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 integrates seismic with 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.
KMS has developed a marine cabled-based acquisition system for tighter acquisition and appraisal and production applications. The tCSEM ocean bottom cable system will record both electric and magnetic field measurements and will provide denser sensor spacing than is typically afforded by nodal systems alone.
Dense sensor spacing is particularly important since lateral resolution of the method is scalable to it. In other words, the denser the receiver spacing, the better your lateral resolution and the integration with single well and borehole-to-surface measurements. As the cable system has a very high degree of precision for positioning repeated deployments and will advance the use of EM technology for reservoir monitoring through the acquisition of time lapse surveys. Additionally, the system will feature buoy based recording and real time quality control of data, and is deployable with VSO seismic cable system to provide a direct integration with the seismic method.
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.
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.
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
AT THIS TIME service for marine EM are restricted to an exclusive customer.