Performance of free gases during the recovery enhancement of shale gas by CO2 injection: a case study on the depleted Wufeng–Longmaxi shale in northeastern Sichuan Basin, China

Abstract

In this work, a novel thermal–hydraulic–mechanical (THM) coupling model is developed, where the real geological parameters of the reservoir properties are embedded. Accordingly, nine schemes of CO2 injection well (IW) and CH4 production well (PW) are established, aiming to explore the behavior of free gases after CO2 is injected into the depleted Wufeng–Longmaxi shale. The results indicate the free CH4 or CO2 content in the shale fractures/matrix is invariably heterogeneous. The CO2 involvement facilitates the ratio of free CH4/CO2 in the matrix to that in the fractures declines and tends to be stable with time. Different combinations of IW–PWs induce a difference in the ratio of the free CH4 to the free CO2, in the ratio of the free CH4/CO2 in the matrix to that in the fractures, in the content of the recovered free CH4, and in the content of the trapped free CO2. Basically, when the IW locates at the bottom Wufeng–Longmaxi shale, a farther IW–PWs distance allows more CO2 in the free phase to be trapped; furthermore, no matter where the IW is, a shorter IW–PWs distance benefits by getting more CH4 in the free phase recovered from the depleted Wufeng–Longmaxi shale. Hopefully, this work is helpful in gaining knowledge about the shale-based CO2 injection technique.

Structural deformation characteristics and its influence on shale gas preservation of the Wufeng−Longmaxi Formation in the Wuxi area, Chongqing, China

“…With the recently substantive breakthroughs and commercial development of marine shale gas in the Changning, Weiyuan, Fuling, Zhaotong, Fushun−Yongchuan, Pengshui, Nanchuan, and Dingshan areas from the Sichuan Basin and its surroundings, China's shale gas exploration and development has entered a very rapid pace, especially the exploration and development progress of shale gas in the complex structural regions at the margin of the Sichuan Basin (Jin et al, 2018;Potter, 2018;Ma et al, 2020;Liu et al, 2021a;Nie et al, 2021;Li et al, 2022;Wang et al, 2022). The Wuxi area of Chongqing city is situated in the transition zone between the northeastern margin of the Sichuan Basin and the Dabashan thrust belt, which belongs to the typical complex structural region of the basin margin.…”

Methane Adsorption and Desorption on a Deep Shale Matrix under Simulative Reservoir Temperature and Pressure

“…12−14 Accordingly, many types of adsorption equilibrium models, for instance, the Langmuir model, 15 the Sips model, 16 the Brunauer−Emmett−Teller (BET) model, 17 the Guggenheim−Anderson-de Boer (GAB) model, 18 the Frenkel−Halsely−Hill (FHH) model, 19 and the Ono−Kondo lattice model 20 13 Thereinto, the celebrated Langmuir model is broadly applied in the adsorption system between CH 4 and shale. 21,22 Despite this, there still exist some limitations in this model. Langmuir model presumes that the adsorption energy over all of the adsorption sites on the adsorbent is constant.…”

“…Instead, the Dubinin–Radushkevich (D–R) model, the Dubinin–Astakhov (D–A) model, and the Dubinin–Serpinsky (D–S) model follow the latter mechanism . Thereinto, the celebrated Langmuir model is broadly applied in the adsorption system between CH 4 and shale. , Despite this, there still exist some limitations in this model. Typically, the Langmuir model presumes that the adsorption energy over all of the adsorption sites on the adsorbent is constant .…”

Phase Behavior of CO2-CH4-Water Mixtures in Shale Nanopores Considering Fluid Adsorption and Capillary Pressure

“…2 In recent years, as a working fluid for enhancing shale gas recovery, CO 2 has attracted considerable interest. 3,4 In this way, both CO 2 sequestration and enhanced gas recovery (CO 2 -EGR) can be achieved. 5,6 However, the injection of CO 2 makes the fluid adsorption and interphase mass transfer more complicated in water-containing shale gas reservoirs.…”

“…Although great progress has been made in horizontal drilling and hydraulic fracturing technology for shale gas production, many challenges remain, such as low natural gas recovery and high water consumption . In recent years, as a working fluid for enhancing shale gas recovery, CO 2 has attracted considerable interest. , In this way, both CO 2 sequestration and enhanced gas recovery (CO 2 -EGR) can be achieved. , However, the injection of CO 2 makes the fluid adsorption and interphase mass transfer more complicated in water-containing shale gas reservoirs . Therefore, it is imperative to deepen our understanding of the phase behavior of gas–water mixtures in shale gas reservoirs.…”