Abstract

At the start of exploitation of any hydrocarbon or geothermal water reservoir, production of reservoir fluids is driven by natural energy in the form of reservoir pressure. Therefore, the primary task for production engineers is to maintain this reservoir pressure for as long as possible, ensuring long-term economic production. Unfortunately, sooner or later it becomes necessary to introduce mechanical methods of fluid lifting. Today, there are numerous solutions on the market for mechanical lifting of reservoir fluids (progressing cavity pumps-PCP, electric submersible pumps-ESP), and one of the oldest mechanical methods for producing reservoir fluids is the sucker rod pump. In the Republic of Croatia, sucker rod pumps are among the most commonly used mechanical methods for lifting reservoir fluids. Although Croatian production engineers have significant experience working with sucker rod pumps, operational problems are common and are accompanied by additional expenses related to workover operations. This paper presents an analysis of workover operations over a tenyear period (from 2011 to 2022) in an oil and gas field in the Republic of Croatia. Based on the collected data, an analysis was conducted to determine the volume of fluid not produced during equipment maintenance and repair, the waiting time for repairs, the duration of equipment maintenance as well as the cost-effectiveness of the repairs. Special attention is given to the analysis of the causes of problems in using sucker rod pumps and the identification of problematic wells.