scholarly journals Full‐Scale Pore Structure and Fractal Dimension of the Longmaxi Shale from the Southern Sichuan Basin: Investigations Using FE‐SEM, Gas Adsorption and Mercury Intrusion Porosimetry

Minerals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 543 ◽  
Author(s):  
Wang ◽  
Jiang ◽  
Jiang ◽  
Chang ◽  
Zhu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Fractal Dimension ◽  
Pore Structure ◽  
Clay Minerals ◽  
Sichuan Basin ◽  
Mercury Intrusion Porosimetry ◽  
Fractal Dimensions ◽  
Full Scale ◽  
Mercury Intrusion ◽  
Longmaxi Shale

Pore structure determines the gas occurrence and storage properties of gas shale and is a vital element for reservoir evaluation and shale gas resources assessment. Field emission scanning electron microscopy (FE‐SEM), high‐pressure mercury intrusion porosimetry (HMIP), and low‐pressure N2/CO2 adsorption were used to qualitatively and quantitatively characterize full‐scale pore structure of Longmaxi (LM) shale from the southern Sichuan Basin. Fractal dimension and its controlling factors were also discussed in our study. Longmaxi shale mainly developed organic matter (OM) pores, interparticle pores, intraparticle pores, and microfracture, of which the OM pores dominated the pore system. The pore diameters are mainly distributed in the ranges of 0.4–0.7 nm, 2–20 nm and 40–200 μm. Micro‐, meso‐ and macropores contribute 24%, 57% and 19% of the total pore volume (PV), respectively, and 64.5%, 34.6%, and 0.9% of the total specific surface area (SSA). Organic matter and clay minerals have a positive contribution to pore development. While high brittle mineral content can inhibit shale pore development. The fractal dimensions D1 and D2 which represents the roughness of the shale surface and irregularity of the space structure, respectively, are calculated based on N2 desorption data. The value of D1 is in the range of 2.6480–2.7334 (average of 2.6857), D2 is in the range of 2.8924–2.9439 (average of 2.9229), which indicates that Longmaxi shales have a rather irregular pore morphology as well as complex pore structure. Both PV and SSA positively correlated with fractal dimensions D1 and D2. The fractal dimension D1 decreases with increasing average pore diameter, while D2 is on the contrary. These results suggest that the small pores have a higher roughness surface, while the larger pores have a more complex spatial structure. The fractal dimensions of shale are jointly controlled by OM, clays and brittle minerals. The TOC content is the key factor which has a positive correlation with the fractal dimension. Clay minerals have a negative influence on fractal dimension D1, and positive influence D2, while brittle minerals show an opposite effect compared with clay minerals.

scholarly journals Pore Structure and Fractal Characteristics of Organic-Rich Lacustrine Shales of the Kongdian Formation, Cangdong Sag, Bohai Bay Basin

2021 ◽  
Vol 9 ◽  
Author(s):  
Shouxu Pan ◽  
Ming Zha ◽  
Changhai Gao ◽  
Jiangxiu Qu ◽  
Xiujian Ding
Keyword(s):  
Organic Matter ◽  
Specific Surface ◽  
Pore Structure ◽  
Surface Area ◽  
Clay Minerals ◽  
Mineral Composition ◽  
Fractal Dimensions ◽  
Nitrogen Adsorption ◽  
Thermal Maturity ◽  
Pore Types

In order to examine the pore structure and reveal the fractal geometric nature of shales, a series of laboratory experiments were conducted on lacustrine shale samples cored from the Kongdian Formation. Based on the low temperature nitrogen adsorption, fluorescent thin section and field emission scanning electronic microscope, a comprehensive pore structure classification and evaluation were conducted on shale samples. Fractal dimensions D1 and D2 (with relative pressure of 0–0.45 and 0.45–1.00, respectively) were obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH) method. With additional means of X-ray diffraction analysis, total organic carbon content analysis and thermal maturity analysis, the relationships between pore structure parameters, fractal dimensions, TOC content and mineral composition are presented and discussed in this paper. The results show that interparticle pores and microfractures are predominant, whereas organic matter pores are rarely found. The pore morphology is primarily featured with wide-open ends and slit-shaped structures. In terms of pore scale, mesopores and macropores are predominant. The value of fractal dimension D1 representing small pores ranges from 2.0173 to 2.4642 with an average of 2.1735. The value of D2 which represents large pores ranges from 2.3616 to 2.5981 with an average of 2.4960. These low numbers are an indication of few pore types and relatively low heterogeneity. In addition, smaller D1 values reveal that large pores have more complicated spatial structures than smaller ones. The results of correlation analysis show that: 1) D2 is correlated positively with specific surface area but negatively with average pore diameter; 2) D1 and D2 literally show no obvious relationship with mineral composition, TOC content or vitrinite reflectance (Ro); 3) both total Barrett-Joyner-Halenda (BJH) volume and specific surface area show a positive relationship with dolomite content and a negative relationship with felsic minerals content. These results demonstrate that the pore types are relatively few and dominated by mesopores, and the content of brittle minerals such as dolomite and felsic minerals control the pore structure development whilst organic matter and clay minerals have less influence due to low thermal maturity and abundance of clay minerals.

