Surface wettability alteration of shales exposed to CO2: Implication for long-term integrity of geological storage sites

Fatah, Ahmed; Bennour, Ziad; Mahmud, Hisham Ben; Gholami, Raoof; Hossain, Mofazzal

doi:10.1016/j.ijggc.2021.103426

Cited by 43 publications

(39 citation statements)

References 55 publications

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“…The clay-rich shales were observed to have transitioned to being CO 2 -wet, compared to the quartz-rich shales, which remained strongly water-wet after SC-CO 2 treatment. In a different study conducted by Fatah et al,223 they compared the shale/water contact angles of three type of shales (Eagle Ford, Wolfcamp, and Mancos) with various mineralogy exposed to SC-CO 2 at different durations, pressures, and temperatures. They observed that, for clay-rich shales (Eagle Ford and Wolfcamp), the CO 2 /shale contact angle continuously increased with increasing treatment time and pressure, caused by dissolution of clay and carbonate minerals, whereas, the quartz rich shales (Mancos) stayed strongly water wet in similar condition.…”

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confidence: 99%

Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration

et al. 2022

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Hydraulic fracturing has transformed the international energy landscape by becoming the go-to method for the exploitation of natural gas from unconventional shale reservoirs. However, in the recent years, the search for an alternative method of shale-gas exploration has intensified, because of various problems (e.g., contamination of ground and surface water, overexploitation of precious water resources, air pollution, etc.) associated with the usage of water-based fracturing techniques. The use of CO2 for shale gas exploitation has emerged as a better alternative to aqueous-based gas exploration techniques. CO2 when injected into deep shale reservoirs, transitions into supercritical CO2 (SC-CO2) when temperature and pressure condition exceeds the critical point, i.e., 31.1 °C and 7.38 MPa. In this paper, we comprehensively review the impact of SC-CO2 on shale gas reservoirs during the different stages of shale-gas exploration, i.e., (i) drilling, which involves the superiority of SC-CO2 over water-based drilling fluids, in terms of achieving under-balanced well condition, higher rates of penetration, and resistance to formation damage; (ii) fracturing, which involves factors affecting the tortuosity of fractures created by SC-CO2 fracturing, breakdown pressure, and proppant-carrying capacity; and (iii) injection, which involves the twin-headed benefit of enhanced recovery due to CO2/CH4 competitive adsorption and geological sequestration, CO2 vs CH4 excess sorption as a function of pressure, etc. Several research works have indicated discrepancies on how SC-CO2 impacts different shale properties. Some studies show low-pressure N2-gas-adsorption-derived surface area and total pore volume to be increasing with SC-CO2 imbibition, while others show a decreasing trend for the same. Similarly, for some shales, the quartz content, along with the clay mineral contents, decreased as the exposure to SC-CO2 increased, while in some other studies, with similar long-term exposure to SC-CO2, the quartz content was observed to increase along with the decrease in clay content and vice versa. Essentially, the increased exposure to SC-CO2 results in the dissolution of primary porous structures and fractures, and reformation of newer porous structure and conduits in shales. Nonetheless, these changes in the mineralogy weaken the microstructure of the rock bringing significant changes in the mechanical properties of the shales with implications on the wellbore stability and fracturing efficiency. The mechanical properties such as uniaxial compressive strength (UCS), Young’s modulus, and tensile strength decrease as the SC-CO2 saturation period increases. However, some studies have shown factors like bedding angle and phase-state of CO2 having varying effect on the strength behavior of the shales. Moreover, changes in the structure of shales caused by the creation of fractures and the reduction of their strength can also pose major risks, because of potential leakage of CO2 through these created pathways. How these processes would i...

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Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration

et al. 2022

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“…Fragments of the core sample were polished with 1500 silicon carbide grit and cleaned with ethanol to be used for SEM analysis. This process ensures the removal of any contaminates after grinding [34]. Whole core plugs (1.5 × 3 inches') were used for core flooding experiments.…”

Section: Methodology Samples and Materialsmentioning

confidence: 99%

The Effect of Silica Dissolution on Reservoir Properties during Alkaline-Surfactant-Polymer (ASP) Flooding

