE OCCURRENCE OF OIL AND GAS

1970 ◽  
Vol 10 (1) ◽  
pp. 35 ◽  
Author(s):  
J. D. Brooks
Keyword(s):  
Organic Matter ◽  
Carbon Content ◽  
Oil And Gas ◽  
Sedimentary Basin ◽  
Total Carbon ◽  
Maximum Temperature ◽  
Mineral Matter ◽  
Hydrocarbon Generation ◽  
Oil Companies ◽  
Upper Limit

Petroleum hydrocarbons are not normal constituents of recent sediments but only appear when a certain stage of diagenesis is reached, through deeper burial. An investigation of the mechanism of formation of oil and gas has shown that an indication of the generation of oil in a sedimentary basin can be obtained by an examination of coals or coaly material encountered during drilling.Coals form a continuous diagenetic and metamorphic series beginning with peat and ending with graphite. Peat and brown coal contain the same type of hydrocarbons as are present in land plants but the composition of coal hydrocarbons changes abruptly in the sub-bituminous to high-volatile bituminous coal range. This is because petroleum-type hydrocarbons are formed at this stage from precursors which are components of waxy leaf cuticles, pollen and spore coatings, by chemical reactions in which oxygen groups are removed from long-chain acids, alcohols and ester waxes. Most Australian oil occurrences are associated with coal-bearing sediments and it appears likely that they are formed at the same stage of alteration, from such land plant residues, finely disseminated in shales and siltstones.The diagenetic changes in coal composition are caused by the increasing temperature accompanying deeper burial, and the composition of a coal, whatever its present depth, is an indication of the maximum temperature to which it has been subjected. The determination of carbon content, reflectivity and other properties of coal samples provided by a number of oil companies, together with laboratory experiments in which petroleum-type hydrocarbons were generated by artificial diagenesis of coal components, indicated that hydrocarbon generation takes place only when the carbon content of the coals approaches 80 percent. In sedimentary basins in Australia the petroleum generation zone occurs at depths varying from 5,500 to greater than 11,000ft., depending upon present or past geothermal gradient.In addition to this lower limit of diagenesis, it has long been maintained that a relation exists (the Carbon Ratio theory) between the likely occurrence of oil and gas reservoirs in a sedimentary basin and the degree of metamorphism of coal if present. The theory sets an upper limit of alteration of organic matter, and states that oil reservoirs are unlikely to occur in areas or at depths in a basin where the 'fixed-carbon' of the coals is greater than about 65 percent (equivalent to a coal of about 85 percent total carbon — dry, mineral-matter free). The Gid-gealpa-Moomba area appears to be a part of the Cooper Basin in which the organic matter is close to this upper limit of metamorphism. The carbon content of the coal at Gidgealpa, associated with gas and light hydrocarbons, is 85-86 percent whereas that at Moomba, associated with dry gas, is higher at approximately 89 percent.Ihus the properties of coal samples encountered during drilling can provide valuable clues for the petroleum geologist in the search for further oil and gas reserves.

scholarly journals Genetic mechanisms and distribution characteristics of overpressures in the Paleogene reservoirs of the Bohai Bay Basin, East China

2018 ◽  
Vol 36 (3) ◽  
pp. 388-413 ◽  
Author(s):  
Fanghao Xu ◽  
Jiaju Liang ◽  
Guosheng Xu ◽  
Haifeng Yuan ◽  
Yong Liu
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Bohai Bay ◽  
Hydrocarbon Generation ◽  
Distribution Characteristics ◽  
Well Drilling ◽  
The Third ◽  
Genetic Mechanisms ◽  
Shahejie Formation ◽  
Tectonic Framework

The Bohai Bay region is a primary accumulation area of oil and gas in offshore China, in which overpressure commonly occurs in the Paleogene strata; the analysis on distribution characteristics and genetic mechanisms of the overpressure would provide geologic evidences for making plans of well drilling and logging as well as oil and gas exploitation; additionally, it could lay the geological foundation for studying how overpressure controlled hydrocarbon accumulation. Based on research, the overpressure of the study area starts from the second member of the Dongying Formation and ends in the third member of the Shahejie Formation. The distribution of overpressure is mainly controlled by the sag–salient tectonic framework within the basin, which means overpressure mainly develops in sags or slopes; however, high areas stay normal pressured. In the study area, pressure develops around Bozhong Sag and in northern Liaodong Bay reaches the peak. The genetic mechanisms of overpressures in the Paleogene reservoirs are mainly disequilibrium compaction, hydrocarbon generation of the organic matter, fluid charging, and transmission or the superimposition of the former two. Different strata have different genetic mechanisms of overpressure. The chief genetic mechanisms for the generation of overpressure of the Dongying Formation are disequilibrium compaction while the genesis of the formation of overpressure in the Shahejie Formation is more complicated in some extent. The first member of the Shahejie Formation dominated by disequilibrium compaction and hydrocarbon generation of the organic matter plays a supplemental role, while the second member of the Shahejie Formation, as the primary reservoir strata, is dominated by fluid charging and transmission, and the third member of the Shahejie Formation is the main source rock interval; its overpressure is closely related to hydrocarbon generation. Each contribution ratio for overpressure forming by different genetic mechanisms has been judged and figured out quantitatively according to geological, geophysical, and geochemical characteristics of the target strata.

