Don-Nan Blog

By Don-Nan 15 Dec, 2017

Gas Lift equipment selection is based on a few variables: tubing size, casing size, and surface capabilities. Depending on the drift ID of the casing and size of tubing, the selection of 1” or 1-1/2” valve will be chosen. Because conventional gas lift equipment has the valve made up on the outside of the gas lift mandrel, the OD of the station (mandrel + valve) is necessary in determining what valve size will fit within the drift of the casing. 

By Don-Nan 10 Nov, 2017

When attempting to efficiently move production fluid from reservoir to surface, one key determining factor is fluid seal within the sucker rod pump. The right combination of plunger and barrel is essential to achieving fluid seal.

The amount of space between the plunger OD and the barrel ID is the fit. Proper fit is required to create fluid seal. If the fit is too tight, there won’t be enough lubrication between the components and the pump will become damaged very quickly in operation; too loose of a fit will result in lost production as excessive fluid slips down around the plunger on every upstroke, making a continuous loop within the pump.

In order to achieve proper fit, an assessment will be performed to establish pump operating depth, casing and tubing size, fluid properties (viscosity and solid content), size and type of surface pumping unit, strokes per minute, and production goals. This assessment will indicate which barrel and plunger combination is best suited for production.

After the appropriate combination has been selected, the barrel and plunger will be further evaluated. The barrel’s internal wall must be inspected for any pits or imperfections that can cause a disruption in fluid seal. Pits typically only emerge in barrels that have seen extensive field use in corrosive downhole conditions. In order to test a barrel, an ID air micrometer is used. The micrometer measures air flow utilizing the resistance created between the inner barrel wall and the micrometer barrel plug. The air resistance will remain constant unless a pit is encountered. After the barrel has been found to be free of any weak points, the plunger may be evaluated.

By Don-Nan 26 Jul, 2017
One of the most fundamental, and often overlooked, subjects of pumping with a sucker rod pump is the influence of downhole pressure. There are 3 basic types of pressure that have direct influence on the ability of a sucker rod pump to work as intended; formation pressure (P1), internal pump pressure (P2), and hydrostatic pressure (P3).

The fluid level outside a sucker rod pump must be at or above the level of the standing valve of the pump in order to allow fluid to fill the pump chamber on the upstroke. This requires sufficient pressure from the formation entering the wellbore, continually pushing fluid above that level. If there is not sufficient pressure and the pump continues to operate, it will enter a pumped-off scenario. If this happens, the pumping unit should be shut down until sufficient pressure is present. This is a common occurrence in rod pumped wells and there are mechanisms to account for this such as variable speed drive pumping units, time clocks, and pump-off controllers. Alternatively, such as in an aging well, the seating depth of the pump may be increased (placed deeper) in order to continue to produce fluid at comparable rates.

Another pressure is where fluid is held in the tubing above the uppermost traveling valve of the pump, called hydrostatic pressure. There is no minimal amount of hydrostatic pressure that must be present in order for a sucker rod pump to operate effectively, it is simply a result of the system design.

The third type of pressure (internal pump pressure) is that which is felt by the pump. In instances where there is incomplete pump fill, perhaps due to insufficient pump intake pressure or gas interference, the pressures placed on the pump when the traveling valve meets the fluid are exponentially increased at the moment of impact to the point that components of the pump between the valves may burst or split.

Rod lift operations should be closely monitored to reduce the occurrence of undue internal pump pressure. Automation equipment has made these issues much easier to manage as well as innovations in downhole pumps and production tools such as the Oversized Cage and Gas Separator .

If you'd like help on solving this or any other rod lift issue, please contact the Don-Nan Tech Team .
By Don-Nan 21 Jul, 2017
There are many factors to consider when choosing a pump. Not the least of which is what the individual components will be made from and any type of coatings or heat treating applications that should be applied. Over time these options have become industry standards and generally recognized as being most applicable to a specific downhole environment.

For example, barrels may be internally chrome plated for optimal performance in wells that must pump a lot of solid material, sand in particular. However, you would not want to use a chrome plated barrel if you are going to be acidizing the well, as the acid will strip the chrome out of the pump. In this scenario you may be better off using a barrel with a nickel-carbide coating, or even no coating.

Digging through text books and metallurgy research papers would allow a person to piece together some of this information, however there have been no definitive tests or threshold levels established for the various options available. A person with experience and knowledge in this area will be able to recommend the most appropriate material options to maximize the life of the pump.

In an effort to make this range of options easier to understand, we have grouped categories of pump components and rated their available options against one another on critical factors. Although each factor can be further analyzed, this is the starting point for all material choices.

We call this our Material Selection Guide, and you can download it here .

Have a specific application question? Contact Don-Nan technical services .
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