Sonar surveys in caverns

Sonar cavern surveys on the basis of ultrasonic and laser systems can be carried out in open and cased caverns in various media: Brine, water, air, gaseous and liquid hydrocarbons as well as nitrogen, helium and hydrogen. Please press the play button below to watch the process of sonar surveys. We apply different survey methods depending on the job in hand to reveal the exact conditions underground.


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Full Survey
Full surveys are carried out to determine the overall cavern geometry. When executed during the leaching phase of a cavern such surveys document the development of the shape and volume. Full surveys of storage caverns always focus on the change in volume (convergence) and any associated change in the shape.

Partial survey
The perfect method of controlling – in less time and less cost – specific zones of a cavern in between two full surveys. For instance, if no significant changes are picked up by a survey of the cavern floor then it can be indirectly assumed that also the uncontrolled rest of the cavern will not have changed significantly.

Cavern neck survey
Cavern neck surveys using sonar caliper measurements supply detailed measurements of the sensitive and relatively narrow cavern neck and open borehole.

Mechanical Integrity Tests

SoMIT® – the test method for precise and fast results

The SoMIT® method (Sonar Mechanical Integrity Testing) was developed and patented by SOCON for performing leak tests.

The way it works: a specially developed ultrasonic probe continuously measures the interface level. In parallel, temperature and pressure are recorded with high accuracy in the test area – and if required at the cavern head. The recording of the parameters temperature and pressure is carried out over the entire borehole length on entry and exit as a log and during the entire test period also in the vicinity of the interface. The probe is clamped into the casing for the entire measurement period in order to exclude depth errors due to cable expansion effects over the measurement period. The SoMIT® method offers increased precision and accuracy with a shortening of the test duration.

The advantage: shorter test periods, reduced downtime, lower costs.


Interface determination

For determining the brine-blanket medium interface we employ 42mm diameter tools (ING42SC) based on the impulse-neutron-gamma technique (ING). These tools contain a neutron generator, which emits controlled neutron pulses. Two gamma detectors installed at different distances from the generator act as sensors. These detect the secondary gamma radiation. In addition, the ING tools include a pressure and temperature sensor as well as an M-CCL sensor system (Multiple Casing Collar Locator) for establishing accurate depth ties. These tools, too, originate from our in-house R&D department. Solely the neutron generator is produced from a specialist company.

Further information about the ING – tool for interface determination:

Logging in caverns

In addition to the actual sonar survey of the cavern it is essential to record in addition diverse physical parameters for ensuring the accuracy of the sonar data. Indeed, layering of media in caverns can be identified by an increased gradient in the temperature and acoustic velocity, and this leads to a deflection of the sonar beam. If this effect is not taken sufficiently into account, the results will be flawed. For this reason, logs are usually recorded during surveying to prevent precisely this from happening. The acoustic velocity in the medium, the pressure, temperature, CCL, M-CCL data, the tool tilt and – if measured – also natural gamma readings supply important and even vital physical data and information on the prevailing cavern conditions.

When surveying in gas caverns a dewpoint module can be combined with the sonar tool to enable the dewpoint distribution to be measured in-situ.
Such measurements provide clues to the moisture distribution as well as information about situations that could promote hydrate formation. Furthermore the logs are used for tying in the survey to the depth reference point and are the basis for carrying out thermodynamic calculations as well as mass-volume calculations.
The modules for recording all the required physical parameters are either already integrated into the sonar tools or can be simply added. For more specific operations and needs, e.g. narrow parts in cavern necks, other special tools are used in separate survey runs. As an example, for the in-situ determination of the density of a liquid medium a special developed tool is available.

Sample Taking

SOCON has tools for taking liquid and gas samples in caverns. These sampling tools have a modular design with an electronics module containing the components for the CCL and for measuring the temperature. The module also includes the controls for opening and closing the individual sampling containers. Up to five carrier modules, each for holding one sampling container, can be attached to the electronics module. Installed at the bottom of the tool is a conductivity module, which detects when the tool dips into an electrically conducting liquid (e.g. brine). If necessary the sampling tool can be combined with the density tool.
A case holds the gas samples and allows them to be transported safely and easily to the laboratory for analysis.

Cavity integrity measurements

To determine the integrity of a salt cavern, the well barrier elements have to be risk assessed, verified and monitored during the life of the cavern.

In addition to sonar cavern surveys in all relevant media, SOCON Sonar Control Kavernenvermessung GmbH together with its partners offers casing and tubing integrity measurements for cavern wells. In particular are the following: Electromagnetic Wall Thickness Measurements, Cement-Bond-Log (CBL-VDL), Multifinger Caliber Measurements (MFC), Downhole Video, Optical and Acoustical Televiewing.

Our service extends from carrying out on-site integrity measurements, through interpretation and reporting, to the final integrity assessment.