Ahmed¹

2022

J Petrochem Eng

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Chemical flooding is one of the effective methods to recover large volumes of oil from sandstone formations after primary depletion. However, silica dissolution often occurs during Alkaline-Surfactant-Polymer (ASP) flooding, affecting the petro-physical properties of the formation. To address this issue, samples from Berea sandstone formations were treated with various brine solutions, through static tube tests and core flooding experiments. Analytical tests such as DR/2800 spectrophotometer and scanning electron microscope were used to evaluate the silica solubility and the alteration in mineral content. The results indicated that the silicate contents decreased after the saturation due to silica solubility in the solution. Increasing brine salinity to 40,000 ppm and introducing Magnesium and Calcium ions to the solution, reduces the silicate contents by 5.03% and 7.32%. Moreover, saturating the samples with ASP solution, further reduced the silicate contents by 14.86%. This reduction is associated with a relative increase in silica solubility and pH of the solution. Silica dissolution affects the pore microstructure, which resulted in increasing the porosity and pore volume after the core flooding. The injection of the ASP solution increased the porosity by 5.83%, thus the pore volume increased from 17.72 to 18.76 cc. This is associated with the high silica solubility and the increase of solution pH in the ASP solution. The permeability of the samples generally reduced after the core flooding, due to the silica solubility. However, injecting the ASP solution, resulted in a major reduction of the permeability by more than 75%. These changes in the petro-physical properties can lead to severe formation damage and affect hydrocarbon production. This study assists in understanding the impact of silica dissolution during ASP treatment and addresses the factors involved. Efficient utilization of chemical flooding can help mitigating silicate scaling within the formation and extend field productivity.

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“…Numerous studies have shown that interactions at the solid-liquid interface have significant effects on flow patterns due to the small pores and narrow throats, as well as the existence of clay minerals in the complicated structures of tight, low-permeability reservoirs (Al-Yaseri et al, 2021;Fatah et al, 2021;Kim and Devegowda, 2022;Zhang et al, 2022). The fluid flow tends to become nonlinear and shows deviations from Darcy's Law.…”

Section: Introductionmentioning

confidence: 99%

Study of nonlinear flow mechanisms and microfracture networks in low-permeability reservoirs

et al. 2023

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As efficient technologies boost oil yields and economic benefits, horizontal wells and hydraulic fracturing are widely used in low- permeability reservoirs. To better evaluate the reserve and improve recovery, it is essential to determine fluid flow patterns and transport mechanisms. Laboratory experiments, field operations, and analytical studies have identified nonlinear flow and microfracture networks during the fluid flow in a reservoir with fractured horizontal wells. However, the interactions between nonlinear flow and microfracture networks are still not fully understood. In this study, nonlinear flow experiments and triaxial compression tests were carried out to analyze nonlinear flow characteristics in the vicinity of microfracture networks. By analyzing the effects of microfracture networks on nonlinear flow, two-phase flow, rock stress sensitivity, and artificial fractures, we found that fluid capacity in capillaries with smaller dimensions decreased along with a drop in the pressure gradient, generating a nonlinear flow pattern. The area of nonlinear flow was diminished by the presence of microfractures, which improved flow efficiency and reservoir quality. Considering the size of fracture apertures, microfractures behave more like matrix pores than natural fractures. Also, microfractures significantly increase rock stress sensitivity and reduce the threshold permeability, which enhances fluid flow capacity. This study contributes to our understanding of flow behavior, predicting production and improving recovery in low-permeability reservoirs.

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Surface wettability alteration of shales exposed to CO2: Implication for long-term integrity of geological storage sites

Cited by 43 publications

References 55 publications

Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration

Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration

The Effect of Silica Dissolution on Reservoir Properties during Alkaline-Surfactant-Polymer (ASP) Flooding

Study of nonlinear flow mechanisms and microfracture networks in low-permeability reservoirs

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Surface wettability alteration of shales exposed to CO2: Implication for long-term integrity of geological storage sites

Cited by 43 publications

References 55 publications

Impact of Supercritical CO2 on Shale Reservoirs and Its Implication for CO2 Sequestration

Impact of Supercritical CO2 on Shale Reservoirs and Its Implication for CO2 Sequestration

The Effect of Silica Dissolution on Reservoir Properties during Alkaline-Surfactant-Polymer (ASP) Flooding

Study of nonlinear flow mechanisms and microfracture networks in low-permeability reservoirs

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Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration

Impact of Supercritical CO₂ on Shale Reservoirs and Its Implication for CO₂ Sequestration