Insights into the pore structure and implications for fluid flow capacity of tight gas sandstone: A case study in the upper paleozoic of the Ordos Basin

Qiao, J.C.; Zeng, Jianhui; Jiang, Shu; Feng, Song; Xiao, Fengchao; Hu, Huiting

doi:10.1016/j.marpetgeo.2020.104439

Cited by 37 publications

(24 citation statements)

References 70 publications

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“…The volume, connectivity, and PSD of sandstone reservoirs can be reflected by the inversion of NMR T 2 results [19,42,43]. In general, a long relaxation time corresponds to large pores, while a short relaxation time corresponds to small pores [5]. On the one hand, the PSD curves derived from the NMR of type I reservoirs predominantly ranged from 0.01 to 10 μm, and the peak value of the pore size varied in the range 0.1-2 μm (Figure 7).…”

Section: Nmr Resultsmentioning

confidence: 99%

“…Compared with conventional oil and gas resources, they are characterized by poor stability, strong heterogeneity, and a complex oilwater interaction mechanism, and are also very difficult to evaluate and explore [3]. Additionally, tight sandstone reservoirs represent one of the important tight oil and gas resources, and a clear understanding of their pore structure is the basis for the study of tight oil and gas accumulation, the associated charging mechanism, and the resource potential [4][5][6][7]. However, their strong heterogeneity as well as their substantial number of nanoscale pore throats make the characterization of their pore structure difficult [8,9].…”

Section: Introductionmentioning

confidence: 99%

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Integration of NMR and NMRC in the Investigation of the Pore Size Distribution of Tight Sandstone Reservoirs: A Case Study in the Upper Paleozoic of Dongpu Depression

et al. 2021

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Exploring appropriate methods to understanding the pore structure and overall pore size distribution (PSD) of tight sandstone reservoir is important for evaluating the quality of the reservoir. An integration analysis comprising X-ray diffraction (XRD), three beams of argon ion (TIB) polishing approach, scanning electron microscopy (SEM), high-pressure mercury intrusion (HPMI), nuclear magnetic resonance (NMR), and nuclear magnetic resonance cryoporometry (NMRC) was applied to determine the pore structure of the tight sandstone reservoirs in the Upper Paleozoic of Dongpu Depression as well as their relationship with the physical properties of the reservoirs. NMRC offered the possibility to obtain the nanoscale (4-1400 nm) pore structure of the reservoirs directly and accurately. Therefore, an attempt by combining NMRC and NMR can reveal the PSD of tight sandstone reservoirs with different pore structures. The results showed that the tight sandstone reservoirs consisted of intergranular, intragranular, and intercrystalline (clay mineral) pores. The full PSD intelligibly showed pore structure characteristics of four different types of reservoirs, with pore sizes ranging from 2 nm to dozens of microns. Specifically, the overall PSD of type I reservoirs showed a broad unimodal distribution pattern with the peaks in the range 0.1–2 μm, indicating an association with dissolution intergranular pores, and for type II reservoirs, the overall PSD showed a bimodal distribution pattern, with their left and right peaks, in the ranges 0.004–0.01 μm and 0.15–0.4 μm, respectively, showing similar amplitudes, implying the predominance of both intergranular (mesopores) and intergranular (macropores) pores. The full PSDs of type III and IV reservoirs showed much lower amplitudes than type I and II reservoirs, indicating a lower pore number and a complex pore structure. Furthermore, NMRC also demonstrated that different diagenesis resulted in a correlation between pore structure and reservoir physical properties.

