Developed Wellbore Abandonment Grout with Fly Ash

摘要

The primary importance of plugging to abandon a well isrnto prevent contamination of groundwater aquifers by surfacernwater, oil or gas seepage, or brine formations below therngroundwater aquifers. Cement grout is the present materialrnused in plugging. Fly ash is known to have properties veryrnsimilar to cement and can be produced with strength similar torncement. Presently, only about half of the fly ash produced byrnthe various coal-fired power plants is used and the rest must berntreated as a waste product and disposed of in landfill. Much ofrnthis fly ash is the higher lime content, more cementitious,rnClass C fly ash.rnThe present research has been funded by IntegratedrnPetroleum Environmental Consortium (IPEC). This researchrnreveals Class C fly ash can be retarded like cement whenrnslurried and it can be pumped and placed like cement withrncoiled tubing instead of employing a rig. To ensure arncomprehensive understanding fly ash grout characteristics as arncement material, the extensive experiments were performed.rnThese involved chemical compositions, size distribution,rncompressive strength, thickening time, durability, andrnrheology of fly ash slurry. Effects of the various additives onrnthe characteristics of fly ash slurries were investigated by thernextensive experiments. Frictional pressure loss tests were alsornperformed with field size equipment in order to apply coiledrntubing technology in placing fly ash slurry to the downhole ofrnwellbores. Fly ash formulations chosen as the best candidatesrnwere pumped through a 2000 ft reeled of 1 ?-in. tubing and arn20 ft straightened 1 ?-in. tubing to determine frictionalrnpressure characteristics. This paper specifically describes arnprocess developed by the Well Construction TechnologyrnCenter at the University of Oklahoma to formulate the best flyrnash grout. This research results provide a cheaper,rnenvironmentally friendly, and more economical method ofrnplugging wells.