Gas storage optimisation & service (GSOS)

Our GSOS department provides scientific advice and support in the field of gas storage and assists with thermodynamic and rock mechanics issues or, in general, with all questions concerning the evaluation of unexpected measurement results.
Focal points and fields of application refer to the scientific support and supervision of our customers in gas measurements as well as to the evaluation and analysis of survey results. Prerequisite for thermodynamic calculations is the information from the echometric cavern surveys, which provide data on cavern shape and volume as well as parameters such as pressure, temperature and dew point.
By means of the program system CavBase GasStorage (CBGS), thermodynamic and rock mechanics simulations can be performed. CBGS consists of a basic program that can be extended by a number of modules. It was created in the mid-nineties and has been further developed in a modular fashion up to the present day. To date, CavBase has been installed locally on 17 gas storage facilities and is currently used by a number of Germany’s largest storage operators, who regularly use it to perform simulations for over 130 natural gas storage caverns.
An updated version is currently being developed so that CBGS is not offered as a web-based software service. For further information please refer to the data sheet of the new software version linked below.

Fields of application of our GSOS department are:

  • Preparation of calculations and studies (thermodynamics and rock mechanics) in the planning and operation of gas cavern storage facilities in rock salt (including conversion from H-gas to L-gas and vice versa, as well as the use of hydrogen or other storage media).
  • Analysis of working gas evolution from individual gas caverns up to the whole storage
  • Development of digital operational management models.
  • Analysis of moisture in caverns and hydrate formation in wells and field pipelines for optimized inhibitor addition.
  • Prediction for pressure and temperature losses in wells, field pipelines and technical installations on the station site.
  • Concepts for optimizing the operation of gas cavern storage facilities.
  • Further development and support of the CavBase Gas Storage program for a number of operators who use the program on a permanent basis to optimize their storage operations.

Mine Surveying

SOCON delivers precise interpretations of mine surveying data that satisfy the highest technical requirements. The interpretation of mine surveying data referred to sonar cavern surveys is entered in the maps that have to be prepared according to the German Mining Act. Such special mine surveying activities in the cavern field focus on precision leveling, which monitor ground movements at the surface. These leveling data, which is then included in the maps, also satisfy the requirements of the mine surveying regulations, including the pertinent standards.

A public certified mining surveyor prepares the maps, which, subsequent to being signed by the surveyor, become officially recognized documents. The computer-aided information-system KARISDAT®, developed by SOCON, is at hand for carrying out the mine surveying work efficiently and in a way to meet future requirements.
KARISDAT® is based on AutoCAD® and is approved by the mining authorities for generating the required maps. Here we have a high performance system whose areas of application far exceed just the compilation and management of the legally prescribed maps.

Developed with an eye to the future is the KARISDAT-SUB module, which allows a prediction of ground movement expected to occur above cavern fields. Parameters that are needed, such as the limit angle and the specific cavern convergence, can be extracted from the KARISDAT® database. Besides subsidence, it is possible to predict ground movement aspects such as tilting, curvature, horizontal displacement as well as compression and strain.

Customer-specific developments

SOCON develops customer-specific hardware components for data acquisition on request. In addition to the systems for permanent monitoring of underground caverns, SOCON also designs and constructs specially adapted winch systems. The electrotechnical planning and installation as well as the installation and the functional test of the systems are carried out entirely in-house.

Customer seminars

For 2021 we are planning another customer seminar on November 25th in the tried and tested manner at our headquarters in Giesen. We are optimistic and assume that by then the infection rate will be contained and that face-to-face events can be held safely again.

In 2022 we hope to be able to offer a “normal” program again, consisting of an excursion with a cavern inspection in May and two seminars in September and November.

Good luck and stay healthy!

The SOCON team



Customer seminars

Since its foundation in 1991, SOCON Sonar Control Kavernenvermessung GmbH has been a communication center for the responsible representatives of cavern operators and engineering companies as well as for all those interested in questions concerning the cavern technology. In the SOCON headquarters in Giesen, we therefore regularly hold seminars and training courses that serve the exchange of experience and opinions and thus provide a suitable forum for the diverse interests of the participants.

Events and seminars are held on a regular basis, mainly on the subject of “caverns and cavities”. The spectrum of lectures ranges from echometric monitoring of caverns and geophysical measurement methods to current topics from the field of cavern construction and operation to the presentation of current software developments from the various departments of SOCON. In addition, seminars on special topics from the fields of mine surveying and GSOS (Gas Storage Optimization & Service) as well as excursions to mines and caverns are offered. During the breaks there will be enough time for discussions, contacts and talks between the participants. Of course, the employees of our company will be available for questions and a tour of our plant.

CavLift (subsurface simulator)

The new subsurface simulator CavLift has been available to our customers since 2011. This mobile information container can accommodate up to a maximum of ten people and gives occupants a virtual ride through individual caverns and even entire cavern fields. The results of sonar cavern surveying, together with other geological and operational data, are used to simulate a journey through underground cavities. Such a journey through the subsurface is of course impossible in reality. The ride in a virtual shaft cage is represented stereoscopically. Before taking the trip, each visitor is given 3D glasses and a hardhat.

The SOCON CavLift is ideal for public events, trade fairs and congresses for allowing a large group of interested people to visualize what it looks like inside a cavern and indeed entire cavern fields. The virtual ride program (animation with sound) can, on request, be individually produced and adapted to suit clients needs.

More information about SOCON – CavLift: