The drilling rig comprises various drilling components that aid in the extraction process. The drill collar is one such equipment along with the drill pipe and heavy weight drill pipe that plays a pivotal role in drilling operations while enduring severe loads and tension. The right drill collar sizes are at the core of a successful drilling operation and mainly depend on the drilling demands or conditions.
What Are Drill Collars
The drill collar is a vital component of the bottom hole assembly (BHA). It is located below the drill pipe and above the bit at the end of the drill string, and it is equipped with tool joint connections at both ends.
Made from carbon steel or a solid bar of high-strength alloy steel as per the mechanical properties stated by the API, it is the heaviest component of the drill string. Its function is to facilitate penetrating the surface more effectively by exerting downward thrust to the rotating bit.
The essential downhole tool features thicker walls than the drill pipe, maintains bottom hole assembly directional control, and stabilizes the drill string by reducing drill pipe buckling and vibration with its added weight.
Types of Drill Collars
Drill collars can be classified into three main types. These include:
Slick Drill Collar
The slick drill collar is a regular and most common drill collar with a rounded, straight outer surface, which simply increases the weight on the bit.
Spiral Drill Collar
The spiral drill collar serves the same function as its standard slick counterpart. However, its main advantage is that it features a specialized design with spiral grooves on the outer surfaces which decrease the contact area between the outer diameter and the wellbore wall and allow the drilling fluid to pass freely around the collar.
Accordingly, that mitigates the chances of differential pressure sticking due to pressure differences.
Non magnetic Drill Collar
Non magnetic drill collars are non-spiral and differ in their mechanical properties. They are made from stainless steel and are used in scenarios where magnetic interference during downhole measurements can be problematic with magnetic measuring tools like compasses, especially during directional drilling.
Drill Collar Sizes
Drill collars are heavier than a drill pipe and have a larger outside diameter. They typically come in different sizes as specified by the API to suit specific drilling conditions and maintain drilling efficiency. However, custom-made non-API sizes are also available.
The three main aspects of drill collar sizes include:
Length
Drill collars are typically divided into three length ranges between 30 to 90 feet. The standard and most common drill collar sizes are 30 to 32 feet long, falling under range 2. The wellbore depth determines the length of the drill collar needed for drilling, with larger holes requiring longer collars and vice versa.
Outer Diameter
The diameter of a drill collar can vary, ranging from 2 1/2 to 11 inches. However, the most common outer diameter range is 3 1/8 to 9 1/2 inches. A larger outer diameter corresponds to a higher weight and increased stiffness on the drill string, preventing buckling and bending.
Weight
Choosing a drill collar with the right weight is indispensable to a successful drilling operation. The type of formation, well depth, and hole size are some of the crucial factors that determine the weight of the drill collar for a drilling operation.
Most drill collars are manufactured with a maximum outer diameter of 9-½ inches, weighing between 214 to 217 lbs. The heavier the drill collar, the more weight it can provide the drill bit to cut through the surfaces.
The heaviest drill collar has the largest outer diameter of 11 inches, weighing about 299 lbs. These types of drill collars are deployed in extreme drilling conditions like extra deep wells or where cutting through formations is highly challenging.
About Sofia Oilfield Supply Services
SOSSUSA has been among the top distributors of high-quality oilfield equipment for over 30 years, helping our valued customers meet their unique needs.
Choose from our extensive inventory of new and used drill pipe for sale and drill collars manufactured under stringent quality control standards using high-grade steel that offers excellent durability and reliability by withstanding in the harshest oilfield conditions.
Contact us today to discuss and get a customized quote for a suitable drill collar that meets your specific drilling requirements. Our team of professionals will gladly assist you in selecting the appropriate-sized drill collar for optimal drilling performance and efficiency.