Formation water geochemistry and the petroleum geological significance in Yanchang Formation of Wuqi Oilfield, Ordos Basin, China

Wang, Xia; Guo-min, FU

doi:10.1504/ijogct.2023.127353

Cited by 4 publications

(2 citation statements)

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“…The structural division stretches across the Tianhuan depression, Yishan slope and Weibei uplift of the current basin (Figure 1). During the late Triassic period, Ordos basin developed a set of lacustrine and shallow water delta sedimentary fillings under the background of a stable inland Craton (Sun et al, 2009; Wang et al, 2013). The Chang 8 Member ranges in thickness between 80 and 100 m. (Figure 2).…”

Section: Geological Settingmentioning

confidence: 99%

Main controlling factors and oil-bearing potential characteristics of a tight sandstone reservoir: A case study of southwest Ordos Basin

Guo

Peng

et al. 2023

Energy Exploration & Exploitation

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Clarifying the main controlling factors of reservoirs and their oil-bearing potential is vital for predicting tight sandstone reservoirs. The Chang 8 reservoir in the southwest of Ordos Basin is a typical tight sandstone reservoir and is widely distributed. Observation description and sampling analysis of cores, the grain size analysis, casting thin section, scanning electron microscope, mercury pressure, nuclear magnetic resonance, and conventional physical analysis are used to clarify the main controlling factors and oil-bearing potential characteristics of the Chang 8 reservoir in southwest Ordos Basin. The results show that delta front subfacies are mainly developed in Chang 8 member, including distributary channel, natural dike, estuary bar and distributary bay. The main rock type of reservoir is lithic feldspathic sandstone, followed by feldspathic lithic sandstone. The types of reservoir space are mainly intergranular pores and intragranular dissolved pores, with a small amount of clay-related pores and micro-fractures. The average porosity and permeability of the reservoir are 11.67% and 0.52 × 10−3μm2, respectively. The reservoirs with high oil saturation are mainly distributary channels and thicker mouth bar sand bodies. Compaction is the main factor of reservoir compaction (porosity loss rate is 55.73%), followed by cementation (porosity loss rate is 29.23%). The favorable diagenesis is the dissolution of feldspar grains and some cement. The Chang 8 tight reservoir contains various nano-scale pore-throat. For tight reservoirs with similar physical properties, the pore-throat structure controls the oil saturation of the tight reservoir. Favorable conditions for tight sandstone reservoirs oil saturation include favorable sedimentary environment (distributary channel or thick mouth bar) and suitable microscopic pore characteristics.

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Section: Geological Settingmentioning

confidence: 99%

Main controlling factors and oil-bearing potential characteristics of a tight sandstone reservoir: A case study of southwest Ordos Basin

Guo

Peng

et al. 2023

Energy Exploration & Exploitation

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“…It is a superimposed development area of two oil-bearing groups including the Triassic Yanchang Formation and the Jurassic Yan'an Formation (Figure 1). The main target bed of this study is the Chang 8 tight sandstone reservoir of the Yanchang Formation, which is located below the Chang 7 oil shale and it is the main production horizon of oil and gas because of its good hydrocarbon storage conditions [30,31]. The geological conditions of the Chang 8 reservoir of the Yanchang Formation are complex.…”

Section: Geologic Setting Of the Study Areamentioning

confidence: 99%

Fluid Identification Method of Nuclear Magnetic Resonance and Array Acoustic Logging for Complex Oil and Water Layers in Tight Sandstone Reservoir

Bai,

Tan,

et al. 2023

Processes

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In order to improve the logging interpretation accuracy for complex oil and water layers developed in tight sandstone reservoirs, this study takes the Chang 8 member of the Yanchang Formation in the Huanxian area as the research object, and two new fluid identification methods were constructed based on nuclear magnetic resonance (NMR) logging and array acoustic logging. Firstly, the reservoir characteristics of physical properties and conductivity were studied in the research area, and the limitations of conventional logging methods in identifying complex oil and water layers were clarified. Then, the sensitive parameters for identifying different pore fluids were established by analyzing the relationship between NMR logging and array acoustic logging with different pore fluids. On this basis, the fluid identification plate, composed of movable fluid apparent diffusion coefficient and effective porosity difference (Da-Δφe) by NMR logging data of D9TWE3 observation mode, and the other fluid identification plate, composed of apparent bulk modulus of pore fluid and elastic parameter sensitive factor (Kf-Fac), were constructed, respectively. Finally, these two fluid identification methods were used for reservoir interpretation of actual logging data. This study shows that the two new fluid identification methods constructed by NMR logging and array acoustic logging can effectively eliminate the interference of rock skeleton on logging interpretation, which make them more effective in identifying complex oil and water layers than the conventional logging method. Additionally, the two methods have their own advantages and disadvantages when used separately for interpreting complex oil and water layers, and the comprehensive interpretation of the two methods provides a technical development direction for further improving the accuracy of logging the interpretation of complex oil and water layers.

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Identification of an oil-bearing layer by formation water resistivity: A case study of the Jurassic reservoir, Southwest Ordos Basin

Guo

Wang

et al. 2023

GEOPHYSICS

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In the southwestern Ordos Basin, the formation water salinity and resistivity of Jurassic sandstone reservoirs are characterized by rapid changes and great variations, which lead to difficulties in the identification of reservoir fluid types and in the development and exploration of hydrocarbons in this area. To explore appropriate methods for reservoir fluid identification provided with complex formation water salinity and resistivity, we conducted three research steps. Firstly, using formation water testing and well logging data, the formation water salinity, spontaneous potential, and reservoir resistivity were used to calculate the formation water resistivity. Secondly, the calculation results were used to separate reservoir fluid types. Thirdly, the calculated formation water resistivities were classified and the relationship of the formation water resistivity and oil-producing interval was established. The results showed that, for oil-producing intervals, the formation water resistivity calculated using the reservoir resistivity is the highest, while that using the formation water salinity is the lowest. Based on this understanding, two identification methods of reservoir fluid types were proposed, including the qualitative curve overlap method and the quantitative ternary graph method. The curve overlap method can be applied to visually distinguish reservoir fluid types through the differentiation of formation water resistivity. Compared with some earlier quantitative methods, the ternary graph method can achieve an efficiency of 87.7% in identifying the type of reservoir fluid. Finally, the reliability of both methods was verified by case studies.

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Formation water geochemistry and the petroleum geological significance in Yanchang Formation of Wuqi Oilfield, Ordos Basin, China

Cited by 4 publications

References 0 publications

Main controlling factors and oil-bearing potential characteristics of a tight sandstone reservoir: A case study of southwest Ordos Basin

Main controlling factors and oil-bearing potential characteristics of a tight sandstone reservoir: A case study of southwest Ordos Basin

Fluid Identification Method of Nuclear Magnetic Resonance and Array Acoustic Logging for Complex Oil and Water Layers in Tight Sandstone Reservoir

Identification of an oil-bearing layer by formation water resistivity: A case study of the Jurassic reservoir, Southwest Ordos Basin

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