Using Light Hydrocarbons to Identify the Depositional Environment of Source Rocks in the Ordos Basin, Central China

2015 ◽  
Vol 33 (6) ◽  
pp. 869-890 ◽  
Author(s):  
Dan Liu ◽  
Cong Yu ◽  
Shipeng Huang ◽  
Chenchen Fang ◽  
Ziqi Feng ◽  
...  
Keyword(s):  
Depositional Environment ◽  
Ordos Basin ◽  
Source Rocks ◽  
Central China ◽  
Light Hydrocarbons ◽  
The Ordos Basin

scholarly journals Genetic types and sources of Lower Paleozoic natural gas in the Daniudi gas field, Ordos Basin, China

2017 ◽  
Vol 35 (2) ◽  
pp. 218-236 ◽  
Author(s):  
Xiaoqi Wu ◽  
Jianhui Zhu ◽  
Chunhua Ni ◽  
Kuang Li ◽  
Yanqing Wang ◽  
...  
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Source Rocks ◽  
Light Hydrocarbons ◽  
Upper Ordovician ◽  
Gas Field ◽  
Lower Paleozoic ◽  
Upper Carboniferous ◽  
Associated Gas ◽  
The Ordos Basin

The molecular composition, stable carbon and hydrogen isotopes, and light hydrocarbons of the Lower Paleozoic natural gas in the Daniudi gas field in the Ordos Basin were investigated to study the geochemical characteristics. The Lower Paleozoic gas in the Daniudi gas field displays methane contents of 87.41–93.34%, dryness coefficients (C1/C1–5) ranging from 0.886 to 0.978, δ13C1 and δ13C2 values ranging from −40.3 to −36.4‰, with an average of −38.3‰, and from −33.6 to −24.2‰, with an average of −28.4‰, respectively, and δD1 values ranging from −197 to −160‰. The alkane gas generally displays positive carbon and hydrogen isotopic series, and the C7 and C5–7 light hydrocarbons of the Lower Paleozoic gas are dominated by methylcyclohexane and iso-alkanes, respectively. The Lower Paleozoic gas in the Daniudi gas field is mixed from coal-derived and oil-associated gases, similar to that observed in the Jingbian gas field. The oil-associated gas in the Lower Paleozoic gas is secondary oil cracking gas and displays a lower cracking extent than that in the Jingbian gas field. The coal-derived gas in the Lower Paleozoic gas in the Daniudi gas field migrated from the Upper Paleozoic gas through the window area where the iron–aluminum mudstone caprocks in the Upper Carboniferous Benxi Formation were missing. The oil-associated gas in the Lower Paleozoic gas in the Daniudi gas field was probably derived from presalt source rocks in the Lower Ordovician Majiagou Formation rather than the limestone in the Upper Carboniferous Taiyuan Formation. It seems unlikely that the marlstone in the Upper Ordovician Beiguoshan Formation and shale in the Middle Ordovician Pingliang Formation on the western and southwestern margins of the Ordos Basin contributed to the oil-associated gas in the Lower Paleozoic gas in the Daniudi gas field.

scholarly journals Analysis of the charging process of the lacustrine tight oil reservoir in the Triassic Chang 6 Member in the southwest Ordos Basin, China

2017 ◽  
Vol 54 (12) ◽  
pp. 1228-1247
Author(s):  
Zhengjian Xu ◽  
Luofu Liu ◽  
Tieguan Wang ◽  
Kangjun Wu ◽  
Wenchao Dou ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Source Rocks ◽  
Driving Mechanism ◽  
Tight Oil ◽  
Geological Time ◽  
Tight Sandstone ◽  
Main Production ◽  
The Ordos Basin ◽  
Homogenization Temperatures ◽  
Quartz Grains

With the success of Bakken tight oil (tight sandstone oil and shale oil) and Eagle Ford tight oil in North America, tight oil has become a research focus in petroleum geology. In China, tight oil reservoirs are predominantly distributed in lacustrine basins. The Triassic Chang 6 Member is the main production layer of tight oil in the Ordos Basin, in which the episodes, timing, and drive of tight oil charging have been analyzed through the petrography, fluorescence microspectrometry, microthermometry, and trapping pressure simulations of fluid inclusions in the reservoir beds. Several conclusions have been reached in this paper. First, aqueous inclusions with five peaks of homogenization temperatures and oil inclusions with three peaks of homogenization temperatures occurred in the Chang 6 reservoir beds. The oil inclusions are mostly distributed in fractures that cut across and occur within the quartz grains, in the quartz overgrowth and calcite cements, and the fractures that occur within the feldspar grains, with blue–green, green, and yellow–green fluorescence colours. Second, the peak wavelength, Q650/500, and QF535 of the fluorescence microspectrometry indicate three charging episodes of tight oil with different oil maturities. The charging timings (141–136, 126–118, and 112–103 Ma) have been ascertained by projecting the homogenization temperatures of aqueous inclusions onto the geological time axis. Third, excess-pressure differences up to 10 MPa between the Chang 7 source rocks and the Chang 6 reservoir beds were the main driving mechanism supporting the process of nonbuoyancy migration.

