Reservoir Characteristics of Tight Sandstone of Shanxi Formation in Linxing Area in the North of Ordos Basin

To explore the source and reservoir characteristics of Chang 6 tight oil in the Zhangjiagou area, we have extracted a suite of Chang 6 tight sandstones and the source rocks from the seventh to ninth members of the Upper Cretaceous Yanchang Formation in the Ordos Basin, China, respectively, using chloroform. We examined group components by fractionations of extracted organic matter. Using low-pressure gas adsorptions and gas chromatography-mass spectrometry, respectively, we analyzed the pore structure of the studied samples before and after extraction and the oil source of the separate saturated hydrocarbon components. The results indicate that the porosity of the Chang 6 tight sandstone is mainly distributed in the 8%–14% range, averaging 10.5%, the permeability of the studied reservoir is only approximately 0.16 × 10−3 μm2, and the pore-throat radius is mainly less than 2 μm. The major type of pores of the reservoir includes the residual intergranular pore, secondary intergranular dissolved pore, and intragranular dissolved pore. The micropore volume of the Chang 6 tight sandstone is in the range of 0.0071–0.0092 cm3/g, and the mesopore volume of the Chang 6 tight sandstone is in the range of 0.0237–0.0343 cm3/g. The micropore volume and micropore surface area significantly increased after chloroform extractions, and soluble hydrocarbons could be stored in micropores of the Chang 6 tight sandstone. The three sets of source rocks from the seventh to ninth members of the Upper Cretaceous Yanchang Formation are high quality by the evaluation of source rocks, and the Chang 7 has the highest value of source rocks, followed by Chang 9 and Chang 8. The pentacyclic triterpene characteristics (Ts-C30H-C30*) of Chang 6 crude oil are similar to those of Chang 7 source rock, and the tight oil of the Chang 6 member in the Zhangjiagou area originated from Chang 7 source rocks.

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Pore Structure Differentiation between Deltaic and Epicontinental Tight Sandstones of the Upper Paleozoic in the Eastern Linxing Area, Ordos Basin, China

Geofluids ◽

10.1155/2021/9015041 ◽

2021 ◽

Vol 2021 ◽

pp. 1-17

Author(s):

Jimei Deng ◽

Huan Zeng ◽

Peng Wu ◽

Jia Du ◽

Jixian Gao ◽

...

Keyword(s):

Hot Spot ◽

Ordos Basin ◽

Central Area ◽

Gas Production ◽

Tight Gas ◽

Gas Reservoirs ◽

Tight Sandstone ◽

The North ◽

Taiyuan Formation ◽

Diagenetic Evolution

Research on tight gas reservoirs in the eastern margin of the Ordos Basin, China, has recently become a hot spot. This paper mainly studies the reservoir characteristics of tight sandstone in the north-central area close to the provenance in eastern Linxing. Cast thin section, scanning electron microscopy, high-pressure mercury injection, and X-ray diffraction (XRD) were applied to discriminate the tight sandstone reservoir differences between the Permian Taiyuan and Shanxi formations in the study area. The results show that the deltaic tight sandstones in the Shanxi Formation are dominated by lithic quartz sandstone and lithic sandstone with an average porosity of 2.3% and permeability of 0.083 mD. The epicontinental tight sandstones in the Taiyuan Formation are mainly lithic sandstone and lithic quartz sandstone, with average porosities and permeabilities of 6.9% and 0.12 mD, respectively. The pore type is dominated by secondary dissolution pores, containing a small number of primary pores, and fractures are not developed. The capillary pressure curves of the Taiyuan Formation sandstone are mainly of low displacement pressure, high mercury saturation, and mercury withdrawal efficiency, while the Shanxi Formation sandstone is mainly of high displacement pressure, low mercury saturation, and withdrawal efficiency. The diagenetic evolution of sandstone in the Shanxi Formation is in meso-diagenesis stage A, and the Taiyuan Formation has entered meso-diagenesis stage B. The siliceous cement in the Taiyuan Formation sandstone enhanced the sandstone resistance to compaction and retained some residual intergranular pores. The pore types in the Shanxi Formation sandstone are all secondary pores, while secondary pores in the Taiyuan Formation sandstone account for approximately 90%. The results can be beneficial for tight gas production in the study area and similar basins.

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Tight Sandstone Reservoirs Classification from Mercury Injection Capillary Pressure (MICP) Data in the North Ordos Basin

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1010-1012.1387 ◽

2014 ◽

Vol 1010-1012 ◽

pp. 1387-1390

Author(s):

Xiao Lei Wei ◽

Xin Li ◽

Rui Xu ◽

Ling Ling Zhi

Keyword(s):

Pore Structure ◽

Capillary Pressure ◽

Ordos Basin ◽

Morphological Characteristics ◽

Tight Sandstone ◽

The North ◽

Mercury Injection ◽

Sandstone Reservoirs ◽

Mercury Injection Capillary Pressure ◽

Structure Evaluation

It is of great importance in classifying reservoirs and establishing the relationship of pore structure and productivity for formation evaluation and reserves estimation. In this study, based on the morphological characteristics and the difference of pore structure evaluation parameters acquired from mercury injection capillary pressure (MICP) data, which were obtained from the experimental results of 20 core samples drilled from Chang 6 tight sandstone Formation of north Ordos basin, the Chang 6 formation is classified into three types, and the corresponding average MICP curves of every types are obtained. These were usable in determining the potential target formation and predicting the productivity in tight sandstone reservoirs.

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Reservoir characteristics and control mechanism of resistivity low-contrast oil pays in Chang 8 tight sandstone of Longdong West area, Ordos Basin

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-021-01195-1 ◽

2021 ◽

Author(s):

Ze Bai ◽

Maojin Tan ◽

Yujiang Shi ◽

Gaoren Li ◽

Simon Martin Clark

Keyword(s):

Control Mechanism ◽

Ordos Basin ◽

Water Salinity ◽

Formation Water ◽

Tight Sandstone ◽

Low Contrast ◽

Reservoir Characteristics ◽

The Difference ◽

Formation Water Salinity ◽

And Control

AbstractLog interpretation and evaluation of tight sandstone reservoir in Chang 8 Member of Longdong West area, Ordos Basin, China, are facing great challenges due to the co-development of normal oil pay and resistivity low-contrast oil pay. To better guide the exploration and development of oil resources in this area, the reservoir characteristics and control mechanism of resistivity low-contrast oil pay were studied. Firstly, the reservoirs were divided into resistivity low-contrast oil pay (RLP) and normal oil pay (NP) based on the relative value of the apparent resistivity increase rate. Then, the difference of reservoir characteristics between RLP and NP is analyzed by comparing a series of experimental data and real logging data in those two reservoir types. Finally, the control mechanism of RLP was studied from reservoir micro-factors and regional macro-factors, respectively. It is found that the chlorite and illite are the most abundant clay minerals in RLP and NP, respectively. Compared with NP reservoir, the average porosity of RLP is better, but the pore space is mainly composed of micropores, which lead to smaller average pore throat radius and poor pore structure. The high irreducible water saturation and high formation water salinity reduced the reservoir resistivity from micro-aspect. Besides, the difference of hydrocarbon expulsion capacity of source rock and the regional difference of formation water salinity controlled the distribution of RLP and NP. Comprehensive consideration of the reservoir micro-factors and regional macro-factors is important to carry out effective logging interpretation and evaluation.

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