U.S. Department of Energy - Energy Efficiency and Renewable Energy

Geothermal Technologies Office

Request for Information: Critical Parameters for Characterization of Enhanced Geothermal Systems (EGS)

U.S. Department of Energy/Energy Efficiency & Renewable Energy EERE 104: Request for Information (RFI)
DE-FOA-0001074

 

Critical Parameters for Characterization of Enhanced Geothermal Systems (EGS)
January 21, 2014

 

Download the official document from EERE-Exchange to provide the feedback here.

DESCRIPTION: The commercial viability of Enhanced Geothermal Systems depends on three broad areas:

  • Reservoir productivity (measured via flow rate per production well) that is sufficient to achieve multi-megawatt power production levels.
  • Sustained production of high-temperature fluids over a 20-30 year interval.
  • Development of replicable, high-performing, sustainable EGS systems in various geologic settings throughout the United States.

Success in achieving each of these elements depends, to a varying degree, on the ability to measure, infer, calculate, and understand the implications of various subsurface parameters. These parameters will evolve over time as an EGS resource advances through its three development phases. EGS developments begin with native, in-situ geologic conditions, then progress to a stimulation phase where native conditions are altered through a variety of engineering methods, and finally reach an operation phase where the heat resource is extracted over long time-scales.

The Geothermal Technologies Office (GTO or the Office) seeks feedback from stakeholders in two areas:

  • The identification of governing subsurface parameters, as well as their relative importance within the three development phases, and
  • An assessment of the level of constraint for each of these parameters (i.e., well constrained to poorly constrained).

BACKGROUND:
Identifying the key governing parameters for EGS, as well as understanding how these parameters change throughout the three EGS development phases, is critical to achieving commercial viability of EGS. As part of this, advancing state-of-the-art means for measurement and quantification of these governing parameters, to acceptable level of precision and accuracy, are necessary achievements.

By understanding the importance and constraints of various subsurface parameters, DOE is able to target and prioritize its limited funding on field characterization activities that are most impactful to EGS development.

PURPOSE:
The purpose of this RFI is to solicit feedback from industry, academia, research laboratories, government agencies, and other stakeholders on issues related to subsurface characterization for engineering of Enhanced Geothermal Systems. Specifically, EERE is interested in information on the relative importance of subsurface parameters as they relate to overall EGS performance. This is solely a request for information and not a Funding Opportunity Announcement (FOA). EERE is not accepting applications.

DISCLAIMER AND IMPORTANT NOTES:
This RFI is not a Funding Opportunity Announcement (FOA); therefore, EERE is not accepting applications at this time. EERE may issue a FOA in the future based on or related to the content and responses to this RFI; however, EERE may also elect not to issue a FOA. There is no guarantee that a FOA will be issued as a result of this RFI. Responding to this RFI does not provide any advantage or disadvantage to potential applicants if EERE chooses to issue a FOA regarding the subject matter. Final details, including the anticipated award size, quantity, and timing of EERE funded awards, will be subject to Congressional appropriations and direction.

Any information obtained as a result of this RFI is intended to be used by the Government on a non-attribution basis for planning and strategy development; this RFI does not constitute a formal solicitation for proposals or abstracts. Your response to this notice will be treated as information only. EERE will review and consider all responses in its formulation of program strategies for the identified materials of interest that are the subject of this request. In accordance with the Federal Acquisition Regulations, 48 C.F.R. 15.201(e), responses to this notice are not offers and cannot be accepted by the Government to form a binding contract. EERE will not provide reimbursement for costs incurred in responding to this RFI. Respondents are advised that DOE is under no obligation to acknowledge receipt of the information received or provide feedback to respondents with respect to any information submitted under this RFI. Responses to this RFI do not bind EERE to any further actions related to this topic.

PROPRIETARY INFORMATION:
Because information received in response to this RFI may be used to structure future programs and FOAsand/or otherwise be made available to the public, respondents are strongly advised to NOT include any information in their responses that might be considered business sensitive, proprietary, or otherwise confidential. If, however, a respondent chooses to submit businesssensitive, proprietary, or otherwise confidential information, it must be clearly and conspicuouslymarked as such in the response.

