Drilling in 1300 Feet of Water - Santa Barbara Channel, California

Abstract

ABSTRACT Available technology and equipment have proven adequate for carrying out successful floating drilling operations in water depths to 1300 feet on Federal Leases in the Santa Barbara Channel. California. System elements directly affected by water depth have performed satisfactorily with only a few minor design modifications. INTRODUCTION During the l2-month period following the Federal Lease Sale in the Santa Barbara Channel of February 6, 1968. Humble has drilled ten wells with floating rigs three of which have been in water depths in the range of 900 to 1300 feet. The adequacy of advance planning has been demonstrated by the few problems that have occurred that are directly related to water depth. The first of the deepwater wells was spudded in 994 feet of water on August 5. 1968. as shown in Figure 1. This rig (WODECO IV) has now completed the drilling of a well in 1300 feet of water. The first deepwater well for the second rig (Blue Water II) was spudded in 941 feet of water on December 3. 1968. Both rigs are shown in Figure 2. It is the purpose of this paper to present information as to:The location and environment of the deepwater drilling program.The criteria governing selection of the rigs used.Details of the systems used including design considerations and methods.Operating procedures.Operating results. THE SANTA BARBARA CHANNEL WINDS, WAVES. AND CURRENTS The Santa Barbara Channel is an area of the Pacific Ocean that is bounded on the north by the portion of the California coastline extending from Point Conception on the west to Ventura on the east and is bounded on the south by the Channel Islands of San Miguel, Santa Cruz and Anacapa. Industry's previous experience with floating drilling in the Channel had shown the environment to be relatively mild. Oceanographic and meterological references provided the best available data on winds waves and currents for guidance in the selection and design of equipment and in the formulation of operating practices. Sites in the area covered by specific reports are also shown on Figure 1. Historical data indicated that the probable yearly maximum conditions in the central Santa Barbara Channel would not exceed:Five-minute average winds of 65 knots from the west and northwest or from the east and southeast.Significant wave heights of 16 feet with a period of 13 seconds. Maximum waves associated with this sea state would probably be approximately 30 feet.Surface or near-surface currents of 2.4 knots parallel to the California coastline. The data showed generally that these conditions would occur for only a very small percentage of the time in winter months in the main part of the Channel east of Point Conception. Near the west end of the Channel, a yearly maximum significant wave height of IS feet might occur with somewhat greater frequency. CRITERIA FOR RIG SELECTION On the basis of the water depths for the leases offered, the rig selection criteria emphasized deepwater operations and the economics of timing.