Experimental Evaluation on Using Coal Combustion Residuals for Controlling Fluid Invasion in Shales

摘要

Drilling fluid invasion into shales is one reason for instabilities while drilling. Invaded drilling fluid affects near wellbore stresses, rock strength, and overbalance wellbore pressure. The fluid invasion is a coupled-transport phenomena mainly due to hydraulic drive and chemical potential drive. The invaded fluid will increase near wellbore pore pressure and reduce effective stresses, therefore the likelihood of wellbore instabilities arise. The flow of fluid through shales’ pores and micro fractures should be mitigated using an effective additives in a water-based drilling fluid system. This paper will experimentally evaluate using of Combusted Carbon Residuals (CCRs) as a shale inhibitor additive. Combusted Carbon Residuals were mechanically grinded. Pressure transient testing was used to evaluate CCRs in a water-based drilling fluid system for controlling fluid invasion into Catoosa shale samples. Also, two chemically made nano silica, AEROSIL & AERODISP were tested in comparison to fine grained CCRs. The testing results shows the positive impact of using fine grained CCRs in controlling fluid invasion rate compared to the conventional water based drilling fluid and the two other nano products were tested.