scholarly journals APPLICATION OF ONE-DIMENSIONAL PALEOTEMPERATURE MODELING TO ESTIMATE THE HYDROCARBON POTENTIAL OF CRETACEOUS SEDIMENTS OF THE MIDDLE AMUR SEDIMENTARY BASIN

2021 ◽  
Vol 40 (4) ◽  
pp. 87-98
Author(s):  
P.N. Prokhorova ◽  
◽  
E.P. Razvozzhaeva ◽  
V.I. Isaev ◽  
◽  
...  
Keyword(s):  
Oil And Gas ◽  
Sedimentary Basin ◽  
Gas Content ◽  
Hydrocarbon Potential ◽  
Hydrocarbon Generation ◽  
Gas Generation ◽  
One Dimensional ◽  
Middle Amur Sedimentary Basin ◽  
History Of ◽  
History Of Formation

The prospects of oil and gas content of the Cretaceous-Paleogene deposits of the Middle Amur sedimentary basin within the Pereyaslavsky graben are clarified on the basis of updated data on the tectonic-stratigraphic complexes of the basin using the method of one-dimensional paleotemperature modeling. It is established that throughout the history of formation of the studied part of Pereyaslavsky graben hydrocarbon generation could occur in lower Cretaceous sediments of the Assikaevsky and Alchansky/Strelnikovsky suites. The gas generation conditions for the Assykaevsky formation are still maintained.

scholarly journals The color of refractory organic carbon

2018 ◽  
Vol 189 (2) ◽  
pp. 9 ◽  
Author(s):  
Maxime Debret ◽  
Yoann Copard ◽  
Antonin Van Exem ◽  
Geneviève Bessereau ◽  
Frank Haeseler ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Content ◽  
Anthropogenic Activities ◽  
Organic Matter Content ◽  
Matter Content ◽  
Mineral Matter ◽  
Organic Carbon Content ◽  
Fast Method ◽  
Wide Range

Organic matter studies find an echo within different topics such as biogeochemical cycles, processes occurring in continental surfaces, anthropogenic activities, climate science, earth and planetary sciences, etc. Today’s challenges include finding and developing the most appropriate method(s) supporting the differentiation and characterisation of various types of recalcitrant organic matter in modern environments. In this study, we focus on combustion residues and coals as these two types of organic matter contain a significant amount of so-called recalcitrant organic carbon (black carbon and fossil organic carbon). Both these materials are ubiquitous, broadly stem from the same living organisms and have similar polyaromatic structures. In this respect, we tested a spectrophotometry method, classically used for sedimentology, as a very fast method for preliminary investigations. Analyses were performed with a wide range of standards and referenced samples. The results discriminate three different spectral signatures related to the degree of transformation of organic matter related to the degree of aromaticity (i.e. carbonisation). Using calibration curves, total organic carbon content can be estimated in experimental mixes with mineral matter and in a real context using subsurface sample (Gironville 101 borehole, Paris Basin, France). This method has particularly high sensitivity to very low organic matter content and is shown to be promising for a rapid evaluation of the organic carbon content.

Comparison of the Domanic outcrops in Volga-Ural and Timan-Pechora basins

2018 ◽  
pp. 57-73
Author(s):  
A. P. Zavyalova ◽  
V. V. Chupakhina ◽  
A. V. Stoupakova ◽  
Yu. A. Gatovsky ◽  
G. A. Kalmykov ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Gas Content ◽  
Thin Sections ◽  
Lower Carboniferous ◽  
Oil Companies ◽  
Pechora Basin ◽  
Geochemical Parameters ◽  
Frasnian Stage ◽  
Lithological Composition

Domanic (and domanicoid) deposits are in a great interest of researchers and oil companies, since they possess authigenic oil and gas content. The article presents the results of study outcrops in the Volga-Ural and Timan-Pechora basins. The stratigraphic interval included sediments from the Middle Frasnian stage of the Upper Devonian to the Turnasian stage of the Lower Carboniferous. The main types of rocks were characterized by microscopic examination of thin sections and geochemical parameters of organic matter. It is shown that the domanic deposits of the Timan-Pechora basin are similar in structure and lithological composition to the deposits of the Volga-Ural Basin. The upper part of the domanic section is distinguished by the predominance of the carbonate-siliceous type of rocks over the kerogen mixed varieties. According to the geochemical parameters, the organic matter in the rocks of the sheltered deposits of the Volga-Ural and Timan-Pechora basins belongs to type II, but on the outcrops of the Volga-Ural region, the organic matter of the high-carbon sequence is more mature than on the outcrops of Timan-Pechora basin.

