Q1 What are the advantages to the Rigger Engineering liner hanger?

Q2 What is the difference between a liner hanger and a liner adapter?

Q3 What is the purpose of a liner hanger?

Q4 What is the purpose of a tie back receptacle?

Q5 What is a casing bowl?

Q6 What is a bottom hole packer?

Q7 What is the true radius feature on the Rigger liner hanger?

Q8 What is the difference between a single slip, double slip, and hold down slip liner hanger?

Q9 What are the components required to install a Rigger Engineering liner hanger?

Q10 Why use a slick joint stinger rather than packer cups?

Q11 What pricing options are available?

Q12 Does Rigger Engineering offer custom engineering?

Q1

What are the advantages to the Rigger Engineering liner hanger?

There are three primary advantages to the Rigger Engineering liner hanger:

  • Recessed pocket design—Rigger was among the first to use a recessed pocket design. In this design the slips are held within a recessed pocket. This eliminates any exterior appendages that may become caught while tripping into or out of the hole. This virtually eliminates setting of the tool prematurely.
  • True radius slips—Our slips have a constant radius rather than the more typical cone shape. This allows the load to be spread evenly over the face of the hanger rather than at stressed contact points which may cause failure due to collapse.
  • Short body length—Our liner hanger has a short body, typically less than three feet in length. This makes the hanger easy to handle on the rig floor and allows it to bypass tight spots and dog legs easier than a liner hanger of longer length.

Q2

What is the difference between a liner hanger and a liner adapter?

When designing a liner program one of the most important questions is “Do I want to leave the liner on bottom?” Usually the operator will want to hang the liner in suspension for a number of reasons. These include but are not limited to buckling of the liner due to weight and damage to the liner due to running of tools in and out of the hole. For this he will need a liner hanger.

Sometimes, though, the operator may prefer to leave the liner on bottom. In this case a liner adapter is the better way to go. In its pure form the adapter is simply a liner hanger without slips. The OD of the adapter is large enough to center the liner in the hole but not so large to restrict flow during circulation and cementing operations.

The adapter does have variations. These include rubber or lead seals, hold down slips, and drive-on heads. Overall, from a cost standpoint, the adapter is much less expensive than a liner hanger.

Q3

What is the purpose of a liner hanger?

There are several reasons to use a liner hanger:

· Cost—Rather than running one long liner, by reducing the size with each stage of the drilling operation the cost of the liner goes down correspondingly.

· Elimination of damage to liner due to axial load—Setting the liner on bottom for an extended period can bring about any number of problems including split casing and permanent distortion of the casing bowing into underground cavities.

· Even cement jobs—Trying to cement a long, continuous liner can cause voids in the formation. By cementing shorter sections the operator maintains a higher degree of control.

· Installation of a production liner—Once the operator has tapped into a producing zone he may want to run a short, slotted liner through which he can produce.

Q4

What is the purpose of a tie back receptacle?

A tieback receptacle is primarily used in a situation where the liner is being run, or tied back, to the surface and is to be cemented in two stages. This makes for a more uniform cement completion. In the Rigger Engineering design the tie back receptacle, sometimes called a PBR, is located below the liner hanger. The ID of the receptacle is approximately the same as the OD of the liner being hung. The liner is hung and cemented in place. A tie back stem, which may or may not have seals, is run in on the end of the liner going to the surface. It passes through the liner hanger and stabs into the receptacle. The receptacle acts to center the surface liner and prevent misalignment. The surface liner is now cemented from above the liner hanger to the surface.

Q5

What is a casing bowl?

A casing bowl is a type of work over tool. Many times when opening up older wells the liner may be damaged or, even in newer wells, may have been perforated during the course of running tools. The liner is cut off below the damaged section and the old liner is removed. The casing bowl is run in on the bottom of the new liner. If the old liner is lying off to the side an entry guide allows the operator to rotate to the right and drive the casing bowl over the liner stub. The casing bowl goes over the stub by 1 ½ to 2 feet. An inner grip ring with case hardened teeth bites into the stub. The liner is put in tension causing the grip ring further bite into the liner. A casing bowl can also have seals if required.

Q6

What is a bottom hole packer?

A bottom hole packer is a type of work over tool. One possible application is to bridge and isolate a section of damaged casing. It is only about 2 feet long and has a seal on the side and end. It screws onto the end of a short liner and is designed to land on top of an existing liner hanger. An adapter is usually attached to the other end of the liner. The assembly is run into the well where the bottom hole packer lands on top of the liner hanger. The seals are set via weight from the rig. The adapter may also have a seal which is set at the same time, thus isolating the bad section of casing.

Q7
What is the true radius feature on the Rigger liner hanger?

Most liner hangers have a “cone” feature located on the outside surface of the liner hanger. When activated, the slips slide down over the cone and engage the casing. By definition a cone does not have a constant radius, i.e. the radius is larger at the base of the cone than at the top. To get maximum hanging capacity from the slips they must, in theory, land in a position on the cone where the radii are in complete alignment. This will transfer the load evenly to the body of the liner hanger. In actual application this is not likely due to a number of variables; slightly larger or smaller casing ID, slightly larger or smaller hanger OD, and total weight on the slips. All of these will cause the slips to engage the casing at a different location on the cone. The liner load is then transferred to “points of contact” wherever the slips come in contact with the liner hanger. This puts tremendous pressure on these points and can result in the slips failing or the liner hanger itself collapsing.

