What are Shock Subs and Its Applications?

Shock subs, also known as vibration dampeners, are used to absorb vibrations and bit shock loads in drill collar strings. They usually feature long integral elastomeric elements, which serve to transmit torque and weight to the bit simultaneously. When drilling is being carried out at shallow depths, intermittent hard and soft streaks, along with broken formations, can transmit vibrations to the surface, where they are easily detected. With greater depths, though, these vibrations might not be detected because the drill string cushions them. However, they will still cause damage to the bit, as well as bottom hole assembly components and the drill string.

Shock Sub (Vibration Dampeners), Hunting (2018)

Shock Sub (Vibration Dampeners), Hunting (2018)

Some advantages of using a shock sub include:

  • Offering faster drilling rates, since optimum bit weight and rotary speed may be used on the bit constantly.
  • Increasing the bit length by reducing shock loads.
  • Cutting damage to drill collars, drill pipe, and downhole tools by reducing bouncing.
  • Reduced connection damage, because the elastomeric element absorbs both torsional and axial loads, so that connections are not at risk if the bit stalls.
  • Reduced damage to surface equipment, including swivels, blocks, and wirelines.

Continue reading

What are Drilling Jars?

Most modern drilling jars are hydraulic. They are also usually double acting, meaning they can deliver an extra-heavy impact should the bottom hole assembly become stuck. They are intended to work as an integral part of the drill string, and can withstand high pressures and temperatures over a long period of time, making them suitable for long-term use.

With almost the same length and diameter specifications as standard drill collars, and with a similar connection strength and slip setting area, they may be used as a component of a stand of drill collars without difficulty.

Usually, jars will be used alongside accelerators, which are run above the jar and work automatically. They serve to amplify the impact force of the jar, and can even double it in some cases. They commonly use the compression of silicon to give added stored energy and optimize jar impact and free-travel distance in both directions. They also have the added benefit of dampening the dynamic load in the drillpipe, since they transmit shock waves poorly, thus helping reduce damage to both string and surface equipment.

Drilling Jars Diagram (Slideshare, 2017)

Drilling Jars Diagram (Slideshare, 2017)

Continue reading

Down hole Reamer – Its Application in Directional Drilling

Not only are reamers important for directional drilling, but they can also be useful in straight hole applications. Reaming assemblies can straighten out and smooth over crooked holes, restore undergauge holes to gauge, and get rid of any irregularities or keyseats. They also help to prevent excessive hole curvature in short intervals, which may be experienced when entering and exiting a section of hole which forms a sharp curve. Finally, reamers can reduce the rotational torque in a wellbore, and may therefore be used as a substitute for a conventional string or near-bit stabilizer.

Reamers are made by almost all major downhole tool manufacturers, and have the same core features: sealed or open (mud lubricated) bearings, cutter types – either “nobbly” or “smooth”, and either one (so called “3-point”) or two (“6-point”) sets of cutters in a tool.

Reamer (Courtesy of NOV, 2017)

Reamer (Courtesy of NOV, 2017)

Continue reading

Basic Understanding of Underbalanced Drilling

Between the fracture pressure and the pore pressure of the formation, the hydrostatic pressure of drilling fluid will always be maintained according to conventional drilling practice. In order to control the transport cuttings to the surface as well as the formation fluids, the drilling fluid is held within the wellbore where it circulates. Furthermore, it also keeps the drill bit cool and lubricated as it acts as a stabilizing agent. For effective use, the fluid must be water- or oil-based and this leads to a maximum weight of 19 pounds for each gallon (minimum of 7.8 pounds). As an attempt at imparting fluid loss, density, and rheological properties, it also contains a mixture of liquid and solid products.

Figure 1 - Conventional Drilling

Figure 1 – Conventional Drilling

For many years, the conventional drilling has been the safest method when drilling a well but there are also some negatives to using the method. For example, fluid invasion is a common problem because the drilling fluid pressure is naturally above the pressure of the natural formation – this can cause permeability damage. Also, physical blockages and washouts are common as the solids and fluids lodge into the formation. Continue reading

Review Well Control Method Presentation by Wild Well Control

Wild Well Control is one of the best well control specialist companies in the world. The company not only provide well control and engineering services to the company’s customers, it also provides free technical knowledge to the public such as Wild Well Control Technical Book that you can download it for free.  Today, we would like to review one of the most useful presentation which is “Well Control Methods” presentation. After you read the review and you like it, we also provide download link for you at the end. Thank Wild Well Control for great contribution to oil and gas industry.

Well Control Methods by Wild Well Control

Well Control Methods by Wild Well Control, Wild Well Control (2017)

Continue reading