Smart Solution

The demanding industry today continues to drill progressively challenging and costly wells, through more challenging formations.

Every year, operators lose hundreds of millions of dollars in their attempt to resolve drilling problems such as shock and vibrations, damage to bits and under-reamers, poor hole cleaning, borehole washouts, stuck pipe, plugged drillstrings and poor or inconsistent drilling performance. An analysis of worldwide drilling operation failure statistics in 2012 showed that a 38% were associated with stuck pipe, 27% caused by shock and vibration and 9% due to drillstring plugging.

Severe downhole drilling dynamics and vibration cause drillstring failures that can incur significant amounts of non-productive time. Drillers must trip out of hole either to replace bits or damaged bottom hole assemblies, perform fishing operations or drill costly sidetracks. Poor performance and reduced rates of penetration can occur when there is sufficient transfer of power to the bit, when cutting structures wear out permanently, or when rigsite personnel apply overly conservative drilling parameters due to a lack of trustworthy real time actionable information on downhole conditions.

PVI has a variety of software packages that can be an smart solution for many of these situations that operators and service companies have to deal with. For example, the software can help users to effectively reduce risks by quickly identifying the type and severity of downhole motions, detecting poor hole cleaning or sticking pipe probabilities at an early stage, plus many more. For directional drilling, users can enhance borehole quality, assist casing running and manage wellbore tortuosity. Users can also increase drilling performance by selecting drill parameters that increase the drilling efficiency and improve overall rate of penetration among many other things. For both onshore and offshore, PVI software can perform engineering calculations that optimize business and technical decisions and also provide quality engineering consulting and customized development.


Naming of Drilling Software

Almost everything on earth has a name in various languages as a point of entry. All names start in someone’s brain, the brain of someone like parents, discoverers, pioneers, inventors, and innovators. Naming is like writing a poem under constraint. You have to evoke shades of meaning in small words, paint a picture with few letters. For commercial products, naming is to link them to ideas that consumers already understand and to make the association vibrate.

Each great name like FedEx, BlackBerry, Porsche or Starbucks has its own story to tell about the new synthetic corporate language. These names are vessels capable of carrying big messages.

By the time I became a software developer and had to create names for drilling software, I was well aware that we live in a world filled with brand names. They are a part of the soundtracks of our lives. Instead of saying a cup of coffee, we say “Go Starbucks.” Mere mention of Chevron reminds us of a giant oil operator, rig floors, gas station, etc. As adman Claude Hopkins writes, the best names “are almost complete advertisements in themselves.”

When we finished our torque and drag program for oil well drilling, I was immediately aware of how hard it was to distinguish a new name from existing ones. At that time, drilling software market was filled with models like DDrag from Maurer Engineering and others. Our torque and drag model is not only for drilling operation, but also covers casing running, casing flotation, packer setting and cementing operations. To capture the broad spectrum of this new torque and drag model, we wanted a name to be more than a label, to have a compelling quality in itself and to flash a dramatically desirable picture in people’s mind. In short, we wanted a name to unlock the power of this new model.

After much brainstorming, we finally settled on TADPRO. A new name was born. I was taken by the symmetry of the name that TAD and PRO have 3 letters each. I felt that a word ending in “O” was approachable and playful. PRO projects a sense of sophistication.

On sound symbolism, when you pronounce the word TAD, it starts out crisp. Both T and D are exploded. Overall, TADPRO delivers a quick, responsive personality. Compared with DDrag, TADPRO is much faster.

Many brand names owned by corporations have gone beyond their original marketing purposes and have become bits and bytes of our modern daily language. We take an Advil and apply ChapStick.

Similarly, someday, drilling engineers, when doing torque and drag analysis for a particular operation, will simply TADPRO operation, just as we FedEx packages.



Torque and Drag - Nuts and Bolts

No matter it is an operation of drilling or casing running; any pipe movement in the deviated wellbore produces torque and drag (T&D) along the pipe. T&D is our weapon to drill a well or run a casing to the bottom. However, excessive T&D will cause equipment and operation failure.

Basically, axial movements such as drilling ahead or tripping creates drag, while rotation produces torque. The magnitude of T&D is determined by the combination of these two movements. Rotation shifts the resistance from drag to torque. In other words, you can shift the drag to torque by rotating the pipe. That is why people tend to rotate the pipe little bit if pipe gets stuck.

Torque and Drag Calculation

Typical T&D analysis starts by dividing the pipe into small elements. Calculation begins from the element at the bottom of the pipe, where weight on bit (WOB) or torque on bit (TOB) is expected. For each element, force and torque are balanced and the T&D at the top of the element are calculated step by step and from bottom to top, calculation is performed for each pipe element, until it reaches the rig floor. We call the torque and drag at the top of pipe surface torque and hook load (with block weight), respectively.

Torque and drag calculationTorque and Drag Common Terms

Some terms often used in torque and drag analysis are listed here with explanations:

  • Friction Factor (F.F.) - the representation of the friction between the wellbore/casing and the work string. The friction factor is dependent on mud type, pipe and wellbore and cutting concentration. Higher cutting concentration leads to higher friction factor.
  • Rotating Off Bottom (ROffB) – pipe rotates without any axial movement, such as rate of penetration or tripping. There is no WOB or TOB because bit is not engaged with formation.
  • Rotating On Bottom (ROnB) – pipe rotates without any axial movement, such as rate of penetration or tripping. However, WOB and TOB are present because bit is engaged with formation.
  • Drilling – pipe rotates with certain rate of penetration and with the presence of WOB and TOB.
  • Slide Drilling - Drilling with no drill string rotation. (only axial movement, no rotation)
  • Sinusoidal Buckling - Sinusoidal buckling occurs when compressive forces on the string become too high, resulting in a snake-like bending in the string. Note that in this mode, the pipe deforms, but still in a 2D plan.
  • Helical Buckling - a more extreme form of buckling which occurs when compressive forces pass through sinusoidal buckling and exceed the helical buckling limit. Helical buckling causes contact between the pipe and the wellbore, exerting force on the wall of the hole. Both drill string fatigue and interference with weight transfer to the bit occur. Helical buckling should be avoided.
  • Helical Lockup - Helical lockup occurs when compressive forces on a string in helical buckling prevent axial movement. Forces at surface are not transmitted to the bit.
  • Tension Limit- The tension limit of a material is based on its yield strength, which is measured in psi. When the minimum yield strength is exceeded, pipe will plastically deform. Plastic deformation occurs when pipe that has stretched does not return to its original shape.
  • Make Up Torque- The rotational force used to make up a connection in the string. Drill pipe failure may occur when the make-up torque of a connection is exceeded.Buckling-Tension-Torsion
  • Stress in the String - The various stress that TADPRO models are axial, bending, torsional, and shear stresses. These stresses are summed up in the Von Mises Stress. Various failures occur as a result of repeated stress to a string, including cracking, washouts, and twist offs, etc.
  • Stress in the String - The various stress that TADPRO models are axial, bending, torsional, and shear stresses. These stresses are summed up in the Von Mises Stress. Various failures occur as a result of repeated stress to a string, including cracking, washouts, and twist offs, etc.
  •  Casing Wear- Prolonged, repeated axial and rotational movement within casing will wear both at the string and the casing, potentially leading to string and casing failure.Casing wear