Abstract

Operational problems associated with tripping drill pipe or running casing become more severe and complicated as drilled holes get deeper and smaller. To reduce the many calculations required, primarily by the men on the rigs, nomographs were developed for solving annular, hole and pipe capacities and displacement volumes. A set of simplified nomographs were also developed, from previously published formulas, which can be used to estimate swab or surge pressures generated when annulus displacement mud flow is laminar. Examples of the use and accuracy of the nomographs are presented. The field results of using these presented. The field results of using these nomographs are mostly in the form of trouble free pipe trips, but some interesting and informative pipe trips, but some interesting and informative field results are presented.

Introduction

The swab and surge pressures generated while tripping pipe, become more critical as wells are drilled deeper and holes get smaller. If abnormal formation pore pressures are encountered which approach the formation fracture pressures, the problem becomes even more pressures, the problem becomes even more critical.

Induced swab or surge pressures while tripping out or into a hole cannot be eliminated but can be reduced to safe values. The most critical conditions exist when the mud hydrostatic pressure is very close to either the formation pore or fracture pressure.

Several methods for predicting swab and surge pressures while tripping pipe have been published. The mathematical methods, published. The mathematical methods, which have been proven to the most accurate by actual test, were found to be too involved and laborious for use by field personnel. The graphical methods found in the literature did not cover all ranges of mud properties and pipe-hole size combinations, and therefore pipe-hole size combinations, and therefore were deemed inadequate for field use. Using the proven mathematical methods developed by J. A. Burkhardt, nomographs were developed and are included in this paper. The nomographs have been in use for approximately one and one-half years and have proven to be reliable. Also included are nomographs for displacement volumes of drill pipe and collars, and annular or hole capacities developed as additional aids for the man on the rig to use in conjunction with tripping pipe.

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