Updated for 2017: This article and associated study guide work book (available for download) detail the exact techniques I used this April (2017) to pass the IWCF Level 4 well control exam scoring a 96% on the IWCF Principles and Procedures, and a 95% on the IWCF Equipment exam.
The intent of this study guide is to help you prepare for the IWCF Level 3 and Level 4 Supervisor Well Control Exam (Surface or Combined Surface and Subsea Qualifications). This guide does not replace the requirement to attend a certified well control school, instead, it is designed to supplement the training received in the classroom and to ensure the IWCF candidate is as prepared as possible PRIOR to attending the IWCF class.
This guide assumes that you have a “general” idea how oil and gas wells are drilled and at least a basic understanding of common well control calculations from an introductory IADC or IWCF well control course and/or company provided training material. This guide also assumes you have at least a month to study BEFORE your IWCF exam.
Strengthening the need for this guide, many companies and organizations (including the one I work for) are pushing for an “Enhanced Standard” of well control requiring students to obtain an average score of at least 80% to be recognized as having passed the course (even though the minimum IWCF passing grade is 70%).
I’ll start with the “basics” and then break down each individual test (Simulator, Equipment and P&P) into its own section with some of the preparation tips that helped me pass the exam.
I’ll also add that this guide is NOT a well control manual. Instead, it is a tool to help you study for and pass the IWCF Level 3 and Level 4 well control certification exams using information that is already available to you on the internet and in my downloadable IWCF Study Pack Workbook.
If you haven’t already, you can purchase my IWCF Study Pack Workbook complete with an Appendix of over 400 IWCF sample questions, IWCF equipment diagrams and worked out IWCF formula problems with explanations.
Firstly, the IWCF test is no joke. Whether you’re taking IWCF Level 2, Level 3, or Level 4, it is as difficult as everybody says it is. If you don’t prepare prior to the class and you’ve never been through IWCF advanced well control before you’re not going to do very well. This is especially true for students pursuing Level 3 or Level 4 certification as it adds a graded practical exam (simulator exercise) to the mix.
The GOOD NEWS is you have control over your own destiny and it’s only a matter of how important passing is to you. You WILL PASS the class if you put the effort in. EVEN BETTER, you can ACE the exam if you follow my techniques.
By far the most IMPORTANT thing you can do to prepare for the IWCF exam is to review my “IWCF Study Pack Workbook“. Even if you know nothing about well control, you’ll pick up a great deal going through the questions over and over. At first it seems like you’re doing nothing but memorizing the answers, but after a while the questions start to “connect” and you begin to get a sense of what is actually going on.
I would estimate that I went through every question in the IWCF Study Pack Workbook at least 5 times (approximately 450 questions spread out over 8 sections). After a while, there will be many questions that will become easier than others. I would highlight the most difficult and challenging questions with a red highlighter so I could focus more on those and not waste time studying the easier questions I already understood (it’s all about efficiency).
The most effective way I found to do this was to hit the material in small 30-45 minutes blocks a few times each day. Not only will this prevent you from burning out, but it will also allow time for the material to sink in so you can build on it during the next study section. I found it was also helpful to take a day or two off every once in a while to reset.
The knowledge you gain from reviewing IWCF Study Pack questions will help you in all three exams required by IWCF Level 3 and Level 4 certification.
The Simulation “Practical Exam”:
If you’ve never had any real drill floor experience at the Assistant Driller or Driller level, you’re going to be out of your comfort zone when it comes to the simulator exercise. This is especially true if you’re taking the ICWF Level 3 or Level 4 supervisor exam.
By registering for the class, it is assumed that you’re comfortable with drilling operations and will know exactly what you need to do to line up the drilling equipment and give the driller “instructions”. The IWCF provides a general “outline” of what points you’ll be graded on but it offers absolutely no help with what you’re actually supposed to say during the exercises (you literally have to act out a scenario and give realistic instructions to the driller who is coming on “tour”).
This was a challenge for me since I’ve NEVER been directly involved in the drilling operation during my career. Not only did I not know much about lining up a choke manifold or standpipe manifold, I knew virtually nothing about what RPM to drill at, how much pressure to maintain on the drillpipe (or SPM on the mud pumps), how much weight to maintain on the drill bit while drilling, etc.
