How to work with PQ3Core Barrel Assembly?

How to Work With PQ3Core Barrel Assembly

PQ3Core Barrel Assembly consists of PQ head assembly, PQ inner tube and PQ outer tube. It is a standard surface diamond drilling core barrel for use with PQ/PHD rods.

Core lifter case mates with the inner tube and houses the core lifter in a tapered socket which controls its movement. Locking coupling threads to the drill rod string and provides a hardened mating surface that the core barrel inner tube assembly latches onto during drilling.

Inner Tube

The inner tube is the core barrel’s main retaining system that carries the core sample during drilling. The inner tube is a cold drawn seamless steel tube with very high tensile strength and straightness. Its tensile strength and radial stiffness improves drill rod performance and hole annulus for increased fluid velocity, faster cuttings evacuation and higher bit life.

The core lifter case mates with the inner tube and houses the core lifter in a tapered socket that controls the movement of the core lifter. As the core is broken out of rock strata, the core lifter bottoms out and transfers the pullback load from the drill string to the core using BWcasing pipe.

A core lifter case can be a basket type for soft or fine grained formations, or standard for hard and thick grained formations. Core lifters can also be case hardened to increase their wear resistance.

Head assemblies are designed with latching and pivoting spear point mechanisms to allow insertion and retrieval of the inner tube. They also incorporate a shut off valve assembly that provides a fluid pressure operating indication to the drill operator when the valve members are compressed, indicating a full or blocked inner tube.

PQ and PHD core barrels are used in a variety of drilling conditions. They are available for application in standard DCDMA P size holes.

PQ/PHD wireline core barrels provide integral core recovery when drilling coal, clay bearing or highly fractured formations. The PQ/PHD core barrel has an inner tube, a core lifter and a split outer tube (referred to as the core liner). It is designed to realize an overall recovery ratio when drilling in a broken or fractured formation with coal or clay, while maintaining the same hole diameter and low fluid pressure.

Core Lifter

The core lifter is a hardened steel, split collar that mates to the inner tube. Its most notable feature is the cleverly designed grip features on its outer surface which catch and retain a core sample as it is lifted from its coring hole. The most effective way to use the core lifter is to load it up with a large diameter core sample and then pull it down to the bottom of the hole, where it can be quickly retrieved from the ground.

The PQ3Core Barrel Assembly comes with a number of core retrieval tools including a holding dog, hoisting plug and circle wrench. A good core retrieval system will also incorporate a multi-angle drill bit and spud for quick and easy drill hole sizing of rock drill rods.

Aside from the aforementioned tools, a core barrel is made up of an inner tube (or two), a locking coupling, and a cleverly engineered adapter coupling. The best core retrieval systems are also accompanied by an assortment of other equipment such as a wellhead logging system and a telescopic rig to capture the most revealing images. It is the requisite equipment that can help the operator to achieve his objectives in an unforgiving drilling environment.

Locking Coupling

The locking coupling is a crucial component of the PQ3Core Barrel Assembly, as it acts as a mating surface for the head assembly latches. The LC is made from precision, cold-drawn mechanical tubing and provides a rugged, long-lasting sleeve that prevents the connection from being disconnected during operation.

The LC also has a latch resting area that is hard-faced to improve latching reliability. The LC is used in conjunction with the outer tube, which serves as the base of the reaming shell, and is connected to the inner tube by an adapter coupling.

In addition to providing a solid, wear-resistant mating surface for the head assembly latches, the locking coupling can serve as a stabilizer to help minimize deviation during drilling. The LC has a set of wear pads made from tungsten carbide-bearing material that wear down against the drill hole wall, preventing snags and limiting hole deviation.

Full-hole locking couplings are a popular choice for many drillers and provide good directional control when ground conditions are reasonable. However, they can be problematic in bad ground where the hole is irregular and the cuttings are not fine.

Fortunately, Boart Longyear has developed an improved version of the original full-hole style locking coupling. It uses a new heat-treated alloy steel material that is significantly stronger and harder than the previous, conventional type.

These upgrades also provided higher thrust capacity and more reliable performance when pushing through difficult, blocky ground. The new style of LC is available in both full-hole and stabilized versions. The stabilized style has a set of tungsten carbide-bearing pads over the length of the body to minimize wear and increase load-carrying capacity.

Adapter Coupling

An adapter coupling is a fitting that connects two pieces together that are not compatible by standard. For example, if you have a BSP threaded pipe and need to connect it to a NPT pipe, an adapter will bridge the gap between the standards.

Often, an adapter will also function as a reducer, or reducing coupling, joining one larger pipe to a smaller size. This can help you to save space and energy.

The adapter coupling mates between the locking coupling, steel drill rod and core barrel outer tube, providing the pocket into which the head assembly latches deploy. It also prevents the core barrel inner tube from rotating inside the adapter coupling and helps to avoid wear on the core barrel head assembly.

It also maintains directional control for the core barrel assembly by means of wear resistant preserving pads that are attached to the mating surface of the locking coupling.

Another important feature of the adapter coupling is that it has a tang that prevents the inner tube head assembly from rotating. This allows the inner tube to remain stationary and prevents damage to it while drilling.

This can be particularly useful when the core sample is very sharp or has hard edges. Those types of samples can quickly erode the internal surface of the inner tube.

The adapter coupling can be used for many different purposes, from connecting two different pipe sizes to bridging standards that normally aren’t compatible. It can be a permanent connection, or it can be a temporary connection to reduce flow.

Landing Ring

The landing ring is a crucial component of the PQ3Core Barrel Assembly, enabling it to be unlocked and transported to the outer end of the drill string. It also prevents the inner tube from becoming stuck in the drill string, which can be very damaging to the core sample and the drill bit.

The Landing Ring is designed to sit in the upper-end of the inner tube and be recollected by the mating coupling between the head assembly and the outer tube. As the inner tube is inserted into the drill string, the landing shoulder on the head assembly collides with the landing ring, setting it in drilling position and preventing the inner tube from being displaced by the rotational motion of the drill string and Flush Jointed Casing.

As the inner tube reaches the bottom of the hole, it collects the core sample and is then retracted by the outer tube. This process is repeated multiple times as the core sample is withdrawn from the formation.

A reversible wear pad, in the shape of a spiral, is provided on the inner tube to promote passage of drilling fluid and cuttings through the inner tube while maintaining stability, and extending the life of the inner tube and the core sample. Additionally, stabilized wear pads on the latches and the latch seats improve the wear resistance of these components.

The movable latch on the sampling unit engages the latch seat in the drill string to connect the unit to the drill string during core taking operations. The unit then produces a signal to the drilling operator when the core sampling unit is properly latched in the coring position, so that the desired core sample can be obtained.