Jurassic source rocks of hydrocarbon fluids in the Eastern part of the Fukan depression (Junggar oil and gas basin)

2020 ◽  
pp. 55-63
Author(s):  
Yang Houqiang ◽  
E. V. Soboleva
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Research Area ◽  
Molecular Composition ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Gas Reservoirs ◽  
Eastern Side ◽  
Oil And Gas Reservoirs

In recent years, significant successes have been achieved in the search and exploration of oil and gas reservoirs in the Jurassic deposits on the eastern side of the Fukang depression, which is the least studied part of the Junggar oil and gas Basin. In order to find out the source of hydrocarbon generation, we studied source rocks, oil and oil-bearing sandstones (24 samples from 13 wells) from the Badaowan, Sangonghe, Xishanyao, Toutunhe and Qigu production beds of the Fukang depression research area. Based on these studies, the composition of the organic matter of the Jurassic source rocks, the properties and molecular composition of oils, as well as the characteristics of the composition of biomarkers in them are examined in detail. The results of research and interpretation of the data showed that the mudstones of the Badaowan formation were source rocks of oil from the Gumudi zone, the Fukan depression, the Bajiahai ledge and the Shaqi ledge.

scholarly journals The Influence of Afforestation on Upland Soils: The Use of ‘Bomb 14C’ Enrichment as a Quantitative Tracer for Changes in Organic Status

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 637-643 ◽  
Author(s):  
D D Harkness ◽  
A F Harrison
Keyword(s):  
Organic Matter ◽  
Carbon Content ◽  
Growth Period ◽  
Soil Samples ◽  
Total Carbon ◽  
Soil Horizons ◽  
Total Carbon Content ◽  
Soil Carbon Content ◽  
Fresh Organic Matter ◽  
Carbon Inventory

A series of soil samples were collected in November 1984 from five stands of Sitka spruce planted at recorded times between 1951 and 1968. Within a comprehensive program of ecologic and biogeochemical analyses, natural 14C measurements on selected organic components of the 0 to 5cm soil horizons serve to quantify progressive changes induced in the organic carbon inventory and relative to that of the original grassland. Points of particular interest are: 1) an enhanced input of fresh organic matter in the years immediately following planting; this, in parallel with a net decrease in the total carbon content of the topsoil; 2) this freshly introduced carbon predominates in the soil profile even after 30 years of afforestation; 3) during the 15- to 30-year growth period, the soil carbon content remains constant but progressive changes occur in its biogeochemical composition and rate of turnover.

scholarly journals Comparative Assessment of Hydrocarbon Generation Potential of Organic Matter from Shale Sediments along Isugwuato – Okigwe Axis, Anambra Basin, SE Nigeria

2021 ◽  
Vol 25 (3) ◽  
pp. 353-362
Author(s):  
M.U. Uzoegbu ◽  
C.U. Ugwueze
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Oxygen Index ◽  
Hydrocarbon Generation ◽  
Hydrocarbon Generation Potential ◽  
Anambra Basin ◽  
Kerogen Type ◽  
Oil Generation ◽  
Carbonaceous Shales ◽  
Petroleum Generation

TRACT: The Cretaceous sediments in the Anambra Basin (SE Nigeria) consist of a cyclic succession of coals, carbonaceous shales, silty shales and siltstones  interpreted as deltaic deposits. The objective of this study is to compare the hydrocarbon generation potential of organic matter from shale sediments along Isugwuato-Okigwe axis in the Anambra Basin, Nigeria. Data obtained indicates the presence of Type III kerogen with Tmax values are between 424 and 441ºC indicating that the shales are thermally immature to marginally mature with respect to petroleum generation. Hydrogen Index (HI) values range from 14 to 388.9mgHC/gTOC while S1 + S2 yields values ranging from 0.2 to 1.0mgHC/g rock, suggesting that the shale have gas generating potential. The TOC values rangesfrom 1.3 to 3.0%, an indication of a good source rock of terrestrially derived organic matter. The high oxygen index (OI) (16.3 mgCO2g-1TOC), TS (1.35) and TOC/TS (1.5) suggest deposition in a shallow marine environment. Based on the kerogen type, shales from the studied area will equally generate oil and gas if its organic matter attained sufficient thermal temperature. Keywords: Shale, kerogen type, maturity, oil generation.

