| Title | Lab-scale Investigation of Multi Well Enhanced Geothermal Reservoir System |
|---|---|
| Authors | HU Lianbo, Ahmad GHASSEMI |
| Year | 2018 |
| Conference | Stanford Geothermal Workshop |
| Keywords | Enhanced geothermal systems, fracture properties, acoustic emission, spontaneous potential, temperature, tracer |
| Abstract | Geothermal energy production by water circulation in natural and/or man-made fracture systems is referred to as enhanced or engineered geothermal systems (EGS). Good understanding of the induced fracture properties is essential for estimating /evaluating the performance of the system. In this work we study the hydraulically induced fracture properties on a laboratory scale using acoustic emission (AE) cloud, spontaneous potential (SP), cold water circulation and tracer analysis. To achieve this goal, we first have performed reservoir stimulation using 13x13x13 inch3 cubical rock samples under representative in-situ stress regimes. And then the rock block was heated up to a uniform temperature about 70 degrees Celsius. Cold water was injected into the central well and collected from nearby multi production wells. Tracer test was conducted to investigate the fracture volume and connectivity between the injection well and production wells. In stimulation phase, excellent correlation between SP and pressure drop was observed, also the AE event cloud had a good agreement with the overall fracture shape. During circulation, temperature in the wells and on the block surfaces was recorded. The maximum temperature drop was as high as 52.6 oC in the injection well and about 23.8 oC in one production well and 10 oC in another production well. Tracer test recording shows some result predicted by numerical simulation and the fracture volume was calculated with method of moments. 3D fracture geometry was reconstructed after the tested block was cut into slabs. This work provides valuable data to investigate the fracture properties to obtain a better understand of the fluid/heat flow in the EGS system. |