ENEL OPEN INNOVABILITY® CHALLENGE | Olfactory impact minimization of atmospheric geothermal well testing

21/12/2022 - Enel

Enel Green Power is 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.

Expires: 15 January 2023

Reward: Up to $20,000

Meet the challenge!



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.


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).



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).


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.


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.

Meet the challenge!


Submissions should address the Solution Requirements available @openinnovability.com.


The submitted proposal should include the following:

  1. An explanation of the proposed solution addressing specific Solution Requirements along with a well-supported rationale and pertinent data
  2. Schematics that illustrate important aspects of the design
  3. A cost assessment and implementation strategy for geothermal fields in Italy
  4. 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.


  • 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.

Meet the challenge!

Tipologia: Bando/Avviso

Fonte: https://openinnovability.enel.com/challenges/call/2022/11/olfactory-impact-minimization-geothermal-wells

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