Drill Collar is a heavy, thick-walled steel tube with threaded connections cut (NB not welded) on both ends that we use in oilfield drilling rigs. They are designed to withstand downhole conditions while under compression and tension. While designing BHA, drilling engineers place DCs below the drill pipes or the heavy drill pipes above the Drill Bit as DCs are the predominant component of the Drilling BHA. To select the proper DC, you must have all the information about Drill collar Weights, Size, Specs, Definition, lengths, and types.
In addition, they are manufactured from chrome-molybdenum alloy 4140 (4140 is a code that indicates the chemical makeup of the metal). Furthermore, they are heat-treated and quenched over their entire length, with a Brinell hardness range of 255 to 341 to obtain mechanical properties as specified by API Spec 7-1. Their bore is accurately machined to ensure smooth, balanced rotation. Collars are manufactured in a wide range of sizes (ODs) and are available in length ranges 2: 9.15 – 9.76 m (30 – 32 ft); and 3: 12.8 – 13.27 m (42 ft-43 ft).Drill Collar can also be manufactured using magnetic steel or spiral collar, including complex threaded connections, weight increases, and spiral grooves on the outside surface for better drilling mud type flow control.
Some of the functions of the collars are as follows:
- Provide weight on bit (WOB) & Increase bit performance.
- Minimize bit rotational stability problems from drill string vibrations, wobbling, and jumping.
- Provide strength needed to run in compression
- Minimize directional control problems by providing stiffness to the BHA to help drill straighter or vertical holes.
- Keep the drill string in tension to reduce bending stresses and drill string failures due to fatigue.
- Provide pendulum effect. (BHA Types).
- Reduce keyseats, doglegs & ledges.
Drill collars are available in many sizes and shapes, such as round, square, triangular, and spiral grooved.The parameters used for identifying drill collar specifications are:
- OD: 9 1/2″, 8″, 6″, 4 3/4″ etc.,
- ID: 3 1/2″, 3″, 2 1/2″", 2 3/8″ etc.,
- Length: Usually range II
- Material: Steel, Monel
- Connection: 6 5/8″ REG etc.
Slick Type
The slick type is the most common one that has been used since the beginning. It has no features. Its major function is to add weight to the bit and increase the stability while drilling.
Spiral Drill Collar
When drilling through certain formations, the large diameter D/Cs can become stuck (Pipe sticking problem) against the borehole (differential sticking). This is likely to happen when the formation is highly porous, using a large overbalance of mud pressure, and the well deviates. One method of preventing this problem is to reduce the contact area of the collar against the wellbore. We can cut the spiral grooves into the collar surface to reduce its surface area.
Non-Magnetic Type
The most common type of DC is the non-magnetic drill collar. It is made from alloy steel with an outer surface machined to a specific smoothness and an elevator recess radius that meets dimensional requirements. We should pay special care when making up NMDCs. This is because the material is more susceptible to the galling of the threads and shoulders than normal DCs. They aim to isolate directional Survey Instruments from magnetic distortion due to the steel Drill String.
Vigor can provide you with all of the above mentioned different models, lengths of drill collars to meet the needs of the site. At present, our drill collars have been used in major oil fields around the world, and have received very good customer feedback. If you are interested in Vigor's drill collar series or other tools for natural downhole drilling and completion of petroleum natural warps, please do not hesitate to contact us for the best technical support.
