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Abstract

Drilling personnel typically base the selection o[a Drilling Contractor and rig an their subjective evaluation of how welt various rig components will meet their envisioned drilling needs. This evaluation process involves rating the capabilities of the drawworks, mud and solids control system, mud pumps, tubulars, power generation equipment, and ancillary equipment such as blow-out preventers, choke manifolds, automatic driller, and instrumentation. Consideration must also be given to the type of geology that the planner expects to encounter. However, the true performance or capability of the selected rig is not known until it is contracted and used to drill a well. Many times the advertised capability of the rig is not achieved in the field.

An Engineering Simulator for Drilling (ESD) has been developed that can simulate the operation of any SCR type drilling rig in any type of drilling environment. The simulator has been used to compare different equipment for specific drilling programs and has predicted which rig would be the best rig to drill the well. The simulator has also been used to up-grade the design of existing rigs to optimize their performance.

This paper presents an overview of the drilling rig simulation algorithms and how they are used to emulate an actual drilling rig. The paper also gives examples of how the simulator is used to evaluate rig capabilities, and how this ability to evaluate rigs, with an unbiased systems approach, can be used by operators to select rigs on a performance basis.

Introduction

A drilling rig, with all of its many components, should be viewed as a complex machine designed for producing one product—a useable wellbore. This complex machine consists of various components such as hoisting, pumping, and power generation equipment, and a drillstring. These components interact in many ways. For example, each piece of equipment on a diesel-electric rig makes a piece of equipment on a diesel-electric rig makes a contribution to the total power consumed and to the apparent power usage. This interaction is a major factor in determining the overall fuel efficiency of the rig. Another example of this interaction between components involves the tradeoff between the use of drillpipe with a larger inside diameter to minimize power losses because of friction and the fact that a larger (heavier) pipe will increase power usage during tripping and rotation. There are power usage during tripping and rotation. There are many other examples of interaction, or cause and effect relationships, between the major components which constitute a drilling rig.

Without the use of a detailed computer simutation planners must base design and selection of drilling rigs on analysis of overall rig capabilities. Often this analysis is as simple as making sure the drawworks and rotary can handle the anticipated loads and that the pumps can produce the specified flowrate and pressure. The reason for this is that the amount of hand calculation required to perform a detailed rig cost analysis for a complete perform a detailed rig cost analysis for a complete welt is prohibitive. A drilling rig represents both a complex machine and a complex process. Analysis of overall capabilities can lead to less than optimum results.

As Millheim, Huggins, Brett, and Summers have reported in recent literature, a significant effort is underway to develop an engineering simutator for the study of the entire drilling process. This simulator uses detailed mathematical models of the processes involved and of the various components of the drilling rig. Simulation is possibly the only viable means of studying complex systems. In the current context, a simulator consists of mathematical models which describe each part of each component of the drilling rig.

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