Advanced developments in low-toxic and environmentally friendly shale inhibitor: A review

Abstract

The hydration and swelling caused by the contact of shale with water during oil and gas drilling have caused many difficulties in drilling operations. Water-based drilling fluids (WBDFs) are considered to be more environmentally friendly and economical than oil-based drilling fluids (OBDFs). However, shale inhibitors are needed to solve the problems of shale hydration swelling caused by water. Reducing water content and liquid intrusion are effective ways to prevent the interaction between water and shale. Extensive researches have been conducted to develop highly effective shale inhibitors that inhibit shale swelling and reduce drilling costs and environmental impact. Especially in recent years, environmentally friendly shale inhibitors with low toxicity have become the main research object. A good shale inhibitor should not only have the ability to efficiently reduce shale hydration swelling, but also need to be compatible with other components of the drilling fluid to develop an effective high-performance WBDF. Besides, the requirements of environmental regulations should be met. Only biodegradable environmentally friendly inhibitors can develop the green and sustainable oil and gas industry. Some researchers have published some reviews about shale inhibitors, but there has been no review about low toxic and environmentally friendly shale inhibitors considered as the trend of the oil and gas industry. The purpose of this paper is to provide a detailed review of inhibitors with low toxicity and environmentally-friendly in recent years, aiming to fully understand the current methods of shale hydration inhibition and provide new ideas for the subsequent research on shale inhibitors.