Diagenetic characteristics and quantitative evolution of porosity in tight gas sandstone reservoirs: A case study from the middle and lower Permian in the northwestern Ordos Basin, China

2020 ◽  
Vol 8 (1) ◽  
pp. T195-T215
Author(s):  
Yang Gao ◽  
Zhizhang Wang ◽  
Shiwei Yi ◽  
Yuanqi She ◽  
Shiguo Lin ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Reservoir Rock ◽  
Lower Permian ◽  
Tight Gas ◽  
Tight Sandstone ◽  
Porosity Evolution ◽  
Rock Types ◽  
Reservoir Permeability ◽  
Volcanic Debris ◽  
Intercrystalline Pores

Tight sandstone gas is widespread in the middle and lower Permian Shan 1 and He 8 Members in the northwestern Ordos Basin. We have studied the diagenesis by means of many petrographic techniques and determined its important influence on reservoir quality. The quantitative characterization of porosity evolution is important when analyzing reservoir consolidation. We found that reservoir rock types are mainly sublitharenite, quartz arenite, and litharenite in the deltaic facies through petrological and mineralogical analyses. Metamorphic rock (quartzite), followed by volcanic rock, dominates the lithic fragment types. In the early diagenetic stage, the reservoirs mainly underwent intensive compaction, hydrolysis, and alteration of volcanic debris. Sandstones in the middle diagenesis stage were characterized by quartz overgrowth, volcanic debris dissolution, cementation, and calcite and kaolinite replacement. Based on the formula from Beard and Weyl, we calculated that the original porosity of tight gas sandstones was 38.61%. The porosity loss during compaction was 26.64%; by cementation, it was 11.46%; and carbonate, siliceous, and authigenic clay cements accounted for 1.31%, 3.61%, and 6.44% loss in porosity, respectively. Dissolution was relatively weak, with an average increase in porosity of 4.86%, whereas the present porosity is 7.47%. We observed that the pore types in the study area are composed of intragranular dissolution pores and kaolinite intercrystalline pores, followed by residual primary pores and intergranular dissolution pores. However, microcracks were not common. Based on the results of the rate-controlled mercury intrusion, the pore diameters in different samples are similar but there were clear differences in the throat diameters. Nuclear magnetic resonance results indicate that the cutoff value is 13 ms with the movable fluid mainly distributed in larger pores. As the pressure increased, fluid in the larger pores was discharged in large quantities but there was no discharge of nonmovable fluid in the small pores. We conclude that intensive diagenetic transformation was the main cause of reservoir consolidation and multistage cementation resulted in a complicated pore-throat network and reduced reservoir permeability.

Cementation and porosity evolution of tight sandstone reservoirs in the Permian Sulige gas field, Ordos Basin (central China)

2019 ◽  
Vol 103 ◽  
pp. 276-293 ◽  
Author(s):  
Aiping Fan ◽  
Renchao Yang ◽  
Nils Lenhardt ◽  
Meng Wang ◽  
Zuozhen Han ◽  
...  
Keyword(s):  
Ordos Basin ◽  
Central China ◽  
Tight Sandstone ◽  
Gas Field ◽  
Porosity Evolution ◽  
Sandstone Reservoirs

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 An improved saturation evaluation method of Chang 8 tight sandstone reservoir in Longdong West area of Ordos Basin, China

2021 ◽  
pp. 014459872110224
Author(s):  
Ze Bai ◽  
Maojin Tan ◽  
Yujiang Shi ◽  
Haitao Zhang ◽  
Gaoren Li
Keyword(s):  
Calculation Method ◽  
Ordos Basin ◽  
Reservoir Rock ◽  
Bundle Theory ◽  
Model Parameters ◽  
Saturation Model ◽  
Tight Sandstone ◽  
Equivalent Radius ◽  
Capillary Bundle ◽  
Sandstone Reservoir

