Study on solubility and solubilisation of drying agent in supercritical carbon dioxide for improving local permeability of tight gas reservoir

Abstract

The AC component of drying agent described in literature 6 can be injected into tight gas reservoir formation to reduce original and residual water saturation caused by completion and stimulation. However, the pore and throat of formation in tight gas reservoir are so small that AC particles are difficult to be injected into them directly. Through experiments, we discovered that a certain amount of AC could dissolve in supercritical carbon dioxide (SCCO₂) and it could separate out from SCCO₂ when pressure decreased. Therefore, SCCO₂ can be used as transport agent and bring it into tight gas reservoir for drying formation. We further study the solubility of AC in SCCO₂ under different temperature and pressure, and also screen solubilizer to enhance the solubility in this paper. The results show that the solubility of AC in SCCO₂ is 0.0005 mol/mol at 40°C and 8 MPa. When temperature is constant, the solubility of AC in SCCO₂ increases with the increase of pressure, but the impact of temperature on the solubility shows different variation principle with pressure increasing. In addition, ethyl alcohol is the best solubilizer for increasing the solubility of AC in SCCO₂, and the optimal concentration of solubilizer in SCCO₂ is 10%.

GRAPHICAL ABSTRACT

KEYWORDS:

• Tight gas reservoir
• drying agent
• supercritical carbon dioxide
• solubility
• solubilizer

Acknowledgments

The technical support of the State Key Laboratory of Oil and Gas Geology and Exploitation, with whom we are working, is also gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We gratefully acknowledge the financial support for this work provided by the National Natural Science Foundation of China (Key Programme) [grant number 51534006].