Factors Influencing Drag, Torque and Cost of Directional Drilling Near a Salt Dome
Authors: Fontenot John E. 
Published: December 2007

This paper was prepared for the 48th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Las Vegas, Nev., Sept. 30-Oct. 3, 1973. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Hole enlargement in salt dome drilling was found to be mainly dependent upon the distance of the well course from the salt. The torque and drag decreased as the hole enlarged. The drilling cost is a function of well depth, hole shape and proximity of the well to the salt. The mathematical correlations developed should be useful in predicting hole drag, torque and drilling predicting hole drag, torque and drilling cost as a function of well geometry and proximity to the salt. proximity to the salt

Introduction

Excessive drill string drag and torque are major problems in offshore directional drilling, particularly near salt domes. High drag and torque can materially slow the drilling operation and add to well cost and the risk of stuck or parted drill pipe. In planning a development drilling program from planning a development drilling program from an offshore platform, the influence of the hole angle, direction, depth and proximity to the salt dome on torque and drag need to be considered. This is especially true when it is necessary to drill high angle holes close to the salt dome in highly stressed rock.

The "C" Platform in Shell's Eugene island 175 Field is located on the north side of a salt dome. It was located so as to be able to drill and complete in multiple, thin, highly-dipping sands close to the salt dome. Wells were drilled along a semi-circle about the northern side of the dome. In many cases it was necessary to rapidly build and then drop hole angle to follow closely the contour of the salt dome. As a result high drag and torque were common problems throughout the drilling program. In several wells the drag and torque approached levels where it would have been impossible to continue drilling without displacing the water-base mud system with an oil-base one. Most of the well courses below 3,000 feet were within 300 feet of the salt.

Subsequent to the completion of the drilling program on "C" Platform, an extensive review of the drilling performance was made. Its purpose was to provide a guide for the planning of future offshore drilling programs. From the data compiled in the review, programs. From the data compiled in the review, correlations were obtained between a number of the drilling parameters. In some cases where correlations were sought none were found.

This paper presents and discusses correlations found between torque, drag and hole enlargement and three other parameters.