A game-changer for geothermal exploration

Swiss 3D seismic breakthrough: A game-changer for geothermal exploration (Inset pictures c/o STRYDE)

The success of a latest 3D seismic survey in Western Switzerland underlines the significance of high-quality seismic information for geothermal exploration.  This pilot challenge across the city of Eclépens within the canton of Vaud might present a safer and environment friendly path to growing geothermal vitality and rising the affect geothermal vitality has on the inexperienced vitality market.

Precision exploration instruments as an enabler for geothermal development

World curiosity in geothermal vitality for each warmth and electrical energy is quickly rising.  88 nations presently produce warmth from geothermal sources and 29 nations have geothermal electrical energy crops (Geothermie Swiss, 2024), nevertheless the affect that geothermal vitality has on the whole vitality market is minimal.

Figuring out potential geothermal assets and pinpointing optimum exploratory drilling areas stays the difficult dimension to profitable geothermal exploitation. A number of deserted makes an attempt to harness geothermal vitality could be linked to lack of know-how of the subsurface which leads to losing money and time and diminishing public assist for future initiatives.

Cautious planning and implementing of detailed seismic surveys within the early phases of geothermal initiatives provides the essential perception wanted for stakeholders to advance confidently with actual information in hand to assist decision-making.  That is acutely necessary in Europe the place geothermal exploration and growth has specific constraints linked to dense urbanisation, strict authorities allowing, and infrequently robust area people objections.

Europe continues to be closely depending on fuel, oil and nuclear energy to succeed in its elevated winter vitality calls for that can not be solely lined by the intermittent vitality equipped by wind or photo voltaic.  Geothermal options exist to fill this hole, linking in with present native vitality suppliers and district heating initiatives.  These initiatives are reliant, nevertheless, on discovering geothermal reservoirs with exact situations and properties tailored to vitality manufacturing.  With latest advances in seismic expertise, high-resolution, dense seismic surveys are serving to kick-start future geothermal initiatives throughout Europe, offering a lower-cost technique for buying a high-quality picture of the subsurface.

A Case Examine in Eclépens, Western Switzerland

A lot of the Swiss plateau has been earmarked for its geothermal potential.  Whereas the regional geology is well-known, there are only a few areas which have been topic to detailed subsurface investigations.  Potential medium depth geothermal targets within the sedimentary layers of the Molasse basin are intersected by zones of faults, fractures and shearing which have been created as sedimentary layers within the Swiss plateau have been pushed up in opposition to the Jura mountains.

Understanding the amplitude and orientation of faults, fractures, and geological options, in addition to particular properties affecting geothermal brine movement and temperature, similar to porosity and permeability, is important for planning nicely location and trajectory.  Detailed geological modelling utilizing excessive -resolution, 3D seismic surveys mixed with present nicely log information and floor geology options, is a necessary software for deciphering the subsurface and planning geothermal initiatives.

Within the seek for potential geothermal assets, the world round Eclépens, within the canton of Vaud was chosen as a goal survey space after robust geothermal indicators have been detected within the 1981 Eclépens-1 nicely (M. Baykulov et al., 2024).  An unusually excessive geothermal gradient was detected within the nicely, with temperatures above 100 °C at depths of 2000m, which signifies a possible geothermal useful resource that would present not solely vitality for district heating programs but in addition geothermal electrical energy manufacturing.  Legacy 2D seismic survey information already existed within the space however didn’t present sufficient element for correct planning and execution of preliminary geothermal nicely placement.

Swiss Geo Vitality’s pioneering 3D seismic acquisition challenge for geothermal vitality is likely one of the world’s densest 3D surveys acquired for geothermal functions, with a hint density of two million hint/km2.  The survey lined an space of 104 km2 and aimed toward producing value environment friendly and high-quality information units, with deep geological penetration and excessive vertical and horizontal decision.   By filling within the present sparse 2D seismic information from the Eclépens space with high-quality 3D information units the ensuing modeling of the subsurface geology will likely be used to assist determine reservoir targets and supply an estimation of the geothermal assets (M. Baykulov et al., 2024).

The survey correct

The survey consists of 3 main phases:

1. Planning and Allowing

An intensive planning and allowing stage was carried out to make sure a consequent clean and speedy acquisition course of.  This leads to decrease affect to the neighborhood and atmosphere, larger effectivity and due to this fact decrease prices.  In addition to receiving all required licensing and permits from the native and regional authorities, the contractors labored with personal, agricultural and industrial landowners to facilitate land entry in the course of the acquisition course of.

Diligent planning of the seismic supply and receiver format was undertaken to realize optimum protection of the world and protect the density of the acquired traces.  A theoretical, preliminary grid format was designed taking in consideration the tectonic fault traces described in earlier, regional fashions and oriented in order that the fault traces might be optimally imaged (M. Baykulov et al., 2024).  This theoretical grid was then considerably adjusted to real-life situations utilizing GIS software program to account for obstacles within the panorama and no-permit zones.

The seismic acquisition contractor, Geo2X, selected STRYDE autonomous nodes for the seismic survey.  These nodes are the smallest and lightest seismic receiver nodes in the marketplace, a revolution that not solely delivers value advantages but in addition significantly adjustments the best way seismic surveys are carried out.

STRYDE has developed a streamlined node, sufficiently small to slot in the palm of your hand and stripped of redundant parts.  These small, light-weight receivers enabled the survey to be performed with minimal affect to the atmosphere and area people due to the lowered tools burden and the convenience of deployment on foot or with smaller autos.  Using light-weight, cable-free nodes additionally will increase hint density because the variety of nodes deployed is well elevated round obstacles or goal areas with little change to acquisition time or workforce dimension.

