Drilling Software Training in Snow

No matter how unpredictable the weather is, drilling software can predict downhole conditions.

One would never think that Denver in May requires a winter coat. That was my judgment before I came here to teach a drilling software course. I did briefly check the weather website and I saw 70 °F. So I assumed a warm spring in the mile-high city. Upon my arrival on April 30th, I became aware that snow was coming and I felt the temperature dropping as evening was coming. I did not bring any jacket. I went to the stores along the street but could not find any coat. See, even the stores thought the winter is over. I finally bought a winter coat in a souvenir store: after all, it is better to spend money on cloth than cold medicine. Surely enough, the snow came as predicted during the night. Here is the picture of downtown Denver on May 1st, 2013.

Drilling Software Training in Snow - Pegasus Vertex

Modern technology, particularly computers and weather satellites, and the availability of data provided by coordinated meteorological observing networks, has resulted in enormous improvements in the accuracy of weather forecasting, despite of people’s intuition. To better prepare our daily life, we do need to pay attention to the hard-to-understand red/green/yellow images on TV.

Snowflakes danced outside the window all day long as I taught 7 drilling engineers from the Rocky Mountain region the HYDPRO software (drilling hydraulic model).

Drilling software, in a sense, is much like weather forecasting for an upcoming drilling operation. With planned well path trajectory and proposed operation parameters, engineering software can pinpoint potential problems and make necessary adjustments on operation. The potential economic benefits of accurate drilling engineering modeling are immense. For example, drillpipe or casing buckling is always a concern during drilling and casing running operations. TADPRO (torque and drag model) predicts the locations of different buckling modes. The following screen shot from TADPRO shows the sinusoidal and helical buckling sections along a drillpipe.

Visualization of buckling in TADPRO - Pegasus Vertex

Generally speaking, sinusoidal buckling can be tolerated, while helical buckling should be avoided,  because helically buckled pipe creates additional drag, which could lead to “lock up” situation.

It is often quoted: Everyone talks about the weather, but no one does anything about it. We cannot change the weather except predict it. In other words, we react to the prediction. However, drilling software like TADPRO can alert engineers the potential downhole problems prior to the operation so necessary measures can be taken to prevent it. This improves safety, saves time and money, and reduces risks.

We use weather forecasting to plan our daily activities. Similarly, drilling professionals should use drilling software to do well planning. The future belongs to people who can predict and prepare for it.

Drilling Software: Your Hot Model

Everyone including drilling engineer seems to be busier than before – There are always more wells to be drilled, more projects to be managed, more well planning to be done and reports to be run. Let us face it: you and I are not supermen or ironmen. We are just normal John and Joe, facing the increasing demanding.

Any help would be helpful. Imagine an assistant, who could be on-call 24/7! And she does not charge overtime or complain about tasks. One might think this kind of helper is a far-fetched idea. But what is in my mind is an assistant you can actually own and this assistant is most likely a super model: drilling engineering model.

All of us hate to do repeated tasks, and that is why we invented dish washer and vacuum cleaner. From abacus, to calculator, to computer, we calculate more and faster. It might be fun to find the greatest common divisor in 3rd grade, but hand calculation of a buoyant weight of pipe in mud is more of a tedious step than an exciting destination. We have important technical decisions to be made in office and on rig floor.

That is why drilling engineering software such as PVI’s TADPRO (torque and drag model) comes handy. It frees us from repeated manual calculation and errors associated. These drilling models do not discriminate vertical, deviated, horizontal or ERD wells. Provided with proper input data, these model assistants perform analysis, run reports, show animation within a few seconds. If you are not sure about certain variable such as friction factor in open hole sections, they like many attentive helpers, even give you sensitivity study to show you the best and worst scenarios.

Sometimes, these models are just like robots, receiving orders and performing tasks. Other times, they give you crucial advices and identify potential problems, such as helical buckling or excessive downhole pressure. They are like a senior consultant who is amiable and does not charge premium.

These models are strictly trained to be friendly. They do not care much if you give them a job after 5pm or in weekends. They are very tolerant if you accidently key in the wrong data. They do not give you an eye. Instead, they kindly remind you of the error and even suggest you the correct input in many cases.

Did I mention that these models are very pretty? Their faces (what we call interface) are carefully designed so that users will not get lost and interaction creates pleasant experience.

Drilling is tough, find good software - your hot model.

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