Evaluation of the pumpability of bentonite-based grouts. Final report

Technical Report · Sat Nov 01 04:00:00 EST 1997

OSTI ID:354805

Selection of an appropriately sized pump for grouting geothermal boreholes with bentonite based grouts has been without scientific and technical basis. Prior experience with a particular grout with the actual tremie size to be used as required before it was known what pump size was needed. Oversizing the pump has always been an option, but the higher the pressure and flow rate a pump is capable of producing, the more the pump will cost. The loop installer will want to keep costs to a minimum in order to keep cost to the customer more competitive. Therefore, being able to properly size a grout pump for its intended use is very important for the beginning as well as the established loop installer. Laboratory tests were conducted to determine the pumping properties of currently available bentonite grouts. The data were used to develop a flow model for predicting the pumping pressure of any of the grouts that were tested. Full-scale pumping tests were then conducted on the various bentonite grouts in order to verify the flow model. The flow model did not correlate well with actual pumping data. Flow model parameters were derived from the pumping data, and a best fit flow model was developed. The best fit flow model provided better predictions for pumping pressure for a given grout, tremie size, and flow rate. Laboratory tests were also performed on bentonite grouts with sand additive. This represented a thermally enhanced grout. Similar experiments which were run with the bentonite-only tests were run with the bentonite and sand tests. The data from full-scale pumping tests with sand were used to develop a flow model which could then be used to predict the pumping pressure of any of he grout/sand mixtures that were tested. Since the bentonite-only testing revealed that the flow model developed from viscometer data was not an accurate predictor of actual pumping pressures, the full-scale pumping data was used to develop the flow model. This resulted in a best fit flow model in order to better predict bentonite with sand mixture pumping pressures.

• Research Organization: Electric Power Research Inst., Palo Alto, CA (United States); South Dakota State Univ., Brookings, SD (United States)
• Sponsoring Organization: Electric Power Research Inst., Palo Alto, CA (United States)
• OSTI ID: 354805
• Report Number(s): EPRI-TR--109163
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
BENTONITE
EXPERIMENTAL DATA
FLOW MODELS
GEOTHERMAL WELLS
GROUTING
PUMPS
RHEOLOGY
SIZE
THEORETICAL DATA
VALIDATION