REPAIR AND
MAINTENANCE
OF WELLS

Well workover

Overhaul is a set of works related to the restoration of well productivity. Most workovers require retrieving tubing from the well with drilling rigs and repairing defects that could result in poor or no well productivity. When the defects are eliminated, the tubing is lowered back into the well.

Well workover - a set of works associated with the restoration of the operability of casing strings, the cement ring, the bottomhole zone, the elimination of accidents, the lowering and retrieval of equipment for the separate operation of reservoirs.

Well workover includes the following types of work:

• repair and isolation works (isolation of fluid flushing), formation waters (fresh, waste), shutdown of facilities from development, transfer to other facilities;
• repair and corrective works - building up cement stone, sidetracking the second wellbore, ribbed strings, restoring the tightness of casing strings;
• impact on the bottomhole formation zone: physical methods, chemical methods, physical and chemical methods;
• fishing;
• well abandonment.

Well development after drilling

Well development is an important stage in preparing it for operation. The degree of hydrodynamic connection of wells with the reservoir, the qualitative and quantitative characteristics of the inflow profile into the well, the duration of the well operation without complications, the reliability of the bottomhole design, the reliability and durability of the well itself will largely depend on the type and quality of the work performed during the development. The choice of well development technology for oil should be closely linked with the geological and physical characteristics of the formation, with the filtration and stress state of the bottomhole zone. The filtration state of the bottomhole zone, as is known, is formed during the primary and secondary opening of the productive formation, changes significantly during underground well workovers, and gradually changes during normal well operation.

Well development after drilling is a complex of technological works on:

• call inflow from the reservoir;
• restoration (if necessary) of rock permeability of the bottomhole formation zone (BFZ);
• establishment of the technological mode of operation of the well.

Well workover

Current workover of wells a set of works to restore the performance of downhole equipment and work to change the mode and method of well operation.

Current repair includes the following types of work:

• elimination of breakage of rods or their lapel;
• changing pipes or rods;
• changing tubing immersion;
• cleaning or changing the sand anchor;
• cleaning wells from sand plugs with a bailer or flushing.

Well abandonment

Well abandonment is the complete write-off of a well due to the inability to use it for technical or geological reasons to continue drilling or operating it. Wells subject to abandonment may not be completed drilling or have been in production.

Reasons on the basis of which the question of liquidation of unfinished wells is raised:

• a complex accident in the well and the proven technical impossibility of eliminating it, as well as the impossibility of using the well for other needs, for example, returning to overlying horizons or using it as an injection or observation station;
• the complete absence of oil and gas saturation of the horizons discovered by this well (exploration) and the impossibility of using it for other needs (return, deepening, etc.).