SBIR-STTR Award

We are proposing research to demonstrate the feasibility of encapsulating bentonite chips to enable them to successfully reach greater plugging depths. APPROACH: Sodium bentonite chips are recognized as a superior well sealing/plugging material for shallow wells. Its tremendous ability to swell when hydrated allows it to resist dislodgement pressures of hundreds of pounds per square inch. Additionally, it is inert, durable, self-healing if disturbed and more economical than Portland cement. NON-TECHNICAL SUMMARY: What can be done to ensure a high level of water quality for wildlife, agriculture, and humans around the world? More and more wells, whether they are for water, oil and gas, or coal-bed methane, are deeper than ever and are at risk from surface pollution and inter-aquifer mixing. Cement, long known as the only alternative, has been shown to have serious drawbacks. This proposal builds on previous research that has demonstrated bentonite sealing and plugging characteristics. Sodium bentonite chips are recognized as a superior well sealing/plugging material for shallow wells. Its tremendous ability to swell when hydrated allows it to resist dislodgement pressures of hundreds of pounds per square inch. Additionally, it is inert, durable, self-healing if disturbed and more economical than Portland cement. But its swelling capacity also makes it difficult to deliver successfully to well depths much deeper than 500 feet. We expect to find compounds and/or materials that will economically transport bentonite chips to well depths over 500 feet. This technique must maintain bentonite's superior sealing characteristics and be economical to ship and to handle at the well site. Successful research will lead to a prototype that will greatly expand bentonite's use as a low cost, safe, superior sealing solution for abandoned drill holes. Primary commercial benefactors are: oil and gas exploration/drilling companies, coal-bed methane producers, water well drillers, and others who will no longer be required to use much more expensive, less safe well-sealing technologies.

Keywords:
well-plugging; well-sealing; bentonite; encapsulation; well abandonment; groundwater protection

Water is the essence of life. Few will disagree that it is a resource that must be protected for the well-being of all: plant and animal. Millions of holes have been and are being drilled in the earth to search for water, uranium, oil and gas, and coal-bed methane. Many thousands of these holes are mid-depth (500-4500 feet) and fill with water if the drills penetrate one or more aquifers. When these water-containing drill holes are abandoned, soil stability and the purity of that exposed groundwater are threatened. A product is needed that is superior to Portland cement, which historically has been the recommended sealing material. But because of cement's heat of hydration and rigidity it can cause stability problems in certain soils, applications and where ground motion is a concern. Additionally, bentonite seals do not alter pH as does cement and can 'heal' if damaged. 'Healing' refers to bentonite's ability to fill in fissures caused by earth or drill casing movement. Currently a technology does not exist to satisfactorily plug mid-depth drill holes without cement. We intend to develop the most ecologically-beneficial, user-friendly, and cost-effective product to seal mid-depth drill holes. The product must be economical to ship and must be easy for a non-technical person to handle at the well site. This product will prevent loss of water (or other natural resources), groundwater contamination from surface chemicals, inter-aquifer mixing, and subsidence which can occur with conventional cement plugging techniques.