Well Completion Planning lec ( 3 )

Introduction

Planning a completion, from concept through to installation, is a complex
process comprising many phases. Many factors must be considered, although
in most cases, a high proportion can be quickly resolved or disregarded.
Regardless of the completion design complexity, the basic requirements of any
completion must be kept in mind throughout the process. A completion system
must provide a means of oil or gas production (or injection) which is safe,
efficient, reliable and economical.
Ultimately, it is the predicted technical efficiency of a completion system, viewed
alongside the company objectives that will determine the configuration and
components to be used.

Completion

Planning Process

This section outlines the principal factors to be considered when planning an
oil or gas well completion. In addition to the technical influences on completion
design and selection, economic and non-technical issues are also detailed.
The relevance of these issues, in common with technical details, is dependent
upon the circumstances pertaining to the specific well, completion or field
being studied.
Although many wells (and fields) may be similar, the success of each completion
system is based on the individual requirements of each well. Therefore, it is
necessary to review and amend generic design or installation procedures as
required.

Principal Phases of

Well Completion Design

Impact of
Non-Optimized
Completions

The economic impact of designing and installing non-optimized completions
can be significant. Consequently, the importance of completing a thorough
design and engineering process must be stressed. Delaying the commencement
of the wells pay out period is one example of how non-optimized completion
design, or performance, can affect the achievement of objectives. However,
while reducing installation cost and expediting start-up are important objectives,
far-reaching objectives such as long-term profitability must not be ignored. As
illustrated, a more costly and complex completion may provide a greater return
over a longer period. In addition, the consequences of inappropriate design
can have a significant effect, (e.g., requiring premature installation of velocity
string or artificial lift).

Optimized Completion
System

Reservoir Parameters

The type of data outlined in this category are obtained by formation and
reservoir evaluation programs such as coring, testing and logging. Typically,
such data is integrated by reservoir engineers to compose a reservoir model.
The reservoir structure, continuity and production drive mechanism are
fundamental to the production process of any well. Frequently, assumptions
are made of these factors which later prove to be significant constraints on the
performance of the completion system selected.
Physical characteristics of the reservoir are generally more easily measured or
assessed. Pressure and temperature are the two parameters most frequently
used in describing reservoir and downhole conditions. The effects of
temperature and pressure on many other factors can be significant. For example,
corrosion rates, selection of elastomer or seal materials and the properties of
produced fluids are all affected by changing temperature and pressure.

Components of a
Reservoir Model

Produced Fluid
Characteristics

The ability of the reservoir fluid to flow through the completion tubulars and
equipment, including the wellhead and surface production facilities, must be
assessed. For example, as the temperature and pressure of the fluid changes,
the viscosity may rise or wax may be deposited. Both conditions may cause
unacceptable back-pressure, thereby dramatically reducing the efficiency of
the completion system.
Although the downhole conditions contributing to these factors may occur
over the lifetime of the well, they must be considered at the time the completion
components are being selected. Cost effective completion designs generally
utilize the minimum acceptable components of an appropriate material. In
many cases, reservoir and downhole conditions will change during the period
of production. The resulting possibility of rendering the completion design or
material unsuitable should be considered during the selection process.

Components of Produced
Fluid Characteristics

Wellbore Construction

The drilling program must be designed and completed with the scope and
limits determined by the completion design criteria.
Most obvious are the dimensional requirements determined by the selected
completion tubulars and components. For example, if a multiple string
completion is to be selected, an adequate size of production casing (and
consequently hole size) must be installed. Similarly, the wellbore deviation or
profile can have a significant impact.

Components of
Wellbore Construction