Page 98 - Drilling Technology in Nontechnical Language

Chapter 4 – PLANNING AND DRILLING A DEVELOPMENT WELL OFFSHORE 89

Fig. 4–4. Water coning up to the well

A well can be drilled that bends up to the point that it is horizontal in
the reservoir. This horizontal section can be thousands of feet long. With a
horizontal well, the contact area between the reservoir and well is large, so

flow rates in the reservoir towards the well will be low, which will reduce
the tendency of gas or water to break through. Also the horizontal bore
can be accurately placed in the best part of the reservoir, even to the extent
that it can follow the top of an oil reservoir to remain as far as possible
above the oil-water contact. This is called geosteering because the well is
steered with reference to the geological conditions in the reservoir. How
this remarkable feat is achieved will be covered later.
Although horizontal wells cost more than vertical wells to the
same reservoir, the well produces more and for longer and so can be a
better investment.

Completion design is normally done by the production engineers.
However, the completion design affects almost every aspect of the well
design, so the drilling engineer must know, at least conceptually, what the
completion will look like.

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