Drilling in supercritical geothermal condition

Periodic Reporting for period 2 - DESCRAMBLE (Drilling in supercritical geothermal condition)

Okres sprawozdawczy: 2016-11-01 do 2018-04-30

The “Drilling in dEep, Super-CRitical AMBient of continentaL Europe” (DESCRAMBLE) project was meant to drill in continental-crust, super-critical geothermal conditions, to test and demonstrate novel drilling techniques to control gas emissions, the aggressive environment and the high temperature/pressure expected from the deep fluids and to characterize the chemical and thermo-physical condition of the reservoir. The experiment has been realized in Larderello, Italy, where supercritical resources are expected within a depth of 4 km.

The main specific objectives were:

• Demonstrate safe drilling of a deep super-critical geothermal well, by identifying existing technical problems created by super-critical conditions, overcoming these problems through novel improved drilling procedures, equipment and well design, and extending the Venelle 2 well into a very high temperature formation.
• Reduce the technical and financial risks of drilling and exploiting deep geothermal wells by improving knowledge of the physical and chemical conditions in deep geothermal formations. Characterisation of the physical and chemical properties of deep crustal fluids and rocks will be performed. In addition to standard logging during drilling, a novel measurement tool was developed and used to measure pressure and temperature in super-critical conditions. The knowledge gained will be disseminated in industry related channels.
• Reduce pre-drill uncertainty in the exploration of deep geothermal wells by applying the latest seismic processing, imaging and interpretation technology for exploring the super-critical reservoir prior to drilling. The seismic methods were calibrated based on results obtained during drilling.
• Investigate the economic potential of exploiting chemicals and minerals by analysing fluid samples for valuable materials.

The Descramble project has proven the possibility of identifying potentially supercritical geothermal resources, and the technical feasibility to reach them. Therefore this project can have a profound impact in encouraging further research and innovation in the area to be followed closely by commercial developments. The outcomes of the DESCRAMBLE project will be exploited through a subsequent project for further investigation about the possible exploitation of this resources.

The DESCRAMBLE project reached its scope with several important achievements. Supercritical conditions were reached at 2,7-2,9 km depth, with measured temperature up to 507-517°C and an inferred pressure from Leak off Test of 300 bar. Unfortunately no commercial fluid has been identified. Due to the unexpected and above design conditions (450°C max) it has been decided do not further penetrate into the seismic reflector down to 3.1 km, where an extrapolated temperature of 600° could be expected, corresponding to the molten phase of granite, resulting in too dangerous conditions for a further deepening of the well.
On the other hand, from the dynamic modelling it is likely that the system we have discovered is in a thermal transient mode, from a very recent magmatic intrusion event lasting 50,000-100,000 year ago.
From all the new knowledge acquired by DESCRAMBLE, a new interpretation of the meaning of the seismic signal (K-horizon) will be achieved and further elaboration will bring more light on such a complex structure.

It is very important to highlight the following major results:

• Drilling: The drilling team gained an extraordinary experience in how to handle very extreme temperature conditions, and the problem derived as a consequences of the high temperature (cementing failure, mud behaviour) have been faced and solved. The experience on special equipments from oil & gas technology and never used in a geothermal well, is a valuable piece of knowledge, which will push upwards the possibility of further high temperature and pressure well drilling in the near future.
• The development of a first-of-a-kind temperature/pressure logging tool: A new high temperature and pressure (up to 450°C, 450 bar) logging tool, has been designed, built and preliminarily tested. the SINTEF tool has been then utilized up to its design limit, with an excellent performance and achieving quality results.
• Data integration and characterization: Several important information have been collected before and during drilling phase: well log data, cores from this well and nearby ones, fluid samples, geophysical data (VSP, piggy back seismic acquisition). The effort of integration and interpretation was challenging, but finally and an excellent reconstruction of the deep drilling target was obtained.
• Modelling: several different models have been realized by the two modelling groups, and their major results are in quite a good agreement with the measured data from the well. Regional and local 3D geological and thermodynamic models have been built, tested and continuously updated with the latest information. Rock and fluid sample were collected for laboratory analysis, which is providing further insight of deep geological, geochemical and geophysical condition.

Replicability
Actual technologies for geothermal power production are not are directly applicable to supercritical conditions, which are naturally present in the continental crust and generated via deep processes. DESCRAMBLE opened a new segment of the geothermal market in other areas of Europe and abroad.

Socio-economic
The DESCRAMBLE consortium, consisting of both European industry and research partners, will ensure a short lead-time from research to innovation, by a) strengthening the European industrial technology base, thereby creating growth and jobs in Europe; b) demonstrating that super-critical wells can be safely drilled with acceptable financial risks; c) improving EU energy security, providing a stable base-load electricity supply where the energy production can be distributed across most of Europe, and reducing dependence on imported energy.

Environmental
DESCRAMBLE has opened the way to the reduction of life-cycle environmental impact, by building an efficient, compact, closed loop, high capacity power plant, with low land occupation per MWe, contributing also to solving the global climate and energy challenges by decreasing CO2 emissions from fossil fuels.

Market Transformation
The time-to-market for a geothermal power plant will be reduced from 3-4 years for a standard hydrothermal field down to 2-3 years for a super-critical one.
From a cost perspective, a reduction of 10-15% is expected in comparison with a standard system at the same depth as the super-critical one. This reduction is only due to the 75% reduction of the drilling costs (reducing the number of wells needed), with additional possibility of a further 10% cost abatement due to the learning curve effect.
Significantly increased technology performance, by increasing the power output by a factor of 10 compared to existing geothermal plants.
The use of the abundant and free heat as a by-product of the electricity production from a super-critical system could be an important add-on to the economic and environmental aspects of such a project, making it more attractive for investors and for the local population, due to the possibility of accessing (large) district heating and cooling technologies cheaply.

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Periodic Reporting for period 2 - DESCRAMBLE (Drilling in supercritical geothermal condition)

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