scholarly journals Characteristics and Genetic Mechanism of Chang Eight Low Permeability and Tight Reservoir of Triassic Yanchang Formation in Central-East Ordos Basin

2022 ◽  
Vol 9 ◽  
Author(s):  
Xingying Wang ◽  
Na Liu ◽  
Junxiang Nan ◽  
Xiaolin Wang ◽  
Dazhong Ren
Keyword(s):  
Ordos Basin ◽  
Physical Property ◽  
Low Permeability ◽  
High Porosity ◽  
X Ray Diffraction ◽  
Yanchang Formation ◽  
Fine Grain ◽  
Tight Reservoir ◽  
Target Layer ◽  
Northern Shaanxi

In this article, the characteristics of Chang 8 reservoir of Triassic Yanchang Formation in northern Shaanxi are studied by using polarizing microscope, field emission scanning electron microscope, image particle size, X-ray diffraction analysis of clay, and constant pressure mercury intrusion. The study shows that the target layer is in a relatively stable and uniform sinking burial period after deposition, and the lithology composition in the area is relatively complex, mainly composed of debris–feldspar sandstone and feldspar sandstone, with the characteristics of fine grain and high content of interstitial material. The porosity of the reservoir is generally between 4% and 12%, with an average of 8.05%. The permeability is generally between 0.03 × 10−3 and 0.5 × 10−3 μm2, with an average of 0.16 × 10−3 μm2. Strong compaction and well-developed cementation of calcareous, siliceous, and authigenic illite are important reasons for the formation of extra-low porosity and extra-low permeability reservoirs. But at the same time, because of the protective effect of chlorite film, some residual intergranular pores are preserved, which makes the some reservoirs with relatively good physical property, forming a local relatively high-porosity and high-permeability section of the “highway.”

Research on Diagenetic Facies Based on Diagenetic Effect in the Low Permeability Sandstone Reservoir - A Case from C81 Reservoir in Huanjiang Region, Ordos Basin

2014 ◽  
Vol 522-524 ◽  
pp. 1274-1279
Author(s):  
Chun Wang ◽  
Zhi Guo Jin ◽  
Cheng Zhi Liu
Keyword(s):  
Physical Properties ◽  
Ordos Basin ◽  
Physical Property ◽  
Low Permeability ◽  
Thin Sections ◽  
Diagenetic Minerals ◽  
Calcite Cementation ◽  
Diagenetic Facies ◽  
Pore Types ◽  
Feldspar Dissolution

The research is carried out on diagenetic minerals, pore types and its impact on the physical properties in Huanjiang C81reservoir of Ordos basin, which is based on reservoir physical property test, thin sections observation and scanning electron microscopy. Several minerals closely associated with reservoir physical properties are identified from diagenetic effect views. It results in that a classification is proposed for the diagenetic facies, consisting of four kinds of diagenetic facies: ferroan calcite cementation facies, hydromica/kaolinite cementation facies, chlorite coating facies and feldspar dissolution facies. The study of C81reservoir in Huanjiang region shows that this scheme is favorable to estimate low permeability reservoir, the result shows fairly good consistency with the distribution of physical property of wells.

scholarly journals Physical Property and Origin of Lowly Permeable Sandstone Reservoir in Chang 2 Division, Zhang-Han Oilfield, Ordos Basin

2009 ◽  
Vol 27 (5) ◽  
pp. 367-389 ◽  
Author(s):  
Chao Gao ◽  
Zhenliang Wang ◽  
Jie Deng ◽  
Jinghui Zhao ◽  
Xianchao Yang
Keyword(s):  
Pore Space ◽  
Ordos Basin ◽  
Physical Property ◽  
Asymmetric Distribution ◽  
Porosity Evolution ◽  
Key Factor ◽  
Northern Shaanxi ◽  
Sandstone Reservoirs ◽  
Diagenetic Facies ◽  
Pore Types

