Deep Offshore Drilling Case History of North Padre Island 960-L #1

Abstract

SPE Members Abstract This paper summarizes the planning and drilling of the North Padre Island (NPI) 960-L No. 1 well. This well was drilled to 24,938-ft. RKB offshore South Texas. The well experienced temperatures in excess of 420 deg. F and pressures above 23,000 psi at total depth. In addition, several other aspects of the well were unique to offshore drilling operations including:Development of a 2,000 kips static hook load offshore rig.Use of newly-developed 30 in, 3,000 psi ram type BOP.Drilling of deep large diameter holes (24-in. to 1,897-ft. RKB, 16-1/2-in. to 15,863-ft. RKB).Designing, testing, running, and cementing of heavy weight casing strings up to 2,110 kips air weight. Land and Geological ARCO Oil and Gas Company acquired thirty-seven (37) Offshore State of Texas Leases in three (3) separate Lease Sales. The units were pooled in October 1982 to form the 43,000+ acre ARCO Oil and Gas Company Monster Prospect. This unit was located approximately five (5) miles offshore Kenedy County Texas as shown in Figure 1. Water depths in the unit varied from +/- 63-ft. to +/- 85-ft. The prospect was located in a downdip stratigraphic portion of the productive Oligocene age Frio trend. The well objective was a very large downthrown Oligocene age Middle Frio anticlinal rollover structure which covered approximately 23,700 acres at a depth of 22,000-ft. (refer to Figure 2). Above the 22,000-ft. level the anticlinal structure was virtually nonexistent. To reach the objective, the well drilled through 9,000-ft. of very sandy Miocene age section and 3,000-ft. of shaly Oligocene age Anahuac Formation before encountering the top of the sandy Oligocene age Upper Frio Formation at 12,000-ft. RKB At 22,000-ft. RKB, the well penetrated the Oligocene age Middle Frio structural objective and encountered reservoir quality sands. Minor gas shows were seen at the structural objective below 23,000-ft. RKB, however economic quantities of hydrocarbons were not present. Planning for the ARCO Oil and Gas Company NPI 960-L No. 1 well was started in March 1982 with the initial proposed total depth of 23,000-ft. The well was spudded April 16, 1985 and reached total depth in 395 days as shown in Figure 3. The purpose of this paper is to present an overview of the drilling process from planning and materials procurement, to rigsite operations and results. Well Design Environmental Design Criteria The environmental design parameters for the NPI 960-L No. 1 were established by surveying then current Frio and general industry deep well experiences. Information was gathered concerning:Temperatures and pressures during drilling(refer to Figure 4) and producing modesGas production ratesGas composition (CO, H S)Produced liquids composition From the drilling and production information obtained and computer simulation of producing well conditions, the environmental design requirements were established as listed in Figure P. 317^