Page 47 - Drilling Technology in Nontechnical Language

38 Drilling Technology in Nontechnical Language Second Edition

Well design

In designing a well, there are five areas that must be defined:

▪ Completion design. The completion forms the conduit for
hydrocarbons to travel up the well, through the wellhead, and
into the surface production facilities. Normally, the drilling
engineer is given the required completion design as part of the
well proposal.

▪ Casing design. Casings are steel pipes that are lowered into
the well and cemented in place. The well is then drilled with a
smaller diameter hole to the next point at which the next smaller
casing should be cemented in. The casing design defines these

pipes and the cement sheath that seals the space between the
casing and hole.
▪ Directional profile. This is the 3-D path that the well should

travel to take the well from the surface rig location to the correct
path in the reservoir. These paths can get quite complex.
▪ Wellhead configuration. The wellhead consists of an assembly

of pressure-tight components on the surface, at the top of the
well. The wellhead must handle all of the loads imposed on the
well, such as the weights of all the casing strings and the internal
pressures from the well.

▪ Well fluids requirements. When the drillers have finished their

work, the well will have different fluids left in different parts of
the well. This is defined as part of the well design.

Completion

A completion consists of many pieces of tubing that are screwed
together. Tubes screwed together in the well are called a string. The device
used to join tubings and casings together is called the connection. A
completion connection must withstand the physical loads from the weight

of the tubing below, plus any other loads that may arise (fig. 3–3). It must

also allow produced fluids (which may include gas) to flow through the

tubing and not leak. It must be easily handled by the rig.

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