scholarly journals Pore structure and its control on reservoir quality in tight sandstones: a case study of the Chang 6 member of the Upper Triassic Yanchang Formation in the Jingbian oilfield in the Ordos Basin, China

2020 ◽  
Author(s):  
Yubin Bai ◽  
Jingzhou Zhao ◽  
Delin Zhao ◽  
Hai Zhang ◽  
Yong Fu
Keyword(s):  
Physical Properties ◽  
Pore Structure ◽  
Clay Minerals ◽  
Mercury Porosimetry ◽  
Ordos Basin ◽  
Reservoir Quality ◽  
Overburden Pressure ◽  
Thin Sections ◽  
The Ordos Basin ◽  
Sandstone Reservoir

AbstractThis study applied vacuum-impregnated casting thin sections, fluorescence slices, scanning electron microscopy (SEM), pressure-controlled mercury porosimetry (PCP), rate-controlled mercury porosimetry (RCP), X-ray diffraction of clay minerals, overburden pressure, and conventional physical property strategies to determine the microscopic characteristics of the Chang 6 member, a typical tight sandstone reservoir in the Jingbian oilfield in the Ordos Basin, China. We also analyzed the controlling effects of pore structure on reservoir quality and oiliness. The results showed that the pore types of the Chang 6 sandstone reservoir can be divided into four categories: residual intergranular pores, dissolution pores, intercrystalline pores between clay minerals, and microfractures. The pore size of the Chang 6 sandstone reservoir ranged from 20 to 50 μm. We employed PCP and RCP strategies to characterize the pore structure of the Chang 6 reservoir. The pore radius was less than 2 μm, and on average, the throat radius was less than 0.3 μm. The reservoir physical properties were affected by diagenesis, particularly compaction, and the average porosity failure rate was 56.3%. Cementation made the reservoir more compact, dissolution improved the physical properties of the reservoir locally, and fracturing effectively improved the reservoir seepage ability; however, its influence on porosity was limited. The pore structure controlled the quality of the reservoir. The physical properties of the reservoir were closely related to the oil-bearing properties. The lower limits of porosity and permeability of industrial oil flow in the reservoir were 7.5% and 0.15 mD, respectively. These results provide an additional resource for the exploration and development of tight oil in the Ordos Basin.

scholarly journals Impact of rock type on the pore structures and physical properties within a tight sandstone reservoir in the Ordos Basin, NW China

2020 ◽  
Vol 17 (4) ◽  
pp. 896-911
Author(s):  
Xiang-Dong Yin ◽  
Shu Jiang ◽  
Shi-Jia Chen ◽  
Peng Wu ◽  
Wei Gao ◽  
...  
Keyword(s):  
Physical Properties ◽  
Rock Type ◽  
Ordos Basin ◽  
Tight Sandstone ◽  
Nw China ◽  
Pore Structures ◽  
The Ordos Basin ◽  
Sandstone Reservoir

scholarly journals Petrological characteristics and the impact of mineral content on reservoir quality in coal-bearing strata of Linxing area, eastern margin of Ordos Basin, China

2018 ◽  
Vol 36 (4) ◽  
pp. 872-894 ◽  
Author(s):  
Chuang Liu ◽  
Jianhua Zhong ◽  
Xi Wang ◽  
Mengchun Cao ◽  
Jianguang Wu ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Mixed Layer ◽  
Ordos Basin ◽  
Gas Reservoirs ◽  
Tight Sandstone ◽  
Thin Sections ◽  
Eastern Margin ◽  
Sandstone Reservoir ◽  
Feldspar Dissolution ◽  
The Impact

Tight sandstone gas is on the first position of unconventional natural gas sources, which can be developed under today’s technical conditions. In recent years, tight sandstone gas reservoirs have been found in several wells in the Linxing area, eastern margin of Ordos Basin, China. In this article, a variety of methods, including cast thin sections, X-ray diffraction analysis, scanning electron microscope, and drill core data were used to study the petrological characteristics and their influences on tight sandstone reservoir in coal-bearing strata of the Linxing area. Based on the analysis of thin section, it can be concluded that the sandstone reservoir is essentially constituted of lithic sandstone as well as lithic arkose and feldspathic litharenite. Cement types are complicated, including carbonate minerals, clay minerals, and quartz overgrowth. Illite, kaolinite, chlorite, illite–smectite mixed layer, and chlorite–smectite mixed layer are found in clay minerals. Compared with other clay minerals, illite is in the dominant position. Pores can be divided into residual intergranular pore, intragranular dissolution pore, intergranular dissolution pore, cement dissolution pore, intercrystalline pore, and microcrack in sandstone reservoir of the Linxing area. Quartz has an average content of 68% with the feature of low compositional maturity and plays a major role in increasing porosity due to dissolution and protecting of quartz. Feldspar dissolution plays a role in decreasing porosity because the by-product materials of feldspar dissolution remain in original place, instead of being transported to other areas. Dissolution pores are 2–20 µm and may be filled with kaolinite, illite, or halite. It is worth mentioning that grain-coating chlorite may be of sufficient thickness to protect reservoirs along with the increasing content of chlorite, which is testified by the crossplot between the chlorite and porosity when the absolute content of chlorite is less than 1.5%.

scholarly journals Study on the sensitivities and damage mechanisms of ultra-low permeability sandstone reservoirs: taking Chang 6 reservoir in Jingbian oilfield as an example