Well Control Simulation Video:
A great resource that helped me was a YouTube video produced by the Arabian Drilling Company that walks you step-by-step through the IWCF well control drilling simulation process:
I’ll be the first to admit that the video is a little cheesy but it follows the IWCF well control script perfectly and covers virtually every aspect of a well control situation that you’ll likely encounter during your IWCF simulation exam. I will add that the well control simulator used in the video is probably a lot more sophisticated than you’ll find in the well control school that you attend but the overall concept and theory is exactly the same.
I basically memorized what the toolpusher’s instructions were to the driller in the video and repeated them during my time in the simulator. The best part about doing this is the “instructions” you give to the driller count for a very large percentage of your IWCF simulator score. Even if you don’t do so hot exercising the choke during the well kill simulation, you can still get a decent score by following the script outlined in the Arabian Drilling Company Well Control Video.
During the week of my well control school I would practice the script in my hotel room by rehearsing what I was supposed to say into the voice recorder on my iPhone again and again until I could go all the way through the “driller instructions” without missing any of the “criteria” on the IWCF score sheet. I know this sounds lame to many of you reading this, but it HELPS!
Here’s a rough transcript of what I practiced saying to the driller during the initial set-up of the drilling operations. The good news is you don’t have to say these in the exact order as long you cover all the basic points as outlined in the IWCF criteria.
“Good morning, driller. I hope you had a good night’s rest. Today we’re going to be drilling at 100 RPM, 25,000 to 30,000 weight on bit with 2500psi on the drillpipe pressure gauge. However, before you get started I want you to check your equipment and make sure you have everything set up the way it needs to be.”
“Please check your BOP panel for proper valve positions and ensure you have the appropriate pressure readings on your gauges. Check your standpipe manifold for proper valve alignment, we’re going to be drilling using mud pump #1 today. Also check your choke and kill manifold and ensure it is set up for a “hard shut-in since this is the method I want you to use as per company policy in the event we do need to shut the well in.”
“You’ll also need to take your slow circulating rates at 25 and 30 strokes per minute (SPM) on mud pumps 1 and 2 as well as find the choke line friction losses for both pumps at 25 and 30 SPM as well.”
“Once you have your pumps up and running. Make sure you set your pit level and flow meter alarms and find your “space out” and “hang-off” positions. In the event we need to hang off, I’d like you to hang-off 50% of the string weight on the upper pipe ram.”
“Finally, I want you to flow check all drilling breaks and shut the well in immediately if you have any concerns or doubts. DO NOT CALL ME FIRST.”
TIP 1: If you have difficulty “memorizing” the well control instruction roll play script you’re supposed to give to the driller, you can also just use the well control equipment in the simulator room to “prompt” you with what to say. For example, the simulator equipment above is typical of what you might find at a common well control school. You can just work your way through each piece of equipment on the control panels and on the computer screen to help you to make sure you don’t miss any of the points covered in the video. On the computer screen you’ll see (from right to left) the choke manifold, drill pipe manifold, drillers panel and BOP panel. You could give your driller instructions in the order the equipment is presented to make sure you don’t miss anything.
“Driller, please check your choke manifold, stand pipe manifold, drillers panel, and BOP panel for proper alignment and settings.”
BOOM, that’s probably 15-20% of your grade right there just using what’s available to you! On the left hand panel, you’ll see the alarm settings for the flow meter and pit gain alarms. If you’ve missed these alarms during your instructions to the driller, you’ll remember them if you go through all the equipment gauges prior to starting up the exercise.
TIP 2: Another invaluable thing to do is take a few pictures of the various screens and panels during your practice simulator exercise that you can review in your hotel room in the evening. Practice your “roll playing” again using these pictures as prompts and guides. It will be tremendously helpful!
TIP 3: On the IWCF practical exam (simulator), you get to decide which method to use to “kill” the well. I HIGHLY recommend that you use the “Drillers” method. The IWCF practical exam concludes after the initial influx is circulated from the well which means if you chose the drillers method, you’ll only have to make the first circulation and not have to worry about following the drillpipe pressure schedule you created on your killsheet (more on this later). You can fool around using the Wait and Weight method if you want to, but following the drillpipe pressure schedule on your kill sheet will make it much more difficult to detect one of the four “problems” (see next paragraph) that will be thrown at you during your exam by your instructor.
