Marine and Land CSEM

KMS Technologies' staff has been involved in developing many geophysical systems for land, airborne, marine and borehole applications. Our present company focus includes ElectroMagnetic (EM) systems such as Magnetotellurics (MT) and Long Offset Transient ElectroMagnetics (LOTEM or Lotem) systems, both land and marine as well as borehole EM systems for LWD and geosteering applications.

Marine ElectroMagnetics

Technology overview            Vision            Services            Products

Technology overview

During the last few years marine electromagnetic (EM) measurements have become an important tool in the exploration of and production of hydrocarbon reservoirs. Physically, the detection of a reservoir is based on the resistivity contrast of the resistive reservoir to its conductive surrounding. Time variant magnetic fields of either natural or artificial origin cause eddy currents within the sediment layers. As these eddy currents are time variant as well they cause a secondary EM-field that can be sensed with magnetic or electric sensors placed on the sea floor or sea surface.

The effectiveness of EM-methods in hydrocarbon detection strongly depends on the source. In the MT method, natural fields are used as source, and therefore only a receiver measuring horizontal electric and magnetic fields is needed to do the measurements. However in a layered subsurface, the natural field induces only horizontally flowing eddy currents. Such current systems are good at detecting conductive layers, but insensitive to the resistive hydrocarbon reservoir itself. To overcome this limitation, artificial fields with a vertical current path are combined with the MT receivers. This vertical current flow causes charge buildups at the reservoir boundaries that allow the detection of the resistive layers. This method is known as controlled source magnetotellurics (CSMT).

A different interpretation approach using the artificial source in a different manner has proven to be extremely useful in hydrocarbon detection; this is called controlled source electromagnetics (CSEM). In the most common application, their source is a continuous square wave of selected frequency; this is frequency domain CSEM (fCSEM) . This method has much in common with the well known DC methods used onshore. At each source-receiver offset, the amplitude and phase is measured and the interpretation is based on the variation of these with offset.

Although very successful, fCSEM does not use the full potential of marine EM. The subsurface signal is always weak, so (just as in seismic) it is best to record it while the source is off. This is realized in the time domain CSEM or tCSEM™ method developed by KMS Technologies. By working in time domain, with an impulsive source, a transient is recorded which contains information over a large depth range at each source-receiver offset. By these means, the sensitivity to certain targets is increased, and other typical limitations of traditional fCSEM methods (as for example the loss of sensitivity in shallow water deployments) are reduced.

Vision

Our long term vision is to take EM in general and tCSEM™ in particular a routine tool in hydrocarbon exploration and production, seen by everybody as a valuable complement to seismic. Beyond exploration, we see the market for monitoring of water and steam-flooding, particularly via installation of permanent arrays as a major growth opportunity. Toward this goal, we have developed various products and offer different kinds of services, as described below.

Services

  • Survey planning: Based on our 3-D modeling capabilities for tCSEM™, fCSEM and MT we are happy to assist oil companies in the planning phase of marine EM surveys. Integration of reservoir information from seismic, well logs and other sources can be done on a high level of detail. Through comparison of different scenarios an optimum survey strategy is developed for each individual project.

  • Data processing: Our own modeling capabilities allow us to offer data processing services for different methods.

  • Interpretation: We interpret marine EM data sets based on 1-D, 2-D and 3-D inversion techniques including constraints given by borehole or seismic information.

  • On board data acquisition QA/QC

Products

(Please call or write to info@kmstechnologies.com for additional information.)

Marine Induction Coil (MIC) 121: This proprietary induction coil magnetometer has been developed specially for the use in fCSEM measurments. Its compact size and moderate weight reduces the space and weight requirements of the ocean bottom receiver, and hence reduces the volume requirement of the flotation units.

Land Induction Coil (LIC) 120: The induction coil magnetometer has been developed to measure variations of the Earth’s magnetic field, particularly for MT applications. It covers a wide frequency range from 0.0001 Hz up to 1,000 Hz. It can be used both autonomously with any analog registration unit, and as a part of a MT station. The magnetometer shows low-noise characteristics, extremely low temperature drift of input offset voltage and offset current, and a very stable transfer function over temperature and time.

IX1D-Marine software: IX1D is a software package for Windows, which allows forward and inverse modeling of resistivity data, with or without IP (Induced Polarization). IX1D also models MT, fCSEM and DC EM data from horizontal and vertical coplanar and vertical coaxial arrays. IX1D Marine can handle anisotropy and up-scaling. tCSEM™ data is supported as well for additional license cost.

Interpex Limited: We also sell the entire product line of Interpex Limited, for more information about their products visit them at www.interpex.com