2020 ◽  
Vol 194 ◽  
pp. 01037
Author(s):  
Xiulan Zhu ◽  
Yanlong Ran ◽  
Zhanjun Chen ◽  
Tai Xu ◽  
Shengling Jiang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Ordos Basin ◽  
Small Hole ◽  
Low Permeability ◽  
Thin Sections ◽  
Acid Sensitivity ◽  
Water Sensitivity ◽  
Sensitivity Evaluation ◽  
Sandstone Reservoir ◽  
Sandstone Reservoirs

This paper takes the ultra-low permeability sandstone reservoir of Jingbian oilfield in Ordos Basin as the research object, analyzes the petrological characteristics, diagenesis, physical characteristics and pore structure characteristics of the reservoir, and carries out reservoir sensitivity evaluation by using rock casting thin sections, X-ray diffraction, and sensitive flow experiments. The research results show that the ultra-low permeability Chang 6 sandstone reservoir has weak velocity sensitivity, medium-weak water sensitivity, weak salt sensitivity, weak alkali sensitivity and strong acid sensitivity; the damage mechanism of reservoir sensitivity mainly depends on the composition of clay minerals and pore structure after diagenesis. The clay mineral content from high to low is chlorite, illite, a small amount of illite / smectite layer, and kaolinite, of which the chlorite content is as high as 75 %; the reservoir has poor physical properties, the types of small hole-thin throat and small hole-fine throat. The reservoir is prone to blockage such as bridge plugging. Therefore, ultra-low permeability sandstone reservoirs are prone to different degrees of sensitivity. The reservoir characteristics are consistent with the reservoir sensitivity evaluation results.

PORE STRUCTURE OF TRANSITIONAL SHALES IN THE ORDOS BASIN, NW CHINA: EFFECTS OF COMPOSITION ON GAS STORAGE MECHANISM

2017 ◽  
Author(s):  
Fengyang Xiong ◽  
◽  
Zhenxue Jiang ◽  
Mohammad Amin Amooie ◽  
Mohamad Reza Soltanian ◽  
...  
Keyword(s):  
Pore Structure ◽  
Ordos Basin ◽  
Gas Storage ◽  
Nw China ◽  
Storage Mechanism ◽  
The Ordos Basin

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.

Lithofacies Analysis and Qualitative Minerology of the Sediments of #3 Well in the Greater Ughelli Depobelt, Niger Delta Basin

2021 ◽  
Vol 13 (2) ◽  
pp. 601-610
Author(s):  
K. Itiowe ◽  
R. Oghonyon ◽  
B. K. Kurah
Keyword(s):  
Physical Properties ◽  
Clay Minerals ◽  
Niger Delta ◽  
Reservoir Quality ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sandy Shale ◽  
Heterogeneous Nature ◽  
Niger Delta Basin ◽  
Shaly Sandstone

The sediment of #3 Well of the Greater Ughelli Depobelt are represented by sand and shale intercalation. In this study, lithofacies analysis and X-ray diffraction technique were used to characterize the sediments from the well. The lithofacies analysis was based on the physical properties of the sediments encountered from the ditch cuttings.  Five lithofacies types of mainly sandstone, clayey sandstone, shaly sandstone, sandy shale and shale and 53 lithofacies zones were identified from 15 ft to 11295 ft. The result of the X-ray diffraction analysis identified that the following clay minerals – kaolinite, illite/muscovite, sepiolite, chlorite, calcite, dolomite; with kaolinite in greater percentage. The non-clay minerals include quartz, pyrite, anatase, gypsum, plagioclase, microcline, jarosite, barite and fluorite; with quartz having the highest percentage. Therefore, due to the high percentage of kaolinite in #3 well, the pore filing kaolinite may have more effect on the reservoir quality than illite/muscovite, chlorite and sepiolite. By considering the physical properties, homogenous and heterogeneous nature of the #3 Well, it would be concluded that #3 Well has some prospect for petroleum and gas exploration.

scholarly journals Multifractal Characteristics and Classification of Tight Sandstone Reservoirs: A Case Study from the Triassic Yanchang Formation, Ordos Basin, China

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2242 ◽  
Author(s):  
Zhihao Jiang ◽  
Zhiqiang Mao ◽  
Yujiang Shi ◽  
Daxing Wang
Keyword(s):  
Pore Structure ◽  
Ordos Basin ◽  
Type I ◽  
Tight Sandstone ◽  
Throat Radius ◽  
Yanchang Formation ◽  
Porosity And Permeability ◽  
Sandstone Reservoir ◽  
And Migration ◽  
Mercury Injection Capillary Pressure

Pore structure determines the ability of fluid storage and migration in rocks, expressed as porosity and permeability in the macroscopic aspects, and the pore throat radius in the microcosmic aspects. However, complex pore structure and strong heterogeneity make the accurate description of the tight sandstone reservoir of the Triassic Yanchang Formation, Ordos Basin, China still a problem. In this paper, mercury injection capillary pressure (MICP) parameters were applied to characterize the heterogeneity of pore structure, and three types of pore structure were divided, from high to low quality and defined as Type I, Type II and Type III, separately. Then, the multifractal analysis based on the MICP data was conducted to investigate the heterogeneity of the tight sandstone reservoir. The relationships among physical properties, MICP parameters and a series of multifractal parameters have been detailed analyzed. The results showed that four multifractal parameters, singularity exponent parameter (αmin), generalized dimension parameter (Dmax), information dimension (D1), and correlation dimension (D2) were in good correlations with the porosity and permeability, which can well characterize the pore structure and reservoir heterogeneity of the study area, while the others didn’t respond well. Meanwhile, there also were good relationships between these multifractal and MICP parameters.

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