scholarly journals Fractal Characteristics of Pores in the Longtan Shales of Guizhou, Southwest China

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Yuqi Huang ◽  
Peng Zhang ◽  
Jinchuan Zhang ◽  
Xuan Tang ◽  
Chengwei Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Fractal Dimension ◽  
Pore Structure ◽  
Shale Gas ◽  
Storage Capacity ◽  
Evaluation Criteria ◽  
Fractal Dimensions ◽  
Gas Absorption ◽  
Relative Pressure ◽  
And Storage

The pore structure of marine-continental transitional shales from the Longtan Formation in Guizhou, China, was investigated using fractal dimensions calculated by the FHH (Frenkel-Halsey-Hill) model based on low-temperature N2 adsorption data. Results show that the overall D 1 (fractal dimension under low relative pressure, P / P 0 ≤ 0.5 ) and D 2 (fractal dimension under high relative pressure, P / P 0 > 0.5 ) values of Longtan shales were relatively large, with average values of 2.7426 and 2.7838, respectively, indicating a strong adsorption and storage capacity and complex pore structure. The correlation analysis of fractal dimensions with specific surface area, average pore size, and maximum gas absorption volume indicates that D 1 can comprehensively characterize the adsorption and storage capacity of shales, while D 2 can effectively characterize the pore structure complexity. Further correlation among pore fractal dimension, shale organic geochemical parameters, and mineral composition parameters shows that there is a significant positive correlation between fractal dimensions and organic matter abundance as well as a complex correlation between fractal dimension and organic matter maturity. Fractal dimensions increase with an increase in clay mineral content and pyrite content but decrease with an increase in quartz content. Considering the actual geological evaluation and shale gas exploitation characteristics, a lower limit for D 1 and upper limit for D 2 should be set as evaluation criteria for favorable reservoirs. Combined with the shale gas-bearing property test results of Longtan shales in Guizhou, the favorable reservoir evaluation criteria are set as D 1 ≥ 2.60 and D 2 ≤ 2.85 . When D 1 is less than 2.60, the storage capacity of the shales is insufficient. When D 2 is greater than 2.85, the shale pore structure is too complicated, resulting in poor permeability and difficult exploitation.

scholarly journals FRACTAL CHARACTERIZATION OF TIGHT OIL RESERVOIR PORE STRUCTURE USING NUCLEAR MAGNETIC RESONANCE AND MERCURY INTRUSION POROSIMETRY

Fractals ◽  
2018 ◽  
Vol 26 (02) ◽  
pp. 1840017 ◽  
Author(s):  
FUYONG WANG ◽  
KUN YANG ◽  
JIANCHAO CAI
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Pore Structure ◽  
Pore Size ◽  
Mercury Intrusion Porosimetry ◽  
Fractal Dimensions ◽  
Structure Characterization ◽  
Tight Oil ◽  
Petrophysical Properties ◽  
Mercury Intrusion

Tight oil sandstones have the characteristics of narrow pore throats, complex pore structures and strong heterogeneities. Using nuclear magnetic resonance (NMR) and mercury intrusion porosimetry (MIP), this paper presents an advanced fractal analysis of the pore structures and petrophysical properties of the tight oil sandstones from Yanchang Formation, Ordos Basin of China. Firstly, nine typical tight oil sandstone core samples were selected to conduct NMR and MIP test for pore structure characterization. Next, with the pore size distribution derived from MIP, it was found that the relationships between NMR transverse relaxation time [Formula: see text] and pore size are more accordant with the power function relations, which were applied to derive pore size distribution from NMR rather than the linear relation. Moreover, fractal dimensions of micropores, mesopores and macropores were calculated from NMR [Formula: see text] spectrum. Finally, the relationships between the fractal dimensions of different size pores calculated from NMR [Formula: see text] spectrum and petrophysical properties of tight oil sandstones were analyzed. These studies demonstrate that the combination of NMR and MIP can improve the accuracy of pore structure characterization and fractal dimensions calculated from NMR [Formula: see text] spectrum are effective for petrophysical properties analysis.

scholarly journals Fractal analysis of bentonite modified with heteropoly acid using nitrogen sorption and mercury intrusion porosimetry

2011 ◽  
Vol 76 (10) ◽  
pp. 1403-1410 ◽  
Author(s):  
Srdjan Petrovic ◽  
Zorica Vukovic ◽  
Tatjana Novakovic ◽  
Zoran Nedic ◽  
Ljiljana Rozic
Keyword(s):  
Fractal Dimension ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Heteropoly Acid ◽  
Mercury Intrusion Porosimetry ◽  
Fractal Dimensions ◽  
Surface Fractal Dimension ◽  
Mercury Intrusion ◽  
Surface Fractal

