Keep in mind that obtaining fluid levels from sonic devices may be inaccurate.  However, if you truly have a consistent high fluid level above the pump, poor performance may be caused by the following situations:

  • ​The down-hole gas separator design is too small for your application
  • 100% gas slugs are periodically vacating the liquids in the casing around the gas separator
  • The oil contains a significant amount of miscible gas or emulsions thereby allowing a high concentration of gas into the separator
  • A restriction or blockage from paraffin, scale, solids, collapsed tubulars, etc
  • Worn pump parts

Run a dynamometer analysis to determine if you can pinpoint the problem. If the problem is due to paraffin or gas interference, GARP can help you. GARP may also be a remedy for severe paraffin problems in which hot water treatments are only effective for a short period of time. Call a GARP representative with your data so that a detailed analysis may be performed.

In the slim hole version of GARP, the rod pump tubing is encased in an outer string of tubing. The annulus between these two strings is used to transport the compressed gas below the pump to lift liquids above the pump. During compression, the temperature of the injection gas increases.  If the temperature inside the rod pump tubing is kept above the cloud point temperature, the paraffin will not come out of solution. Even if the temperature cannot be maintained above the cloud point temperature, the outer tubing string will still insulate the crude oil from the colder regions of the wellbore and will act to delay the formation of paraffin. If paraffin does form, the well can be hot watered much more efficiently than pumping hot water down the casing annulus since the inner tubing string’s annulus is much smaller and therefore provides a more efficient transfer of heat to the inner rod pump tubing. This method also reduces treating costs since the required volume of hot water will be less. Additionally, a standing valve can be incorporated at the bottom of the GARP assembly to prevent the hot water from entering the reservoir. This may be important in preventing reduced production rates due to water sensitive formations, water blockages in the reservoir, and overwhelming low pressure reservoirs.
The GARP design will work with any pump but the gas separator design for GARP is designed to work with a single acting plunger type pump. The attractiveness for a rod pump is that it comes in slim hole sizes for smaller casing sizes, is economical at a wide range of production rates, it is widely understood and can use natural gas or electric motors, parts are readily available and they can be repaired economically and timely, and they lower the bottom hole pressure more effectively than any other current artificial lift method. We are very interested in using pumps that do not use rods to stroke the pump for pad drilled wells that are directionally drilled with shallow deviations. The technology is available and is being tested and we are working to incorporate GARP with this technology. We will keep you posted!
GARP works without a gas supply in two instances. One is if the well has sufficient reservoir energy to naturally lift liquids from below to the pump to above the pump by virtue of the inherent velocity string in the GARP designs. The second instance is if we replace the gas lift with power fluid to operate a small hydraulic jet pump below the rod pump. If this is utilized, the rod pump must be large enough to pump the reservoir fluid and the power fluid from the well.
The answer to this question could fill a book. Long story short, all the lift methods listed are great at moving large quantities of fluids and have their place in the world of artificial lift for limited operating conditions, but all are at best a temporary solution. Ultimately, over 85% of all the wells in the world use rod pumps for artificial lift since it is the most reliable and best economical artificial lift method that achieves the lowest bottom-hole pressure and thus the most reserves.

Basically a well is a GARP candidate as follows:

  • Any well that has the existing artificial lift equipment installed a significant distance above the reservoir. Note: highly permeable reservoirs have lower distance requirements than less permeable reservoirs.
  • Wells with reservoirs that are depletion drive or partial depletion drive and do not currently have artificial lift installed
  • Wells that have 4-1/2” casing sizes or larger
  • Wells with liners larger than 4” (it may be possible for 3-1/2” liners). Contact us
  • Wells with severe paraffin problems
  • Wells that need a more effective chemical treatment system
  • Wells with remaining reserves that justify the installation costs (Higher EUR wells generally have more remaining reserves than lower EUR wells)
  • Oil wells with or without a gas lift supply
  • Gas wells with liquid loading issues
  • Wells with or without electricity

Experience has shown that this is not a good idea for the following reasons:

  1. Workover costs will increase substantially due to frictional wear of the tubulars
  2. Down-hole gas separators are designed to function in the vertical portion of the well. Therefore gas interference will become more of an issue resulting in lower production rates, lower liquid pumping efficiency, lower run time, and higher failure rates since the curve and lateral are areas with a high concentration of solids.
  3. It is very difficult to engineer a trustworthy design for rod guide placement, buckling, and energy transfer to the pump. A great deal of engineering time may be spent to tweak the correct design and pumping parameters for changing well conditions.

