Performance of nanoparticles as fluid loss additives in polymer-clay drilling fluids

Abstract

As oil discoveries become deeper and hostile, there is a need to improve the existing drilling fluids or to design a new ones which is more environmentally friendly with zero impact on the environment. Polymers and bentonite have been used as viscosifier and fluid loss control in drilling fluids and also can be used in almost any type of water and as a suspending agent. The applications of nanoparticles in drilling fluids is mainly to form a thin layer of non-erodible and impermeable nanoparticles membrane around the wellbore which prevents common problems like clay swelling, spurt loss and mud loss due to the circulation. The nanoparticles have high surface to volume ratio, therefore for any application the quantity of nanoparticles required will be less and hence there is cost advantage. In this study, the performance of nanosilica and multi walled carbon nanotubes (MWCNT) as fluid loss additives in polymer-clay mud were investigated at HPHT conditions with varying nanoparticles concentration and temperature. Before aging, plastic viscosity, yield point and gel strength of mud with nanoparticles shows an increasing trend as the concentration of nanoparticles increased from 0.01g to 1g. Mud with nanosilica gives the highest filtrate loss of 12ml and mudcake thickness of 10.24inch at 1g concentration and 300°F.Whereas, mud with MWCNT shows a decreasing trend in filtrate loss and mudcake thickness as nanoparticles concentration increased. However, filtrate loss for mud with nanoparticles is still high as compared to control mud. The finding shows that xanthan gum containing 1g MWCNT gives 4.9ml filtrate loss and mudcake thickness of 4.48inch at 200°F. After aging, plastic viscosity, yield point and gel strength of mud containing nanoparticles decrease significantly especially for 1g of nanosilica and 0.01g MWCNT. Filtrate loss and mudcake thickness also increased when the mud is exposed to temperature above 250°F. As a conclusion, xanthan gum with MWCNT gives a promising result in terms of rheological performance and form a thin, stable and uniform mudcake.