scholarly journals The Influential Factors and Characteristics of Tight Sandstone Gas Reservoir: A Case Study in Ordos Basin in China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Dazhong Ren ◽  
Fu Yang ◽  
Rongxi Li ◽  
Yuhong Li ◽  
Dengke Liu
Keyword(s):  
Physical Properties ◽  
Ordos Basin ◽  
Influential Factors ◽  
Coarse Grained ◽  
Reservoir Quality ◽  
Tight Sandstone ◽  
Reservoir Compaction ◽  
Capillary Pressure Curves ◽  
The Impact

To analyze the impact of the factors on physical properties and the mechanism of tightness as well as favorable accumulation space of tight sandstone reservoir, comprehensive analysis is conducted using various kinds of experiments. The results show that the predominant rock type is medium-coarse grained lithic quartzarenite, and the main accumulating space is the dissolved secondary pores. Reservoir pore-throat structures can be divided into four categories. Based on morphologies and parameters which derived from capillary pressure curves, the physical properties rank in the following descending sequence: Type   I > Type   II > Type   III > Type   IV . The reservoir quality is influenced by both sedimentation and diagenesis synthetically. The underwater distributary channel is the dominant space for favorable reservoir. Compaction and cementation play dominant roles in the reduction of permeability. The loss of primary pores caused by both those diagenesis are 20.52% and 16.91%, respectively. Secondary pores formed by dissolution improve the reservoir quality by increase the porosity (2.68%). This suggests that weak diagenesis greatly contributes to the improvement of reservoir quality.

scholarly journals Diagenesis Evolution and Pore Types in Tight Sandstone of Shanxi Formation Reservoir in Hangjinqi Area, Ordos Basin, Northern China

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 470
Author(s):  
Yue Zhang ◽  
Jingchun Tian ◽  
Xiang Zhang ◽  
Jian Li ◽  
Qingshao Liang ◽  
...  
Keyword(s):  
Physical Properties ◽  
Oil And Gas ◽  
Ordos Basin ◽  
Northern China ◽  
Late Triassic ◽  
Reservoir Quality ◽  
Tight Sandstone ◽  
Quantitative Calculation ◽  
Pore Evolution ◽  
Pore Types

Diagenesis and pore evolution of tight sandstone reservoir is one of the most important issues surrounding clastic reservoirs. The tight sandstone of the Shanxi Formation is an important oil and gas producing layer of the Upper Paleozoic in Ordos Basin, and its densification process has an important impact on reservoir quality. This study determined the physical properties and diagenetic evolution of Shanxi Formation sandstones and quantitatively calculated the pore loss in the diagenetic process. Microscopic identification, cathodoluminescence, and a scanning electron microscope were used identify diagenesis, and the diagenesis evolution process was clarified along with inclusion analysis. In addition, reservoir quality was determined based on the identification of pore types and physical porosity. Results show that rock types are mainly sublitharenite and litharenite. The reservoir has numerous secondary pores after experiencing compaction, cementation, and dissolution. We obtained insight into the relationship between homogenous temperature and two hydrocarbon charges. The results indicated that there were two hydrocarbon charges in the Late Triassic–Early Jurassic (70–90 °C) and Middle Jurassic–Early Cretaceous (110–130 °C) before reservoir densification. The quantitative calculation of pore loss shows that the average apparent compaction, cementation, and dissolution rates are 67.36%, 22.24%, and 80.76%, respectively. Compaction directly affected the reservoir tightness, and intense dissolution was beneficial to improve the physical properties of the reservoir.

scholarly journals Diagenetic controls on reservoir quality of tight sandstone: A case study of the Upper Triassic Yanchang formation Chang 7 sandstones, Ordos Basin, China

2018 ◽  
Vol 22 (2) ◽  
pp. 129-138 ◽  
Author(s):  
Haihua Zhu ◽  
Guangchen Liu ◽  
Dakang Zhong ◽  
Tingshan Zhang ◽  
Jun Lang ◽  
...  
Keyword(s):  
Late Stage ◽  
Ordos Basin ◽  
Mineral Dissolution ◽  
Reservoir Quality ◽  
Tight Sandstone ◽  
Pore Characteristics ◽  
Mechanical Compaction ◽  
Primary Porosity ◽  
The Impact