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Section: Nmr Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Integration of NMR and NMRC in the Investigation of the Pore Size Distribution of Tight Sandstone Reservoirs: A Case Study in the Upper Paleozoic of Dongpu Depression

et al. 2021

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“…The main types of pores developed in different sedimentary facies are diverse, and the pore throat configuration relationship is different. Due to the attachment and blockage of clay minerals, various types of pores will form a seepage network with various structures, which has a direct impact on the mobility of the occurrence fluid. − Previous studies have often neglected the influence of pore types on movable fluids, some studies simply set a T 2 spectrum value in the NMR pore distribution to represent the boundary of different types of pores, , but most of the pore sizes of different types have crossed. Cast thin sections and scanning electron microscopy (SEM) methods can more accurately measure the distribution characteristics of different types of pores, , but the experimental results have difficulty in establishing a relationship with the pore parameters obtained by NMR.…”

Section: Introductionmentioning

confidence: 99%

Pore Structure and Movable Fluid Characteristics of Typical Sedimentary Lithofacies in a Tight Conglomerate Reservoir, Mahu Depression, Northwest China

Yang

Gan

et al. 2021

ACS Omega

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The pore structure and movable fluid characteristics of tight conglomerate reservoirs are complex, which are greatly different from conventional reservoirs. The depositional mechanism is the fundamental factor controlling the physical properties of conglomerate reservoirs. However, there is a lack of systematic research on the pore structure and movable fluid characteristics of conglomerate reservoirs with typical sedimentary facies. This paper investigates the pore structure and movable fluid characteristics of conglomerate of different sedimentary facies based on various experiments. Casting thin sections, X-ray diffraction, scanning electron microscopy, high-pressure mercury injection, and nuclear magnetic resonance experiments were conducted on 32 conglomerates samples from the Mahu Sag, Junggar Basin, China. The quality classification method of tight conglomerate reservoirs is established. The results show that the conglomerate can be divided into three sedimentary facies; traction flow conglomerate (TFC) and pebbled sandstone (PSS) mainly develop intergranular pores and dissolved pores; and the pore diameter curves are mainly a double peak, single peak, and flat peak. Gravity flow conglomerate (GFC) mainly develops dissolved pores and interstitial micropores, and the pore diameter curve is mainly a single peak. PSS includes pebbled gritty sandstone (P(G)SS) and pebbled fine sandstone (P(F)SS). TFC and P(G)SS are favorable class I reservoirs, while GFC and P(F)SS are nonfavorable class II reservoirs. A new parameter, the ratio of the major axis to the minor axis of the pore outer ellipse (axial ratio), is proposed to quantitatively describe the compaction effect. The average axial ratios of the three lithofacies are 3.04, 3.98, and 8.78, respectively, indicating that the compaction is intensified and the pore structure becomes worse. By analyzing the correlation between pore structure parameters and permeability, it is found that the main controlling factors of permeability of GFC and TFC are sorting and connectivity, respectively, and the main flow radius is the most suitable parameter to describe permeability. A linear spectral decomposition method was used to establish a new quantitative calculation method of movable fluid saturation for different types of pores, and the results show that the movable fluid saturation of intergranular pores is the highest (average: 65.43%), and the movable fluid saturation of TFC and P(G)SS with more intergranular pores is the highest. Movable fluid saturation is inversely proportional to the content of I/S and the compaction rate and positively proportional to the content of quartz and feldspar and the cementation rate. The fluid mobility of water-wet samples is weaker. The research results provide theoretical support for the identification of favorable reservoirs and the cognition of a development mechanism.

