The United States Qepastment of Energy is involved in a variety of scientific w d engineeribg feasibili$r studies requiring extensivq drilling in hard cryst dline rock. In many cases well depths extwd froxp 6,000 to 20,000 feet in high-temperature, granitic fqw&ioas E~~n p l k s of such projects are the Hot Dry Rock well system at Fentpn Bill, New Mexi& aqd the plwned exploratory p a p well nqw Mammoth Lakes, California. In addition to these p r o g r w , there i s also contipubg interest in

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... porting 9 programs to reduce drilling costs associated with the production of geothermal energy from undergpund sources such as the Geysers area near San Francisco, California. The overd1 progressiop in these efforts is to drill deeper holes in higher temperature, harder formations. In conjunction with this trend is a desire to improve the capability to recqver geological informatioq. Spot wring and continuous coring we important elements in this effort. It iis the purpose pf this report to examine the current methods used to obtaip core from deep wells and to suggest projects which will impmve existing cqpabili t ies ,