Experimental Study on Eco-Friendly Additives for Improving Water-Based Drilling Fluid Stability at High Temperature Application

With the trend towards increased drilling of high-temperature wells, as well as the requirement to use eco-friendly drilling fluids, additional demands are being placed on water-based drilling fluids (WBDFs) to address issues such as high-temperature flocculation of clay particles and to reduce fluid losses. Higher temperatures in deep well drilling are known to have effect drilling mud rheological and gel properties; the gel strength being the most affected as compared to viscosity. In order to counter high-temperature effects, which can flocculate bentonite or clay additives it is required to minimize the solids content and maintain the use of stable flocculation control. Another significant issue when drilling high-temperature wells using WBDFs is formation damage and wellbore instability caused by fluid invasion.
This study will focus on examining 3 types of WBDFs with two potential environmentally safe additives for each purpose, Sodium Tripolyphosphate Technical Grade, 85% (STPP) for flocculation control and Suspension of Cellulose Nanocrystals as a filtration control. The sequences are started with preparing the equipment and drilling fluid samples, ageing the drilling fluids at desire high temperature application either 140oC or 160oC depends on the WBDFs type for 16 hours, then respectively tested for flocculation and filtration measurement, followed by mud density, pH, rheological measurement, then finalized with performing thixotropy and hysteresis measurement.
From the three types of Water Base Drilling Fluids (WBDFs), which have been evaluated on this Master Thesis, for flocculation control, STPP with 0.1% is proven to improve Clay Water Base Drilling Fluid (CWBDF) with 65% liquid yield recovery which is better than CWBDF main composition, and with the other two STPP concentrations added to the main composition. While for filtration control, 0.5% Cellulose Nanocrystals (CNC) concentrations can decrease filtration volume of CWBDF to 17 ml while providing sufficient filter cake of 3/32” which is providing the better result than the other BWBDF compositions tested. Overall, STPP and CNC works best for CWBDF than Clay Polymer Water Base Drilling Fluid (CPWBDF), and Polymer Water Base Drilling Fluid (PWBDF). From the experimental results and analysis, both STPP and CNC have been showing a good result to improve drilling fluids performance when applied for WBDFs in high temperature application.