The Rigger liner hanger uses a “true radius” slip. This means that each slip AND the pocket it is contained in have a constant radius. The radius of the slip and the pocket are the same. This can be checked by simply turning the slip upside down and fitting it in the pocket. Although it is not designed to be used this way one can see that the radius, the area of slip and pocket contact, is the same. What this means is that when the slips engage the casing the entire surface of the slip is in contact with the pocket. In this way the load is spread evenly over the surface of the pocket. There is less chance of slip failure due to damage from too much weight on the slip. There is less chance of hanger failure due to too much weight on contact “points”, thus providing higher reliability and load capacity.

Q8
What is the difference between a single slip, double slip, and hold down slip liner hanger?

Every liner hanger has slips. These are case hardened wedges that, when activated, support the weight of the liner. The slips are arranged in a row around the outside of the liner hanger. In this way the weight of the liner is spread evenly around the liner hanger. As a rule-of-thumb any liner up to about 80,000 pounds can be supported by a Rigger liner hanger with a single row of slips. A double slip liner hanger has a second row of slips located below the first row. This allows the weight of the liner to be spread out over a larger area, thus reducing the load/sq. in. The total liner weight that a Rigger Engineering double slip liner hanger can support is between 250,000 and 300,000 pounds. Hold down slips are another type of slip arrangement where the hanger has a second row of slips that are opposed to the slips in the first row. This liner hanger is best used when the liner to be hung is less than 30,000 pounds. The hold down slips act to anchor the liner to the casing when running tools in and out of the well.

Q9
What are the components required to install a Rigger Engineering liner hanger?

That would depend on the type of completion. Generally there are two types of completions—hanging a production liner or cementing a liner in place.

When hanging a slotted production liner, all the operator wants to do is hang the liner and pull the tools. This is a very simple straightforward operation and the only tools needed are the kelly bar and releasing assembly and possibly an off bottom tool if the operator wants to stay off bottom during the hanging process. The same tools would be used in a gravel packing operation as well. If the production liner is being hung hydraulically the tools would consist of the hydraulic setting tool in place of the kelly and releasing assembly and the optional off bottom tool isn’t required.

The other type of completion is a cemented liner. This is a somewhat more complex operation where the liner is cemented in place after the hanging operation. The same setting tools mentioned above are used here whether the liner is hung mechanically or hydraulically. In addition, certain accessory items will be required for the cementing process. These include a swivel located below the kelly bar (mechanical) or setting mandrel (hydraulic). Below the swivel one of two options are available—packer cups or a slick joint stinger. The operator will determine which option he wants to use. If packer cups are used, a six foot long (or longer) pup joint is an optional piece of equipment the operator may want to use between the swivel and cup mandrel in order to space out the cups to be sure they stay inside of the liner. At the bottom of the cementing string (below the cup mandrel or stinger) is a shear pin adapter, which holds the wiper plug in place. Additionally, a cement head and a complete set of plugs consisting of a liner wiper plug and drill pipe dart will be needed. Float equipment may also be needed. While Rigger Engineering does not manufacture float equipment we do work with several manufacturers and can supply whatever type of float equipment the operator specifies.

Q10
Why use a slick joint stinger rather than packer cups?

The choice of a slick joint stinger over packer comes down to three factors: safety, pressure, and cost—and in that order. Downhole pressures will work to push the liner back up the well bore, especially in the deeper wells being drilled in the industry today. When that pressure encounters the packer cups in the work string it is spread out over the surface area of the cups. The larger the liner ID, the larger the surface area, the higher the pressure as measured in psi. If large downhole pressures are anticipated this may result in an unsafe condition on the rig. Conversely, a slick joint stinger has a diameter of only 4-1/2”. That diameter remains constant so overall pressure pushing on the work string is greatly reduced creating a safer work environment. Of course cost is always a factor. When using a slick joint other accessory items are required in addition to what is necessary with a packer cup type completion. These items include a 6’ long extension located just below the liner hanger and a pack off bushing with a seal bore receptacle. Again, safety is key. Rigger recommends using a slick joint whenever a liner of 9-5/8” or larger is being run.

Q11
What pricing options are available?

Rigger Engineering works off of a standard price list. For large orders and/or long term contracts we do offer quantity discounts. While we are competitively priced we will work with our customers on pricing when necessary.

Q12
Does Rigger Engineering offer custom engineering?

We do offer specialty tools. If you don’t see it in the catalog or on the web site it doesn’t mean we don’t, or can’t make it. We have a full machine shop at our disposal and a lot of very clever guys with many years of oil field experience. If your well has some “special circumstances” and you require a special tool for the job, we can work with you. You can tell us what you need and we can design something “on the fly” so to speak, or you supply the design and prints and we can build it to your specification. Whichever works best in your situation we will get the job done.

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