Investigation for the novel use of a typical deep eutectic solvent as a potential shale inhibitor

ABSTRACT

The hydration and swelling of shale cause borehole instability and seriously threaten the drilling safety, especially for the use of water-based drilling fluids. In this paper, the potential application of a typical deep eutectic solvent CU-DES comprised of choline chloride and urea (molar ratio 1:2) as a novel shale inhibitor was investigated for the first time. The inhibitive properties of CU-DES were evaluated by experiments such as bentonite inhibition test, linear swelling test, and shale cuttings hot-rolling dispersion test. Compared with traditional inhibitors KCl and polyether diamine (PDA), CU-DES with a lower concentration exhibited the much higher inhibitive capacity. Furthermore, CU-DES maintained excellent performance even at high temperature (160°C), which made it possible to utilize in high-temperature well drilling. To explain the inhibition mechanism of CU-DES, a series of analytical methods, including particle size distribution measurement, Zeta potential measurement, SEM, FTIR, and XRD were conducted. The results demonstrated that the great inhibitive properties of CU-DES were mainly dependent on both the electrostatic attraction and the hydrogen bond between CU-DES and clay.

KEYWORDS:

• Deep eutectic solvent
• shale hydration and swelling
• clay
• inhibition
• drilling fluids

Conflict of interest

The authors declare that they have no conflict of interest.

Additional information

Funding

The authors are grateful for funding from the Key Project of the National Natural Science Foundation of China (No. U1762106), and the Fundamental Research Funds for the Central Universities (19CX02064A).

Notes on contributors

Han Jia

Han Jia is an associate professor at the China University of Petroleum (East China). He currently focuses on the use of novel surfactants in chemical-enhanced oil recovery.

Pan Huang

Pan Huang is a graduate student at the China University of Petroleum (East China), and is studying at the school of petroleum engineering. His research deals with the synthesis of novel shale inhibitors.

Yugui Han

Yugui Han is a senior engineer at CNOOC China Limited. He has devoted years of research to the application of the novel surfactants in the oilfield.

Qiuxia Wang

Qiuxia Wang is a senior engineer at CNOOC China Limited. She has devoted years of research to the additives of drilling fluids.

Kaile Jia

Kaile Jia is an undergraduate student at the China University of Petroleum (East China), and is studying at the school of petroleum engineering. His research deals with the inhibition evaluation of shale inhibitors.

Tunan Sun

Tunan Sun is an undergraduate student at the China University of Petroleum (East China), and is studying at the school of petroleum engineering. His research deals with the inhibition mechanism of shale inhibitors.

Fan Zhang

Fan Zhang is a PhD student at the China University of Petroleum (East China), and is studying at the school of petroleum engineering. His research topic was the drilling fluids chemistry.

Hui Yan

Hui Yan is an associate professor at Liaocheng University. His main research interest was in molecular simulation.

Kaihe Lv

Kaihe Lv is a professor at China University of Petroleum (East China). He currently focuses on advanced technology in drilling fluid and enhanced oil recovery.