Modeling of EOR in Shale Reservoirs Stimulated by Cyclic Gas Injection

Fig. 1—Effect of natural-fracture spacing and hydraulic fractures on CO2 huff ’n’ puff oil recovery.

Cyclic gas injection combined with modern technologies such as horizontal drilling and hydraulic fracturing has achieved promising results in low-permeability formations. This paper focuses on the effects of injected-gas composition and fracture properties on oil recovery, concluding that cyclic gas injection in hydraulically fractured shale oil reservoirs is feasible for improving oil production substantially over primary production.


Cyclic gas injection is an effective and quick-responding enhanced-oil-recovery (EOR) method in intensely naturally fractured or hydraulically fractured reservoirs. The short payout is a characteristic that should attract industry’s interest in investing in these types of projects. Recent studies showed that cyclic gas injection could be a viable method to improve the oil recovery in shale oil reservoirs, but those studies were performed on the basis of black-oil models without detailed analysis of the phase behavior of the reservoir-oil/injected-gas system. The reliability of using the black-oil model to simulate the cycling of gas/condensate reservoirs is questionable because the two-component description may not be able to represent the active compositional phenomena adequately. This paper describes the use of an equation-of-state (EOS) approach to model the phase behavior of the oil and injected-solvent system.

Description of Models

The reservoir-fluid-composition data are from the published data of the fifth SPE comparative solution project, which aimed to illustrate the comparison of results between a four-component black-oil miscible-flood simulator and a fully compositional reservoir-simulation model.

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 169069, “Compositional Modeling of EOR Process in Shale Oil Reservoirs Stimulated by Cyclic Gas Injection,” by Tao Wan, Xingbang Meng, James J. Sheng, SPE, and Marshall Watson, SPE, Texas Tech University, prepared for the 2014 SPE Improved Oil Recovery Symposium, Tulsa, 12–16 April. The paper has not been peer reviewed.
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Modeling of EOR in Shale Reservoirs Stimulated by Cyclic Gas Injection

01 January 2015

Volume: 67 | Issue: 1


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