GARP can optionally use a five step approach for solids separation and containment that is not available elsewhere in the industry.

The first stage consists of one or more solids collection chambers that separate solids and traps them in a concentric tubing arrangement located in the curve or lateral. The collection chambers force the reservoir fluid stream in a downward direction to encourage the separation of solids from the liquids. Momentum and gravity carry the solids downward to the low side of the concentric tubings where they become trapped, while the liquids and gases travel up the well-bore to the next stage of separation.

A second stage containment device consists of a Packer Shield consisting of a 361L stainless steel thin-walled tubular that is open at the top and closed at the bottom which surrounds and is attached to the tubing string just above the packer. Solids that would have fallen on top of the packer, now fall into the Packer Shield and are trapped inside. The shield can be made in different lengths to increase the solids holding capacity of the shield. The top of the Packer Shield contains a flexible yet stiff brush ring gasket which effectively prevents solids from traveling between the annulus of the Packer Shield and the casing. The brush ring bristles are rated up to 500 deg F.

A third stage separation device consists of the TRI-FLOW tool which installed above the Packer Shield in the Slim Hole version of GARP.  Flow from the reservoir is forced through the TRI-FLOW tool which forces the reservoir liquid stream in a downward direction. Any remaining solids in the liquids continue to fall due to momentum and gravity into the open upper end of the Packer Shield and become trapped.

A fourth stage is a solids separation and containment system inherent in the Gas Shroud that surrounds the BI-FLOW tool. Fluids from the third stage travel up above the Gas Shroud and liquids and any remaining solids fall into the shroud due to gravity. During the downstroke of the rod pump, the fluid velocity stops inside the shroud which allows solids in the liquids to fall into the mud anchor portion of the shroud below the BI-FLOW tool, where they become trapped.

The fifth and final stage of the solids separation and containment system occurs on the bottom of the BI-FLOW tool which contains a mud anchor. During the down-stroke of the rod pump when no flow is occurring, any remaining solids that exist between the bottom of the rod pump and the BI-FLOW tool can settle out and become trapped in this mud anchor.

There are currently three versions of GARP as follows

  • GARP Lite (uses a velocity string to lift liquids from the below the pump, i.e., does not require second form of artificial lift).
  • Two Step GARP (allows GARP Lite to be converted to Full GARP)
  • Big Bore GARP
GARP Lite and Two Step GARP are both slim hole versions of GARP and are second generation designs. They are more universal in that they can be run in any well that has a casing diameter of 4-1/2” or larger. The Big Bore GARP is a first generation design and must have 7” or larger casing.

The decision on whether to run the GARP Lite version depends on whether your well has sufficient gas production and/or bottom hole pressure to lift liquids up the inherent velocity string in the GARP Lite design. If not, a Full GARP installation with a secondary artificial lift method will be necessary. If you are unsure, the Two Step GARP version allows a Full GARP installation to be implemented without having to remove the existing well bore tubulars.

The answer depends on numerous factors such as:

  1. The existing gas rate and reservoir pressure and the future pressure decline
  2. The reservoir’s system permeability and porosity which includes the permeability and porosity contribution from the matrix + the natural fractures + the induced fractures
  3. Economics of a full GARP installation (considering the increase in production, changes in LOE costs, and the cost of installation).
GARP Lite works when the existing reservoir energy is sufficient to lift the liquids from below the pump to above the pump. We calculate that only 25 MCF/D is necessary for a relatively short lift length; however, lower gas rates may result in lower production rates unless the well has a higher reservoir pressure. Call GARP Services for a more detailed analysis.

Advantages of GARP Lite vs a full GARP install

  • ​The GARP Lite version is less expensive since an additional inner rod pump tubing string does not need to be installed
  • Does not require a wellsite compressor, buy gas meter, power fluid pump, or additional well-head
  • Once the well requires the additional artificial lift from a full GARP installation, the GARP Lite installation remains in place and an additional inner tubing string is placed in the well. This design is more cost efficient than if the GARP Lite bottom hole assembly required removal for a full GARP installation.

Advantages of a full GARP installation vs GARP Lite

  • ​Higher production rates are possible if the well starts to load up below the rod pump
  • More reserves will be recovered
  • The life of the leases will be extended