Evolution Characteristics of Mechanical Properties under Supercritical Carbon Dioxide Treatment in Shale Reservoirs

Meng, Siwei; Xu, Jinkai; Tao, Jiaping; Wang, Xiaoqi; Zhang, Chenjun

doi:10.1021/acsomega.0c05136

Cited by 16 publications

(13 citation statements)

References 21 publications

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“…Contrary to previous studies, they reported a minor change in pore morphology, inferred through the change in hysteresis behavior of N 2 LPGA isotherms. Meng et al, 187 although focused on SC-CO 2 -induced geomechanical changes in shales from Songliao Basin, China, noted that the mineral matter content, especially calcite, strongly decreased, because of dissolution, with increasing exposure to SC-CO 2 . Similar to other researches, they observed the primary porous structures and fractures to be dissolved and replaced by newer structures formed because of exposure.…”

Section: Influence Of Sc-co 2 On Shale Petrophysics Geomechanics and ...mentioning

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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Section: Influence Of Sc-co 2 On Shale Petrophysics Geomechanics and ...mentioning

confidence: 99%

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

et al. 2022

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“…Furthermore, these changes in the rock structure may lead to a dramatic decrease in the rock material strength. 27 3.2. Study on the Interaction between Supercritical CO 2 and Formation Fluid.…”

Section: Resultsmentioning

confidence: 99%

“…This resulted in a significant increase in the complexity of the fracture network. Furthermore, these changes in the rock structure may lead to a dramatic decrease in the rock material strength …”

Section: Resultsmentioning

confidence: 99%

Stimulation and Sequestration Mechanism of CO₂ Waterless Fracturing for Continental Tight Oil Reservoirs

Tao

Meng

et al. 2021

ACS Omega

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CO2 fracturing is a promising technology for oil field development in tight, continental deposits, with potential advantages of enhanced oil recovery (EOR), CO2 sequestration, and water conservation. Compared with CO2-EOR techniques, such as CO2 huff and puff and CO2 flooding, CO2 can interact with reservoir rock and fluid under higher pressure conditions during fracturing, resulting in CO2 stimulation and sequestration effects that differ from those that occur during conventional CO2-EOR. In this paper, the CO2 interactions between CO2 and reservoirs in continental tight oil reservoirs under fracturing conditions are systematically studied through laboratory experiments. The results show that under high pressure, CO2 effectively changes the pore structure through the extraction of hydrocarbons, dissolution of the rock matrix, and migration of minerals. CO2 dissolution of the rock matrix can significantly increase the number and complexity of fractures. Furthermore, CO2 has a higher solubility in formation fluid under high-pressure conditions. Given the higher pressures, CO2 forms a miscible phase with crude oil, diffuses more deeply into the formation, and reacts fully with the reservoir minerals and fluid during CO2 fracturing. Accordingly, CO2 can improve the permeability of the reservoir and flowability of crude oil significantly. Hence, CO2 fracturing can enhance oil recovery and CO2 sequestration more effectively. Core displacement experiments indicate that oil recovery of CO2 soaking process after CO2 fracturing is 36%, which is 12% and 9% higher than those of CO2 huff and puff and CO2 flooding with 5 pore volume, respectively. Field tests show that average oil production after CO2 fracturing is 1.42 times higher than that after CO2 flooding, which further validates the advantage of CO2 fracturing and demonstrates its huge application potential.

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“…The CO 2 −shale interaction induced mechanical weakening in shale will increase the stress sensitivity of shale; with the injection of CO 2 , the variation of gas pressure will induce the perturbation in geostresses, which will significantly impact on the permeability of shale. 154 In the unstressed state, the chemical reaction enlarges the pores in the shale, leading to the increase in porosity and the initial permeability of the shale. 163 In the stressed state, the permeability of shale is controlled by the chemical−mechanical coupling effects, and the permeability enhancement of shale by ScCO 2 dissolution effects may not be guaranteed.…”

Section: Adsorption Behaviormentioning

confidence: 99%

“…Additionally, it should be noted that the CO 2 –shale interaction induced mechanical weakening of shale also significantly affects the permeability of shale, which has been not of concern at present. The CO 2 –shale interaction induced mechanical weakening in shale will increase the stress sensitivity of shale; with the injection of CO 2 , the variation of gas pressure will induce the perturbation in geostresses, which will significantly impact on the permeability of shale . In the unstressed state, the chemical reaction enlarges the pores in the shale, leading to the increase in porosity and the initial permeability of the shale .…”

Section: Alterations In Physical and Chemical Properties Of Shalementioning

confidence: 99%

Comprehensive Review of Property Alterations Induced by CO₂–Shale Interaction: Implications for CO₂ Sequestration in Shale

et al. 2022

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CO2–shale interaction performs a crucial role in determining the capacity and leakage risk of CO2 storage in shale reservoirs. In this paper, the alterations of physical and chemical properties of shale triggered by CO2–shale interaction are reviewed, and then the implications for CO2 sequestration in shale formations are discussed. CO2–shale interaction induced the mineral alterations in shale and then further induced the pore structure alterations. The pore structure alterations are mainly controlled by mineral dissolution/precipitation and extraction and CO2 adsorption induced swelling in shale, which is closely related to the reservoir pressures and temperatures. Furthermore, the mineral and pore structure alterations may also influence the wetting behavior of shale. After CO2 exposure, the contact angle of shale increased, indicated the weakening in the hydrophilicity of the shale surface. The microscopic property alterations induced the macroscopic mechanical properties of shale to be weakened after CO2–shale interaction. The permeability variation of shale is significantly influenced by chemical–mechanical coupling effects including mineral dissolution/precipitation, adsorption induced swelling, wettability, and mechanical weakening induced by CO2–shale interaction. The shale property alterations will ultimately affect the CO2 storage capacity and security in shale. Future research needs to focus on the CO2–shale interaction covering multiple spatial and temporal scales at in situ conditions and considering the chemical–mechanical coupling effect on CO2 sequestration in shale.

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Evolution Characteristics of Mechanical Properties under Supercritical Carbon Dioxide Treatment in Shale Reservoirs

Cited by 16 publications

References 21 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

Stimulation and Sequestration Mechanism of CO₂ Waterless Fracturing for Continental Tight Oil Reservoirs

Comprehensive Review of Property Alterations Induced by CO₂–Shale Interaction: Implications for CO₂ Sequestration in Shale

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Evolution Characteristics of Mechanical Properties under Supercritical Carbon Dioxide Treatment in Shale Reservoirs

Cited by 16 publications

References 21 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

Stimulation and Sequestration Mechanism of CO2 Waterless Fracturing for Continental Tight Oil Reservoirs

Comprehensive Review of Property Alterations Induced by CO2–Shale Interaction: Implications for CO2 Sequestration in Shale

Contact Info

Product

Resources

About

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

Stimulation and Sequestration Mechanism of CO₂ Waterless Fracturing for Continental Tight Oil Reservoirs

Comprehensive Review of Property Alterations Induced by CO₂–Shale Interaction: Implications for CO₂ Sequestration in Shale