CO2 and N2 injection to enhance shale gas recovery

Ziyan Li, Derek Elsworth

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We investigate the potential benefits of injecting the mixtures of CO2 and N2 into shale reservoirs to both optimize recovery of natural gas and to sequester CO2. In this work, we develop dual-porosity, dual-permeability finite element models to simulate multicomponent gas flow in porous media coupled with shale deformation and sorption behavior. We use this model to explore the injection of pure CO2, pure N2, and mixtures of CO2 and N2 in different ratios to enhance shale gas recovery (ESGR). This behavior necessarily includes the evolution sorption-induced strain by competitive adsorption and its influence on permeability of matrix and fractures to ultimately define cumulative production history of CH4. The results show that injecting pure CO2 can increase shale gas recovery by ∼20%. Injection of N2 works as an ESGR agent and can increase shale gas recovery by ∼80%. Injecting a mixture of N2 and CO2 of different gas ratios results in recovery ranging between ∼20% and ∼80% (pure component end-member cases). Moreover, injecting N2 in higher proportions relative to CO2 is more beneficial since N2 shows higher recovery in ESGR. Therefore, increasing injection pressure is not the only means to achieve higher production, instead, increasing N2-CO2 gas ratio can achieve the same goal. The observations also show that although CO2 is not sensitive to pressure in performing ESGR, it is sensitive to pressure when accounting for sequestered CO2. Furthermore, the sequestration of CO2 by injecting CO2-N2 mixtures does not simply increase as CO2-N2 gas ratio increases. Since higher CO2-N2 ratio results in a decrease in shale gas recovery, which leads to more CH4 left in the reservoir to compete with CO2 for sorption sites, this also results in reduced CO2 sequestration.

Original languageEnglish (US)
Title of host publication51st US Rock Mechanics / Geomechanics Symposium 2017
PublisherAmerican Rock Mechanics Association (ARMA)
Pages274-279
Number of pages6
ISBN (Electronic)9781510857582
StatePublished - Jan 1 2017
Event51st US Rock Mechanics / Geomechanics Symposium 2017 - San Francisco, United States
Duration: Jun 25 2017Jun 28 2017

Publication series

Name51st US Rock Mechanics / Geomechanics Symposium 2017
Volume1

Other

Other51st US Rock Mechanics / Geomechanics Symposium 2017
CountryUnited States
CitySan Francisco
Period6/25/176/28/17

Fingerprint

gas recovery
injection
Recovery
sorption
recovery
Sorption
permeability
Gases
gases
Shale
shale
natural gas
gas
Shale gas
shale gas
gas flow
dual porosity
proportion
histories
porosity

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology
  • Geophysics

Cite this

Li, Z., & Elsworth, D. (2017). CO2 and N2 injection to enhance shale gas recovery. In 51st US Rock Mechanics / Geomechanics Symposium 2017 (pp. 274-279). (51st US Rock Mechanics / Geomechanics Symposium 2017; Vol. 1). American Rock Mechanics Association (ARMA).
Li, Ziyan ; Elsworth, Derek. / CO2 and N2 injection to enhance shale gas recovery. 51st US Rock Mechanics / Geomechanics Symposium 2017. American Rock Mechanics Association (ARMA), 2017. pp. 274-279 (51st US Rock Mechanics / Geomechanics Symposium 2017).
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abstract = "We investigate the potential benefits of injecting the mixtures of CO2 and N2 into shale reservoirs to both optimize recovery of natural gas and to sequester CO2. In this work, we develop dual-porosity, dual-permeability finite element models to simulate multicomponent gas flow in porous media coupled with shale deformation and sorption behavior. We use this model to explore the injection of pure CO2, pure N2, and mixtures of CO2 and N2 in different ratios to enhance shale gas recovery (ESGR). This behavior necessarily includes the evolution sorption-induced strain by competitive adsorption and its influence on permeability of matrix and fractures to ultimately define cumulative production history of CH4. The results show that injecting pure CO2 can increase shale gas recovery by ∼20{\%}. Injection of N2 works as an ESGR agent and can increase shale gas recovery by ∼80{\%}. Injecting a mixture of N2 and CO2 of different gas ratios results in recovery ranging between ∼20{\%} and ∼80{\%} (pure component end-member cases). Moreover, injecting N2 in higher proportions relative to CO2 is more beneficial since N2 shows higher recovery in ESGR. Therefore, increasing injection pressure is not the only means to achieve higher production, instead, increasing N2-CO2 gas ratio can achieve the same goal. The observations also show that although CO2 is not sensitive to pressure in performing ESGR, it is sensitive to pressure when accounting for sequestered CO2. Furthermore, the sequestration of CO2 by injecting CO2-N2 mixtures does not simply increase as CO2-N2 gas ratio increases. Since higher CO2-N2 ratio results in a decrease in shale gas recovery, which leads to more CH4 left in the reservoir to compete with CO2 for sorption sites, this also results in reduced CO2 sequestration.",
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Li, Z & Elsworth, D 2017, CO2 and N2 injection to enhance shale gas recovery. in 51st US Rock Mechanics / Geomechanics Symposium 2017. 51st US Rock Mechanics / Geomechanics Symposium 2017, vol. 1, American Rock Mechanics Association (ARMA), pp. 274-279, 51st US Rock Mechanics / Geomechanics Symposium 2017, San Francisco, United States, 6/25/17.

CO2 and N2 injection to enhance shale gas recovery. / Li, Ziyan; Elsworth, Derek.

51st US Rock Mechanics / Geomechanics Symposium 2017. American Rock Mechanics Association (ARMA), 2017. p. 274-279 (51st US Rock Mechanics / Geomechanics Symposium 2017; Vol. 1).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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Li Z, Elsworth D. CO2 and N2 injection to enhance shale gas recovery. In 51st US Rock Mechanics / Geomechanics Symposium 2017. American Rock Mechanics Association (ARMA). 2017. p. 274-279. (51st US Rock Mechanics / Geomechanics Symposium 2017).