Abstract: A seismic acoustic signal source includes a hull that has a wetted surface in contact with a body of water. When underway, the draft of the hull is substantially zero. An acoustic signal generator is provided with a linear actuator that is resiliently mounted in the hull. The linear actuator is acoustically coupled to the hull bottom such that when the signal generator is activated, the hull radiates an acoustic wavefield into the water.

Abstract: A method for determining a substantially optimal NMO velocity function for use in stacking a CMP gather of seismic data traces. The method begins with an initial estimate of the NMO velocity function for the CMP gather. This initial estimate is typically determined through conventional seismic velocity analysis. The method then picks a first velocity-traveltime pair falling on the initial estimate of the NMO velocity function and conducts a two-dimensional interpolative search of trial velocity-traveltime pairs in the neighborhood of the pick to find a substantially optimal velocity-traveltime pair. This substantially optimal velocity-traveltime pair is the trial velocity-traveltime pair having the highest stack response and is substituted for the pick in the NMO velocity function. The method then proceeds to find substantially optimal velocity-traveltime pairs to replace each of the other picks on the initial estimate of the NMO velocity function.

Abstract: Marine seismic data sets are generally under-sampled spatially because of the relatively long listening times required in deep water. It is customary to use very long spreads in the field thereby enhancing aliasing and interference from coherent noise. A seismic-signal data processing method is proposed that applies a combination of a forward parabolic Radon transform and a linear Radon transform to the data, followed by a further transform to a three-dimensional frequency domain. In this domain, a deterministic operator is applied to the data to sharpen the Radon-domain response thereof. The data are then scavenged of noise in the Radon domain and inversely transformed back into the time-space domain.

Abstract: A method for determining ocean bottom reflectivities from dual sensor seismic data, whereby a first time windowed pressure signal and a first windowed velocity signal are summed to generate a first summed signal, and a second time windowed pressure signal and a second time windowed velocity signal are summed to generate a second summed signal. The first summed signal and the second summed signal are transformed from the time domain to the frequency domain to generate a first transformed sum and a second transformed sum, respectively. A value R for said ocean bottom reflectivity is selected and used to calculate an inverse Backus filter (1+Rz).sup.2, where Z is the Z-transform of the two-way travel time delay filter. The first transformed sum and the second transformed sum are multiplied by the inverse Backus filter to generate a first filtered sum and a second filtered sum, respectively. A cross spectrum is calculated from the first filtered sum and the second filtered sum to generate a trial cross spectrum.

Abstract: A discrete, minimally-equipped standard seismic calibration system is permanently installed over a subsurface reservoir structure that contains fluids of economic interest. Changes in the fluid content as a function of long-term time lapse may introduce changes in the acoustical characteristics of the reservoir rock layers, producing a corresponding change in the seismic signature recorded by the calibration system. The difference between two signatures over a selected time epoch defines a time-lapse calibration signature. The time lapse calibration signature can be applied to reduce the results of different conventional seismic data-acquisition systems of different vintages and technologies to a common standard.

Abstract: A magnetic coupling for substantially synchronously transferring linear motion through a non magnetic barrier from a first movable element to a second movable element. The coupling comprises magnets disposed at spaced apart locations along the first element. The magnets each have a magnetization direction substantially perpendicular to a direction of motion of the first element along the non magnetic barrier. The coupling includes magnets disposed at spaced apart locations along the second element at locations corresponding to locations of the magnets op the first element. Each of the magnets on the second element has a magnetization direction inclined at an oblique angle with respect to the magnetization direction of the corresponding magnet so as to capture magnetic flux from the magnets on the first element when either of the elements is moved along the barrier.

Abstract: A system has been invented for producing a final earth model of part of an earth formation having N (one or more) layers, the method including, in one aspect, generating an initial earth model based on raw data produced by a wellbore logging tool at a location in a borehole through the earth, performing 2-D forward modeling on the initial earth model to produce an interim earth model that includes a set of synthetic tool responses data for the wellbore logging tool, comparing the synthetic tool response data to the raw data to determine whether there is misfit between them; if misfit between the synthetic tool response data and the raw data is acceptable, saving and storing the interim earth model as the final earth model; if misfit between the synthetic tool response data and the raw data is unacceptable, performing 1-D forward modeling N times on the interim earth model, producing a secondary earth model; performing 1-D inversion on the secondary earth model; and either saving the secondary earth model as t