Responses containing confidential, proprietary, or privileged information must be conspicuously marked as described below. Failure to comply with these marking requirements may result in the disclosure of the unmarked information under the Freedom of Information Act or otherwise. The U.S. Federal Government is not liable for the disclosure or use of unmarked information, and may use or disclose such information for any purpose.

If your response contains confidential, proprietary, or privileged information, you must include a cover sheet marked as follows identifying the specific pages containing confidential, proprietary, or privileged information:

Notice of Restriction on Disclosure and Use of Data:
Pages [list applicable pages] of this response may contain confidential, proprietary, or privileged information that is exempt from public disclosure. Such information shall be used or disclosed only for the purposes described in this RFI (DE-FOA-0001074). The Government may use or disclose any information that is not appropriately marked or otherwise restricted, regardless of source.

In addition, (1) the header and footer of every page that contains confidential, proprietary, or privileged information must be marked as follows: "Contains Confidential, Proprietary, or Privileged Information Exempt from Public Disclosure" and (2) every line and paragraph containing proprietary, privileged, or trade secret information must be clearly marked with double brackets or highlighting.

EVALUATION AND ADMINISTRATION BY FEDERAL AND NON-FEDERAL PERSONNEL:
Federal employees are subject to the non-disclosure requirements of a criminal statute, the Trade Secrets Act, 18 USC 1905. The Government may seek the advice of qualified non-Federal personnel. The Government may also use non-Federal personnel to conduct routine, nondiscretionary administrative activities. The respondents, by submitting their response, consent to DOE providing their response to non-Federal parties. Non-Federal parties given access to responses must be subject to an appropriate obligation of confidentiality prior to being given the access. Submissions may be reviewed by support contractors and private consultants.

REQUEST FOR INFORMATION CATEGORIES AND QUESTIONS:
Responses to this RFI are requested on the two sections described below:

Section 1: Identification and Relative Priority of Subsurface Parameters for EGS Development

In response to Section 1, information is requested on the identification and relative importance of the ability to accurately and precisely measure, infer, and/or calculate various reservoir parameters during three phases of EGS development (Native, Stimulation, and Operation) to achieve the objectives of each phase, as defined below.

After reviewing the definitions, objectives, and Table 1 below, GTO seeks detailed responses to Section 1 of this RFI as follows:

  1. Please review Table 1 and comment on the accuracy of the categorization of the level of priority per phase for each subsurface parameter. If you agree with the placement of parameters in each of the phases in their respective "Critically Important," "Important but Not Critical," and "Of Less Importance" priority levels, simply leave them in their current positions.
    • If you would like to change the relative priority of a parameter within the table, please highlight the parameter in yellow and notate the update to the priority level in parenthesis. Please use "(CI)" for Critically Important, "(INC)" for Important but Not Critical, and "(LI)" for Of Less Importance, for example "Fracture Length Distribution (INC)" communicates the change of Fracture Length Distribution to Important but Not Critical. Please provide a rationale for this change (e.g., results from a numerical model, constitutive relationship, empirical field evidence, etc.) in comments below the table.
  2. Please add parameters in red text that have been omitted, and include a rationale for their inclusion, as well as the assignment of their relative importance in comments below the table.
  3. Please delete parameters that are of no importance (please use strikethrough effect), and include a rationale in comments below the table.

Native Phase
Description: This represents the phase of EGS development where the potential reservoir has not yet been accessed through drilling of an exploratory or production well to the target depth. Offset or shallow wells may be drilled, but characterization is typically achieved through remote means. Parameters for consideration in this phase are those that help determine the viability of a target for geothermal engineering activities and development.

Objective(s): Determine the optimum targets (depth, lithology, wellbore orientation) for drilling and stimulation of well(s).

Stimulation Phase
Description: Access to the formation/target depth has been achieved through drilling of exploratory or production-sized well(s). Rock cuttings and core logs have been collected successfully from relevant lithologies. EGS project development activities focus on enhancing and/or creating permeable flow paths for fluid circulation and long-term heat extraction. Parameters for consideration in this phase are inputs into the design and execution of reservoir stimulation(s), as well as those parameters that diagnose the effectiveness/results of the stimulation(s) as they relate to long term system heat extraction performance.

