Page 60 - Hydrocarbon

CHA P T E R 4

Drilling Engineering

Introduction and Commercial Application: Drilling operations are carried out during all
stages of the project life cycle and in all types of environments. The main objectives
are the acquisition of information and the safeguarding of production. Expenditure
for drilling represents a large fraction of the total project’s capital expenditure
(CAPEX) (typically 20–60%), therefore an understanding of the techniques,
equipment and cost of drilling is important.
An initial successful exploration well will establish the presence of a working
petroleum system. In the following months, the data gathered in the first well will
be evaluated and the results documented. The next step will be the appraisal of the
accumulation requiring more wells. If the project is subsequently moved forward,
development wells will have to be engineered. The following section will focus on
these drilling activities, and will also investigate the interactions between the drilling
team and the other E&P functions.

4.1. Well Planning

The drilling of a well involves a major investment, ranging from a few million
US$ for an onshore well to 100 million US$ plus for a deepwater exploration well.
Well engineering is aimed at maximising the value of this investment by employing
the most appropriate technology and business processes, to drill a ‘fit for purpose’
well, at the minimum cost, without compromising safety or environmental
standards. Successful drilling engineering requires the integration of many
disciplines and skills.
Successful drilling projects will require extensive planning. Usually, wells are
drilled with one, or a combination, of the following objectives:

to gather information
to produce hydrocarbons
to inject gas or water to maintain reservoir pressure or sweep out oil
to dispose of water, drill cuttings or CO 2 (sequestration).

To optimise the design of a well it is desirable to have as accurate a picture as
possible of the subsurface. Therefore, a number of disciplines will have to provide
information prior to the design of the well trajectory and before a drilling rig and
specific equipment can be selected.
The subsurface team will define optimum locations for the planned wells to
penetrate the reservoir and in consultation with the well engineer agree on the
desired trajectory through the objective sequence. In discussions with production
and well engineers maximum hole inclination and required wellbore diameter will

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