A packer is defined as a sub-surface tool used to provide a seal between the tubing and casing (or wall) of a well, thus preventing the vertical movement of fluids past this sealing point. Packers are sometimes referred to as production packers but this term is generally used with reference to a particular class.
1 Introduction
The principal reasons for running a packer include:
- production control;
- production testing;
- protection of equipment;
- well repair and well stimulation;
- safety.
1.1 Production control
Packers are used:
- to prevent annulus surge (heading);
- with a packer-type gas anchor;
- when a casing pump is installed.
In a gas lift well:
- to keep casing pressure off the formation (intermittent or chamber lift);
- to facilitate kick-off (and, incidentally, to prevent passing well liquids, which might be abrasive, through the gas lift valves).
- In a dual or multiple completion well, to segregate the producing layers for one of the following reasons:
- incompatibility of pressures of producing intervals;
- separate production, and gathering, of two crudes of distinctly different qualities;
- control of an individual layer for high GOR, or for water cut.
In a steam injection/steam soak well:
- to maintain an empty annulus and thus prevent loss of heat from the tubing (and reduce expansion of the casing).
1.2 Production testing
Packers are used:
- during the production test of an exploration well, i.e. producing a discovery well, where the performance and properties of the formation are as yet unknown;
- when testing a producing well to locate the point of gas or water entry (where production logging services are not ready available).
1.3 Protection of equipment
Packers are used:
- to keep undesirably high oil or gas pressures off the casing or the wellhead;
- to protect the casing from the effects of corrosive fluids;
- in an injection well, to keep high water or gas injection pressures off the casing or the wellhead.
1.4 Well repair and well stimulation
Packers are used:
- when pressure testing the production casing;
- to locate a casing leak;
- during isolation of a casing leak, either temporarily or permanently;
- during squeeze repair of a casing leak;
- to shut-off temporarily undesirable gas or water entry;
- during squeeze cementation of perforations or part of perforations (particularly on a low pressure or depleted well);
- during fracturing, to keep high 'frac' pressure off the casing;
- during acidising, to ensure acid enters formation;
- to avoid formation damage by workover fluid during well repair (the packer would probably be in the well already, for some other purpose).
1.5 Safety
Packers are used:
- in a marine well, to protect against the effect of collision, or other surface hazards;
- to reduce the risk of wellhead leaks on a high pressure well;
- to provide environmental protection of prolific high pressure wells in a populated area.