Underwater Inspection of Hondo Deepwater Platform Using a Microcomputer Offshore
Authors: Gray W.E. , Devine W.B. 
Published: October 2008

Exxon has completed an underwater inspection of the Hondo Platform located in the Santa Barbara Channel, California.

The survey was performed by an ROV in"flyby" mode and examined over 600 inspection points including external nodes and members from the splash zone to the mudline at -850 feet. A portable microcomputer was pre-programmed with the desired locations to be inspected. The software developed allowed for real-time entry and review of all data and findings from the inspection. This microcomputer system has subsequently been used for a hull inspection by divers on the Hondo Field floating production facility.

The application of the microcomputer as a tool ~o aid in the survey effort proved to be an effective and reliable means to document inspection results. Other features of the system were improved inspection discipline, on-site data sorting, and improved cross-cataloging with the video tapes of the inspection. It is believed that this was the first time a computer has been used as a practical offshore inspection tool.

INTRODUCTION

A most important consideration in achieving safe and reliable long term operations in an offshore environment is the proper design, construction, and installation of platform. In place inspection alone will not necessarily assure structural integrity. While no inspection program can guarantee that all defects or degradation can be detected in the structure, it must provide sufficient information for the implementation of routine maintenance programs. In addition, it must indicate whether or not further inspection or extraordinary remedial or restorative measures are needed.

In addition to valuable above water inspections by field personnel, formal inspections are necessary to satisfy special requirements. Among these are annual cathodic protection potential surveys, post installation inspections, post storm inspections, and periodic platform inspections.

After the Hondo Platform (Figure 1) had been in service for over six years, Exxon completed an inspection of the underwater structure. This inspection required a thorough visual survey as well as measurements of the marine growth, cathodic potentials, and anode size. This level of inspection would reveal corrosion or gross structural damage from substantial overloading from severe environmental events or accidents. Should any evidence of damage be found, a plan for a more detailed examination would be formulated. All the data gathered needed to be recorded, indexed, and referenced for ease of retrieval at any future date.

DEFINITION OF INSPECTION REQUIREMENTS

The Hondo Platform, installed in July of 1976, is located 20 miles west of Santa Barbara, 5 miles off the California Coast in 850 feet of water. The platform (Figure 2) is constructed of eight main vertical members 54 inches in diameter, 13 horizontal frames below water from 16 inches to 24 inches in diameter, and numerous diagonals from 18 inches to 30 inches in diameter. In addition, there are 28 well conductors in a straight vertical 4 × 7 array. The jacket is 45 feet by 130 feet at the water surface and 169 feet by 233 feet at the mudline.