All pipelines are subject to erosion as well as the removal of' protective earth covering due to the elements of nature. If permitted to continue to its ultimate conclusion, that of a long unsupported pipe span, failure of the pipe is almost sure to result. While it is fairly easy to patrol land pipelines to guard against excessive erosion, a measure specified by the Federal Minimum Standards, patrol of submarine pipelines have, for the most part, been unfeasible in the past. Attempts by divers and miniature submarines have been prohibitively expensive, and in many cases the findings have been inconclusive.
The advent of more sophisticated underwater electronic and sonic equipment suggested the possibility of an almost totally electronic survey, thereby increasing reliability and substantially decreasing costs. This paper presents the equipment and techniques utilized in such an offshore cover survey of a 16-in. submarine pipeline located off the Galveston coast. It begins with a detailed description of the equipment used, such as the differential proton precession magnetometer, recording fathometer, low frequency acoustic subbottom profiler and the ultra-sensitive dual channel side scan' sonar. All of these are readily available through most offshore survey contractors. Methods and techniques are developed enabling any offshore pipeline operator to conduct such a survey.
The actual survey, conducted during the summer of 1972, substantiates the belief that such surveys are both practical and economically feasible. Important side benefits of such a survey are
the precise location of the pipeline in the event that a leak must be located and a repair made at a later date
the detection of the presence of debris on or near the pipeline and
the assurance that the pipeline has not been moved an appreciable distance by a storm.
The purpose of this project was to perform a detailed investigation and determine the existence and extent of any bridged sections of the approximately 36.4 miles of ballasted 16-in. pipeline owned by Black Marlin Pipeline Co., Inc. Located offshore, the Black Marlin pipeline extends from off the Texas coastline in High Island Block 136 to a point on the Bolivar Peninsula in High Island Block 194. Methods for the performance of this underwater location and cover survey utilized the latest and most modern equipment and techniques for obtaining the field data and for purposes of preparing the final report.
In order to establish the scope of work, a list of the information required with regard to the present status of the pipeline was set out. The desired information was
horizontal location of the pipeline,
vertical location of the pipeline,
existence and extent of a bridged sections of the pipeline and
location of any large metallic objects, exposed wrecks, sand waves, or other obstructions appearing in the immediate area of the pipeline right-of-way.
