Evaluation of Annular Pressure Buildup in Oil Wells

Resumo

In the search for new sources, the oil wells become increasingly deep and, consequently, new challenges

arise in their construction and operation. Annular Pressure Build-up (APB) is a phenomenon caused by the resis-
tance imposed by the casing strings, that limit the annulus, against the free thermal expansion of the trapped fluid.

This balance between the pressure increase and the volume changes due to deformations in the well structure,
which cannot be treated as a totally rigid system, is fundamental to the correct scaling of the problem according to
the multistring casing design philosophy. APB usually occurs in the production phase, when the hot fluid from the
reservoir flows through the tubing, radially transferring heat to the outermost layers. In this paper, a computational
APB model was developed, considering the effect of the interaction between casing strings (multistring), and it is
applied in a case study in order to validate the formulation and illustrate its efficacy. This model can be broken
down into selecting a thermal simulator, a Pressure-Volume-Temperature (PVT) model suitable for annular fluids,
a casing displacement model, and a numerical method to solve the APB equations.