scholarly journals Genetic Types and Source of the Upper Paleozoic Tight Gas in the Hangjinqi Area, Northern Ordos Basin, China

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-14
Author(s):  
Xiaoqi Wu ◽  
Chunhua Ni ◽  
Quanyou Liu ◽  
Guangxiang Liu ◽  
Jianhui Zhu ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Source Rocks ◽  
Lower Permian ◽  
Tight Gas ◽  
Upper Paleozoic ◽  
A Minor ◽  
Gas Component ◽  
Oil Type ◽  
Coal Type

The molecular and stable isotopic compositions of the Upper Paleozoic tight gas in the Hangjinqi area in northern Ordos Basin were investigated to study the geochemical characteristics. The tight gas is mainly wet with the dryness coefficient (C1/C1–5) of 0.853–0.951, andδ13C1andδ2H-C1values are ranging from-36.2‰to-32.0‰and from-199‰to-174‰, respectively, with generally positive carbon and hydrogen isotopic series. Identification of gas origin indicates that tight gas is mainly coal-type gas, and it has been affected by mixing of oil-type gas in the wells from the Shilijiahan and Gongkahan zones adjacent to the Wulanjilinmiao and Borjianghaizi faults. Gas-source correlation indicates that coal-type gas in the Shiguhao zone displays distal-source accumulation. It was mainly derived from the coal-measure source rocks in the Upper Carboniferous Taiyuan Formation (C3t) and Lower Permian Shanxi Formation (P1s), probably with a minor contribution from P1s coal measures from in situ Shiguhao zone. Natural gas in the Shilijiahan and Gongkahan zones mainly displays near-source accumulation. The coal-type gas component was derived from in situ C3t-P1s source rocks, whereas the oil-type gas component might be derived from the carbonate rocks in the Lower Ordovician Majiagou Formation (O1m).

scholarly journals Light hydrocarbon geochemical characteristics and their application in Upper Paleozoic, Shenmu gas field, Ordos Basin

2016 ◽  
Vol 35 (1) ◽  
pp. 103-121 ◽  
Author(s):  
Wenxue Han ◽  
Shizhen Tao ◽  
Guoyi Hu ◽  
Weijiao Ma ◽  
Dan Liu ◽  
...  
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Light Hydrocarbon ◽  
Source Rocks ◽  
Higher Plant ◽  
Gas Field ◽  
Gas Source ◽  
Upper Paleozoic ◽  
Methyl Cyclohexane ◽  
Normal Stage

Light hydrocarbon has abundant geochemical information, but there are few studies on it in Shenmu gas field. Taking Upper Paleozoic in Shenmu gas field as an example, authors use gas chromatography technology to study light hydrocarbon systematically. The results show that (1) The Shenmu gas field is mainly coal-derived gas, which is mixed by partial oil-derived gas due to the experiment data. (2) Based on K1, K2 parameter and Halpern star chart, the Upper Paleozoic gas in Shenmu gas field belongs to the same petroleum system and the depositional environment of natural gas source rocks should be homologous. (3) The source rocks are mainly from terrestrial higher plant origins and belong to swamp facies humic due to methyl cyclohexane index and Mango parameter intersection chart, which excluded the possibility of the Upper Paleozoic limestone as source rocks. (4) The isoheptane ranges from 1.45 to 2.69 with an average of 2.32, and n-heptane ranges from 9.48 to 17.68% with an average of 11.71%, which is below 20%. The maturity of Upper Paleozoic gas in Shenmu gas field is low-normal stage, which is consistent with Ro data. (5) The Upper Paleozoic natural gas in the Shenmu gas field did not experience prolonged migration or secondary changes, thus can be analyzed by light hydrocarbon index precisely.