2. Seismic Survey Acquisition

A complete of 21,475 particular person STRYDE autonomous nodes have been deployed by Geo2X on the Eclépens web site over 11 days following the pre-planned orthogonal supply and receiver grid format.  The realm was cut up into 4 workforce quadrants with one vibroseis truck working in every quadrant.  Cautious consideration was utilized to the space between sources (to keep away from interference) and the vibration ranges in proximity to buildings (as per the Swiss laws).

The simplicity of STRYDE nodes and their consequent recording reliability and robustness leads to minimal discipline qc.  These nodes have exact time synchronization and GNSS positioning and have performed away with redundant and pointless capabilities that relay dwell info to the sector workforce in the course of the survey – a hangover from the times of fragile, cabled programs and sparse survey spacing the place any information gaps have been an obstacle to survey outcomes.

The reliability of the STRYDE nodes implies that, as soon as deployed and synched, they don’t must be tracked within the discipline.  In distinction, seismic receivers that relay information to the sector workforce in real-time are costlier, bulkier, want extra battery life and have extra parts inclined to malfunction.  Within the Eclépens survey, 99% of information was recovered from the STRYDE nodes (M. Baykulov et al., 2024) and materials loss or injury was minimal.

Preliminary evaluation of the information could be carried out when the nodes are harvested or redeployed.  Knowledge QCs could be carried out on preliminary information units utilizing specialised, on-site software program parts.  STRYDE’s streamlined node harvesting programs and distinctive in-field software program processing instruments enable for speedy turnover of node acquisition and deployment and a dependable first take a look at information whereas operations are persevering with.  This course of has changed the redundant, in-field QC strategy of cumbersome actual time geophones which gave restricted, positioning info and reflection information with none processing capabilities.

To realize the excessive channel rely required for dense, 3D, city surveys, massive numbers of receiver nodes must be deployed throughout typically difficult city areas.  The danger of receivers being misplaced, broken or tampered with is larger in city areas and can lead to incomplete information units or added delays and price will increase to the challenge, that is no matter real-time QC or monitoring seen on greater and extra expensive geophone programs.

STRYDE is understood for its low node loss document, with very small numbers of deployed nodes lacking by means of tampering, theft or injury.  The compact dimension of the STRYDE node permits it to be simply buried or hidden and due to this fact not apparent to passersby.  The node loss rely for the Eclépens survey was lower than 2 % and didn’t affect information continuity.  The small dimension of the nodes additionally implies that they’re extremely cell, simply carried on foot with streamlined deployment and retrieval utilizing smaller crew sizes.  This flexibility was useful in a survey space like Eclépens with difficult mixed-purpose city and agricultural areas and restricted heavy automobile entry.

3. Knowledge Processing, Interpretation and Properly Placement

Quick-track processing of the acquired information units gave an early overview of the standard of the information and enabled comparisons to the regional macro-structures and the legacy 2D information units. The information went by means of preliminary conditioning strategies which embrace noise discount, sign enhancement, and correction for any information inconsistencies. This ensures that the information units are of the very best high quality earlier than additional, extra subtle processing.

A primary-look, comparative evaluation of pre-STM information imaging already confirmed the improved element of the 2023 3D information set, in contrast with the classic 2D seismic pictures with lowered seismic noise, much less chaotic signatures and extra continuity in reflectors.  Comparability of the NW-SE linear 2D line with an an identical spatial line from the brand new information confirmed the shortage of continuity in seismic reflectors of the 2D information and an general chaotic signature (M. Baykulov et al., 2024).

Widespread city obstacles similar to roads and buildings restrict the acquisition of straight line 2D seismic.  3D surveys, nevertheless, can mix info from all instructions with many various source-receiver mixtures which may work round obstacles or voids within the survey space.  Given the excessive quantity and density of the information, information gaps may also be compensated by superior interpolation strategies throughout information processing.

Due to the excessive decision of the seismic sign obtained within the Eclépens survey, a sequence of subtle information processing strategies have been utilized to the dataset so as to produce a extra full and correct seismic mannequin of the world.  These strategies embrace, for instance, Full-Waveform Inversion (FWI), Widespread Reflection Angle Migration (CRAM), rock property inversion and Reverse Time migration (RTM) which assist to additional refine the seismic picture and improve subsurface characterisation.

By integrating the processed seismic survey information with present nicely log information, detailed and correct 3D geological fashions could be produced.  The ultimate fashions are key challenge administration instruments which are important to determination making for nicely location, trajectory, depth and so on.  These fashions present the absolute best estimation of the goal useful resource and are key in supporting all features of geothermal initiatives, from planning to engineering, mitigating dangers and challenge value discount.

Conclusions

The advantages of high-density, 3D seismic surveys have already been extensively exploited in different industries similar to petroleum, nuclear waste storage, mineral exploration, and so on.  The Eclépens case examine reveals how seismic reflection surveys could be carried out to excessive business requirements, with high-quality information units and streamlined operational efficiency, whereas conserving acquisition prices low sufficient to learn the renewable vitality business.

These surveys add actual worth to geothermal exploration initiatives by bringing extra readability to the subsurface and aiding decision-making.  Excessive-resolution geological fashions from dense 3D geophysical surveys are probably the most strong instruments out there to judge the goal useful resource and plan nicely areas and trajectories.

By way of a mixture of thorough and diligent planning and allowing phases together with superior seismic acquisition expertise such because the STRYDE receiver node, it’s now doable to carry high-density, 3D surveys to the geothermal market.