Hole fluids for deep ice core drilling

This paper is based on the data published in reseurch report of P,G, Talalay and N,S, (inndestrup: Hole fluids for deep ice core clrMing: A review. Copenhagen University, Copenhagen, 1999. 12ep, ln the practice ofdeep ice petroteum oll core drilling on[y three t),pes of bore-hole fiuidshave been usedi 1) products (fueLs er solvents) containing densifier. 2) aqueous etbylene glycol ethunol soLutions, 3) n-butyi acetate, The main parameters ofdrilling fluids are 1) denslry and fluid top: 2) viscosity: 3) fi'ost-reslstance; 4} stability: 5) compatibility ",ith polymers and metats: 6) vo[atility; 7) fiammabilit}': 8) ice and waler solubility: 9) toxicological and enx,ironmental characterisEics: 10} coht. The main propertics of bore-hole fiuids which have been used in practiee for deep ice dritling as well as potential bore-hole fluids are described, The ana]yzing ef the property's data showed that there are no ideal drilling fiuids, All types er used and potential dril]ing fluids huve their own advantages and disadvantuges. Prebabl}, one of the most promising types of driMng fiuid is low-temperature siLicone oil. It is non-aggressive. inert. and non-toxic. 'I'he main prohlern of silicone oil use is the re[atively high viscosity at negative tempei'atures thut have inHucnce on the travel time ot' the driLi string and finally on the total time drilling, The final choice of the drilling fluid epends on the possibilities and the ways of solving orindicating problems and depends on the rational correlatien between the cos! ofdriHing fluid and c}ther properties ofthe fiuid.