SEISMIC EXPLORATION METHOD

• US 3,812,457 A
• Filed: 11/17/1969
• Issued: 05/21/1974
• Est. Priority Date: 11/17/1969
• Status: Expired due to Term

• Current Assignee: Charles E. Weller
• Original Assignee: Charles E. Weller
• Inventors: Weller, Charles E.
• Primary Examiner(s): Farley, Richard A.
• Assistant Examiner(s): Moskowitz, N.
• Application Number:
  US04/877,350
• Time in Patent Office: 1,646 Days
• Field of Search: 340/15.5R,15.5CD 343/100.7
• US Class Current: 367/36
• CPC Class Codes: G01V 1/366 by correlation of seismic signals
• CPC Class Codes: G01V 2210/3248 Incoherent noise, e.g. white noise

Abstract

Seismic exploration is conducted without using a seismic sound source by recording a plurality of relatively long stretches of ambient earth noise data at each of an array of seismic receiving stations, preprocessing the data from each station and producing correlation functions in which the data from each station is presented as a seismic data trace analogous to a conventional seismogram.

Claims

1. A method of seismic exploration, comprising:

disposing a plurality of seismic receiving stations at horizontally spaced locations near the surface of the earth, operating said receiving stations to produce earth noise data signals indicative of the amplitudes with time at which acoustic energy appears at a plurality of said station locations during a time period many times greater than the travel time of acoustic energy from the vicinity of said stations to a subterranean reflecting structure and back, subjecting the noise data signals to preprocessing including summing selected groups of said noise data signals to provide signals that are selectively responsive to the energy that emerges along selected directions from locations within the earth, isolated portions of the data signals being adapted to be correlated with each other, the isolated portions representing acoustic energy received at the surface and reflected back down to the subterranean structure then reflected back up to the receiving stations; and

correlating said isolated portions of the data signals to provide a plurality of correlograms that are adapted to be visually displayed for seismic data analysis and interpretation.

2. The process of claim 1 in which said preprocessing includes an automatic spectrum whitening of said data signals.

3. The process of claim 1 in which said preprocessing includes a condensation of said data signals by, in effect, increasing the frequency of the amplitude fluctations of the data.

4. A method of seismic exploration, comprising the steps of:

placing a large number of seismometers in an array at the earth'"'"''"'"'s surface;

summing signals from said seismometers to produce a seismic signal in which horizontal waves are rejected and waves generally vertically traveling are enhanced, the seismic signal being produced continuously over a very long period;

correlating data in the seismic signal to obtain correlation signals which represent earth noise impulses which are received at the seismometers then are reflected back down to subsurface formations then reflected back up to the array whereby similar impulses are received which are spaced in time by a period corresponding to the travel time of the noise impulse from the surface to the formation and back to the surface; and

recording the correlation signals to provide a seismogram.

5. The method of claim 1 wherein said correlograms are one-sided auto-correlation functions.

6. The method of claim 1 wherein said correlating is a cross-correlation of one seismic receiving station with at least one other seismic receiving station.