An experimental marine sediment instrumentation system incorporating a high data rate acoustic telemetry link has been designed, fabricated, and successfully field tested. Data has been transmitted acoustically at data rates up to 2,400 bits per second through up to 600 ft of sea water with fewer than 1 error per 1,000 bits transmitted. A limited number of sensors have been tested, and the capability to detect, measure, process, store, and transmit seismically induced acceleration data has been demonstrated. The high data rate acoustic telemetry link provides a means of retrieving large quantities of data from sea-floor instrumentation systems in a relatively short period of time. In addition, the acoustic system provides a heretofore unavailable capability to check periodically the status of ocean-bottom systems and retrieve data as often as desired during the lifetime of the system.
The experimental system consists of three principal subsystems: a data gathering subsystem, which is on the sea floor, a command and recording Subsystem, which is carried onboard a ship, and an optional buoy relay subsystem, which is moored over the data gathering subsystem.. All subsystems are controlled by similar microcomputers consisting of a microprocessor, programmable read-only memory, read/write random access memory, clock, universal asynchronous receiver/transmitter, and additional input/output devices as required by each subsystem.
This paper describes the design features of the experimental system, presents and discusses field test results, and outlines future work and potential applications of the technology developed.
In the future, offshore exploration and production of oil and gas will be extended from the principal sites of present reserves in the Gulf of Mexico and offshore Southern California to the Alaskan offshore and the Atlantic and Arctic Oceans. There is a recognized need in both government and industry for an expanded environmental hazards and engineering forces data base in the outer continental shelf, especially in these frontier areas. The federal government requires the data to fulfill its regulatory responsibilities. Private industry requires the data to design and construct safe, cost-effective production facilities. Recognizing this need, the Dept. of Energy (DOE) has established the offshore instrumentation program, managed by Sandia Laboratories, to develop unique instrumentation systems that will assist government and industry in characterizing the environmental and engineering conditions of the outer continental shelf.
The offshore instrumentation program was initiated in July 1976, by the Energy Research and Development Administration (ERDA), now the DOE, to investigate the application of earth-penetrating weapon technology to petroleum and gas production problems in offshore regions. In the initial months of the program, the Marine Sediment Penetrometer, a hardwire, real-time data system, was tested in the Gulf of Mexico. These tests provided penetrometer acceleration data that are being analyzed in an effort to derive sediment shear strength profiles.
In Feb. 1977, the program was reoriented to address the problem of long-term measurement of marine soil response to environmental forces, specifically seismic activity. Initial emphasis was placed on the development of elements common to remote instrumentation applications, such as data acquisition, processing, storage, and retrieval plus command and control of the sea-floor package.
