Seismic Survey in Transit Zone. Krab System Full-Scale Tests (Stage 2)

Abstract

It is emphasized that the Russian complex of "KRAB-400" seismic bottom stations was developed for hydrocarbon survey on the continental shelf of the Russian Federation within the framework of import substitution program. The tests carried out on a limited sample of 10% of the complex bottom stations in the first stage have revealed unavailability of the complex for further tests. This fact has dictated the necessity to develop procedures for hardware integrated check to identify engineering faults. The second stage of full-scale tests performed on the basis of the developed integrated check procedures is described in the paper. The test procedures to validate the key parameters of bottom stations are explained. They include the adjustment of seismic signal source, accuracy assessment for seismic station timer, identity evaluation for bottom station seismic channels, assessment of station displacement on the seabed with respect to the shipboard launch point, analysis of station compass and tiltmeter indications on the seabed, definition of hydrophone channel optimum gain. The technology of seismic profile mapping using MultiChannel Seismic (CDP method) at test range is offered. The performed tests have revealed that the overall reject rate of stations by the various parameters (failed hydrophones, reversed polarity of connection, channels nonidentity, failure to meet timer specifications) is 9.18% of total number of stations. This reject rate is unacceptable for the field trials. Regardless of hardware engineering deficiencies the second stage of tests has validated the general system availability to gain high-quality seismic data. Hardware performance is rated at the level of the best world-class products. The processed seismic data has enabled evaluating the accuracy of the obtained results, developing recommendations for designer to enhance reliability and efficiency of the stations ready for pilot testing at one of the licensed areas of the continental shelf of the Russian Federation.