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

Wu, Jianbang; Yang, Shenglai; Gan, Bowen; Cao, Yushun; Zhou, Weili; Kou, Gen; Wang, Ziqiang; Li, Qiang; Dong, Wengang; Zhao, Binbin

doi:10.1021/acsomega.1c02952

Cited by 10 publications

(7 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The movable fluid porosity of a sample is influenced by multiple factors such as mineral composition and rock grain size. Previous studies have shown a weak positive correlation between movable fluid porosity and rock brittle mineral content and grain size. − Sample NS1 had a large grain size and developed large dissolution pores contributing to the movable fluid porosity (Table and Figure ). In contrast, the movable fluid of samples NS2 and NS3 was mainly distributed in nanopores and submicrometer pores leading to an unclear relationship with mineral content and grain size.…”

Section: Resultsmentioning

confidence: 85%

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Jiang,

Zhu,

et al. 2023

Energy Fuels

View full text Add to dashboard Cite

The movable fluid porosity can be used as a sensitivity factor to reflect the seepage capacity of tight reservoirs. However, the stress sensitivity and compressibility of samples differ and it is worth investigating whether the movable fluid porosity reflects the relative magnitude of the overburden permeability of the sample. In this study, the static pore information on three tight sandstones was characterized based on low-temperature nitrogen adsorption (LTNA), mercury intrusion porosimetry (MIP), and nuclear magnetic resonance (NMR) experiments. The stress sensitivity, compressibility, and movable fluid porosity of the samples at different pressures were discussed based on NMR, centrifugation, and permeability tests. The results show that the pore information on the nanopores of the samples obtained from LTNA, MIP, and NMR was consistent. Moreover, the NMR results reflected more submicron and micron pores in the samples compared to the MIP results that were affected by pore connectivity. The permeability was more sensitive to pressure than the porosity, and a small change in porosity was sufficient to cause a rapid decrease in permeability. The stress sensitivity and compressibility of nanopores were smaller than those of submicron and micron pores. The relative magnitude of stress sensitivity of micron pores and submicron pores varied from sample to sample. The variable compressibility coefficients of the samples decreased with increasing pressure (<12 MPa). The increase in the compressibility coefficients of nanopores and submicron pores for the samples at 12−15 MPa may result from the increase in the compressible space due to the transformation of the micron pores. The initial movable fluid porosity of the samples was positively correlated with the air permeability. The movable fluid porosity under pressure conditions (1−15 MPa) cannot reflect the relative magnitude of the overburden permeability, resulting from the difference in stress sensitivity between the porosity and permeability.

show abstract

Section: Resultsmentioning

confidence: 85%

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Jiang,

Zhu,

et al. 2023

Energy Fuels

View full text Add to dashboard Cite

show abstract

“…The porosity surpasses the values obtained under the resolution of 13 µm/voxel; however, pores under 2.3 µm remain unidentified at the current resolution. Based on other scholars' research on pore types and characteristics in this area [21], as well as the analysis at micron scale CT images, it reveals that the conglomerate in the study area predominantly comprises three types of pores: (1) secondary dissolution pores, characterized by highly irregular edges in grayscale images, exhibiting isolated spots and pits. These solution holes are believed to result primarily from the dissolution of unstable minerals, such as feldspar cleavage cracks or debris, during early diagenesis.…”

Section: Pore Structure Characteristicsmentioning

confidence: 86%

“…The tight conglomerate is composed of large-sized gravel sediments and the interstitial material, and the pores inside the interstitial material are the main flow channel. The grain size in the interstitial material also varies greatly [21,22]. Therefore, the representative volume size of the tight conglomerate in pore modeling usually needs to be larger than that of tight sandstone or shale, and the range of corresponding pore sizes is also relatively wider.…”

Section: Introductionmentioning

confidence: 99%

Seepage Simulation of Conglomerate Reservoir Based on Digital Core: A Case Study of the Baikouquan Formation in Mahu Sag, Junggar Basin

