Title: Development of an Environmentally Friendly and Ecomomical Material for Plugging Abandoned Wells
Author(s): Hyun Cho and Subhash Shah
Presentation: Integrated Petroleum Environmental Consortium, Houston, TX, November 2001
Abstract: The primary importance of plugging to abandon a well is to prevent contamination of groundwater aquifers by surface water, oil or gas seepage, or brine formations below the groundwater aquifers. Cement grout is the present material used in plugging. Fly ash is known to have properties very similar to cement and can be produced with strength similar to cement. Presently, only about half of the fly ash produced by the various coal-fired power plants is used and the rest must be treated as a waste product and disposed of in landfill. Much of this fly ash is the higher lime content, more cementitious, Class C fly ash.
The present research is funded by Integrated Petroleum Environmental Consortium (IPEC). This research reveals Class C fly ash can be retarded like cement when slurried and it can be pumped and placed like cement with coiled tubing instead of employing a rig. To ensure a comprehensive understanding fly ash grout characteristics as a cement material, the extensive experiments were performed. These involved chemical composition, size distribution, compressive strength, thickening time, durability, and rheology of fly ash slurry. Effects of various additives on the characteristics of fly ash slurries were investigated by the extensive experiments. This paper specifically describes the process developed by the Well Construction Technology Center at the University of Oklahoma to formulate the best fly ash grout. This research results provide a cheaper, environmentally friendly, and more economical material for plugging wells.
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