A Permian Hydrozoan Mound, Yukon Territory

1971 ◽  
Vol 8 (8) ◽  
pp. 973-988 ◽  
Author(s):  
G. R. Davies
Keyword(s):  
Growth Form ◽  
Yukon Territory ◽  
Source Rocks ◽  
Lower Permian ◽  
Canal System ◽  
Rock Types ◽  
System A ◽  
Upper Paleozoic ◽  
Paleozoic Rocks ◽  
Richardson Mountains

A carbonate mound built by the hydrozoan Palaeoaplysina has been found in a poorly-exposed sequence of Lower Permian rocks in the northern Richardson Mountains of the Yukon Territory. Similar hydrozoan mounds have been described from Russia and northwestern United States. The Yukon mound is 12 ft (3.7 m) thick and at least 70 ft (21 m) long. It is underlain by marine siltstones and sandstones, and probably shale. The main mound rock is composed of curved hydrozoan plates enclosed in a bioclastic wackestone matrix, and is overlain successively by tubular–foram packstone and oolitic grainstone. Palaeoaplysina is characterized by a plate-like, laterally-expanding growth form, an internal canal system, a cellular calcareous skeleton, and 'mamelons' on the upper surface of well-preserved plates; 'mamelons' are the principal criterion for placing Palaeoaplysina in the Class Hydrozoa of the coelenterates.The Yukon mound is part of a thick sequence of Lower Permian terrigenous clastic and carbonate rocks deposited on the northern shelf of the ancestral Aklavik Arch. The repetition of similar rock types in the sequence indicates cyclicity, a thesis supported by similarities between the Yukon mound sequence and the Virgilian mound cycles in New Mexico.Lower Permian hydrozoan mounds and associated facies in the Pre-urals of Russia are known oil producers. The possibility exists that hydrozoan mounds, perhaps in multiple cyclic build-ups, may occur in upper Paleozoic rocks in the subsurface of the Yukon Territory. With suitable porosity development and source rocks, these predicted subsurface mounds could become hydrocarbon reservoirs and thus targets for oil exploration.

scholarly journals Natural gas migration and accumulation model and favorable exploration targets in Ordovician dolomite in Jingxi, Ordos Basin

2017 ◽  
Vol 36 (3) ◽  
pp. 373-387
Author(s):  
Jingdong Liu ◽  
Youlu Jiang ◽  
Xinshe Liu ◽  
Rongwei Zhu
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Source Rocks ◽  
Late Triassic ◽  
Gas Migration ◽  
Formation Model ◽  
Long Distance ◽  
Gas Reservoir ◽  
Upper Paleozoic ◽  
Bottom To Top

The Ordovician dolomite reservoir in Ma55–Ma510 sub-members in Jingxi in Ordos Basin is a newly discovered field with multiple natural gas pools. The gas accumulation patterns of the reservoir are unclear. Considering the geological background, the genesis, migration, and accumulation of natural gas in Jingxi were studied systematically, and favorable exploration targets were predicted. Natural gas in Ma55–Ma510 sub-members is a mixture of Upper Paleozoic and Ordovician products. The Upper Paleozoic coaliferous gas was mainly expulsed downward through the hydrocarbon-providing window where the coal-bearing source rocks made contact with the dolomite reservoirs. The gas then migrated from west to east and accumulated under the condition of lithology variation. The Ordovician petroliferous gas mainly migrated from bottom to top through fractures and mixed with the coaliferous gas in Ma55–Ma510 sub-members. The natural gas reservoir formation model was summarized as the migration of gas over a short distance and partial charging into the dolomite reservoirs from the Late Triassic to Middle Jurassic, and the migration of gas over a long distance and massive charging into the dolomite reservoirs during the Late Cretaceous. Ma55 and Ma56 sub-members are the focus of further exploration, and petroliferous gas in Ma57–Ma510 sub-members deserves attention. The dolomite reservoirs of the hydrocarbon-providing windows and the east of these locations are the favorable exploration targets.

scholarly journals Triassic Low Temperature Hydrothermal Activities(LTHA) From the Ordos Basin of Northern China

2021 ◽  
Author(s):  
Jiyuan You ◽  
Yiqun Liu ◽  
Dingwu Zhou ◽  
Yiyao Yang
Keyword(s):  
Hydrothermal Vents ◽  
Sedimentary Environment ◽  
Ordos Basin ◽  
Sedimentary Rocks ◽  
Northern China ◽  
Source Rocks ◽  
Three Samples ◽  
The Ordos Basin ◽  
Hydrothermal Activities

