Methods to Assess the Reliability of Downhole Completions: The Need for Industry Standards
Authors: Turner Will 
Published: October 2008

Reliability of downhole completion equipment is a key factor in the total return on well investment. Although the need to reduce failures and minimize risk has brought about increased desire for operating companies to share information, no industry standards have been established for reliability assessment of completion equipment. This paper will discuss examples of assessment schemes developed in the North Sea that could be used in the process of establishing industry measurement standards. Establishment of these standards would significantly support the goals of the oil industry to improve operational and cost efficiencies.

Introduction

Requirement for 20-year equipment reliability is both common and justified. Some of the earliest platforms in the North Sea are still in place after more than 25 years, but the majority of wells have been worked over at least once. The average tenure of completion/production engineers responsible for design, selection and performance of downhole completion equipment is much less than 20 years - so, how do these engineers make informed decisions? The larger operating companies rely on the experience of experts who provide input on completion design but even so, this input is usually influenced by the personal experiences of those individuals. Unfortunately, broad-range sharing of information across the industry for benchmarking of completion equipment performance has been poor or non-existent.

Since equipment integrity is essential not only for cost efficiency but also for safety of personnel and the environment, more information is needed on long-term reliability benchmarking during the initial stage of completion design.

The key factors needed to assess equipment reliability are collection, storage, and analysis of well data. However, failure to agree on how to establish industry-wide reporting methods and performance benchmarks for the data will retard the process of continuous improvement in our industry. Additionally, if the methodology used to collect and interpret the data is not understood and accepted by both the operating companies and the equipment manufacturers, the goal to develop a tool that can provide significant value to the industry will not be accomplished. For these reasons, development of reliable standards will require commitment and participation from all parties.

Reliability Factors

Prevention of equipment failure is similar to the prevention of accidents. The goal must be zero, and there must be systems in place to help the industry make continuous improvement towards attaining that goal. Industry standards have been implemented for accident reporting, and the lost-time incident frequency (LTIF) index has been widely accepted as the benchmark measure for continuous improvement. Unfortunately, equivalent standards for reporting and benchmarking equipment failures and completion performance have not yet been implemented although an International Standard ISO/142241 was issued in July 1999. This standard has an expansive scope, and it is too early to predict its widespread acceptance for downhole equipment.

Factors that affect well completion reliability and the fundamental considerations that must be considered to reduce probability of failure are shown in Table 1. These factors are listed in order of time rather than importance.