Norskhydro Asa

Multifield Geophysics As

Statoil Petroleum As

Statoil Asa

Svein Erling Johnstad

Harald Westerdahl

Brian Anthony Farrelly

Fan-nian Kong

Fan-Nian Kong

A geophysical sensor cable has one or more sensor cable sections. Each of the sensor cable sections is provided with seismic and electromagnetic sensors arranged along said cable. The seismic sensors include a hydrophone and a seismic component receiver for seismic vector measurements while the sensor cable is at the sea-floor. The electromagnetic sensors include both E-field sensors and H-field sensors. The E-field sensors include pairs of first and second electrodes arranged with different positions along the cable and connected to a voltage amplifier. The H-field sensors include three mutually orthogonally arranged H-field component sensors.

Electromagnetic and seismic streamer cable and method for using such a streamer cable

A method for electromagnetic geophysical surveying of rock formations () under a sea-floor () comprising the following steps: *&#x2014;towing first and second alternating field (E, E) emitting sources (s, S) in first and second depths below the sea surface, said first field (E) having a first phase (&#x3a6;);&#x2014;said second alternating field (E) given a second phase (&#x3a6;) different from said first phase (&#x3a6;), said sources (S, S) constituting a phased array emitter antenna with directivity for transmitting a major proportion of the combined electromagnetic energy downwards;&#x2014;said first and second fields (E, E) for propagating partly down through the sea-floor () and being reflected and/or refracted through said rock formations () and partly propagating back through the seafloor ();&#x2014;said first and said second fields (E, E) for merging to a total field and being measured by electromagnetic receivers (r, r, . . . , r) recording corresponding field registrations (E(t), E(t), E(t), . . . , E(t)).

Method for electromagnetic geophysical surveying of subsea rock formations

A method for analyzing acquired electromagnetic measurements (R) made at or in a sea () over a seafloor () with rock formations () having relatively low resistivity (&#x3c1;) for detecting a possibly underlying petroleum bearing reservoir formation () having relatively high resistivity (&#x3c1;), wherein a low frequency electromagnetic transmitter () arranged in the sea () emits an electromagnetic field (P) propagating in the sea (), in the rocks () and in the air () above the sea; wherein electromagnetic sensors () are arranged with desired offsets (x) in the sea () for measuring the electromagnetic field (P(x)) while the field propagates, characterized in that one or more component of the electromagnetic field (P) is measured at least one large offset (x) from the transmitter () where the field (P) essentially only has its origin from the field propagating as a field (P) through the air (); that the one or more components of the electromagnetic field (P) measured at the large offset (x) is calculated back to a recalculated field (F(x)) to one or more offsets (x) being shorter than the large offset (x); that the recalculated field (P(X)) is subtracted from the field (P(x)) for possibly highlighting a field which arising due to the possibly petroleum bearing reservoir formation () having relatively high resistivity (&#x3c1;).

Electromagnetic method on shallow water using a controlled source

A method for determining electrical properties of a submarine petroleum fluid-bearing formation () under overburden geological layers () of thickness (s) under a seafloor () of a sea. The method includes: *arranging one or more transmitter antennas () in the sea, and arranging one or more electromagnetic receivers () in the sea, *the sea having a shallow sea depth (d) of 50-350 meters; *using the transmitter antenna () transmitting electromagnetic signals () of one or more pulses () having frequency of very low frequency between 0.01 Hz and 0.10 Hz; *using the receiver antennas () having an offset from the transmitter (), for receiving propagated electro-magnetic signals () due to the emitted electromagnetic signals (); *analyzing one or more components of the received signals () from receivers () having offsets between about 1 km and 12 km, whether the signals () differ significantly from a corresponding signal that would occur from a water-bearing formation (), indicating a petroleum fluid-bearing formation ().

Shallow marine electromagnetic hydrocarbon prospecting

A method for monitoring a high-resistivity reservoir rock formation () below one or more less resistive formations (). The method includes transmitting an electromagnetic signal (S) propagating from near a seafloor or land surface () by means of an electromagnetic transmitter () powered by a voltage signal generator (G). The electromagnetic signal (S) propagates from the seafloor () and is guided along a conductive string () to the high-resistive formation (), and propagates as a guided-wave electromagnetic signal (S) at a relatively higher speed (V) inside the high-resistivity formation () than a propagation speed (V) in the less resistive formations (). The guided-wave electromagnetic signal (S) gives rise to an upward refracting electromagnetic signal (R) having the relatively lower propagation speed (V) in the less resistive formations () and having an exit angle nearer to the normal (N) to the interface between the high-resistivity formation () and the lower-resistivity formation (), and gives rise to a steeply rising refraction wave front (F). The refracted electromagnetic wave front (F) includes refracted electromagnetic signals (R) detected along an array of sensor antennas (, . . . ,) positioned along the seafloor. The array having a direction away from the transmitter ().

Method for monitoring low-resistivity formation using polarized waves

A device for monitoring the position of an oil/water contact (OWC,) between an oil-continuous fluid () overlying a water-continuous fluid () inside a casing pipe (). The device includes a transmitter () for a generating an electromagnetic signal (ST) and the transmitter () is provided with electrical energy (G) from a voltage signal generator (G). The transmitter () is arranged inside the casing pipe () in the oil-continuous fluid () and above the oil-water contact (). The electromagnetic wave signal (S) partly propagates downwards from the transmitter (), is partly reflected from the oil-water contact (), and is partly reflected by the end of the casing, giving rise to an upward propagating, reflected electro-magnetic signal (S). The device also includes a sensor () for detecting the reflected electromagnetic signal (S), and the sensor () is also arranged above the oil-water contact (), providing a sensor signal (R) to a receiver () for receiving the sensor signal (R) and further to an analyzing device () for analyzing the sensor signal (R), e.g. with respect to two-way propagation time or amplitude in order to calculate an elevation level for the oil-water contact.

Device for monitoring of oil-water interface

The invention includes a geographical sensor apparatus for use under water in the sea, including a plurality of seismic sensors () for sensing seismic waves associated with underground formations, and a plurality of EM-sensors constituted preferably by electrodes () for sensing electromagnetic waves associated with the underground formations. In a preferred receiver cable configuration embodiment of the invention, the geophysical sensor apparatus includes a seismic receiver cable with a linear array of a plurality of seismic sensors () and EM-sensors arranged inside a flexible outer skin (), with the EM-sensors having electrodes on the outside of the outer skin. The cable is operated on the seafloor by a surface vessel, the vessel towing an electromagnetic transmitter antenna in addition to the seismic source.

Growing community of inventors

Bønes, Norway

Svein Erling Johnstad