A Method of Utilizing Existing Information To Optimize Drilling Procedures
Authors: Langston J.W. 
Published: December 2007

Optimising is a term implying accomplishment of a desired objective at lowest cost through use of the most effective procedures. When optimizing drilling procedures, engineers ordinarily think in terms of factors affecting rate of penetration. These factors are bit weight and rotary speed, rock bit factors, hydraulics and drilling fluid characteristics. The contractor must optimize these and other factors to be successful. The objective of this paper is not to present the results of another series of carefully engineered and controlled tests, but to describe a way to use existing information under day-today competitive drilling circumstances. Some pitfalls to watch for when striving for optimization are noted; i.e., if one procedure increases drilling rate, this facet of the operation should not be overemphasized to the neglect of others.

Introduction

Most of the basic information for optimizing drilling procedures is established. A Weight-Speed-Penetration Subcommittee of the AAODC has been active for several years. Their reports of field tests are an accurate guide to optimizing procedure. Galle and Woods accurately described the relationship of factors on which optimization of weight and rotary speed depends. Bentson clearly illustrated rock bit design factors affecting bit performance. Bentson's work is enlarged upon by Hughes Tool Co. The best bit selection and utilization is achieved by a procedure described by Highbarger. The significance of bottom-hole cleaning to rate of penetration is clearly apparent in a phase of the work by Cunningham and Eenink. Bobo described a procedure that is probably the best approach to hydraulic program design for full utilization of pump capacity and Eckel described how mud factors affect drilling rate. Lummus and Ray updated that material, but reached essentially the same conclusions. The interrelationship of factors that affect drilling rate are described by Speer. Moore made a significant contribution to the knowledge of factors that affect drilling rate in a series of articles. More recently, Bingham presented a series of articles that describe a method for predicting drilling performance in the field.

Procedure for Planning an Optimum Drilling Program

Every well drilled by a contractor who wishes to stay in business is drilled according to an optimization plan. This plan will vary from contractor to contractor, and even from rig to rig in the contractor's domain. Yet each contractor, according to his own knowledge, ability and intent, is drilling the lowest-cost well possible. Fig. 1 shows a method of presenting a planned-well program for guiding the personnel who perform the drilling operations. The top part (Fig. 1a) shows anticipated progress at various depths, as well as a plot of actual progress. Other information included on this form (Fig. 1b) is hole size, casing points, deviation limits, bit information, recommended weight and rotary speed. drill-string assembly, pump and hydraulic information, mud program to be used, formation tops and anticipated trouble zone. Decisions must be made concerning all of these factors prior to spudding a well. Control and coordination is provided by recording the actual performance on the planning sheet. An operational plan, such as is illustrated, provides the means for incorporating conclusions from carefully documented laboratory and field studies in the day-today drilling operation.

PreparationIn preparing bids for footage contract work, as well as in many instances of daywork, the engineer responsible for bid preparation accumulates all available information concerning lithology problems likely to be encountered, such as abnormally high formation pressure, circulation loss zones, drift tendencies and otherwise troublesome formations. Where available, pertinent well jogs are obtained, as well as bit records and the over-all performance records on offset wells. If Geolograph records are available, they can be used to good advantage in log correlation. The drilling mud program, a key factor in anticipated progress, is obtained from the operating company when possible. Such information is a minimum requirement to bid with reasonable intelligence.

JPT

P. 677ˆ