Title:

The EGS Collab Project: Learnings from Experiment 1

Authors:

Timothy J. KNEAFSEY, Doug BLANKENSHIP, Patrick F. DOBSON, Joseph P. MORRIS, Mark D. WHITE, Pengcheng FU, Paul C. SCHWERING, Jonathan B. AJO-FRANKLIN, Lianjie HUANG, EGS COLLAB TEAM

Key Words:

enhanced geothermal systems, EGS Collab, stimulation, crystalline rock, Sanford Underground Research Facility, coupled process modeling, experimental, field test, flow test

Conference:

Stanford Geothermal Workshop

Year:

2020

Session:

EGS Collab

Language:

English

Paper Number:

Kneafsey

File Size:

1687 KB

View File:

Abstract:

The primary objective of the EGS Collab Project sponsored by DOE is to increase the understanding needed to efficiently implement enhanced geothermal systems (EGS). One goal of the EGS Collab project is to create a collaborative research environment in which to study stimulation of crystalline rock at the 10 meter scale. Key to this effort is the collection of high quality data during stimulation and flow tests to allow comparison to numerical coupled process models in an effort to build confidence in the codes and modeling techniques used. In response to this research need, the EGS Collab team has created an underground test bed at the Sanford Underground Research Facility (SURF) in Lead, SD at a depth of approximately 1.5 km to examine hydraulic fracturing (Experiment 1). We are currently designing a second test bed aimed at investigating shear stimulation (Experiment 2). At the Experiment 1 location, we have characterized our host rock using laboratory testing and numerous field-based geophysical and geologic techniques, and created a well-instrumented test bed to allow us to carefully monitor fracture stimulation events and flow tests. In addition to the installed geophysical sensors, we have used tracer tests, differences in the ambient microbial communities at flow collection locations, and cold water injection to inform us about dynamic flow pathways. In Experiment 1, we have hydraulically stimulated the host rock a number times at several locations in one well, creating new fractures that connect to existing fractures between the injection and production boreholes. We have performed long-term ambient and chilled water injection tests as an analog to EGS, and have monitored system changes resulting from these water injections through geophysical monitoring, flow and pressure measurements, tracer tests, and microbiology. Here, we summarize the tests performed, issues identified including poroelastic and thermoelastic effects, Joule-Thomson effects, restarting effects, indications of flow channeling, and the primary learnings to date from Experiment 1.


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