The Four IWCF Simulator Problem Scenarios:
As mentioned above, you’re expected to know what to do in the event you encounter any “problems” during your IWCF practical simulator exam. Fortunately, the Arabian Drilling Company well control video covers the four basic problems that you’ll likely encounter during your well control simulator exam. I’ve summarized each below but you’ll probably get more out of just watching the video a few times until you understand exactly what the choke operator is doing. You can count on experiencing at least one of the below problems during your practical exam so mastering these concepts is time well spent and an easy way to pad your exam score.
Choke is Washing-Out:
Detecting a Washed-out Choke: If you have to keep closing the choke to maintain drillpipe, casing and kill-line pressure, you can reasonably assume that the problem is a washed-out choke (you’ll notice the casing and kill-line pressure start to drop first followed a short time later by the drill pipe pressure). If you use the driller’s method like I recommend, this scenario will be relatively straightforward to detect.
Dealing with a Choke Wash-out: If you detect that your choke is washing out you should immediately order the driller to isolate the choke by closing a valve upstream of the choke. Once the washed out choke is isolated, you need to quickly shut down the pump to avoid adding too much bottom hole pressure (from pumping against a closed choke). Once the pump is shut down you can line up on choke #2 (backup choke) and resume the kill. (Note: This was the scenario I was given during my practical exam).
Choke is Plugging:
Detecting a Plugged Choke: If you have to keep opening the choke frequently to maintain drillpipe, kill-line and casing pressure, you can reasonably assume that the choke is plugging (you’ll notice the choke pressure and kill line pressure start to rise first, followed a short time later by the drillpipe pressure gauge). Again, if you elect to use the driller’s method during your IWCF simulator exercise this scenario will be much easier to detect.
Dealing with a Plugged Choke: If you detect that your choke is plugging, you should immediately shut down the mud pump. After the pump is off, line up on choke #2 and start back up the well killing process.
Mud Pump Trips Offline:
Detecting a Tripped Mud Pump: Detecting a tripped mud pump is probably the easiest problem to detect during an IWCF well control simulator exam. In this scenario, you’ll notice your strokes per minute counter either go to “0” or go blank and your drill pipe pressure drop off quickly. If the simulator room is equipped with sound effects (like the one I was in), you’ll also notice the room get very quiet.
Dealing with a Tripped Mud Pump: If your mud pump trips offline during your well control scenario, all you have to do is immediately close the choke and then line up to use mud pump #2. Even if you chose to use the driller’s method to kill the well, you’ll need to remember to recalculate your Initial Circulating Pressures and Final Circulation Pressures, as well as your “step down” pressure schedule on your kill sheet since you’ll be using a different mud pump that likely has a different “slow pump rate” (more on this later).
Detecting a Plugged Bit: The forth and final “problem” that could be thrown at you during your IWCF simulator exercise is the plugged bit. In this case, you’ll see your drillpipe pressure gauge increase sharply while the casing gauge and kill-line gauge (assuming you’re on a subsea well) will remain approximately the same.
Dealing with a Plugged Bit: If you encounter a plugged bit, take note of the pump pressures. It will be expected that you slowly stop the mud pump (gradually slowing the pump maintaining casing and kill-line pressure). Once you’re confident that the issue is indeed a plugged bit, you’ll start the pump back up and the new Initial Circulating Pressure will likely be whatever the drillpipe pressure gauge was reading before you started shutting the pump down.
Creating Simulator Flash Cards:
To help me prepare for any of the above issues, I made four flash cards (one for each possible scenario). On the front of the card, I drew little gauges with pressure readings with a brief description that represented the tell tales of each possible problem that the simulator instructor could throw at me. On the back of the card, I would write out what I needed to do to remedy the problem. Every once in a while I would run through these cards until it became second nature to identify the problem and what would need to be done to solve it. Since you’re guaranteed to get at least one of these problems during your exercise, it is another excellent opportunity to master these areas to pad your final practical exam grade.