Experimental adsorption isotherms were used to evaluate the specific surface area and the surface fractal dimensions of acid-activated bentonite samples modified with a heteropoly acid (HPW). The aim of the investigations was to search for correlations between the specific surface area and the geometric heterogeneity, as characterized by the surface fractal dimension and the content of added acid. In addition, mercury intrusion was employed to evaluate the porous microstructures of these materials. The results from the Frankel-Halsey-Hill method showed that, in the p/p0 region from 0.75 to 0.96, surface fractal dimension increased with increasing content of heteropoly acid. The results from mercury intrusion porosimetry (MIP) data showed the generation of mesoporous structures with important topographical modifications, indicating an increase in the roughness (fractal geometry) of the surface of the solids as a consequence of the modification with the heteropoly acid. By comparison, MIP is preferable for the characterization because of its wide effective probing range.

Study on the Influence of Air-Entraining Agent on the Impermeability of Cement-Based Composites Based on its Pore Structure by Fractal Theory

2010 ◽  
Vol 168-170 ◽  
pp. 615-618
Author(s):  
Zhi Qin Du ◽  
Wei Sun
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Mercury Intrusion Porosimetry ◽  
Fractal Theory ◽  
Mercury Intrusion ◽  
Pore Structures ◽  
Cement Based Materials

The effect of different quantity of air-entraining agent on the impermeability of cement-based materials are studied in this paper. Impermeability test and mercury intrusion porosimetry (MIP) method were used to characterize the impermeability and pore structures. The fractal dimension is used to describe the characteristic of pore structure and calculated by the data of MIP experiment. The result shows that owing to the improvement of pore structure, the impermeability performance of the cement-based composites is noticeably enhanced when air-entraining agent is added with appropriate quantity.

The Fractal Characteristic Analysis of Coal Pore Structure Based on the Mercury Intrusion Porosimetry

2013 ◽  
Vol 353-356 ◽  
pp. 1191-1195 ◽  
Author(s):  
Nai Hao ◽  
Yong Liang Wang ◽  
Ling Tao Mao ◽  
Qing Liu
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Pore Volume ◽  
Coalbed Methane ◽  
Mercury Intrusion Porosimetry ◽  
Shanxi Province ◽  
Characteristic Analysis ◽  
Mercury Intrusion ◽  
Specific Pore Volume ◽  
Radius Size

The pore structure of coal rock atYangquan Xinjing mine in Shanxi Province is analyzed with mercury intrusion porosimetry to obtain the specific pore volume data and calculate the fractal dimension of coal pore surface. The pores are divided into macropore, mesopore and micropore according to radius size considering the calculated fractal dimension. The distribution characteristics of pore radius size, specific surface area and specific pore volume of different types are effectively analyzed. The research results show that mesopore surface has significantly fractal characteristics, which features could be discussed quantitatively. The proposed method in this paper has reference significance for studying the sorption and desorption properties, the diffussion and permeation of coalbed methane.

scholarly journals Petrophysical Characterization and Fractal Analysis of Carbonate Reservoirs of the Eastern Margin of the Pre-Caspian Basin

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 78 ◽  
Author(s):  
Feng Sha ◽  
Lizhi Xiao ◽  
Zhiqiang Mao ◽  
Chen Jia
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Fractal Dimensions ◽  
Core Sample ◽  
Carbonate Reservoirs ◽  
Structure Characterization ◽  
Caspian Basin ◽  
Thin Sections ◽  
Mercury Intrusion ◽  
Eastern Margin

Petrophysical properties including pore structure and permeability are essential for successful evaluation and development of reservoirs. In this paper, we use casting thin section and mercury intrusion capillary pressure (MICP) data to investigate the pore structure characterization, permeability estimation, and fractal characteristics of Carboniferous carbonate reservoirs in the middle blocks of the eastern margin of the Pre-Caspian Basin. Rock casting thin sections show that intergranular and intragranular dissolution pores are the main storage spaces. The pore throats greater than 1 μm and lower than 0.1 μm account for 47.98% and 22.85% respectively. A permeability prediction model was proposed by incorporating the porosity, Swanson, and R35 parameters. The prediction result agrees well with the core sample data. Fractal dimensions based on MICP curves range from 2.29 to 2.77 with an average of 2.61. The maximum mercury intrusion saturation is weakly correlated with the fractal dimension, while the pore structure parameters such as displacement pressure and median radii have no correlation with fractal dimension, indicating that single fractal dimension could not capture the pore structure characteristics. Finally, combined with the pore types, MICP shape, and petrophysical parameters, the studied reservoirs were classified into four types. The productivity shows a good correlation with the reservoir types.

Sign in / Sign up

Export Citation Format

Share Document