Abstract Because few well-preserved hydrothermal channels have been found in terrestrial sedimentary rocks, research on LTHA in geological history is relatively sparse. In this study, we present our original discovery of “hydrothermal channels” from the Chang 7 source rocks of the Triassic Yanchang Formation in the Ordos Basin, China, and provide the best evidence for deciphering LTHA preserved in the geological record (i.e., sedimentary rocks). Three possible LTHA samples (i.e., samples 1551.6, 1551.6-2 and 1574.4) were collected for this study; they were interbedded with mudstones and oil shales, indicative of a deep-lake sedimentary environment. All three samples consist mainly of anhydrite, pyrite, and dolomite with the formation of mineral zoning across the walls of these structures, suggesting a sulfate-dominated stage and a carbonate-sulfide replacement stage. Moreover, their in situ geochemistry is characterized by high Eu, U, Th, Sr, Mn and U/Th ratios, which are typical indicators of hydrothermal vents. In addition, their S isotopes range from 7.89% to 10.88%, the magmatic sulfur accounted for approximately 94.3%, implying a possible magmatic trigger for these hydrothermal channels. All this evidence shows that the Triassic sedimentary rocks of the Ordos Basin probably contain LTHA. Comparing ancient LTHA to modern hydrothermal chimneys, we should note the important implications of LTHA; their formation mechanism may have been related to oil production, and they are possible indicators for future oil investigations. Further, they have great significance for studying the hydrothermal properties of primary dolomite.

Charging time of tight gas in the Upper Paleozoic of the Ordos Basin, central China

2013 ◽  
Vol 64 ◽  
pp. 38-46 ◽  
Author(s):  
Yanhua Shuai ◽  
Shuichang Zhang ◽  
Jingkui Mi ◽  
Se Gong ◽  
Xuanjun Yuan ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Central China ◽  
Tight Gas ◽  
Charging Time ◽  
Upper Paleozoic ◽  
The Ordos Basin

Discovery and geological significance of the Magma-hydrothermal micro-jets at the bottom of a lake: A case from the Chang 7 section of the Yanchang Formation of the Triassic in the Ordos Basin, China

2020 ◽  
Author(s):  
Jiyuan You ◽  
Yiqun Liu ◽  
Dingwu Zhou
Keyword(s):  
Hydrothermal Vents ◽  
Ordos Basin ◽  
Hydrothermal Activity ◽  
Life Forms ◽  
Major Elements ◽  
Source Rocks ◽  
Geological History ◽  
Yanchang Formation ◽  
The Ordos Basin

<p>The "black chimney" type of hydrothermal vents in the modern deep sea have become a popular research topic in many disciplines. Due to the actual conditions, the research on palaeo-thermal vents in geological history is relatively low. Fortunately, the discovery of hydrothermal vents and bio-fossils from the Chang 7 source rocks of the Yanchang Formation of the Triassic in the Ordos Basin, China, provides the best evidence for deciphering hydrothermal activity during geological history. Here, we report a case study. Through ordinary sheet observation, scanning electron microscopy and electron probe observation, layered grained siliceous rocks, dolomites, and hydrothermal mineral combinations, such as pyrite + dolomite + gypsum and calcite + barite, are found. Their unique petrological characteristics, mineral composition, and structure confirm the existence of palaeo-thermal fluid vents. We further analysed the geochemical characteristics and in situ isotope characteristics. The study found that Cs, U, Th, Pb, Ba and other trace elements of the sample showed positive abnormalities, in which values of U/Th were high; in addition, the enrichment of major elements such as Sr, Mn, and the in situ sulphur isotopes of pyrite reached 7.89%-10.88%. This study of hydrothermal vents over geological history is expected to provide new insights on the life forms of various extreme microorganisms in hydrothermal environments and on their formation of high-quality source rocks.</p>

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