The ZH field located in Kazakhstan is comprised of shallow, unconsolidated sandstone reservoir that is being produced medium sandy oil by the help of progressive cavity pumps (PCP). The nature of unconsolidated reservoir makes overall production inefficient; due to sand production being a major concern in the field. High frequency of workover operations and limited productivity of wells were caused by sand production. Moreover, pump seizure happens more often because of the low fluid velocity, there is sand inside the production wells can not move up to the surface.
The goal of this study is to increase oil production by optimizing the progressive cavity pumps operation. Improving production requires minimizing workover frequency, therefore sand should be lifted out of the well continuously with the fluid. This can be achieved by controlling the ratio of the actual fluid velocity to the sand settling velocity. The fluid velocity in the tubing should be enough to lift most of the produced sand particles from the bottomhole of a well.
The statistics showed that production wells with fluid velocities of 75% of sand settling velocity or less were likely to have pump seizure with the lack of sand carrying capacity in the tubing. By increasing pump size, modifying tubing size, and increasing pump rotation per minute (RPM), PCP performance was significantly improved. This paper shows the significance of the parameters stated above.
Field cases in PCP optimization are summarized. The successful cases highlight an incremental oil production of 126 m3/d with seldom workover. Unsuccessful cases were characterized by often and sudden pump seizures with increased watercut. This study has shown that maintaining production rate through PCP operation coupled with continuous sand lifting is more beneficial than controlling the sand production such as installing gravel packs.