Objective(s): Execute stimulation(s) in target well(s). The objective of the stimulation(s) is to engineer a reservoir that, with the completion of additional wellbores, can support multiple megawatts of power generation. As a result of the stimulation phase, thermal drawdown of the produced fluid should be minimized over the economic lifetime of the power production facilities (>20 years). The performance target is 5 MWe and greater per production well within an EGS system. Production rates of 80-100 kg/sec of 200º C fluids are required for ~ 5 MW of power generation from an air-cooled binary power plant.

Operation Phase
Description: Multiple wells for fluid injection and production have been successfully stimulated, and a power plant has been constructed. The EGS development enters long term operations. Transient pressure effects from the stimulation phase have diminished, and coupled thermal and chemical processes are likely to dominate system behavior/dynamics. Parameters for consideration include reservoir properties that have been modified during the stimulation phase, as well as the evolution of those properties over time. Reservoir management techniques can be employed to maintain reservoir pressure and minimize thermal drawdown.

Objective(s): Fluid mass production rate and the temperature are ideally constant over the economic lifetime of the power plant facilities (>20 years). Operational percent fluid loss, as measured by the ratio of injected mass to produced mass, must be less than a few percent per year to be economically sustainable.

Table 1. Identification and Relative Priority of Subsurface Parameters, by Phase

Priority Level Native Phase Stimulation Phase Operation Phase

Critically Important (CI)
Achieving the objective(s) of the phase is highly sensitive to these parameters

  • Temperature and pressure at depth
  • Location and geometry of features/faults
  • Hydraulic properties of features/faults
  • Lithology/ formation at target depth
  • Lithologic units/zones of hydrothermal alteration/mineralogical composition
  • Fracture orientation distribution
  • Fracture length distribution
  • Fracture transmissivity
  • Magnitude and orientation of principal stresses
  • Matrix to fracture heat transfer area
  • Fracture spacing
  • Formation/volume/bulk stiffness
  • Wellbore pressure/hydraulic test data
  • Mechanical properties of fracture secondary minerals in fracture (friction coefficient, sliding stability, ductility, etc.)
  • Sonic velocity profiles
  • Degree of saturation
  • Thermal expansion coefficient
  • Fluid mean residence time
  • Thermal-coupling parameters (thermal conductivity and heat capacity)
  • Production and injection fluid properties (density, viscosity) and chemistry
  • Reservoir temperature profiles
  • Chemical properties of fracture/secondary minerals in fracture
  • Swelling properties of secondary minerals (clays)

Important but Not Critical (INC)
Achieving the objective(s) of the phase is somewhat sensitive to these parameters

  • Gravity
  • Electric and magnetic properties
  • Regional geologic structures/analogue outcrops/offset well data
  • Porosity
  • Volume and location of injection induced acoustic emission
  • Dilation angle
  • Fracture aperture distribution
  • Stimulation fluid and flow-back fluid geochemistry
  • Rock mechanical properties (Young's moduli, Poisson ratios, cohesion, compressive strength, shear strength, tensile strength, etc.)
  • Friction coefficients
  • Rate and state parameters to describe frictional stability (i.e.; a, b, Dc)
  • Rock density
 

Of Less Importance (LI)
Achieving the objective(s) of the phase is not especially sensitive to these parameters

     

Comments

  •  
  •  

Section 2: Constraint of Parameters

For Section 2, information is requested on the level of constraint of each of the aforementioned reservoir parameters, and how much improvement beyond the current state-of-the-art would be possible, as defined below.

After reviewing the definitions and Table 2 below, GTO seeks detailed responses to Section 2 of this RFI as follows:

  1. Please identify the proper level of constraint for the subsurface parameters identified in Table 2 by checking the appropriate constraint level per parameter. Please update Table 2 with changes you made based on your response to Section 1. If necessary, additional parameters can be added to the bottom of Table 2.
  2. To the extent possible, please provide GTO with rationale for the level of constraint you assign to each parameter. Please include literature references, direct GTO to results of computational analyses, describe field experience, etc.

Well Constrained: The parameter can be directly observed/quantified with a high level of certainty.