Operating the Choke:
The final piece of the simulator exam is learning to properly operate the choke to circulate out the influx while maintaining bottom hole pressure. This was a very intimidating skill for me to obtain especially after the first day in the simulator (during one of the practice exercises) when I just couldn’t figure out how to keep the drill pipe pressure where I wanted to. Fortunately, as the week went on I got better and better.
Remember, there is a “lag time” between opening or closing the choke and noticing a change in your drill pipe pressure gauge (approximately 2 sec for every 1,000 ft MD of the well). Most of the scenarios you’ll be doing in your simulator exercises are between 5,000 and 8,000 feet so you can expect a 10-20 second delay for choke adjustments to be reflected in your drillpipe pressure. This was one of the most challenging aspects of the simulations for me until I learned to simply use the casing gauge and kill gauges (for subsea wells) to monitor and detect sudden changes in the annulus’s pressure. For example, if you close the choke, you’ll see the affect on the casing gauge almost immediately vs. waiting 10-20 seconds to see the change in your drill pipe gauge.
Here’s the pressure graph from my actual IWCF Level 4 simulation exam:
Minutes 0-40: The first 40 minutes or so of the exam was going over the “instructions” to the driller as well taking the slow pump rates (SPR) and choke line friction (CLF) values.
Minutes 40-70: During this time frame, the driller starts actually drilling the well and the supervisor (Level 4 candidate) is actually out of the simulator room. The blue line represents the drill pipe pressure and you can see he actually shut down the mud pumps a couple of times to “flow check” some drilling breaks that he recognized (Drilling Breaks: Drilling breaks are when the rate of penetration (ROP) of the drill bit increases dramatically over a short period of time).
Minutes 70-73: The driller detecting a kick and the well is flowing. He shuts the well in and calls the supervisor (Level 4) into the simulator room.
Minute 73-105: The mud pump is slowly brought up to kill rate speed in 5 SPM intervals while the Level 4 supervisor slowly opens the choke to maintain the original casing pressure. Once the mud pump is slowly brought up to the kill rate speed, you need to take note of the Initial Circulating Pressure to make sure it is close to what you calculated on your kill sheet (more on Kill Sheets in a bit).
Minute 105: At approximately minute 105, you can see where the black line (bottom hole pressure) started to drop off. This was when the simulator instructor initiated a “problem” into the scenario. The problem in my case was a washed out choke. You can see where I had the driller isolate the choke and we lined up on choke #2 to resume the scenario. You’ll also note that bottom hole pressure (black line) never dipped below the formation pressure (green line).
Minutes 105 to End: The rest of the simulation was simply adjusting the choke to account for the expansion of the gas from the well. This gets particularly challenging once the gas enters the choke lines and you really need to pay close attention to your kill and casing gauges to “check” any sudden increases and decreases to ensure you can maintain drill pipe pressure constant (which will ensure bottom hole pressure remains constant). Don’t make the same mistake that I made near the end of the scenario where I was so excited to have gotten through “most” of the scenario that I let bottom hole pressure drop below formation pressure. The scenario isn’t over until the instructor says it’s over! Fortunately for me the scenario was over before any additional influx came which could have affected my score.
The Equipment Exam:
One of the biggest complaints I hear about the IWCF exam is that the equipment covered is outdated at best and even obsolete in some cases whether you’re taking the surface or subsea exam. This is especially true if you are fortunate enough to have started out offshore on a 4th, 5th, or 6th generation drilling rig.
As I mentioned above, the most helpful thing for me was going through the equipment sections in the IWCF Study Pack over and over. You eventually start picking up on things and making connections between the questions and the various pieces of equipment (even if you’ve never seen or heard of the equipment before).
As you learn more and more about the various equipment and their components, the next group of questions in the IWCF Study Pack become easier and easier.
Approximately 25% of your test grade will be based on your ability to identify various components of well control equipment. Included in the IWCF Study Pack is a section with diagrams and drawings of most (if not all) of the equipment that you’ll likely encounter on your exam. Study the drawings and practice memorizing the various components. After a while, you can white out the labels on the equipment and test yourself to see if you can make it all the way through the equipment drawings without referring to an un-whited out version. When you can do this you’re ready for the exam.