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“…Whether San Juan, Alberta, Uinta, Piceance, Green River basins in North America, or Ordos, Sichuan, Songliao, Tarim basins in China, a series of important breakthroughs have been made in the research and exploration of tight gas (Andra´s et al, 2012;Dai et al, 2019;Law and Curtis, 2002;Li et al, 2012;Masters, 1979;Shanley et al, 2004;Sun et al, 2019;Zhao et al, 2019;Zou et al, 2015). However, with the deepened of tight gas exploration and development, the problems of formation water output of tight sandstone with low porosity and permeability, strong heterogeneity, nanoscale pores and high water saturation have gradually emerged (Clarkson et al, 2012;Lai et al, 2018;Nie et al, 2021;Qiao et al, 2020). For example, the water/gas ratio of tight sandstone gas reservoirs in the Piceance Basin in the United States exceeds 1.2m 3 /10 4 m 3 , and the proportion of producing wells reaches 27.2% (Wei et al, 2017); the water/gas ratio of the Upper Paleozoic in the western Ordos Basin in China exceeds 1m 3 / 10 4 m 3 (Zhou et al, 2016); and the daily water production of some wells exceeds 100 m 3 (Wu et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…The accumulation theory of "broad and gentle slope structure, extensive hydrocarbon generation, large area charging, micro-nanometer pore features, coupled transport between pores and fractures, and near migration and accumulation" effectively guided the early exploration of tight gas (Fu et al, 2013;Nelson, 2009;Qiao et al, 2020;Schmitt et al, 2015;Xu et al, 2012;Yang et al, 2008Yang et al, , 2012Zhao et al, 2012;Zou et al, 2012), but the complex distribution of gas and water in tight sandstone is beyond the reach. With the improvement of geological theory and the increase of exploration degree, the condition of source rock is considered to be an important aspect to control the formation of tight sandstone gas.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of coal-measure source rock and its controlling effect on gas-water distribution of tight sandstone of He8 Member in Sulige Gas Province, Ordos Basin

Chen

et al. 2021

Energy Exploration & Exploitation

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Characteristics of complex gas-water distribution affect the efficient exploration of tight gas. The paper aims at tight sandstone gas-water distribution characteristics of He8 Member in Sulige Gas Province (SGP), describes thickness and TOC of source rocks from Benxi Formation in Carboniferous to the Second Member of Shanxi Formation in Permain, evaluates its hydrocarbon generation potential, discusses its controlling effect on tight sandstone gas-water distribution, and determines the threshold values of Ro and HGI of commercial gas flow wells. Research shows that the coal-measure source rock has the characteristics of extensive and superimposition. The coal seam and dark mudstone is the lithology of source rock, and its Ro is chiefly distributed 1.2% ∼ 2.1% in the stage of high mature thermal evolution, which is mainly type III kerogen. Among them, the thickness of coal seam is mainly ranged from 5 ∼ 15 m with an average of 9.32 m, and its average TOC is 64.08% and the distribution of HGI is (1∼36) ×108 m3/km2. No.8 and No.5 coal seams are relatively stable. The extent of thickness of dark mudstone is mainly between 10m and 30m with an average of 21.2m, and its average TOC is 2.11%, HGI is between (0.2∼10)×108m3/km2. Gas reservoir of He8 Member is tight sandstone lenticular reservoirs with the large-area quasi-continuous distribution. When the gas testing production is less than 1 × 104m3/d, the controlling effect of Ro and HGI are relatively obvious, and its controlling effect is obviously weakened with the increase of gas production. When Ro is more than 1.6%-1.7%, or HGI is larger than 15 × 108m3/km2, the decreasing trend of water/gas ratio is evident, especially in commercial gas flow wells (including high producing gas flow wells). In comparison, the controlling effect of HGI is stronger than Ro. 1.33% and 8 × 108 m3/km2 are the threshold values of Ro and HGI for commercial gas flow wells, respectively.

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Insights into the pore structure and implications for fluid flow capacity of tight gas sandstone: A case study in the upper paleozoic of the Ordos Basin

Cited by 37 publications

References 70 publications

Integration of NMR and NMRC in the Investigation of the Pore Size Distribution of Tight Sandstone Reservoirs: A Case Study in the Upper Paleozoic of Dongpu Depression

Integration of NMR and NMRC in the Investigation of the Pore Size Distribution of Tight Sandstone Reservoirs: A Case Study in the Upper Paleozoic of Dongpu Depression

Pore Structure and Movable Fluid Characteristics of Typical Sedimentary Lithofacies in a Tight Conglomerate Reservoir, Mahu Depression, Northwest China

Characteristics of coal-measure source rock and its controlling effect on gas-water distribution of tight sandstone of He8 Member in Sulige Gas Province, Ordos Basin

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