Research Progress and Prospects of Nano Plugging Agents for Shale Water-Based Drilling Fluids.

Maintaining wellbore stability is one of the most critical technical issues in drilling operations. The shale stratigraphy is characterized by the development of laminations, microfractures, and nano/micrometer pores. Water intrusion accelerates the shale swelling, reduces the intergranular bonding force, and increases the risk of wellbore instability. Effective plugging of drilling fluid intrusion channels is a prominent way to accomplish the wellbore stability. Nanoparticles have the advantages of small size, large specific surface area, and matching of the shale pore size. Therefore, it can be used as a shale nanoplugging agent. This paper summarizes the types of nanoplugging agents, evaluation methods, and mechanisms for existing shale water-based drilling fluids (WBDFs) nanoplugging agents. To meet the plugging requirements of shale formations and accommodate increasingly complex drilling environments, the developement of novel stimuli-responsive nanomaterials that are smaller in size, have better dispersion stability, and possess the ability to leverage high temperature to enhance interactions is essential. It is a significant direction for nanosealing in shale WBDFs. However, all of this should be predicated on reasonable and reliable evaluation methods.