Repairing an oil well sometimes requires a workover. It is commonly called by several names such as completion rig, workover rig, or pulling unit.
Function of workover rig
In many cases, workover implies the removal and replacement of the production tubing string after the well has been killed and a workover rig has been placed on location. Through-tubing workover operations, using coiled tubing, snubbing or slickline equipment, are routinely conducted to complete treatments or well service activities that avoid a full workover where the tubing is removed. This operation saves considerable time and expense.
Companies that supply this type of equipment are Key Energy Services, Pool Workover Services, and Basic Well Services.
Of all the problems that can occur during production, three stand out the most: equipment failure, wellbore problems, and saltwater disposal.
Sanding, formation damage, paraffin accumulation, oil-water emulsions, and corrosion are common wellbore problems.
GN workover rig solids control system is mainly used for sanding problem. The system can separate large particles sand from the drilling fluids so the drilling mud can be recycled for drilling and “kill”the well. The working principle is to clean the drilling mud by 4 phase cleaning, they are shale shaker, desander, desilter, decanter centrifuge. But usually for workover operation, sometimes you can use a shale shaker and centrifuge only, because the sand size is not so large, but it needs to separate finer particles than oil& gas drilling.
In wells which produce from loosely consolidated sandstone formations, a certain amount of sand is usually produced with oil. Continued accumulation of the sand in the wellbore will eventually cut the oil-producing rate and may even halt production altogether. If a well continues to present sanding problems, preventive action may be needed.