Impacts of pore-throat spaces on movable fluid: Implications for understanding the tight oil exploitation process

Qu, Yiqian; Sun, Wei; Wu, Haijun; Huang, Sheng-Jun; Li, Teng; Ren, Dazhong; Chen, Bin

doi:10.1016/j.marpetgeo.2021.105509

Cited by 19 publications

(9 citation statements)

References 39 publications

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“…Dimension. The complexity of pore-throat structure was affected by their mineral content and composition in the tight sandstone reservoirs [49][50][51]. It is shown in Figure 10, the relationship between fractal dimension and the content of rock-forming minerals (quartz and feldspar) was analyzed.…”

Section: The Mechanism Of Mineral Composition Effect On Fractalmentioning

confidence: 99%

Pore-Throat Structure and Fractal Characteristics of Tight Sandstones: A Case Study from the Chang 63 Sublayer, Southeast Ordos Basin

Han

Zhou

Wei³

et al. 2023

Geofluids

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The micropore-throat structure is a controlling factor on the capacity of storage and seepage for the tight sandstone reservoirs. Therefore, quantitatively analyzing the pore-throat structure is crucial for realizing the oil accumulated in the tight reservoirs. To study the micropore-throat, a battery of experiments such as casting thin sections, scanning electron microscopy, high-pressure mercury injection, and the petrophysical characteristics of reservoirs were conducted on ten samples gathered in the Late Triassic Chang 63 sublayer in the Southeast Ordos Basin, China. The main pore types of the samples are intergranular pores, feldspar dissolved pores, and intergranular dissolved pores. Meanwhile, the pore-throat structure of each sample was identified as large pores, medium pores, and small pores by combining the result of HPMI with fractal theory. The corresponding mean values of the fractal dimension D for large, medium, and small pores are 2.83, 2.69, and 2.31, respectively, indicating that the complex structure and strong heterogeneity were presented in the large pores according to the maximum fractal dimension. In addition, the fractal dimension of the medium pores ( D P − 2 ) has a negative correlation with porosity, permeability, median pore-throat radius, maximum mercury saturation, mercury withdrawal efficiency, displacement pressure, and content of quartz, while a positive correlation with feldspar content, sorting coefficient, and coefficient of variation. Thus, the reservoir space and seepage capacity of all samples in this study were determined by the size, complexity, and distribution of the medium pores. Furthermore, the content of quartz contributes to the storage of the reservoir and the homogeneity of the pore-throat structure, thereby the storage capacity improves with the increase of quartz content. Feldspar dissolution pores are developed widely in the study area, leading to various pores with diverse types, sizes, complex structures, and large fractal dimensions. Although the storage capacity of tight sandstone reservoirs was enhanced with increasing feldspar content, the pore-throat structure complexity was also stronger, resulting in the reduction seepage capacity of fluid.

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Section: The Mechanism Of Mineral Composition Effect On Fractalmentioning

confidence: 99%

Pore-Throat Structure and Fractal Characteristics of Tight Sandstones: A Case Study from the Chang 63 Sublayer, Southeast Ordos Basin

Han

Zhou

Wei³

et al. 2023

Geofluids

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“…22,23 The essence of NMR is to characterize the pore structure by the difference of resonance relaxation properties. 24 The NMR T 2 (transverse relaxation) spectrum reflects the ratio of fluid at different scales pore and can be used to quantitatively characterize the pore size distribution of rocks. 25,26 Unlike conventional reservoirs, tight/shale reservoirs contain various hydrogen-containing components, such as kerogen, bitumen, oil, and water.…”

Section: Introductionmentioning

confidence: 99%

“…The nuclear magnetic resonance (NMR) method is a nondestructive, rapid, and simple method for characterizing the pore structures of fine-grained sedimentary rocks . Therefore, NMR is an effective tool for measuring tight/shale reservoir fluid parameters and quantifying pore properties. , The essence of NMR is to characterize the pore structure by the difference of resonance relaxation properties . The NMR T 2 (transverse relaxation) spectrum reflects the ratio of fluid at different scales pore and can be used to quantitatively characterize the pore size distribution of rocks. , …”