Because of the outdated equipment covered in the ICWF Level 2, Level 3 and Level 4 you’re best option for learning the material is to simply study as many of the questions in the IWCF Study Pack over and over again. I cannot emphasize this enough, you really do learn about the equipment by studying the questions and it all starts to make sense after a while.
The P&P Exam:
The P&P exam is probably the most difficult part of the test for most people I’ve talked to. It is also the longest. Level 3 candidates are given 2 hours to complete the exam and Level 4 candidates are given 2 ½ hours to complete the exam (not really sure why Level 4 gets more time).
The P&P test covers a variety of skills and knowledge including the completion of a “Kill Sheet”, gauge interpretation, various drilling formula calculations, and “general” theory questions.
Practice the Kill Sheets:
Another easy way to pad your grade on the IWCF Level 3 and Level 4 exam is to master filling out IWCF Kill Sheets. Kill sheets may seem intimidating at first but they’re actually quite easy to learn using the IWCF preformatted kill sheets that you’re allowed to use during the test. I’ve included a sample IWCF Kill Sheet Exercise below to show you how to fill out a typical Kill Sheet similar to what you’ll find on an IWCF Level 2, Level 3 or Level 4 exam. You can download a blank IWCF Kill Sheet from the IWCF website here to fill out and follow along over the next section of this study guide.
Example Kill Sheet Problems with Explanations:
Hole Size: 8-1/2 inch
Hole Depth: 10450 (TVD/MD)
Casing Shoe: 9-5/8 inch 7800 feet (TVD/MD)
Drill Pipe: 5 inch 0.0172 bbl/ft
Heavy Weight Drill Pipe: 5 inch, length 723 feet, capacity 0.0088 bbl/ft
Drill Collars: 6-1/2 x 2-13/16 inch, length 912 feet, capacity 0.0077 bbl/ft
Choke Line: 2-1/2 inch ID, length 415 feet, capacity 0.0061 bbl/ft
Marine Riser Length: 400 feet, capacity 0.3892 bbl/ft
Annulus Capacities Between:
Drill Collars in Open Hole: 0.0292 bbl/ft
Drill pipe/HWDP in Open Hole: 0.0447 bbl/ft
Drill pipe/HWDP in Casing: 0.0478 bbl/ft
Drill Pipe in Riser: 0.3638 bbl/ft
Mud Pump Data:
Displacement at 98% volumetric efficiency 0.12 bbl/stroke
Slow pump rate data:
@45 SPM through the riser 780 psi
@45 SPM through the choke line 900 psi
Other relevant information:
Active surface volume 480 bbls
Drill pipe closed end displacement 0.0254 bbl/ft
Formation strength test data:
Surface leak-off pressure with 11 ppg mud 1900 psi
The well kicked at 10450 ft vertical depth
Shut in drill pipe pressure 550 psi
Shut in casing pressure 820 psi
Pit gain 10 bbl
Mud Density 11.5 ppg
Completed IWCF Subsea Kill Sheet with Detailed Explanations:
The following IWCF kill sheet has been completed with the above data:
Remember to put your name and date on your sheet!
Formation Strength Data:
For this section, you need to fill in the blocks using the data from the example kill sheet data pages above. For (A) you use the surface leak-off pressure from the “Formation Strength Test Data” section. For (B) you use the mud weight used during the surface leak-off pressure test from the same section. (C) is calculated by plugging (A) and (B) into the formula given to you in the box.
Caution: If you do your calculations correctly, you’ll come up with 15.6844 ppg. Since mud weights are generally recorded to one decimal place (tenths) you’ll need to round 15.6844 ppg. However, you CAN’T round up because you will exceed the maximum allowable mud weight if you round up to 15.7. You must round down to 15.6 ppg to record the proper maximum allowable mud weight on the kill sheet.
Mud Pump Data and Slow Pump Rate Pressures:
The mud pump pressure section of the kill sheet is filled out almost entirely from information from the data sheet you’re given at the start of the test. The displacement per stroke of the pump is given to you as well as the slow pump rate data through the riser and the choke line. The only thing you’ll need to calculate in this section is the choke line friction loss which is simply the difference between the slow pump rate in the Choke Line (900) and the slow pump rate in the riser (780) = 120.
