System and method for accurate determination of ocean bottom seismometer positioning and timing

摘要

There is provided herein a system and method of seismic exploration that produces improved locations and timings for ocean bottom seismometers. The instant method utilizes linearized inversion in conjunction with a conventionally accurate clock to provide both time and positioning for each OBS unit with high accuracy as compared with the prior art approach. Inversion is one mathematical tool that effectively performs the requisite triangulation. Furthermore, the clock drift can be accounted for in the inversion scheme. The inversion not only determines the OBS position and shot timing errors, but also estimates the accuracy of the position and timing determination.

主权项

1. A method of geophysical exploration within a predetermined volume of the earth containing subsurface structural and stratigraphic features conducive to the generation, migration, accumulation, or presence of hydrocarbons, wherein is provided an OBS seismic survey that was collected by recording seismic waves using a plurality of receivers that are situated within a body of water, each of said receivers being associated with a plurality of seismic traces in said OBS seismic survey, and each of said receivers having a clock associated therewith, comprising the steps of:
a. selecting one of said plurality of receivers; b. selecting a plurality of seismic traces associated with said selected receiver; c. determining a direct arrival first break time through the water for each of said selected plurality of seismic traces associated with said selected receiver, thereby obtaining a corresponding plurality of first break times; d. determining a location of a seismic source associated with each of said plurality of seismic traces associated with said selected receiver; e. determining a length of time since a clock associated with said selected receiver was last synchronized; f. using any of said determined first break times, said determined length of time since said clock associated with said selected receiver was last synchronized, and any of said determined locations of said seismic sources to simultaneously determine a location in three dimensions of said selected receiver and a drift correction associated with said selected receiver; g. associating said determined location of said selected receiver and said determined drift correction associated with said selected receiver with each of said selected plurality of seismic traces; h. imaging at least a portion of said predetermined volume of the earth using said selected plurality of seismic traces, said determined location of said selected receiver, and said determined drift correction associated with said selected receiver; and, i. using at least said imaged portion of said predetermined volume of the earth to explore for hydrocarbons therein.