Publications
Development and testing of insulated drillpipe
The Geothermal Research Department at Sandia National Laboratories, in collaboration with Drill Cool Systems, Inc., has worked to develop and test insulated drillpipe (IDP). IDP will allow much cooler drilling fluid to reach the bottom of the hole, making possible the use of downhole motors, electronics, and steering tools that are now unusable in high-temperature formations. Other advantages of cooler fluid include reduced degradation of drilling fluid, longer bit life, and reduced corrosion rates. The paper describes the theoretical background, laboratory testing, and field testing of IDP. Structural and thermal laboratory testing procedures and results are described. Results are given for a field test in a geothermal well, in which circulating temperatures in IDP are compared with those in conventional drillpipe (CDP) at different flow rates. A brief description of the software used to model wellbore temperature and to calculate sensitivity to IDP design differences is included, along with a comparison of calculated and measured wellbore temperatures in the field test. Analysis of mixed (IDP and CDP) drill strings and discussion of where IDP should be placed in a mixed string are presented.