Reliability 101
Authors: Schlater Donald R. 
Published: October 2008

This paper is an attempt to define what is actually meant by reliability from a deepwater subsea well perspective. It will discuss how historical failure data should be treated. But, most importantly, it proposes a method of assuring reliability on the new equipment required for the myriad of upcoming deepwater discoveries.

Reliability is classically defined as "The ability of a piece of equipment to perform its intended function for its intended lifetime". This statement usually brings to mind component reliability. But to an operator well reliability is simply the ability to economically produce hydrocarbons at a desired rate for a certain length of time with specified health, safety and environmental safeguards.

We usually base the reliability of equipment on existing data. Historical failures are recorded in several databases to varying degrees of accuracy and completeness. Do we have enough data to bring statistical significance to more than one database? I don't think so. In deepwater we are for the most part extrapolating the data for now. However, our profession must produce a single uniform database with historical knowledge and henceforth populate it with data collected and analyzed in a consistent manner. A three dimensional database with equipment on the "Y" axis, problem definition on the "X" axis and root cause on the "Z" axis will capture the required information. For the next few years this collection of data will play only a minor role in assessing the reliability of new equipment in deepwater. The reliability of new equipment for deepwater should be evaluated based on an agreed upon set of criteria. The following items should be included: similar component reliability from the database records, manufacturer's past performance, component testing, system verification, and actual field tests. We must stop discussing the subject and form a small committee lead by the deepwater operators and define the criteria for determining reliability of new subsea systems.

Introduction

Simply stated, "The survival of our profession rests squarely on the shoulders of reliable equipment for deepwater production". In the next decade a significant portion of our new hydrocarbon production and reserves will be in deepwater. Before a field development commences, operators expend significant resources to predict recovery volumes, capital outlays and operating costs. Although reliable reservoir predictions are extremely important they are beyond the scope of this paper and the knowledge of the author. I submit that our profession is very good at coming up with an accurate estimate of the capital expenditure required for a deepwater development. It is the operational costs we struggle with because we are not sufficiently confident that we can predict the reliability of our systems. I contend, and will cite an example later in this paper, that capital expenditures will not increase with increased system reliability. In addition to planned and unplanned repair and maintenance on a well system, the cost of a catastrophic failure looms when we are not confident in the reliability of a well system.