Diagenesis in Upper Jurassic marine sandstones from the North Sea Well 14/26-1 and its significance

Clay Minerals ◽  
1986 ◽  
Vol 21 (4) ◽  
pp. 513-535 ◽  
Author(s):  
C. V. Jeans ◽  
M. J. Fisher
Keyword(s):  
Organic Matter ◽  
North Sea ◽  
Upper Jurassic ◽  
Immature Stage ◽  
Maximum Temperature ◽  
Burial Depth ◽  
Hydrocarbon Generation ◽  
Clay Formation ◽  
Later Phase ◽  
Ferroan Dolomite

AbstractA tightly cemented series of marine sandstones, interbedded with shales and mudstones, occurs in the lower part of the Kimmeridge Clay Formation (Kimmeridgian to Ryazanian) of Arco Well 14/26-1 (Core No. 5, 8067–8085 ft). The well is on the northern flank of the Fraserburgh Spur Basement Ridge. The sediments are in the immature stage of hydrocarbon generation and are now at their maximum temperature and burial depth: the bottom hole temperature is 75°C. The sandstone diagenesis was complex, essentially of an intrinsic type, and took place under considerable overpressures. Initially a series of early cements was precipitated (minor chalcedony, quartz, feldspar, ferroan calcite, non-ferroan dolomite and major ferroan dolomite). A later phase of diagenesis embraced two periods of intrastratal solution (each affecting both the silicate and the carbonate components of the sediment) separated by a phase of calcite precipitation and followed by a phase of kaolinite cementation. The early cements are interpreted as being of the intrinsic miagenetic type. The later phase of diagenesis (alternating intrastratal solution and cement precipitation) resulted from the interaction of (i) the biotic breakdown of organic matter by thermophyllic micro-organisms and (ii) the abiotic thermal alteration of organic matter with the mineral components of the sediment: of particular importance were varying PCO2 and the generation of carboxylic and phenolic acids. The diagenetic pattern is closely comparable to that known from various Upper Jurassic sandy shelf sediments in other parts of the northern North Sea which have very different burial histories.

Characteristics of the Overpressure Resulted from Hydrocarbon Generation

2013 ◽  
Vol 295-298 ◽  
pp. 2707-2710
Author(s):  
Hai Yan Hu ◽  
Hui Wang
Keyword(s):  
Organic Matter ◽  
Oil And Gas ◽  
Vitrinite Reflectance ◽  
Junggar Basin ◽  
Hydrocarbon Generation ◽  
Sonic Velocity ◽  
Gas Generation

Overpressure is often encountered in the Jurassic tight sandstones in the central Junggar Basin. In this studt, a new mechanism of overpressure formation related to gas generation is proposed. Organic-rich mudstones have sonic velocity well-line reserves but their densities continue to increase in the over-compacted mudstone system resulting in the overpressure development during the conversion of the organic matter to oil and gas. The top of the overpressure zone correlates with the depth required for a large quantity of gas generation in which the vitrinite reflectance (Ro) is about 0.7%, showing that the overpressure in organic-rich mudstones is closely associated with gas generation.

Diagenesis of the Sappington Formation in the Bridger Range, Montana: Implications for the burial and thermal history of the Western Crazy Mountain Basin

2019 ◽  
Vol 56 (1) ◽  
pp. 45-67 ◽  
Author(s):  
Clayton Schultz ◽  
Michael Hofmann
Keyword(s):  
Thermal History ◽  
Oil And Gas ◽  
Maximum Temperature ◽  
Hydrocarbon Generation ◽  
Burial History ◽  
Burial Diagenesis ◽  
Early Paleocene ◽  
History Of ◽  
Feldspar Dissolution ◽  
Ferroan Dolomite

The Devonian-Mississippian Sappington Formation in the Bridger Range, Montana was investigated for its paragenetic sequence and thermal history. These results were used to establish a burial history for the area and compared to data from nearby oil and gas wells. The paragenetic evolution of the Sappington includes early diagenetic feldspar dissolution, formation of quartz overgrowths, and illite precipitation during early diagenesis at temperatures < 50 °C. Subsequent burial diagenesis resulted in the precipitation of non-ferroan and ferroan dolomite, followed by calcite cementation and replacement, pyrite replacement, and hydrocarbon generation and expulsion at temperatures > 130 °C. Devonian formations were the source of the non-ferroan dolomite cement and began precipitating in the latest Mississippian. Subsequent growth of ferroan dolomite resulted from clay transformation reactions in the Upper and Lower Sappington Members and was initiated during rapid burial in the late Cretaceous. The Bridger Range and the adjacent Western Crazy Mountain Basin underwent similar Paleozoic and Mesozoic burial histories. Vastly different Cenozoic burial histories resulted from movement along the Cross Range and Pass thrusts that caused the Bridger Range to begin uplift prior to the cessation of deposition of the Livingston Group in the early Paleocene. The discrepancies in burial history caused the Sappington Formation to reach a maximum temperature of ~135 °C in the Bridger Range and ~230 °C in the western Crazy Mountain Basin.

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