Patching Hele-Shaw Cells to Simulate Silica Scale Deposition in Discrete Fracture Networks

Abstract

Due to mineral deposition in geothermal reservoirs, the electrical production of geothermal power plants decreases over time. Specifically, silica can form extremely hard and dense scales not only in power-plant equipment and pipelines but also within and around wells, restricting flow and reducing power-plant efficiency. Understanding the effect of silica scaling on flow rates can inform the required maintenance during different stages of the geothermal plant lifetime. Accordingly, a detailed analysis of silica scale growth offers powerful insight to predict the productive lifetime of the reservoir and mechanical infrastructures. Fluid within many geothermal reservoirs is largely transported along a network of fractures. However, available simulation methods to study mineral deposition within large-scale fracture networks are computationally expensive. We have developed a new modeling framework based on representing individual fractures using the Hele-Shaw cell analogy and simulating fracture networks by connecting these Hele-Shaw cells together using pressure constraints at intersecting nodes of the computational mesh. This methodology allows the rapid computation of flows in realistically large fracture networks. This paper will discuss how this modeling framework can be used to study the transport of diluted specious in rock fractures, which provides a backbone for the simulation of silica scale deposition in a discrete fracture network.