Abstract
Geothermal power is derived from the Earth’s own heat. Geothermal wells are tested periodically to assess pressure and flow rates and measure the temperature underground. We are searching for a system able to eliminate or at least strongly reduce the olfactory impact caused by atmospheric geothermal well testing with a focus on both mitigating the nuisance of smells upon areas close to well and controlling hydrogen sulfide levels in the well operation site.
OVERVIEW
Enel Green Power performs both drilling and operation activities on geothermal wells located in Italy (in Tuscany mainly), United States (Nevada) and Chile.
Gaseous emissions, in agreement with Italian regulation and laws, are discharged in the atmosphere during the well testing phase, performed after the completion of the drilling activity, with the aim to both assess the production capability and determine the physical-chemical characteristics of the fluid. Depending on the geothermal fluid characteristics, the area close to well may be subjected to smells related to the presence of both hydrogen sulfide naturally present in the geothermal fluid and other volatile organic compounds (VOC).
Description
SCENARIO
Two main issues occur during the well testing activity:
a) Release in the atmosphere of hydrogen sulfide around the well head during the first well opening phase (typical duration up to around half an hour). In this phase, it is important to maintain in-air concentration level which allows the work site personnel to continue executing normal operations.
b) Release in the atmosphere of both hydrogen sulfide and VOC during the well test (typical duration 2 – 10 days).
The well testing begins by opening the well head valve, leading to the discharge in the atmosphere of both non-condensable gas and liquids accumulated in the upper part of the well, i.e., non-condensable gases, water and environmental friendly lubrication oil residuals; the duration of this phase depends on the well characteristics and varies from several seconds to some minutes.
Once both gas and liquids present in the upper part of the well have been completely released through the head valve, the geothermal fluid coming from the reservoir, composed by water steam and non-condensable gases, reaches the well head;
The test facility (see picture) is composed of two lines in a parallel configuration, used sequentially: the cyclon separator line and silencer line. When the test operator closes the head valve and opens the cyclon separator line valves, the geothermal fluid, still characterized by a significant amount of liquid fraction, starts to flow in the facility. In this line, two pieces of equipment are installed: a remotely controlled regulation valve and the James tube. The regulation valve leads pressure value dropping below a typical absolute value of about 6 bar while the James tube allows the measurement of the fluid flow rate. Fluid exiting the James tube flows through a cyclone separator which releases the gas fraction in the atmosphere and discharges the liquid fraction in a tank. The liquid content gradually decreases during the test; once it is considered negligible, the operator performs the line switch: the cyclon separator line is closed while the silencer line is gradually opened. As well as the cyclon separator line, the silencer line is equipped with a pressure regulation valve. Nowadays, the duration of the well tests varies between two and ten days. During the test, air quality monitoring campaign is performed through stationary and mobile stations capable to measure the hydrogen sulfide concentration in air with the aim to verify the respect of threshold limits indicated by the WHO (World Health Organization).
BACKGROUND
Previous preliminary tests were carried out by Enel regarding the in-well injection of hydrogen peroxide through coil tubing. While the abatement of hydrogen sulfide was largely successful, this solution was not permanently implemented due to significant plant complexity along with the large amount of effort needed to commercialize this procedure. Moreover, in some cases a compressor is used before starting the test to push gases accumulated in the upper part of the well within the reservoir fractures; in this way, when the head valve is opened, in the initial phase the gas release is considerably reduced.
A preliminary commercial scouting analysis conducted in early 2022 did not identify technical solutions suitable for the proposed applications. However, it was recognized that dry granular media scavengers, mixtures of iron oxides and/or mixed metal oxides, or an inert inorganic carrier may be suitable components of a feasible solution. Acceptable methods may separate the hydrogen sulfide from the water stream or treat the whole fluid.
THE CHALLENGE
Identify and test a solution able to eliminate or at least strongly reduce the olfactory impact produced during geothermal well testing with particular regard on hydrogen sulfide and other VOC. The solution must be applicable to wells having different characteristics in terms of fluid flow rate, temperature, pressure, gas content and chemical composition. The preferred method does not involve in-well treatment. Finally, the solution must be transportable to different testing locations.
SOLUTION REQUIREMENTS
Submissions should address the following Solution Requirements.
