Analysis of workover causes for wells with installed downhole sucker-rod pumps
- 1 Faculty of Mining, Geology and Petroleum Engineering – University of Zagreb, Croatia
Primary oil production represents the process of production only by exploiting the natural reservoir energy (reservoir pressure), i.e. eruption phase. This mode of production lasts until the reservoir pressure drops, so that it is no longer capable of pushing the oil to the surface. Oil wells which can’t erupt, must apply one of the methods of artificial lifting. The artificial lift system of oil production by using downhole sucker-rod pumps with piston rods is the oldest system for lifting fluids from wellbore to the surface. It is also the most widespread artificial lift system in practice in the world (over 80%). The basic principle of the operation of a downhole sucker-rod pumps is based on the transfer of the drive energy from the surface to the pump by piston rods. In principle, downhole sucker-rod pumps with piston rods can be applied in oil wells from depth of 500 to 2500 m while enabling production ranging from 1 to 100 and more m3/d of liquid. This system is suitable for wells with a smaller gas factor and consolidated production layers. The advantage of downhole sucker-rod pumps is their efficiency and economy because initial capital investments per well are lower. The disadvantages of downhole sucker-rod pumps are higher maintenance costs, i.e. more frequent workovers. This paper analysis the most common causes for well workover that produce oil with downhole sucker-rod pumps and recommendations in order to reduce their number.
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