Mohammadreza Kamyab

Challenges of cuttings transport in micro–borehole coiled tubing drilling for mineral exploration

Coil tubing (CT) technology has been in use in the oil and gas industry since the 1990s. Since then, the applications of CT have expanded rapidly. Coiled tube drilling can offer more efficient and faster drilling operations resulting in lower operational costs. Micro-borehole CT drilling (CTD) has been used in oil and gas applications and is very attractive as a method for minerals exploration drilling due to the faster drilling i.e. high rate of penetration (ROP) that can be achieved resulting in reduced drilling costs. Due to the narrow annulus space there is a certain degree of uncertainty with regards to cuttings transport. In this paper we review the fluid flow and cutting transport models available for conventional drilling. Different aspects of fluid flow in micro-borehole CT will be addressed and discussed. The discussion illustrates the important parameters, including fluid properties, cuttings properties, fluid hydraulics and annular geometry affecting cutting transports in micro-borehole CT drilling in oil and gas as well as mineral exploration.

Rheological properties and slurry behaviour in hard rock drilling

Abstract Coiled tubing (CT) drilling offers more efficient drilling operations compared to normal drilling practises resulting in lower operational costs and drilling time in oil and gas operations. This technology is recommended to be used for mineral exploration drilling in hard rock. This requires drilling micro-boreholes at very high speed with small size cuttings. A large volume of such small size cuttings can influence the rheological properties of the drilling fluids significantly. The aim of this study is to understand the effect of small size inert cuttings on the rheological properties of drilling fluids and its consequences on pressure drop changes in the annulus space. Experimental tests were performed on cuttings collected from a mining site, and the results indicated that the fluid rheology is sensitive to the cuttings size. This conclusion suggests that careful measurement of rheological properties of the mud is necessary when it is designed for drilling hard rocks.