Lowly permeable sandstone reservoirs play an important role in the exploration and exploitation of natural gas and petroleum in China. The reservoirs are major lowly permeable sandstone reservoirs in Chang 2 division, Yanchang Formation, Upper Triassic in Zhang-Han oilfield, which located in the northern Shaanxi slope of Ordos Basin. According to the distribution and composition of sand beds, integrated measured physical properties, micro-pore structure analysis, cast thin section observation, scanning electron microscopy, the impacts of deposition and diagenesis on porosity evolution are analyzed. The essential diagenesis causing the porosity loss is evaluated quantitatively, and finally the origin mechanisms of low permeability reservoir in Zhang-Han oilfield are discussed. The results show: (1) Fine particle and low compositional maturity arkose are the material foundation of the formation of poor physical property sandstone; (2) The main pore space of reservoir is secondary pores. There are two types of combined pores that including dissolve-residual pores and dissolve-micropores. The porosity values display an approximately normal distribution, and permeability values are asymmetric distribution of the logarithm in lowly permeable sandstones. Their correlation coefficient becomes more and more worse with the decrease of permeability; (3) There are four diagenetic facies, in which three diagenetic facies belong to extra-lowly permeable and ultra-lowly permeable reservoir sandstones and widely distributed, and they are diagenetic lithofacie background of lowly permeability sandstone; (4) In low compositional maturity arkose, its initial porosity is 1/4 lower than conventional reservoir, the secondary and dissolved pores are main pore types of lowly permeable reservoir rocks. It is also a key factor of effective oil-bearing of lowly permeability sandstone.

scholarly journals Study on Fracability of Tight Reservoir on the basis of Geophysical Logging: a Case Study of Chang 7 Formation in Longdong Area, Ordos Basin

CONVERTER ◽  
2021 ◽  
pp. 518-527
Author(s):  
Zhenhua Li, Et al.
Keyword(s):  
Fracture Toughness ◽  
Oil And Gas ◽  
Thermal Evolution ◽  
Ordos Basin ◽  
Laboratory Data ◽  
Physical Property ◽  
Field Application ◽  
Analysis Model ◽  
Form Complex ◽  
Tight Reservoir

Fracability is the ability to form complex fracture to Increase production in tight reservoir under the same fracturing condition. The factors influencing fracturing include reservoir brittleness, fracture toughness, crack system,thermal evolution andmineral content etc. The tight reservoir physical property are poor, and the oil and gas produced under natural conditions is too little, so it is necessary to fracture the reservoir.In this paper, the brittleness and fracture toughness of Chang 7 Formationof Ordos Basinare calculated by logging data under the constraint of laboratory data. In combination with production practice, a new analysis model of reservoir hydraulicfracturing is constructed. The new analysis method is used to evaluate the fracability of Chang 7 stratum in the Ordos Basin, which ranges from 38.7% to 51.4%. It is basically consistent with the practical fracturing effect of typical wells in this area, which shows that the new method is accurate in calculation, convenient in field application, and can provide experience for the reservoir hydraulic fracturing .

Pore structure and fractal characteristics of ultra-low permeability sandstone reservoirs in Upper Triassic Yanchang Formation, Ordos Basin

2021 ◽  
pp. 1-59
Author(s):  
Quanpei Zhang ◽  
Tao Jiao ◽  
Hao Huang ◽  
Zhao Qi ◽  
Tao Jiang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Quality Evaluation ◽  
Pore Space ◽  
Ordos Basin ◽  
Upper Triassic ◽  
Reservoir Quality ◽  
Low Permeability ◽  
Yanchang Formation ◽  
Fractal Characteristics ◽  
Sandstone Reservoirs

The complex pore structure and high heterogeneity of ultra-low permeability sandstone reservoirs have a significant effect on reservoir quality evaluation and hydrocarbon resource assessment. We collected 10 reservoir samples from the Upper Triassic Yanchang Formation Chang 8 in the Zhenbei area of the Ordos Basin. We measured the pore size distribution (PSD) and fluid occurrence characteristics of the reservoir by Pressure-controlled porosimetry (PCP), rate-controlled porosimetry (RCP) and nuclear magnetic resonance (NMR), and then analyzed the results via the fractal theory to determine the pore space fractal characteristics. Our analysis indicates that the three major pore types of these reservoirs are residual intergranular pores, dissolution pores and intercrystalline pores. The pore structure of the ultra-low permeability sandstone reservoirs is highly heterogeneous with pore throats of various scales, and the corresponding fractal characteristics are notably different, exhibiting multi-fractal features. Compared to macropores and mesopores, micropores are more uniform and regular in terms of their PSD and thus only slightly influence the reservoir quality. The complexity of the throat distribution and whole pore space is attributed to the development of dissolution pores and the content of feldspar minerals. Fractal features depend on the movable fluid pore space and effective pores, whose fractal dimensions reflect the complexity of interconnected pores and correlate well with the porosity and permeability. The development of different types and sizes of pore throats in these ultra-low permeability sandstone reservoirs resulted in the observed pore structure heterogeneity. The difference in mineral composition and content of these reservoirs aggravates the pore structure complexity and affects reservoir quality evaluation and further oilfield development.

