Temperature-Induced Fracture Reconsolidation of Diatomaceous Rock During Forced Water Imbibition

摘要

We conducted a series of forced water-imbibition experiments to study the role of solution pH, temperature, salinity, and various divalent metal ions on silica dissolution and fracture reconsolida-tion of outcrop diatomite core. The experimental results suggest that temperature and pH are two of the most important factors that have an impact on silica dissolution of diatomite, in agreement with the literature. The presence of steam hinders silica dissolu-tion because less aqueous phase is available to carry ions. Fracture healing and rock reconsolidation were observed when fluid was injected at elevated temperature. Tests suggest that both silica dissolution and confining stress are necessary for fracture recon-solidation. Fractures that are not closed by the confining stress do not tend to heal. The proposed mechanism for this process has three steps: (i) aqueous silicate production by silica dissolution, (ii) silicate gelation within the pore space and fracture, and (iii) stress closure of fractures to ensure that deposited silica cements the fracture closed. Given sufficient heating and liquid, fracture reconsolidation occurs.