Computational Module for Reliability Calculation of Well Drilling Fluids and Casing Tubes

Adriano da Silva Rocha¹; João Paulo Lima Santos¹

¹ Federal University of Alagoas (UFAL)

doi:10.20906/CPS/CILAMCE2017-0796

Resumo

In studies about oil well integrity, an important concept that must be addressed is the one of the well safety barriers, which represents complex systems of equipment and components presents in all stages of an oil well lifetime. They act avoiding the occurrence of unwanted flows and pressure transmission from/to the surroundings of the well. Regular wells have their barriers arranged in two different and independent systems (a primary and a secondary system), configuring in well integrity failure only when a fault happens on both systems simultaneously. For its part, in order to occur a fault on a system, it is sufficient that only one of its components fails. Therefore, it is possible to estimate the chances of a well integrity failure based on the probability of failure of the equipment that compose the two well safety barrier systems. Failure probability analyses can also be performed on two specific barriers (one for each well safety barrier system) in order to know the existing chances of these two barriers to fail, resulting in a well integrity failure. Such procedure can assist in the design of specific barriers. Within this scope, this paper has as objective to develop a computational module capable of calculate the probability of failure of two drilling well safety barriers: the drilling fluid (representing the primary system) and the production casing string (representing the secondary system). The methodology of this paper is divided in three stages: I) implementation of an algorithm to calculate the probability of failure for each barrier; II) coupling the algorithm to an environment with a graphical interface for intuitive usage; III) validation of acquired results. The result of this project is a computational module which can assist the decision-making process during the design stages of the casing tubes and the drilling fluids.

Palavras-chave: Well Integrity; Well Barriers; Reliability; Failure Probability