Integrated Approach to Use Natural Chemical and Isotopic Tracers to Estimate Fracture Spacing and Surface Area in EGS Systems Geothermal Lab Call Project

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Last modified on July 22, 2011.

Project Title Integrated Approach to Use Natural Chemical and Isotopic Tracers to Estimate Fracture Spacing and Surface Area in EGS Systems
Project Type / Topic 1 Laboratory Call for Submission of Applications for Research, Development and Analysis of Geothermal Technologies
Project Type / Topic 2 Tracers and Tracer Interpretation

Project Description To provide a sustainable heat extraction rate, an EGS system requires adequate circulation of the working fluid through a heat exchanger, which is comprised of a network of open fractures. The permeability of the fracture network constrains the fluid flux, and the surface area of the matrix rocks in contact with the fluid constrains the power or efficiency of the heat exchanger. Consequently, these parameters (surface area and permeability) are crucial for determining the capacity and longevity of EGS systems.

At present, there are no proven techniques for quantifying the surface area for heat exchange along a fluid flow path or the change in surface area created by well stimulation. Although considerable effort has been made in developing conventional tracers for characterizing geothermal reservoirs, most of these studies have focused on estimating well-to-well connectivity, flow rates, residence times associated with connectivity and sweep volumes, rather than fracture surface area. Exceptions are recent studies that propose to develop a combination of conservative and sorbing tracers to determine fracture surface areas in liquid-dominated reservoirs.

State California
Objectives Develop an innovative approach to estimate the change in fracture surface area induced by well stimulation using natural chemical and isotopic tracers.
Awardees (Company / Institution) Lawrence Berkeley National Laboratory

Funding Opportunity Announcement DE-PS36-09GO99017

DOE Funding Level (total award amount) $941,000.00

Total Project Cost $941,000.00

Principal Investigator(s) B. Mack Kennedy

Targets / Milestones To quantify mineralogy of the rock and the chemical composition of the fluid for incorporation into the numerical models, LBNL will conduct a series of laboratory experiments using reservoir rocks from EGS systems that have been mineralogically characterized and fluids that approximate the chemistry of the fluids that will be injected into the systems. The project is broken into 3 main tasks:

- Reactivity measurements: A series of experiments will be conducted to evaluate the reactivity of different solutes as a function of surface area, temperature, fluid chemistry and time.
- Development of the tracer-interpretation technique, through iTOUGH2
- Evaluation and verification

Location of Project Berkeley, CA
37.8715926°, -122.272747°

Funding Source American Recovery and Reinvestment Act of 2009

References EERE Geothermal Technologies Programs[1]


  1. EERE Geothermal Technologies Programs