scholarly journals Hydrocarbon geochemistry and charging history of the deep tight sandstone reservoirs in the Dabei Gas Field, Kuqa Depression, Tarim Basin, NW China

2020 ◽  
Vol 38 (6) ◽  
pp. 2325-2355
Author(s):  
Qiang Wei ◽  
Xianqing Li ◽  
Kexin Sun ◽  
Guangwu Zhang ◽  
Wanle Liang ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Natural Gas ◽  
Source Rocks ◽  
Tight Sandstone ◽  
Gas Field ◽  
Kuqa Depression ◽  
Natural Gases ◽  
History Of ◽  
Sandstone Reservoir ◽  
Sandstone Reservoirs

The geochemical feature and evolutionary history of hydrocarbons from the deep Cretaceous Bashijiqike (K1 bs) Formation tight sandstone reservoir in the Dabei Gas Field, Kuqa Depression were investigated using gas chromatography, gas chromatography–mass spectrometry, inclusions petrography and micro-thermometry, laser Raman spectroscopy, and quantitative grain fluorescence. The result indicates that natural gases from the deep sandstone reservoir are mainly composed of alkanes and belong to dry gases, of which methane accounts for 94.30–97.20% (avg. 95.64%), and ethane is 1.23–2.45% (avg. 1.95%). The stable carbon isotopic value of methane and ethane is −31.9‰ to −29.3‰ (avg. −30.3‰) and −24.2‰ to −19.4‰ (avg. −21.7‰), respectively, and this reflects the features of high-mature coal-derived gases. In addition, natural gases in the Dabei Gas Field have characteristics of coal-derived gases which were sourced from Jurassic coal measures. Oils in the Dabei Gas Field predominately originated from Triassic Huangshanjie (T3 h) Formation mudstones with some contributions from Jurassic coaly rocks. Petrological and micro-thermometry results of fluid inclusions suggest that the K1 bs Formation tight sandstone reservoirs have experienced two phases of hydrocarbons charge histories, namely “early oil and later gas.” The quantitative grain fluorescence analysis indicated that sandstone samples with quantitative grain fluorescence index value >5 and quantitative grain fluorescence-extraction intensity >40 pc in Wells DB101 and DB2 can be used as indicators for the paleo oil layers or the migration channels of later charged natural gas. The aforementioned analyses and burial and thermal histories of K1 bs sandstone reservoir demonstrated that oil charged at 10 Ma and natural gas charged at approximately 3 Ma in the study area. Furthermore, paleo-tectonic evolution enabled source rocks to mature and expel hydrocarbons, and the structurally related faults and traps provided pathways and places for hydrocarbon migration and accumulation.

Fracture and Gas Potential in Tight Sandstone Reservoirs in the Eastern Part of Sulige Gas Field, Ordos Basin (China)

2012 ◽  
Vol 524-527 ◽  
pp. 1236-1240
Author(s):  
Ren Chao Yang ◽  
Yi Jun Li ◽  
Tao Zhang ◽  
Ai Ping Fan ◽  
Yan Long Wang
Keyword(s):  
Natural Gas ◽  
Ordos Basin ◽  
Sem Analysis ◽  
Tight Sandstone ◽  
Gas Field ◽  
High Productivity ◽  
Distribution Laws ◽  
Sandstone Reservoirs ◽  
Gas Potential ◽  
Better Than

Sulige gas field in Ordos Basin is the largest discovered gas field in China. But tight sandstone reservoirs is becoming the main limitation of natural gas exploration and exploitation in Sulige gas field. Intensively analysis on micro-pore structure of sandstone reservoirs in Shan1 member of Shanxi formation and He8 member of Shihexizi formation in Permian system in the eastern part of Sulige gas field are conducted by means of drill core observation, slice identification, SEM analysis, casting slice and mercury injection etc. analytical methods. Result shows that fracture is well developed in sandstone reservoirs in the northern part of the interest area, by which petrophysical property of tight sandstone reservoir is improved distinctly. Types of fracture are dominated by diaclase and the diagenesis cracks. Main direction of the fractures is NE and NW, and the angle of the two groups fractures is nearly 90°.But one set of the conjugate shear fractures would develop well and the other was rest rained by the influenced of strong anisotropism of sandbodies. Diaclase and the diagenesis cracks developed along the boundery of tectonic divisions. Fracture is one of the important reasons for improvement of permeability in tight sandstone reservoirs. Gas potential of sandstone in fracture-developed section is much better than that of non-fracture section. Consequently, it is signaficant for all of reservoir forecasting, high productivity gas pool seeking, design and construction of natural gas exploitation to grasp distribution laws of fracture.

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.

scholarly journals Microscale Pore Throat Differentiation and Its Influence on the Distribution of Movable Fluid in Tight Sandstone Reservoirs

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Fengjuan Dong ◽  
Xuefei Lu ◽  
Yuan Cao ◽  
Xinjiu Rao ◽  
Zeyong Sun
Keyword(s):  
Ordos Basin ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Throat Radius ◽  
Thin Sections ◽  
Small Pore ◽  
Sandstone Reservoir ◽  
Sandstone Reservoirs ◽  
Classification Evaluation ◽  
Better Than

Tight sandstone reservoirs have small pore throat sizes and complex pore structures. Taking the Chang 6 tight sandstone reservoir in the Huaqing area of the Ordos Basin as an example, based on casting thin sections, nuclear magnetic resonance experiments, and modal analysis of pore size distribution characteristics, the Chang 6 tight sandstone reservoir in the study area can be divided into two types: wide bimodal mode reservoirs and asymmetric bimodal mode reservoirs. Based on the information entropy theory, the concept of “the entropy of microscale pore throats” is proposed to characterize the microscale pore throat differentiation of different reservoirs, and its influence on the distribution of movable fluid is discussed. There were significant differences in the entropy of the pore throat radius at different scales, which were mainly shown as follows: the entropy of the pore throat radius of 0.01~0.1 μm, >0.1 μm, and <0.01 μm decreased successively; that is, the complexity of the pore throat structure decreased successively. The correlation between the number of movable fluid occurrences on different scales of pore throats and the entropy of microscale pore throats in different reservoirs is also different, which is mainly shown as follows: in the intervals of >0.1 μm and 0.01~0.1 μm, the positive correlation between the occurrence quantity of movable fluid in the wide bimodal mode reservoir is better than that in the asymmetric bimodal mode reservoir. However, there was a negative correlation between the entropy of the pore throat radius and the number of fluid occurrences in the two types of reservoirs in the pore throat radius of <0.01 μm. Therefore, pore throats of >0.1 μm and 0.01~0.1 μm play a controlling role in studying the complexity of the microscopic pore throat structure and the distribution of movable fluid in the Chang 6 tight sandstone reservoir. The above results deepen the understanding of the pore throat structure of tight sandstone reservoirs and present guiding significance for classification evaluation, quantitative characterization, and efficient development of tight sandstone reservoirs.

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).

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