Ultra Low Permeability Reservoir Characteristics and Origin Analysis

2011 ◽  
Vol 361-363 ◽  
pp. 51-54
Author(s):  
Hong Yan Yu ◽  
Hong Qi Li
Keyword(s):  
Large Scale ◽  
Ordos Basin ◽  
Physical Property ◽  
Research Area ◽  
Low Permeability ◽  
Storage Space ◽  
Low Permeability Reservoir ◽  
Microscopic Feature ◽  
Depositional Setting ◽  
High Range

As the result of its special structural feature and depositional setting, Ordos Basin formed large scale low-permeability reservoir. According to scanning electron microscope, casting sheet image, core observation, physical property analysis and core analysis testing, this paper summarized and analyzed ultra low permeability reservoir microscopic feature of Ordos Basin Baibao area Chang63. Reservoir microscopic feature is controlled by deposition and diagenesis. Deposition decided reservoir lithology, interstitial content and sizes of primary pores. Compaction and cementation of diagenesis destroyed primary pores, but denudation provided high range secondary pores, which improved storage space of the research area.

scholarly journals Diagenetic facies quantitative evaluation of low-permeability sandstone: A case study on Chang 82 reservoirs in the Zhenbei area, Ordos basin

2017 ◽  
Vol 36 (3) ◽  
pp. 414-432 ◽  
Author(s):  
Baoquan Ma ◽  
Shaochun Yang ◽  
Hong Zhang ◽  
Qingdong Kong ◽  
Chunting Song ◽  
...  
Keyword(s):  
Quantitative Evaluation ◽  
Ordos Basin ◽  
Physical Property ◽  
Reservoir Quality ◽  
Low Permeability ◽  
Data Envelopment ◽  
Reservoir Evaluation ◽  
Diagenetic Facies

Quantitative characterization of diagenetic facies has great significance for reservoir evaluation and prediction. In order to find out the method to evaluate diagenetic facies, the author took Chang 82 reservoir low-permeability sandstone in Zhenbei area of Ordos basin as research object and divided the reservoir into six types of diagenetic facies by analysis of casting thin section, scanning electron microscope, cathode luminescence, and physical property. According to 14 quantitative evaluating parameters which were related with petrology characteristic, diagenesis strength, pore structure, etc. quantitative evaluation of diagenetic facies of low-permeability sandstone reservoir was done by data envelopment analysis. The result showed that in the Chang 82 reservoir low-permeability sandstone in Zhenbei area of Ordos basin, quantitative representative indexes of diagenetic facies ranged from 0 to 1.00. Various diagenetic facies and their indexes had interval corresponding relation. The diagenetic facies of weak corrosion with chlorite mat and the diagenetic facies of corrosion of unstable components had the best reservoir quality. Their diagenetic facies indexes ranged from 0.66 to 1.00. The reservoir quality of the diagenetic facies filled with kaolinite was not as good as the former. The indexes ranged from 0.50 to 0.66. The diagenetic facies of quartz secondary enlargement and the diagenetic facies of clay mineral cementation replacement had poor reservoir quality. Their diagenetic facies indexes ranged from 0.30 to 0.40. The diagenetic facies of carbonate cementation had the poorest reservoir quality. It hardly possessed fluid storage capability. After comparing diagenetic facies indexes, absorption strength and remaining oil saturability, the perfect corresponding relation between quantitative evaluation results and reservoir quality could be verified.

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