scholarly journals Study on Geochemical Characteristics of tight sandstone gas accumulation in Linxing area

2020 ◽  
Vol 206 ◽  
pp. 01017
Author(s):  
Yangbing Li ◽  
Weiqiang Hu ◽  
Xin Chen ◽  
Litao Ma ◽  
Cheng Liu ◽  
...  
Keyword(s):  
Source Rock ◽  
Ordos Basin ◽  
Source Rocks ◽  
Hydrocarbon Generation ◽  
Light Hydrocarbons ◽  
Tight Sandstone ◽  
Source Type ◽  
Reservoir Type ◽  
Sandstone Reservoir ◽  
Main Component

Based on the comprehensive analysis of the characteristics of tight sandstone gas composition, carbon isotope, light hydrocarbons and source rocks in Linxing area of Ordos Basin, the reservoir-forming model of tight sandstone gas in this area is discussed. The study shows that methane is the main component of tight sandstone gas, with low contents of heavy hydrocarbons and non-hydrocarbons, mainly belonging to dry gas in the Upper Paleozoic in Linxing area. The values of δ13C1, δ13C2 and δ13C3 of natural gas are in the ranges of -45.6‰ ~ -32.9‰, -28.9‰ ~ -22.3‰ and -26.2‰~ -19.1‰, respectively. The carbon isotopic values of alkane gas show a general trend of positive carbon sequence. δ13C1 value is less than -30‰, with typical characteristics of organic genesis. There is a certain similarity in the composition characteristics of light hydrocarbons. The C7 series show the advantage of methylhexane, while the C5-7 series mainly shows the advantage of isoalkane. The tight sandstone gas in this area is mainly composed of mature coal-derived gas, containing a small amount of coal-derived gas and oil-type gas mixture. According to the mode of hydrocarbon generation, diffusion and migration of source rocks in Linxing area, the tight sandstone gas in the study area can be divided into three types of reservoir-forming assemblages: the upper reservoir type of the far-source type (upper Shihezi formation-shiqianfeng formation sandstone reservoir-forming away from source rocks), the upper reservoir type of the near-source type ( the Lower Shihezi formation sandstone reservoir-outside the source rock), and the self-storage type of the source type (Shanxi formation-Taiyuan formation source rock internal sand reservoir).

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.

Rare Earth Elements in No. 2 Coal of Huangling Mine, Huanglong Coalfield, China

2012 ◽  
Vol 30 (5) ◽  
pp. 803-818 ◽  
Author(s):  
Cunliang Zhao ◽  
Dujuan Duan ◽  
Yanheng Li ◽  
Jianya Zhang
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Depositional Environment ◽  
Ordos Basin ◽  
Average Concentration ◽  
Source Rocks ◽  
Tectonic Activity ◽  
Geochemical Anomaly ◽  
Metallogenic Belt ◽  
Reported Data

Rare earth elements (REEs) can provide lots of information relevant to the evolution of source rocks, depositional environment, and epigenetic tectonic activity. In this study, 14 bench samples (including 11 coals, 1parting, 1roof and 1floor) of the No. 2 coal seam from Huangling Mine, Huanglong Coalfield, Ordos Basin, China were collected to study the REE geochemistry. The average concentration of REEs is 44.03 μg/g, and it is lower than those in coals of the Chinese and world coal. The coals are enriched in light REEs and the LREEs-HREEs have been highly fractionated, with an average (La/Yb) N of 11.38. The values of Ce/Ce* are more or less than 1 (with an average 0.92) and indicates that the anomaly of Ce is very slight. However, the values of Eu/Eu* (with an average 7.69 of coal) are distinctly higher than reported data of coals. The extremely high contents of Ba caused the geochemical anomaly of REEs. The Ba2+ was origin from the barium metallogenic belt in Qinling Old-upland.

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