The proposed solutions must:
- TRL ≥7
- be compliant with European safety standards, especially regarding pressure vessel and piping;
- be transportable by trucks;
- reduce the hydrogen sulfide and other gaseous olfactory emissions released in the atmosphere of at least 90%;
- process the fluid during all test phases described above (gas discharge through the head valve, flow through the cyclon separator line, flow through the silencer line);
- be suitable for wells whose fluid has the following characteristics:
- pressure in the range 1 – 40 bar ( values refer to fluid at well head upstream the regulation valve);
- temperature in the range 100 – 300°C
- typical chemical fluid composition as follows (by volume): water 88 – 98%, non-condensable gas: 2 – 12%; non condensable gas has the following typical composition (by volume): carbon dioxide 87 – 97%; methane 0.4 – 4%; hydrogen 0.3 – 6%; hydrogen sulfide 0.4 – 4.5%; nitrogen 0.5 – 4.5%;
- presence of VOC (Volatile Organic Compounds)
- condensate, as possible representative example, described a possible chemical composition as follows:
|
pH |
5.5 – 7.6 |
|
T.D.S. (salinity) |
50 – 700 ppm |
|
NH4+ |
34 – 210 ppm |
|
H3BO3 |
50 – 650 ppm |
|
SO4 |
Trace – 19 ppm |
|
Cl- |
Trace – 35 ppm |
|
Ca++ |
Absent – 5 ppm |
|
Mg++ |
Absent – 4.5 ppm |
| H2S | 10 – 500 ppm |
- mass flow rate: 10 – 100 t/h (50 t/h to be considered as average statistically representative value);
Moreover, the solution should:
- not require pressurized vessels to store by-products.
- work on fluid downstream the pressure regulation valves mentioned above;
- reduce the hydrogen sulfide and other gaseous olfactory emissions released in the atmosphere of at least 98%;
PROJECT DELIVERABLES
The submitted proposal should include the following:
- An explanation of the proposed solution addressing specific Solution Requirements along with a well-supported rationale and pertinent data
- Schematics that illustrate important aspects of the design
- A cost assessment and implementation strategy for geothermal fields in Italy
- Application references of the proposed technologies/processes with focus on industrial plants.
The proposal should not include any personal identifying information (name, username, company, address, phone, email, personal website, resume, etc.) or any information the Solvers may consider as their Intellectual Property they do not want to share.
SDGs
This challenge provides contribution to the following sustainable development goals (SDGs) to transform our world:
- SDG 11: Sustainable Cities and Communities
- SDG 13: Climate Action
- SDG 17: Partnerships to achieve the Goal.
Challenge rules
All proposers are invited to read carefully the Challenge and the Regulation of this Challenge, attached below in the Attachments section, before submitting a solution.
By submitting a solution they automatically accept the attached Regulations other than the Terms of Use of this platform.
Explain your proposal clearly in English, attach documents (max 5 files, 25MB total size) if needed.
Deadline
Submissions to this Challenge must be received by 11:59 PM (Central European Time) on January 15, 2023.
Late submissions will not be considered.
Eligibility
Except for the people involved in the organization and management of the OPEN INNOVABILITY® CHALLENGE and their spouses or partners and their relatives up to the fourth degree calculated according to Italian law, the proposals could be submitted by all the employees working in the legal entities pertaining to the perimeter of Enel Green Power worldwide.
Challenge, award, IP rights
This is a Theoretical Challenge, which requires only a written proposal to be submitted. The Challenge award will be contingent upon theoretical evaluation of the submission by the Seeker.
To receive an award, the Solvers will not have to transfer the exclusive IP rights to the Seeker. Instead, Solvers will grant to the Seeker a non-exclusive license to practice their solutions.
Without prejudice to the article 5.5 of the Terms of Use, the obligation to grant the IP rights set in this article does not apply if the winning solution is proposed by an employee of an Enel company, unless the employee is the owner of the solution according to the relevant national law.
Specific regulation in the CSA attached at the bottom of this page.
Regulation
Olfactory impact minimization of atmospheric geothermal well testing Regulation
What happens next?
Enel will evaluate the proposal using the following criteria:
- Overall scientific and technical feasibility of the proposed solution;
- Economic potential of concept (e.g. Total Cost of Ownership);
- Business potential for Enel;
- Novelty and creativity;
- Potential for proprietary position (i.e., is the technology novel or protectable);
- User's capabilities and related experience;
- Realism of the proposed solution;
- Maturity level of the proposal.
Once suitable solution/s have been identified, Enel will reserve the opportunity to start a collaboration, by way of example, all or part of the following activities:
- Test execution;
- Supply of prototypes (if an equipment);
- Installation and site tests;
- Follow up and monitoring of the proposed idea behavior.
Upon completion of the evaluation, you will receive feedback.
In case of success, an Enel contact person will get in touch with you to discuss the next steps.
The final award for this Challenge is contingent upon satisfactory completion of the verification process, including acceptance of the Challenge-Specific Agreement (CSA) that is the regulation for this Challenge.
The verification process includes obtaining the following from the Solver: signed affidavit (based on the CSA), employee waiver (if applicable), proof of identify, and Counterparty Analysis Questionnaire (CAQ).
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