Constrained: The parameter can be directly observed/quantified with a modest degree of certainty OR the parameter is an extrapolation of intrinsic properties. The current state-of-the-art extrapolation methods may be a source of error/uncertainty; improvements to the relevant state-of-the-art technologies may or may not result in a higher degree of constraint or reduction of uncertainty.

Poorly Constrained: The parameter cannot be directly observed with current level of technologies AND the parameter is an extrapolation of intrinsic properties. Current state-of-the-art extrapolation methods are a source of significant error/uncertainty; improvements to the relevant state-of-the-art technologies will result in a higher degree of constraint or reduction of uncertainty.

At Theoretical Limit: Measurement, inference, or calculation of the parameter is currently highly accurate and precise with application of current technologies.

Technological Improvement Possible: Measurement, inference, or calculation of the parameter is not necessarily accurate and/or precise with application of current technologies. Further technological development is required in order to better characterize the parameter in order to have an impact on EGS development.

Table 2. Parameter's level of constraint

Parameter Well Constrained Constrained: Poorly Constrained: Rationale
At Theoretical Limit Improvement Possible At Theoretical Limit Improvement Possible

Temperature and pressure at depth

Location and geometry of features/faults

Hydraulic properties of features/faults

Lithology/formation at depth

Gravity

Electric and magnetic properties

Regional geologic structures/analogue outcrops/offset well data

Lithologic units/zones of hydrothermal alteration/
mineralogical composition

Fracture orientation distribution

Fracture length distribution

Fracture transmissivity

Magnitude and orientation of principal stresses

Matrix to fracture heat transfer area

Fracture spacing

Formation/volume/bulk stiffness

Wellbore pressure/hydraulic test data

Mechanical properties of fracture secondary mineralogy (friction coefficient, sliding stability, ductility, etc.)

Sonic velocity profiles

Degree of saturation

Thermal expansion coefficient

Porosity

Volume and location of injection induced acoustic emission

Dilation angle

Fracture aperture distribution

Stimulation fluid and flow-back fluid geochemistry

Rock mechanical properties (Young's moduli, Poisson ratios, cohesion, compressive strength, tensile strength, etc.)

Rate and state parameters to describe frictional stability (i.e.; a, b, Dc)

Rock density

Fluid mean residence time

Thermal-coupling parameters (thermal conductivity and heat capacity)

Production and injection fluid properties (density, viscosity) and chemistry

Reservoir temperature profiles

Chemical properties of fracture/secondary minerals in fracture

Swelling properties of secondary minerals (clays)

Additional Parameter:

Additional Parameter:

Detailed feedback to the questions associated with both tables is very important. While feedback provided on the categorizations presented in Tables 1 and 2 is valuable, it is the rationale provided that will help GTO best incorporate your feedback into its decision making process. Although all feedback is valuable to GTO, stakeholders can focus responses to their specific areas of expertise and are not expected to respond and comment on each parameter presented in Tables 1 and 2.

The Geothermal Technologies Office thanks you for your interest and contributions.

REQUEST FOR INFORMATION RESPONSE GUIDELINES: Responses to this RFI must be submitted electronically to EGSinfo@go.doe.gov no later than 5:00pm (EST) on February 11, 2014. Responses must be provided as attachments to an email. It is recommended that attachments with file sizes exceeding 25MB be compressed (i.e., zipped) to ensure message delivery. Only electronic responses will be accepted.

Please identify your answers by responding to a specific question or topic if possible. Respondents may answer as many or as few questions as they wish.

EERE will not respond to individual submissions or publish publicly a compendium of responses. A response to this RFI will not be viewed as a binding commitment to develop or pursue the project or ideas discussed.

Respondents are requested to provide the following information at the start of their response to this RFI:

  • Company / institution name;
  • Company / institution contact;
  • Contact's address, phone number, and e-mail address.

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This is a Request for Information (RFI) only. EERE will not pay for information provided under this RFI and no project will be supported as a result of this RFI. This RFI is not accepting applications for financial assistance or financial incentives. EERE may or may not issue a Funding Opportunity Announcement (FOA) based on consideration of the input received from this RFI.