Tag Archives: casing design

A Small World in a Big Airplane

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More than 6000 miles away from Houston and 30,000 feet above the ground, I shared a row of seats with a Turkish man who happened to have visited our office 6 years ago. Can anyone tell me what the chance of this occurring is?

After the Abu Dhabi International Petroleum Exhibition and Conference (ADIPEC), I took a flight from Abu Dhabi to Istanbul. During that 4-hour flight, I began sketching some interface designs for our next version of casing wear software. The man seated right next to me was quietly reading a book. After a while, he asked me, “Are you developing a casing design software?” He had obviously seen me write “casing wear” and thought it was “casing design.” I felt pleasantly surprised with his question. “Casing” is a frequently used word in the drilling industry. It is a steel pipe that is assembled and inserted into a wellbore and typically held into place with cement. Outside the petroleum world, it has a very different meaning. Generally, if someone asks me a question about a casing design, not only does that tell me that he is in the industry and familiar with it, but also that he is in the drilling side and familiar with drilling software.

Finding something in common is a good way to break the ice. We began to chat enthusiastically. He was Turkish, but had received an education in the U.S. and was now working with Schlumberger as a drilling engineer. I gave him my business card and he spent a little bit longer than usual looking at it.  He then murmured, “I know you guys…I have been to your office. Don’t you have a software package called MUDPRO?” (MUDPRO is our mud reporting software). Dale Carnegie once said, “A person’s name is to that person the sweetest sound in any language.” This same rule applies to names of family members, friends or even one’s own software products! I felt touched. He explained to me that he has a friend, who owned a mud company. The owner of the mud company visited our office in Houston 6 years ago and he happened to be with him during this trip. It must have been the logo on my business card that reminded him of the meeting, which I had not been a part of.

“What a small world!”  We exchanged mutual feelings.

Chatting with him not only made the flight shorter, but also memorable.

I would never have anticipated this meeting, but an unnoticed event years ago led to this very occasion. “Don’t judge each day by the harvest you reap, but by the seeds that you plant,” said Robert Louis Stevenson, a Scottish novelist from the 19th Century.

Though we are not guaranteed to have harvests every day, we can plant seeds as often as we wish, even every day. The world gets smaller as we plant more seeds daily.

Calculation and Prediction

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The pulling and running of pipe causes pressure surges and the prediction of these is a matter of economic importance in wells where the pressure has to be maintained within narrow limits to prevent formation-fluid influx and lost circulation. When these types of situations occur, the drilling engineer needs the best possible method of calculating and predicting surge pressures to drill these wells with a minimum of risks.

Pressure surges have been known for a very long time to cause well-control problems. For instance in 1934, pressure surges were identified as a result from pipe swabbing the possible cause of fluid influx, and in worst cases, blowouts. Also In 1951, positive pressure surges were measured and linked to lost-circulation problems.

For most wells, the extent of the pressure surges is not critical when the proper casing design and mud programs leave large enough margins between fracture pressures and formation-fluid pressures. However, a certain fraction of wells cannot be designed with large surge-pressure margins and in this situation the pressure surges may still be a concern.

The need to predict pressure surges in critical wells is the reason PVI developed SurgeMOD.

SurgeMOD - Surge Pressure Prediction SoftwareWith this surge and swab pressure prediction model, the annular pressures are calculated to be consistent with frictional pressure drops caused by fluid motion; the drilling mud can be well displaced by the pipe motion. This model is sufficient for an effective use for both drilling and completion. It analyzes the complex downhole hydraulics when running the casing for various pipe conditions and circulation sub tools. SurgeMOD not only predicts the surge and swab pressures for a given running speed, but also calculates maximum running speeds at various depths. After the casing or liner is set, it will calculate the maximum acceptable circulation rate before fracturing the formation.

This surge and swab pressure model shows an excellent agreement with the measurements of surge and swab pressures collected during the field tests. It accurately predicts maximum surge and swab pressures as well as the variation of pressure with time at any position in the well bore. Predicting surge and swab pressures using SurgeMOD can minimize potential problems in a well bore and allow more efficient trip speeds for running or pulling pipe.

Casing Wear Series – 3: Prevention

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Computer casing wear modeling reduces risks and can identify potential problems prior to its occurring. Necessary modifications on casing designs and drilling parameters could be made before the pumping starts once we can predict the location and magnitude of wear.

Figure 1 shows the 3D visualization of magnitude and location of wear in a previously set casing.

Figure 1. 3D Visualization of Casing Wear
Figure 1. 3D Visualization of Casing Wear

The knowledge we have acquired through decades of studies, lab testing, post-job analyses and computer modeling provides a good foundation for the following casing wear preventive measures:

  • Minimize dogleg severity and expect real dogleg at least 1.5 times higher than the planned value.
  • Use casing friendly tool joint materials.
  • Reduce rotor speed and use downhole motor.
  • Increase ROP.
  • Select proper mud type and add lubricants to reduce wear and friction.
  • Use drill pipe protectors.
  • Use thick wall casing in the anticipated wear section area.
  • Use software to reduce risks.

Please go to www.pvisoftware.com/white-paper/Casing-Wear-Causes-Prediction-and-Prevention.pdf to download the complete Casing Wear white paper.

Flying Among The Clouds

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Louis D. Brandies once said:

“Most of the things worth doing in the world had been declared impossible before they were done. Impossible means that you haven’t found the solution yet.”

A little over 100 years ago there were things that were considered impossible to do and that there was no way they could ever be achieved. For instance, to be able to fly among the clouds, but was it really an impossibility? Time proved that it wasn’t.

Just like flying among the clouds was impossible to do once, there are many things that thanks to the advancement of technology now are possible. For instance, a few decades ago horizontal or extended-reach drilling was considered impossible as well as casing wear prediction. In these environments, casing design is critical to a safe and successful drilling operations and well production, and unexpected casing wear can result in significant costs or even the loss of the well itself. This is the problem that drilling companies want to prevent.

So the question is: Is there any tool or software to calculate and predict casing wear severity? Yes there is! It’s called CWPRO.

2D wellbore schematic in CWPRO

This casing wear model uses the number of drill string rotations and contact force between the drill pipe and casing to calculate wear. The contact force is calculated using the dogleg severity inside the well. The maximum dogleg severity frequently determines the location and extent of the most severe casing wear. CWPRO helps operators and service companies identify, control and prevent potential problems. In overall the goal of CWPRO is to more accurately quantify casing wear risks and to ensure that the integrity of the casing is maintained during drilling operations.

Like mentioned before, there are many things that were considered an impossibility not too long ago like for instance, flying among the clouds. Likewise, thanks to software like CWPRO, predicting casing wear is no longer impossible; it is a fact.