Incorporation of fibres in geothermal well cements

Fibre-reinforced cements are of potential value in geothermal well cementing jobs due to their ability to withstand higher tensile stresses than conventional cements. Screening tests were performed to evaluate different fibre types with the objective of identifying systems offering the greatest improvement in cement tensile strength. The fibres investigated included steel, stainless steel, carbon, basalt and glass. The baseline cement matrix was standard Class G cement/40% silica flour and variations on this were latex-modification and lightweight formulations incorporating either perlite or microspheres. The fibres that showed the best performance at low volume fraction were 13 mm brass-coated round steel fibres. Steel and carbon microfibres also improved the tensile strength provided the volume fraction was high enough. Thermal and hydraulic properties of cements reinforced with steel fibres were measured and compared with unreinforced mixes. Based on the results, selected fibre types will be used in further property characterization studies and engineering analysis of geothermal wells completed with fibre-reinforced materials. # 2002 CNR. Published by Elsevier Science Ltd. All rights reserved.