Current Well Data:
The information for this section is also pulled from the example kill sheet problem data. Marine Riser and Choke line length are given to you on the data sheet in the “Internal Capacities” section. Drilling mud weight is given to you in the “Kick Data” section. Casing size and measured depth (MD) and total vertical depth (TVD) are given to you at the very top of the kill sheet problem as well as the Hole Size and Hole Depth in MD and TVD.
Caution: Remember the difference between Total Vertical Depth (TVD) and Measured Depth (MD). Measured depth is used when calculating volumes of fluids. TVD is used when calculating hydrostatic pressures. For example, you would use MD when calculating the volume of fluid in the drill pipe but you would use TVD when calculating the hydrostatic pressure of the fluid in the drill pipe.
Drill String Volume:
Calculating the drill string volume is as simple as plugging the length of your drill pipe, heavy weight drill pipe (hevi wall or HWDP) and drill collar into the drill string volume section. The capacities for all three are given to you in the problem in the “Internal Capacities” section. The only tricky thing is figuring out the drill pipe length. Since the length of Heavy Weight Drill Pipe and Drill Collars are given to you, all you need to do is subtract these two values from the total MD of the well to find the drill pipe length. In our example problem this would be 10,450 – 723 – 912 = 8815.
Once you’ve plugged in the length of each section of drill string and the capacities you simply multiply each row to find the barrels of mud in each section and add them up to find the total drill string volume. After you find the total drill string volume (165 bbls in our example) you divide the bbls by the pump displacement per stroke (.12 bbls in our example) to figure out how many strokes of the mud pump are needed to completely displace the drill string (165/.12 = 1375). Once you’ve calculated the pump strokes needed to displace the riser, you divide the total strokes by the strokes per minute (SPM) of the mud pump to find out how much time would be needed to totally displace the volume of the drill string. Since our mud pump is pumping at 45 SPM we get 1375/45 spm = 30.5 minutes.
Open Hole and Total Annulus/Chokeline Volume:
This section is filled out very similar to the section above except now you’re calculating the volume of mud in the open hole and casing minus the space taken up by the drill pipe, HWDP and Drill Collars.
You’re given the length of the drill collars in the data sheet for the problem. To find the length of DP and HWDP in the uncased section of the well (the open hole section) you need to first find out how much open hole you have. You do this by subtracting the shoe TVD from the TVD of the entire well (10450-7800 = 2650 feet of open hole). Since 912 feet of this open hole is filled with drill collar, the rest (2650’ – 912’ = 1738’) is the length of drill pipe/HWDP in the hole.
Total Well System Volume:
The total well system volume is calculated by adding values (D) and (I) from above which gives you 624.8 bbls. Divide this by your pump displacement per stoke (.12 bbls/stroke) to calculate the total strokes this represents (5207 strokes). From here divide this by the SPM you’re using (45 SPM) and this will tell you how long it will take to displace the Total Well System Volume with the mud pump (115.7 minutes).
The active surface volume is given to you in the data sheet so you record it in this section and then divide it by the pump displacement (.12 bbls/stroke) to find out how many strokes it would take to displace the active surface volume.
Total active fluid system volume is calculated by adding the previous two volumes and strokes together.
Marine riser length is given to you on the data sheet in the “Internal Capacities” section as well as the annulus capacity with drill pipe in the riser in the “Annulus Capacities Between” section.
Caution: Make sure you use the Riser capacity with drill pipe in the riser vs. the riser capacity that is listed in the “Internal Capacities” section which does not account for lost capacity due to the drill pipe being in the riser.
Kick Data Section:
The kick data section is filled with information directly off the kill sheet data page in the “Kick Data” section.
