Abstract: The invention is a method for inferring the saturation and pressure change of a reservoir by combining the information from 4D (time-lapse) seismic and time lag data volumes (7) derived from the 4D seismic, well logs (4), and reservoir simulation results (when simulator results are available) and featuring one or more 4D well ties (1) for a quantitative 4D interpretation. The inventive method uses model-based inversion incorporating rock physics (2) at well locations (5), and is statistical-based (6) away from wells. The method thus allows integration (8) of rock physics model and reservoir simulation and honors 4D seismic change.

Abstract: Techniques are disclosed for performing time-lapse monitor surveys with sparsely sampled monitor data sets. An accurate 3D representation (e.g., image) of a target area (e.g., a hydrocarbon bearing subsurface reservoir) is constructed (12) using the sparsely sampled monitor data set (11). The sparsely sampled monitor data set may be so limited that it alone is insufficient to generate an accurate 3D representation of the target area, but accuracy is enabled through use of certain external information (14). The external information may be one or more alternative predicted models (25) that are representative of different predictions regarding how the target area may change over a lapse of time. The alternative models may, for example, reflect differences in permeability of at least a portion of the target area. The sparsely sampled monitor data set may then be processed to determine (23) which of the alternative models is representative of the target area.

Abstract: Techniques are disclosed for performing time-lapse monitor surveys with sparsely sampled monitor data sets. An accurate 3D representation (e.g., image) of a target area (e.g., a hydrocarbon bearing subsurface reservoir) is constructed (12) using the sparsely sampled monitor data set (11). The sparsely sampled monitor data set may be so limited that it alone is insufficient to generate an accurate 3D representation of the target area, but accuracy is enabled through use of certain external information (14). The external information may be one or more alternative predicted models (25) that are representative of different predictions regarding how the target area may change over a lapse of time. The alternative models may, for example, reflect differences in permeability of at least a portion of the target area. The sparsely sampled monitor data set may then be processed to determine (23) which of the alternative models is representative of the target area.

Abstract: The invention is a method for inferring the saturation and pressure change of a reservoir by combining the information from 4D (time-lapse) seismic and time lag data volumes (7) derived from the 4D seismic, well logs (4), and reservoir simulation results (when simulator results are available) and featuring one or more 4D well ties (1) for a quantitative 4D interpretation. The inventive method uses model-based inversion incorporating rock physics (2) at well locations (5), and is statistical-based (6) away from wells. The method thus allows integration (8) of rock physics model and reservoir simulation and honors 4D seismic change.

Abstract: A method and apparatus for estimating the earth's resistance (conductivity) as a function of depth using electroseismic prospecting (ESP) or inverse ESP techniques. Resistance is determined by the frequency-dependent attenuation of reflected EM signals which are produced by application of seismic signals to the earth. A seismic wave is generated by conventional means into the earth, and EM waves are generated back to the surface by different reflectors at different depth levels. This propagation attenuates the high frequencies preferentially. EM waves generated at lower depths are further attenuated relative to those waves generated at more shallow depths. The method and apparatus determines the difference in spectral content between the reflected signals from different horizons based on their relative attenuation and uses this difference as a direct measure of the conductivity between the horizons.

Abstract: A marine geophysical prospecting system employs a hydrophone streamer cable containing electromagnetic field sensors, modified to be towed at a preselected distance above the sea floor by a first marine vessel senses electromagnetic energy from selected substrata beneath bodies of water. The voltage between sensors may be amplified by amplifiers in the cable or by amplifiers aboard the towing vessel. Optionally, a second similarly modified cable is preferably located above the near-bottom cable. Both cables may also contain hydrophones and/or accelerometers, as well as depth and position sensors. Optionally, a second vessel tows at least one conventional seismic source to create compressional energy which propagates downwardly through the water into the substrata beneath the body of water. At appropriate porous subsurface formations, the acoustic energy is converted to electromagnetic energy.

Abstract: A method of seismic prospecting using electromagnetic grounded antennas to detect electromagnetic waves that are produced from acoustic waves in the earth's formation. Seismic waves reflected by a formation in the earth are converted into electromagnetic waves in the vicinity of the antenna according to the streaming potential theory. The antenna has two electrodes which detect the horizontal component of the electromagnetic waves, thus providing additional seismic information that is not readily available using standard geophones. Antennas are also not subject to coupling problems and thus provide more accurate information than traditional geophones. For example, using multicomponent detection, all three components of the seismic pressure gradient can be detected.