Abstract: Elastic nonlinear effects, which cause frequency spectral broadening and the effects of the presence of the Slow-Wave in the reservoir rocks, are investigated. The creation of new frequencies due to elastic nonlinearity of the reservoir rocks and their presence in the reflected seismic signals is used to map the location and extent of the reservoir formations. The large differences in the velocities of the Compressional Wave and the Slow-Wave cause changes in their reflection and refraction characteristics. The reflection due to Slow-Wave appears as a low-frequency artifact, delayed in time. The delay time of this artifact is used to calculate the Slow-Wave velocity and the tortuosity of the reservoir rocks. Based on the tortuosity and the wellbore data, permeability can be estimated.

Abstract: A method for determining the location and the orientation of the open natural fractures in an earth formation from the interaction of the two seismic signals, one signal transmitted into the formation from one wellbore and the second signal transmitted from the surface of the earth, the interaction of the two seismic signals as they simultaneously propagate through the fractured space is recorded in the second wellbore. The seismic signal transmitted from the surface is a lower frequency acoustic pulse of large amplitude identified as ‘modulation’ wave and the signal transmitted from the wellbore is a higher discrete frequency seismic signal, identified as ‘carrier’ wave. The interaction of the ‘carrier’ wave during the compression and rarefaction cycles of the ‘modulation’ signal is recorded.

Abstract: Permeability is one of the most important factors in influencing the commercial viability of a hydrocarbon reservoir. So far, permeability cannot be measured directly in-situ in reservoir formations. This invention relates to the field of estimating in-situ permeability of the reservoir rock formations. The measurements can be made across two wells or in a single well. Due to the morphology of their pore interconnections and the pore fluids in the rock, permeable rocks are elastically nonlinear. In a permeable rock, which is elastically nonlinear, the interactions between two elastic waves can be used in a unique way to map its physical properties. In this invention, the interaction of an elastic wave generated within the permeable rock with an externally generated seismic signal is used to determine the bulk tortuosity and bulk permeability of a reservoir rock formation.

Abstract: This invention relates to mapping the hydrocarbon reservoir characteristics by mapping the reservoir formations that display dynamic elastic nonlinearity responses to the seismic signals. The main reason of this nonlinear behavior in the reservoir rocks is their bulk rock property: the porosity, fractures, differential pressure and pore saturation. To map these bulk rock properties, the interaction of the two seismic waves as they propagate through elastically nonlinear rocks is recorded. Two compressional seismic signals are transmitted from the surface. Seismic reflection data using surface or borehole detectors are recorded. One of the transmitted signals is a conventional swept frequency and the other is a mono-frequency signal. During the propagation of these two signals through the elastically nonlinear reservoir rocks, there is an interaction between the two signals. The sum and difference frequencies of the two primary seismic signals that were transmitted from the surface are created.

Abstract: A method for determining the location and the orientation of the open natural fractures in an earth formation from the interaction of the two seismic signals, one signal transmitted into the formation from one wellbore and the second signal transmitted from the surface of the earth; the interaction of the two seismic waves as they are transmitted through the fractured space is recorded in the second wellbore. The two seismic waves have two selected discrete frequencies. The seismic signal or the seismic wave transmitted from the surface is a low frequency of large amplitude identified as ‘modulation’ wave and the signal transmitted from the wellbore is a higher frequency by an order of one hundred times, identified as ‘carrier’ wave. The interaction of the ‘carrier’ wave during the compression and rarefaction cycles of the ‘modulation’ wave is spectrally analyzed.

Abstract: A method for determining a degree of acoustic non-linearity of an earth formation from seismic signals transmitted into the formation from within one wellbore and received from the formation in another wellbore. The seismic signals include two selected discrete frequencies. The method includes spectrally analyzing the received signals, determining from the spectral analysis the presence of a frequency representing a sum of the two selected frequencies, and determining a relative amplitude of the sum frequency with respect to the amplitudes of the two selected discrete frequencies. In a particular embodiment, the method includes determining the presence of a frequency in the spectrally analyzed signals representing the difference between the selected discrete frequencies, and determining the presence of harmonic multiples of one of the two selected discrete frequencies.

Abstract: A method of determining the continuity of earth formations between wellbores by analyzing seismic energy imparted to the formations. The energy is imparted to the formations at a plurality of depths in one wellbore and is received at a plurality of depths in another wellbore. Compressional and shear components of the seismic energy received in the other wellbore are separated. A frequency spectrum is determined for the compressional component and the shear component of the seismic energy at each selected depth. Common imparted depth stacks of the compressional components and shear components are assembled at the depths at which the seismic energy is imparted. Common received depth stacks of the compressional components and the shear components are assembled at the selected depths at which the energy is received.

Abstract: A method of determining the continuity of earth formations between wellbores by analyzing seismic energy imparted to the formations. The energy is imparted to the formations at a plurality of depths in one wellbore and is received at a plurality of depths in another wellbore. Compressional and shear components of the seismic energy received in the other wellbore are separated. A frequency spectrum is determined for the compressional component and the shear component of the seismic energy at each selected depth. Common imparted depth stacks of the compressional components and shear components are assembled at the depths at which the seismic energy is imparted. Common received depth stacks of the compressional components and the shear components are assembled at the selected depths at which the energy is received.

Abstract: A method is provided for significantly reducing the distortion and crossfeed from any selected order harmonic for any number of vibratory seismic sources operated concurrently, at the same time providing for separation of the signals from the different sources and for improving the signal-to-noise ratio. After determining the highest order harmonic likely to cause distortion, a number of sweeps of each source in each position is selected. This number depends upon the number of sources and the highest order harmonic to be suppressed. Initial phase angles for each sweep of each source are then selected to permit signal separation while suppressing harmonics up to and including that highest order harmonic.

Abstract: A method of seismic exploration and a system which provides the capability for increasing the number of depth points from which seismic data are acquired are disclosed. This increase in data is realized without increasing the number of recording channels or the number of geophone stations employed in the system. A higher common depth point multiplicity is achieved by separating energy sources in relation to geophone stations. The recording system is capable of automatically sorting out the data from different energy sources and storing it in different blocks of a memory. Since substantially all available recording time is fully utilized by using energy sources to their optimum efficiency, higher common-depth-point multiplicity can be achieved with minimum field costs.

Abstract: Apparatus is provided for determining the conformity of an energy pulse generated by a weight drop seismic source to a defined energy pulse characteristic in order that reflections associated with a non-conforming energy pulse can be rejected. The apparatus operates to compare the signature of a weight drop with a signature standard. Incoming seismic data is rejected and not recorded if the difference between the incoming signature pulse shape and the standard signature pulse shape is too great. The pulse shape of the incoming signature is analyzed by comparing a sample of the incoming signature amplitude to upper and lower rejection limits derived from a time correlated amplitude sample of the standard signature. The upper and lower rejection limits against which an incoming signature sample is compared are proportional to the amplitude of the time correlated standard signature sample.