Characteristics and distribution of clay minerals and their effects on reservoir quality: Huagang Formation in the Xihu Sag, East China Sea Basin

Sun, Xiaoming; Lin, Chengyan; Zhang, X. G.; Jiang, Lin; Zhao, Zhongying; Huang, Dong; Duan, Dongping

doi:10.1080/08120099.2019.1610795

Cited by 10 publications

(4 citation statements)

References 25 publications

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“…The average content of the illite-montmorillonite mixed layer is higher than that of other minerals in the low-resistivity gas reservoir. The illitemontmorillonite mixed layer has a higher cation exchange capacity, and its additional conductivity is the fundamental reason for the reduction in the formation resistivity [22,23]. For the distribution form of the clay minerals, it can be seen from the thin sections that the clay minerals mostly appear in parallel layers or fill in the pores among the rock particles in fibrous form or are attached to the surface of rock particles in thin-film form (as shown in Figure 5).…”

Section: Additional Conductivity Of Clay Mineralsmentioning

confidence: 99%

Analyzing the Origin of Low Resistivity in Gas-Bearing Tight Sandstone Reservoir

Jiang

Jian

et al. 2021

Geofluids

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Complex characteristics exist in the resistivity response of Gs reservoirs in the central inversion belt of the Xihu Sag, East China Sea Basin. Some drilling wells have confirmed the existence of abnormally low resistivity in gas reservoirs of the area; and the electrical logging response was unable to reflect fluid properties of the reservoir accurately. Therefore, it is necessary to analyze the origin of the low resistivity and determine its controlling factors. Based on experimental data of core analysis and numerical simulations of mud invasion, this study thoroughly explores the origin of low resistivity in the subject gas-bearing reservoir considering both internal and external factors. The results indicated that when there is no or a low degree of mud invasion, the fine lithology, complex pore structure, additional clay mineral conductivity, and high content of pyrite are the main internal factors driving the conditions present in the studied gas reservoir. When mud invasion occurs, the invasion of highly saline mud is the main external cause of low resistivity. The numerical simulation results indicated that a formation with good permeability and high overbalance pressure has a deep invasion depth. The resistivity around the well is obviously reduced after the invasion, and low resistivity would form easily. Combined with actual data of several wells, the main influencing factors of the reservoir’s electrical characteristics were analyzed, and the main controlling factors of low resistivity in the gas reservoirs are given. This study provides valuable support for studying the low-contrast complex reservoir conductivity mechanism. The study also offers novel ideas for accurate calculation of saturation and the meticulous evaluation of reservoir for subsequent studies.

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Section: Additional Conductivity Of Clay Mineralsmentioning

confidence: 99%

Analyzing the Origin of Low Resistivity in Gas-Bearing Tight Sandstone Reservoir

Jiang

Jian

et al. 2021

Geofluids

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“…The effect of diagenetic minerals on reservoir properties has long been acknowledged [2,[6][7][8][9][10][11][12]. IIlite occurs as pore-lining and pore-filling cement, reducing size and closing pore throats, and consequently affecting the reservoir quality [13]. Smectite may bridge the gap between adjacent detrital grains and reduce the pore throat connectivity.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Diagenetic Minerals on the Petrophysical Properties of Sandstone Reservoir: A Case Study of the Upper Shallow Marine Sandstones in the Central Bredasdorp Basin, Offshore South Africa