Through a range of petrological techniques, the petrology, diagenesis, pore characteristics, and controlling factors on the regional variations of reservoir quality of the Chang 7 sandstones were studied. These sandstones, mainly arkoses, lithic arkoses, and feldspathic litharenites, were deposited in a delta front and turbidites in semi-deep to deep lacustrine. The detrital constituents were controlled by the provenance and sedimentary condition, which resulted in a spatially variable composition; e.g., high biotite and feldspar contents in the northeast (NE) of the study area, and high contents of rock fragments, especially dolomite, matrix, and quartz in the southwest (SW). Diagenesis includes intense mechanical compaction, cementation, and dissolution of unstable minerals. Diagenetic minerals which were derived internally include quartz, ankerite, ferrous calcite, albite, illite, kaolinite, and chlorite. Thus the original sandstone composition hadfirm control over the development and distribution of cement. Mechanical compaction and late-stage cementations contribute to the porosity loss of sandstones of Chang7 member. The dissolution porosity in major sandstone, slightly higher than primary porosity is principally dependent on the accessibility of acid fluid. The high content of plastic component facilitated the reduction of primary porosity and limited the mineral dissolution. The best reservoir sandstones are found in W, and partly from NE, M districts, with porosity are primary. The relatively high textural maturity of these sandstones reduces the impact of compaction on primary pores, and commonly existed chlorite rims limited the precipitation of pore filling quartz and carbonate cementation in late stage.

scholarly journals A reservoir quality evaluation approach for tight sandstone reservoirs based on the gray correlation algorithm: A case study of the Chang 6 layer in the W area of the as oilfield, Ordos Basin

2021 ◽  
pp. 014459872199851
Author(s):  
Yuyang Liu ◽  
Xiaowei Zhang ◽  
Junfeng Shi ◽  
Wei Guo ◽  
Lixia Kang ◽  
...  
Keyword(s):  
Quality Evaluation ◽  
Comprehensive Evaluation ◽  
Ordos Basin ◽  
Reservoir Quality ◽  
Pore Throat ◽  
Tight Sandstone ◽  
Evaluation Approach ◽  
Correlation Algorithm ◽  
Gray Correlation ◽  
Sandstone Reservoir

As an important type of unconventional hydrocarbon, tight sandstone oil has great present and future resource potential. Reservoir quality evaluation is the basis of tight sandstone oil development. A comprehensive evaluation approach based on the gray correlation algorithm is established to effectively assess tight sandstone reservoir quality. Seven tight sandstone samples from the Chang 6 reservoir in the W area of the AS oilfield in the Ordos Basin are employed. First, the petrological and physical characteristics of the study area reservoir are briefly discussed through thin section observations, electron microscopy analysis, core physical property tests, and whole-rock and clay mineral content experiments. Second, the pore type, throat type and pore and throat combination characteristics are described from casting thin sections and scanning electron microscopy. Third, high-pressure mercury injection and nitrogen adsorption experiments are optimized to evaluate the characteristic parameters of pore throat distribution, micro- and nanopore throat frequency, permeability contribution and volume continuous distribution characteristics to quantitatively characterize the reservoir micro- and nanopores and throats. Then, the effective pore throat frequency specific gravity parameter of movable oil and the irreducible oil pore throat volume specific gravity parameter are introduced and combined with the reservoir physical properties, multipoint Brunauer-Emmett-Teller (BET) specific surface area, displacement pressure, maximum mercury saturation and mercury withdrawal efficiency parameters as the basic parameters for evaluation of tight sandstone reservoir quality. Finally, the weight coefficient of each parameter is calculated by the gray correlation method, and a reservoir comprehensive evaluation indicator (RCEI) is designed. The results show that the study area is dominated by types II and III tight sandstone reservoirs. In addition, the research method in this paper can be further extended to the evaluation of shale gas and other unconventional reservoirs after appropriate modification.

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