Mechanism of Silica Deposition in Formation and Management Options Investigated in Laboratory Study

Abstract

Managing silica scaling in plant surface facilities, injection wells and near-wellbore formation is a major challenge in geothermal field operations. Determining which management option is appropriate depends on the overall understanding of the mechanism of silica deposition both at the surface and within the reservoir formation. Factors driving silica deposition in plant facilities and injection wellbores seem to be well understood and hence effective control of scaling has been implemented by several geothermal plant operators, such as the use of pH-modification technology. The mechanism of silica deposition in a near-wellbore formation however is not as well understood.
A series of autoclave experiments were conducted to study silica scaling in a near-wellbore formation. These experiments were mostly designed to investigate water-rock interaction of acid-dosed brine with greywacke and its influence on silica deposition. These tests have been used to understand things such as the effects of adding chemical inhibitor and filtrate injection from a silica extraction plant. This paper discusses the autoclave testing methodology and how the results of the study provide better understanding of the mechanism of silica deposition in the reservoir formation, including how the autoclave testing can be used to assist with pre- and post-development risk mitigation.