Preparation of Early-strength Protective Wall Plugging Cement for Fractured Geothermal Deep Wells

Abstract

The development of geothermal energy is progressing rapidly, but the solutions for well wall instability and leakage in fractured geothermal deep wells are not perfect. The existing protective wall plugging cement has a setting time of more than 24 hours, low early strength, and not much pumpable period. This paper prepared an early-strength protective wall plugging cement suitable for fractured geothermal deep wells. The results show that: a) Calcium formate is preferably used as a set-adjusting agent in cement components through the influence of setting time, uniaxial compressive strength compressive, and flow characteristics, Silica fume is used as the early strength agent component, and the naphthalene pumping agent is used as the pumping agent component. b) Through the orthogonal test, the cement formulations suitable for different depths are screened out. The compressive strength of the cement stone has reached 3.5MPa or more when the setting time is 16 hours, and the pumpable period can be adjusted from 40~120min.