Abstract

ABSTRACT An operational wellbore friction simulator (WBFS) utilizing full-scale components for measuring drillstring torque and drag in simulated high-angle holes is described. The 15-ft long test section accommodates 8.5-inch (216-mm) to 12.25-inch (311-mm) ID permeable and cased wellbore inserts. Drilling and tripping operations at angles of 45-90° from vertical are simulated by moving a full-scale tool joint along a 4.0- inch (102-mm) diameter drive shaft. Axialvelocity 0-110 ft/min (0-0.559 m/s) and rotational speed 0-165 rpm represent typical field conditions. The wellbore insert can be pressed against the tool joint with a contact force up to 1000 Ibf (4448 N). The WBFS was used to study effects of six operating factors on friction coefficients of unweighted lignosulfonate mud with and without a lubricant. Simulated cuttings beds were added for half of the tests. Effects of cuttings beds on friction coefficient were unexpected. In WBFStests, cuttings beds composed of crushed coal slag reduced friction coefficient. Results from large-scale WBFS tests with bare wellbore generally agree with results from certain small-scale lubricity tests. The WBFS results clearly show benefits to using top drives which allow rotation while tripping.

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