A method for high-resolution seismic recording with increased bandwidth using detectors planted at shallow depths below the earth's surface. In one embodiment, an optimum depth where the amplitudes of high frequency signals increase relative to that of the noise during high-resolution recording is determined, geophones are then planted at that optimum depth and signals are recorded at that depth. To find this optimum depth, detectors are planted at various depths below the earth's surface in order to record the signals at those various depths. The frequency spectra for each detected signal is generated and a velocity profile of the depths covered by the detectors is also generated from the signals. The bandwidth of the frequency spectra and the velocity profile are used to determine a depth for planting the detectors that is closer to the earth's surface than the depths previously considered.
An apparatus and method are provided for ensuring good coupling and vertically planting of seismic receivers while substantially reducing the need for interconnecting wires and costly surveys. The apparatus includes an acquisition unit (AU) 20 for measuring seismic energy and a planting member 12 for engaging and planting the AU 20. An electronic surveying instrument 14 is coupled to the planting member 12 for determining the location of the AU 20. An installer 16 plants the AU 20 in the terrain 22 in near vertical alignment using the planting member 12. Once the AU 20 is planted in near vertical alignment, coordinates are downloaded from the electronic survey unit to locate the planted AU 20.
A method for reducing the time, cost and apparatus required for monitoring the geometry of the oil/water, oil/gas, or gas/water interface in an underground reservoir. By strategically placing sources and sensors, and by fixing the sensors to the solid earth surface beneath the water, and by knowing the velocity fields in the overburden, the changing edges and geometry of the oil may be determined with significantly reduced data gathering. The strategic positions of the sources and receivers is determined by referencing to the known geometry from past surveys. In addition the velocity of the overburden is known by these prior surveys. In addition, higher resolution of reflectivity areas is achieved by use of sound sources capable of generating higher frequencies compensated for the earth's attenuation and by utilizing long integration times to improve signal to noise ratio. These sound sources can be smaller than prior art sources since they provide directed beams of narrower widths. Smaller computers may be used for analyzing the reduced data collected.
A method for the acquisition of seismic signals, in which at least two sources of the air gun type are placed within one or more vertical holes extending in the subsoil and in which one or more seismic sensors record the seismic propagated from said sources, that arrive at said sensors either directly, or by being reflected by the interfaces between the various layers of the subsoil, characterised in that the triggering of the various sources is adjusted so that the various seismic signals generated by said sources are simultaneously received by at least one reference sensor which is placed in a vertical hole which extends at the vicinity of the hole(s) which receive(s) the sources or which is one of said holes.
A method and related apparatus for high speed digital data conmunications from multiple distributed modems to a single central modem or a common transmission medium. In one embodiment, multiple downhole modems, with each modem associated with a geophone, transmit data to a surface modem over a single transmission medium. In a second embodiment, multiple transmission mediums are used and a plurality of downhole modems associated with geophones communicate to the surface modem over the downhole modem's respective transmission medium.