Zhang,

Hu,

Dong

et al. 2023

Processes

View full text Add to dashboard Cite

Pore structure and flow characteristics are key factors affecting oil recovery rates in heterogeneous tight conglomerate reservoirs. Using micron computed tomography (CT) and modular automated processing system (MAPS) techniques, the pore structure of downhole core samples taken from Mahu’s tight conglomerate reservoirs was analyzed in detail, and a two-scale digital core pore network model with both a wide field of view and high resolution was constructed based on these pore structure data; the digital pore model was corrected according to the mercury intrusion pore size distribution date. Finally, we simulated flow characteristics within the digital model and compared the calculated permeability with the indoor permeability test date to verify the dependability of the pore network. The results indicated that the pore–throat of the conglomerate reservoir in Mahu was widely distributed and exhibited significant bimodal characteristics, with main throat channels ranging from 0.5 to 4 μm. The pore structure showed pronounced microscopic heterogeneity and intricate modalities, mainly consisting of dissolved pores, intergranular pores, and microfractures. These pores were primarily strip-like, isolated, and played a more crucial role in enhancing pore connectivity rather than contributing to the overall porosity. The matrix pores depicted by the MAPS were relatively smaller in size and more abundant in number, with no individual pore type forming a functional seepage channel. The permeability parameters obtained from the two-scale coarse-fine coupled pore network aligned with the laboratory experimental results, displaying an average coordination number of two. Flow simulation results indicated that the core’s microscopic pore structure affected the shape of the displacement leading edge, resulting in a tongue-in phenomenon during oil–water flow. The dominant flow channel was mainly dominated by water, while tongue-in and by-pass flow were the primary microscopic seepage mechanisms hindering oil recovery. These findings lay a foundation for characterizing and analyzing pore structure as well as investigating flow mechanisms in conglomerate reservoirs.

show abstract

“…The marl comprehensive pore distribution can be reflected by the NMR T 2 spectrum (Wu et al, 2021;Zhao et al, 2022). The T 2 spectrum of laminated marl revealed clear bimodal characteristics (Figure 9A), and the right peak was more noticeable, indicating that laminated marl developed not only nanometer micropores but also a certain amount of micrometer macropores.…”

Section: Pore-throat Size Distributionmentioning

confidence: 99%

Reservoir characteristics and factors influencing shahejie marl in the shulu sag, bohai bay basin, eastern China

Fu²,

Zhu³

et al. 2022

Front. Earth Sci.

View full text Add to dashboard Cite

Shahejie marl in the Shulu Sag is a crucial resource for unconventional hydrocarbon exploration in China. Although breakthroughs have been made in tight oil exploration in this area, the mechanisms underlying the formation of this marl reservoir and factors controlling its ‘sweet spots’ have not been thoroughly studied. To understand the pore structure characteristics and factors influencing the marl reservoir, we analyzed core samples from Wells ST1 and ST3. A series of experiments was conducted on the samples, such as X-ray diffraction, focused ion beam scanning electron microscopy, micro-CT, and total organic carbon test. Additionally, the physical properties of different marl rock fabrics were studied with auxiliary tests, such as mercury intrusion capillary pressure analyses, nuclear magnetic resonance, porosity and permeability tests, and thin-section observation. The results revealed that the marl reservoir is characterized by low porosity (1.61%) and low permeability (2.56mD). The porosity and permeability (1.61% and 3.26mD) of laminated marl were better than those (0.92% and 1.68mD) of massive marl. Clay minerals and quartz content in laminated (11.8 and 8.2%) was less than in massive marl (16.2 and 13.3%). The marl pores include intercrystalline pores, dissolution pores, and microfractures. Additionally, the laminated marl pores were primarily distributed along the dark lamina, with good connectivity. A few isolated and uniform holes were observed in the massive marl. Influenced by rock fabric and mineral composition, layered fractures were mainly developed in the laminated marl, while structural fractures were the main type of microfractures in the massive marl. The primary sedimentary mechanism was the main geological action underlying the differences in marl rock fabric; this mechanism affects the physical properties of the marl reservoir, which are key factors to be considered when searching for the marl reservoir ‘sweet spots’. Particular attention should be paid to these factors during tight oil exploration and development in similar sedimentary basins.

show abstract

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

Cited by 10 publications

References 45 publications

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Analysis of Stress Sensitivity and Movable Fluid Characteristics of Tight Sandstone Based on NMR and Permeability Experiments

Seepage Simulation of Conglomerate Reservoir Based on Digital Core: A Case Study of the Baikouquan Formation in Mahu Sag, Junggar Basin

Reservoir characteristics and factors influencing shahejie marl in the shulu sag, bohai bay basin, eastern China

Contact Info

Product

Resources

About