Section: Introductionmentioning

confidence: 99%

Oil Mobility Evaluation of Fine-Grained Sedimentary Rocks with High Heterogeneity: A Case Study of the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China

et al. 2023

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The oil mobility in unconventional tight/shale oil reservoirs is complex because of the high heterogeneity in the matrix pore structure and connectivity. Thus, it is difficult to evaluate hydrocarbon exploration potential precisely. In this study, multistep temperature pyrolysis (MTP) Rock-Eval and 1D (dimensional) as well as 2D nuclear magnetic resonance (NMR) techniques were employed to systematically characterize the oil mobility in lacustrine fine-grained sedimentary rocks from the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China. The results show that the Lucaogou Formation fine-grained sedimentary rocks can be subdivided into six types of lithofacies. With the increase of organic matter richness, the content of adsorbed oil increases, whereas the content of movable oil increases first and tends to stabilize (when total organic carbon (TOC) > 4%). This is because when TOC is low, the fine-grained sedimentary rocks need to self-adsorb before oil production; when TOC increases further, the generated oil will break through the absorption limit and charge into the adjacent reservoirs; therefore, the movable oil ceases to increase. Permeability is found to have a greater impact on movable fluid saturation than porosity. Meanwhile, good throat radius and pore connectivity are conducive to oil flow as movable oil is more sensitive to throats rather than pores. Furthermore, a higher content of brittle minerals is not necessarily favorable for oil flow; alternatively, more clay minerals are easy to from cements causing pore blockage, which will essentially hinder oil mobility. Overall, the organic matter content, reservoir pore structure, and rock mineral composition are the main factors affecting tight/shale oil mobility. On the basis of the above research, a conceptual model of oil mobility in different lithofacies’ reservoirs is established. These results have a reference significance for evaluating oil recoverability in fine-grained sedimentary rocks.

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“…In recent years, an increasing number of studies have shown that the T 2 cutoff value varies with the characteristics of the sample, and it cannot be simply assumed that the cutoff value is fixed. ,, The range of the movable fluid begins at the point where the T 2 curve separates before and after centrifugation . After centrifugation, the bound water is distributed around the pore–throat in a film shape, , and the thickness and shape of the water film change with the pore–throat structure . Due to the strong heterogeneity of tight reservoirs, the fluid mobility in different spaces of the same sample may also be different, so it needs to be studied in more detail in different regions.…”

Section: Introductionmentioning

confidence: 99%

Impacts of the Pore–Throat Structure on Fluid Mobility in Tight Sandstone: Insight from an Improved Method Based on Rate-Controlled Porosimetry and Nuclear Magnetic Resonance

et al. 2022

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The microstructure of pores strongly influences fluid mobility in tight sandstone reservoirs. The impacts of the pore–throat structure on fluid mobility are restricted due to the limitations of existing methods for determining pore–throat structures. Therefore, the methods utilized to obtain more comprehensive and accurate pore–throat information need to be further discussed by combining multiple experiments. In this research, eight samples were selected from the Upper Triassic Yanchang Formation in the Ordos Basin to investigate the microstructure and its impacts on fluid mobility by means of nuclear magnetic resonance (NMR), rate-controlled porosimetry (RCP), scanning electron microscopy, and thin sections. The throat radii in the throat, pore–throat, and pore areas were studied by combining NMR and RCP with an improved method. The throat radius and pore–throat volume affect the movable fluid from connectivity and movable ratio, respectively. The throat and pore–throat (pore) areas belong to unrelated movable fluid networks. Each area contains intragranular and intergranular spaces. Irregularly shaped pores commonly occur in the intragranular space, with strong connectivity. The pores with regular shape in the intergranular space connect a small amount of throat, and a large number of clay minerals divide the space into small throats. Clay minerals reduce fluid mobility by increasing the thickness of the water film in the throat. Therefore, fluid mobility in the intragranular space is greater than that in the intergranular space from the perspective of water film thickness and movable probability in the same area. This research improves the accuracy of the combined method of NMR and RCP and clarifies the distribution mechanism of movable fluids in different spaces.

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Impacts of pore-throat spaces on movable fluid: Implications for understanding the tight oil exploitation process

Cited by 19 publications

References 39 publications

Pore-Throat Structure and Fractal Characteristics of Tight Sandstones: A Case Study from the Chang 63 Sublayer, Southeast Ordos Basin

Pore-Throat Structure and Fractal Characteristics of Tight Sandstones: A Case Study from the Chang 63 Sublayer, Southeast Ordos Basin

Oil Mobility Evaluation of Fine-Grained Sedimentary Rocks with High Heterogeneity: A Case Study of the Lucaogou Formation in the Jimusar Sag, Junggar Basin, NW China

Impacts of the Pore–Throat Structure on Fluid Mobility in Tight Sandstone: Insight from an Improved Method Based on Rate-Controlled Porosimetry and Nuclear Magnetic Resonance

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