Magoba,

Opuwari,

Liu

2024

Minerals

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The upper shallow marine sandstone reservoirs of the Barremian-to-Valanginian formation are the most porous and permeable sandstone reservoirs in the Bredasdorp Basin and an important target for oil and gas exploration. There is a paucity of information on the reservoir characterization and effect of diagenetic mineral studies focusing on the upper shallow marine sandstone reservoirs in the central Bredasdorp Basin; thus, there is a need to investigate the effect of diagenetic minerals and to characterize these reservoirs due to their high porosity and permeability. Datasets, including a suite of geophysical wireline logs, routine core analysis, geological well completion reports, description reports, and core samples, were utilized. A total of 642 core porosity measures, core water saturation, and core permeability data were used for calibration with the log-derived parameters, ranging in depth from 3615 m to 4259 m. Rock samples were prepared for diagenetic mineral analyses, such as thin sections and Scanning electron microscopy, for each well to investigate the presence of diagenetic minerals in the selected reservoir units. The petrophysical analyses showed the results of porosity, volume of clay, water saturation, and permeability, ranging from 9% to 27%, 8.6% to 19.8%, 18.9% to 30.4%, and 0.096 mD to 151.8 mD, respectively, indicating a poor-to-good reservoir quality. Mineralogical analyses revealed that micrite calcite, quartz cement, quartz overgrowth, and authigenic pore-filling and grain-coating clay minerals (illite–smectite and illite) negatively affected intergranular porosity. Porosity-versus-permeability cross plot showed good correlation of 0.86 for ZN1 and 0.83 for ZN3 reservoirs, suggesting that although porosity is the main drive of permeability, there were other geological factors at play, such as diagenetic minerals and compaction.

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“…These minerals typically fall into five major groups which include kaolinite, chlorite, illite, smectite (montmorillonite), and illite-smectite mixed-layer clays. In the oil and gas industry, clay minerals could play a very positive role as the colloidal base of almost all water-based drilling muds or as the regulator of the pH of the pore fluids [1]. Nevertheless, they bring about serious challenges from the perspective of reservoir quality.…”

Section: Introductionmentioning

confidence: 99%

Fractal Properties of Various Clay Minerals Obtained from SEM Images

et al. 2021

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Clay minerals significantly alter the pore size distribution (PSD) of the gas hydrate-bearing sediments and sandstone reservoir rock by adding an intense amount of micropores to the existing intragranular pore space. Therefore, in the present study, the internal pore space of various clay groups is investigated by manually segmenting Scanning Electron Microscopy (SEM) images. We focused on kaolinite, smectite, chlorite, and dissolution holes and characterized their specific pore space using fractal geometry theory and parameters such as pore count, pore size distribution, area, perimeter, circularity, and density. Herein, the fractal properties of different clay groups and dissolution holes were extracted using the box counting technique and were introduced for each group. It was observed that the presence of clays complicates the original PSD of the reservoir by adding about 1.31-61.30 pores/100 μm2 with sizes in the range of 0.003-87.69 μm2. Meanwhile, dissolution holes complicate the pore space by adding 4.88-8.17 extra pores/100 μm2 with sizes in the range of 0.06-119.75 μm2. The fractal dimension ( D ) and lacunarity ( L ) values of the clays’ internal pore structure fell in the ranges of 1.51-1.85 and 0.18-0.99, respectively. Likewise, D and L of the dissolution holes were in the ranges of, respectively, 1.63-1.65 and 0.56-0.62. The obtained results of the present study lay the foundation for developing improved fractal models of the reservoir properties which would help to better understand the fluid flow, irreducible fluid saturation, and capillary pressure. These issues are of significant importance for reservoir quality and calculating the accurate amount of producible oil and gas.

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Characteristics and distribution of clay minerals and their effects on reservoir quality: Huagang Formation in the Xihu Sag, East China Sea Basin

Cited by 10 publications

References 25 publications

Analyzing the Origin of Low Resistivity in Gas-Bearing Tight Sandstone Reservoir

Analyzing the Origin of Low Resistivity in Gas-Bearing Tight Sandstone Reservoir

The Effect of Diagenetic Minerals on the Petrophysical Properties of Sandstone Reservoir: A Case Study of the Upper Shallow Marine Sandstones in the Central Bredasdorp Basin, Offshore South Africa

Fractal Properties of Various Clay Minerals Obtained from SEM Images

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