Engineering Planning and Supervision of Directional Drilling Operations

Abstract

Abstract For many years the planning and supervision of directional drilling operations have been more-or-less limited to those organizations and individuals specializing in directional work. Without attempting to minimize the importance of and necessity for these directional specialists, operating companies have become increasingly aware of the contributions which competent engineering planning and supervision can make toward a successful directional drilling campaign. The part which such planning and supervision can play in directional operations is illustrated by a recent drilling campaign undertaken by Sun Oil Co. To test a Marginulina sand structure underlying a portion of the lower Texas Gulf Coast, three relatively large-displacement directional wells were drilled from Padre Island out under the Gulf of Mexico. While the hazards and limitations involved in drilling high-angle wells were recognized, the cost advantage of a successful directional campaign, as compared with other methods of drilling in the 20- to 40-ft waters, made the calculated risk well worth accepting. Careful and detailed planning preceded the operation. Among the factors considered were:selection of directional drilling specialists,study of rig requirements and selection of contractor,target tolerance,kickoff depth,casing and hole-size program, anddrilling mud program. With the exception of one short fishing operation, the directional operations progressed in a satisfactory and troublefree manner. On each of the wells approximately 9,000 ft of hole were drilled to secure horizontal displacements ranging from 3,900 to 4,500 ft at true vertical depths of 7,900 ft. Maximum angles ranged from 31 ½ to 43 ½. All holes bottomed well within target limits, and the drilling times, raging from 32 to 42 days, are considered quite good for this specialized operation. No difficulty was experienced with any of the casing or casing operations. Average cost of the directional wells was $125,000; it is estimated that vertical wells drilled by platform and tender or drill barge would have cost a minimum of $300,000 and probably $500,000. Sun's successful directional program may be attributed largely to the following factors, all of which enhance the chance for success on any directional program:careful planning; close, informed supervision, andadequate drilling rig and equipment; cooperative and experienced rig personnel; a competent and responsible directional specialist.