This study focus on saturation evaluation of Chang 8 tight sandstone reservoir in Longdong West area of Ordos Basin, China. An improved saturation calculation method was proposed based on the equivalent rock capillary bundle theory. Firstly, according to characteristics of reservoir pore structure and rock conductivity, the conductive space of reservoir rock is equivalent to the parallel conductive of micro capillary bundle representing the micro pores and the coarse capillary bundle representing the macro pores. Then, the variable cementation index(m) saturation model was deduced by using Poiseuille flow equation and Darcy's law. During the calculation of model parameters, the T2 spectrum data of nuclear magnetic resonance (NMR) was used to calculate the equivalent radius of reservoir micro pores and macro pores, which ensured the ability of model popularization and application. Finally, the proposed saturation calculation method is applied to reservoir evaluation of the study area, and compared with the classical Archie saturation model. The application effect shows that the calculated saturation from the proposed variable m model is much closer to the sealed coring data than that from classical Archie model, and the average relative error of saturation calculated by the variable m model is within 7%, which proves that the proposed saturation calculation method is applicable and effective.

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

Geofluids ◽  
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.

scholarly journals A New Quantitative Approach for Element-Mineral Determination Based on “EDS (Energy Dispersive Spectroscopy) Method”

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Peigang Liu ◽  
Zhelin Wang ◽  
Zhiqiang Zhang
Keyword(s):  
Energy Dispersive Spectroscopy ◽  
Ordos Basin ◽  
Hydrocarbon Exploration ◽  
Energy Dispersive ◽  
New Method ◽  
Reservoir Rock ◽  
Tight Sandstone ◽  
Composition And Structure ◽  
Diagenetic Evolution ◽  
Xrd Techniques

With the continuous development of hydrocarbon exploration, how to efficiently, economically, accurately, and comprehensively obtain mineral species, composition, and structure and diagenesis information has become one of the hot topics in both the academia and industry. By scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), a new method of qualitative mineral identification and quantitative measurement is established. Typical tight sandstone reservoir rock samples in the Ordos Basin are selected; through the element surface scanning image of “mineral element composition” and “pixel element combination”, mineral types are distinguished, and mineral parameters such as types, characteristics, and content are rapidly and accurately determined. Meanwhile, such results achieved via the new method are compared with conventional XRD and TIMA methods. The results show that the new method exhibits several advantages: cost advantages compared to XRD experiment analysis technology and TIMA system and ability to analyze low content minerals which XRD techniques are hard to identify; it allows quantitative characterization on the phenomenon of mineral miscibility, which is of great significance to explore the mineral diagenetic evolution.

scholarly journals Quantitative evaluation of the diagenesis and porosity evolution of tight sandstone reservoirs: A case study of the Yanchang formation in the Southern Ordos basin, China

2019 ◽  
Vol 9 (1) ◽  
pp. 15-26
Author(s):  
Meng Xiao ◽  
Dawei Chen ◽  
Guiqiang Qiu ◽  
Xuanjun Yuan ◽  
Chunfang Chen
Keyword(s):  
Pore Size ◽  
Average Pore Size ◽  
Ordos Basin ◽  
Influential Factor ◽  
Tight Sandstone ◽  
Average Pore ◽  
Yanchang Formation ◽  
Porosity Evolution ◽  
Pore Evolution ◽  
Sandstone Reservoirs

Evaluation of the pore evolution is key to gaining a better understanding of oil migration and accumulation in tight oil exploration for tight sandstone; to study the diagenesis and porosity evolution of tight sandstone reservoirs, we analysed the 8th member of the Yanchang Formation by core observation, thin section observation, cathodoluminescence, scanning electron microscopy, and logging data analysis. The following conclusions can be drawn (1) In the typical tight sandstone reservoir, numerous secondary pores developed at burial depths in the range of 1300 m to 1400 m, and approximately 1500 m to 1600 m. (2) Compaction was the most influential factor of reservoir density and decreased the average pore size by 24.8%. Carbonate cementation decreased the porosity by 8.2%. The most important diagenetic process for increasing the reservoir porosity was dissolution, which increased the pore size by 5.1%. In addition, chlorite played an active role in inhibiting secondary quartz growth and preserving primary pores. (3) The early gas invasion can inhibit diagenesis, and the organic acids produced by the later oil can increase dissolution, so that the high oil saturation phenomenon becomes more obvious.

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