Evaluation of grouting materials for drill-hole abandonment
- Montana Bureau of Mines and Geology, Billings, MT (United States)
- Dept. of Environmental Quality, Billings, MT (United States)
Proper grouting of boreholes and wells is the principle step in avoiding adverse impacts to ground-water resources from drilling activities. Several bentonite and cement-based grouts were evaluated in this research. Bentonite produces a hydraulically competent, flexible hydraulic seal; whereas, cement produces a strong, rigid seal. Of the grouts tested, bentonite tends to re-establish a seal if it is disturbed, whereas cement-based grouts do not reseal. In seismic-shot holes, both low- and high-grade bentonite performed well, except in one low-grade plugged hole where a blow-out occurred. In an unobstructed borehole at depths of as much as 2,000 feet, gravity-fed bentonite chips appear to provide the best seal, being both hydraulically and physically strong. If obstacles such as centralizers on well casing preclude the use of chips, then a high-solids bentonite slurry provides an excellent flexible grout and can be installed with pump pressures of 200 psi or less. Slurries should contain at least 8 percent (preferably more) bentonite by volume. Volumetric (not weight based) measurement of solids content of abandonment slurries is appropriate. Of the grouts tested, neat-cement is the most expensive technique at about $3.75/foot in a 6-inch hole. Bentonite-slurry grouts are about $2.65/foot and high-grade bentonite chips are about $1.60/foot. Low-grade bentonite chips are less expensive than high-grade chips, but the exact amount is difficult to determine because no commercial mines are currently selling low-grade products.
- OSTI ID:
- 272663
- Report Number(s):
- CONF-9607116-; ISSN 0149-1423; TRN: 96:003409-0072
- Journal Information:
- AAPG Bulletin, Vol. 80, Issue 6; Conference: American Association of Petroleum Geologogists (AAPG) Rocky Mountain section meeting, Billings, MT (United States), 28-31 Jul 1996; Other Information: PBD: Jun 1996
- Country of Publication:
- United States
- Language:
- English
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