Controle da pressão anular de fundo na perfuração de poços de petróleo - rejeição de perturbação: kick de líquido

Abstract

A dynamic methodology was developed for controlling inflows of liquid (kick), during the oil wells drilling, in the presence of disturbances (kick liquid), based on a scheme of control structure reconfiguration using feedback and feed forward control laws reversibly. The opening index of the choke valve was used as the manipulated variable for regulation of the bottom-hole pressure. The developed control reconfiguration, allows structural and / or parametric system changes, enabling the transition between the regions of the operating space. Thus, the control structure is taken as changeable and dependent on the operating conditions of the process. With the dynamic method to control kick, proposed by this dissertation, it was possible to obtain faster control of inflows than conventional methods. An experimental unit was built to represent the control problems commonly observed during drilling of oil wells: tracking the desired bottom-hole annular pressure value (working within operational windows) and disturbance rejection (kick). Different phenomena that occur during the drilling process are depicted in the experimental unit. First, the structure of the process, containing the drilling and annular sections is represented using the configuration of the U-tube, separated by a valve that imposes restriction to the flow of a typical drill bit. It is worth mentioning that the studies in the literature mostly employ modeling and simulation to control the bottom-hole pressure, during the oil wells drilling. There were not found in the literature, experimental studies where one unit was used for this purpose, demonstrating the unprecedented nature of this dissertation work