Nanoscale Laponite as a Potential Shale Inhibitor in Water-Based Drilling Fluid for Stabilization of Wellbore Stability and Mechanism Study

TLDR

Shale hydration is the primary cause of wellbore instability in oil and gas drilling operations. The study investigates nanoscale laponite as a shale inhibitor to stabilize wellbores. The authors evaluated laponite’s inhibition performance with immersion, swelling, and shale recovery tests, and examined its mechanism through CST, thixotropy, plugging, and theoretical analyses, revealing that electrostatic plugging, a house‑of‑cards structure, and thixotropic nanofilms reduce water invasion and shale permeability. Laponite outperformed potassium chloride and poly(ester amine), lowered filtrate volume, and, via integrated electrostatic, structural, and thixotropic effects, effectively inhibited shale hydration, presenting a promising drilling fluid additive.

Abstract

Shale hydration is the main reason causing wellbore instability in oil and gas drilling operations. In this study, nanoscale laponite as a shale inhibitor was employed to stabilize wellbores. The inhibition property of laponite suspensions was evaluated by an immersion experiment, linear swelling measurement, and a shale recovery test. Then the shale inhibition mechanism was studied by using capillary suction time (CST) measurement, a thixotropy study, plugging performance evaluation, and related theoretical analysis. Evaluation experiment results showed that laponite had a better inhibition property than widely used inhibitors of potassium chloride (KCl) and poly(ester amine) (PA). The mechanism study revealed that integration of several factors strengthened the inhibition property of laponite suspensions. Laponite nanoparticles could plug interlayer spaces of clays by electrostatic interaction to reduce water invasion; the "house of cards" structure of laponite suspensions enables large CST values and low free water contents; the excellent thixotropy of a laponite nanofluid could allow a nanofilm to form in order to reduce water invasion into the formation; the nanoscale laponite particles could substantially reduce the shale permeability and form less porous surfaces. Furthermore, laponite could considerably decrease the filtrate volume of the drilling fluid, while KCl and PA had negative influences on the properties of the drilling fluid. This approach described herein might provide an avenue to inhibit shale hydration.