Drilling in 1,300 Feet of WaterSanta Barbara Channel, California

Available technology and equipment have proven adequate for carrying out successful floating drilling operations in water depths to 1,300 feet on federal leases in the Santa Barbara Channel of California. System elements directly affected by water depth have performed satisfactorily with only a few minor design modifications. Introduction During the 12-month period following the Feb. 6, 1968, federal lease sale in the Santa Barbara Channel, Humble drilled 10 wells with floating rigs, three of which are in water depths of 900 to 1,300 ft. The adequacy of advance planning has been demonstrated by the fact that few problems have occurred directly related to water depth. The first of the deep-water wells was spudded in 994 ft of water on Aug. 5, 1968 (Fig. 1). This rig (WODECO IV) bas now completed the drilling of a well in 1,300 ft of water. The first deep-water well for the second rig (Blue Water II) was spudded in 941 ft of water on Dec. 3, 1968. (See Fig. 2)It is our purpose here to present information on the location and environment of the deep-water drilling program; the criteria governing selection of the jigs used; details of the systems used, including design considerations and methods; and operating procedures and 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 meteorological references provided the best available data on winds, waves and currents for guidance in selecting and designing equipment and in formulating operating practices. (Fig. 1 shows sites in the area covered by specific reports.) Historical data indicated that the probable yearly maximum conditions in the central Santa Barbara Channel would not exceed 5-minute average winds of 65 knots from the west and northwest or from the east and southeast; significant wave heights of 16 ft 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 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 18 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 deep water operations and the economics of timing. Factors considered for selecting from the available vessels are as follows. Sufficient drilling-depth capability of the rig. Strength and stability of basic hull configuration. JPT P. 27