Kill Mud Weight:
Kill mud weight is calculated by plugging the numbers into the formula provided in the section. You’re already given Shut-in Drill Pipe Pressure (SIDPP), the TVD of the well and the current mud weight. All you need to do is plug the numbers in and calculate the mud weight needed to kill the well. If you’ve run the numbers correctly you should get a calculated kill weight mud of 12.5121 ppg. Kill mud is usually recorded to one decimal place so it would be natural to want to round this value down to 12.5 ppg. However you always round up kill mud weight to the nearest tenth so 12.5121 would be rounded to 12.6 ppg. The reason being if you made it 12.5 ppg, there wouldn’t be enough hydrostatic pressure created in the well to “kill” the well.
Caution: Remember you always round up Kill Mud Weight to the nearest tenth and you always round down your Maximum Allowable Mud Weight to the nearest tenth.
Initial Circulating Pressure:
You calculate initial circulating pressure (ICP) by simply adding the Dynamic Pressure Loss through the riser (780 in our example) to the Shut In Drill Pipe Pressure (550) given us 1330 PSI in our example. This is the pressure you expect to see on the drill pipe pressure gauge when first starting to circulate out the kick.
Final Circulating Pressure:
You calculate the final circulating pressure by dividing your new kill mud weight by the current mud weight and then multiply this value by the same dynamic pressure loss you used above. This is the pressure you expect to see on the drill pipe gauge once all of the kill mud is pumped down the drill string and is starting to enter the annulus.
PSI Drop Per 100 Strokes:
This section is where you calculate the pressure drop per every 100 strokes of the mud pump as you start pumping heavier kill weight mud down the hole. All you do is find the difference between the ICP and FCP that you calculated above and then plug that number into the next formula where you multiply it by 100 and divide it by the (E) which is the number of strokes needed to displace the drill sting.
When you start pumping kill weight mud down the hole you need to be at or above the ICP to ensure you don’t let more formation fluids into the hole. As the drill string is displaced with the heavier weight mud (and therefore creating more hydrostatic pressure) you’ll need to adjust the drill pipe pressure down using the choke to keep the bottom hole pressure constant. In other words, for every 100 strokes you pump with your mud pumps the drill pipe pressure should drop 34.5 psi (based on our example kill sheet).
Pressure per Stroke Table:
Once you’ve calculated your ICP, FCP and pressure drop per 100 strokes, you can fill out the strokes/pressure table (step down chart) to the right. In the left hand column start at 0 and increase in 100 stroke increments until you get to the total number of strokes needed to displace the drill string (1375 in our example). On the right hand side start with your ICP and decrease the pressure by 34.5 psi (calculated in the previous section) for every 100 strokes until you get to the FCP. It looks complicated but it really isn’t after you’ve done it a couple times.
Graphing the Pressure Drop from ICP to FCP:
The last part of the ICWF Kill Sheet is plotting out the pressure drop per 100 strokes as you go from ICP to FCP when pumping kill weight mud down the drill string. It is usually not required on an actual IWCF exam but in case you wanted to know what it might look like, here you go!
Understanding the Formulas:
One nice thing about the IWCF exam is that you’ll be given a copy of the IWCF formula sheet to use as part of your test. Although this is convenient, I’ll warn you not to get over confident about taking the exam. At first, I thought that as long as I had the formula sheet available I didn’t really need to study the problems. The truth is, the more you understand the formulas and when to use them, the better off you’ll be come test day.
The IWCF exam almost always gives you WAY more information than you need to answer the question. This is why it is so important to understand exactly what the question is asking and which specific formula is needed to answer the question.
There will be many instances when you’ll need to refer to two or more formulas to get the correct answer. Likewise, there will be times when you’re given a ridiculous amount of information and the answer is actually given to you as part of the problem.
The more problems you go through, the more you will be exposed to the “tricky” problems and the better prepared you’ll be for test day.
Try solving as many problems as you can without referring to the formula sheet. Try to think your way through what the problem is asking and what you actually need to solve for to get the answer.
For example, if you’re tripping pipe out “wet” and you want to know what the bottom hole pressure drop is per stand of drill pipe, try to think your way through what you need to solve for…
In this case you’re solving for three things:
First you need to figure out the volume of mud being displaced by the metal in each stand of drill pipe that is being removed from the casing or riser (depending on if you’re on a surface or subsea well). Since you’re pulling it “wet” you’ll also need to account for the internal capacity of the drill pipe (full of mud) being removed as well (not just the metal displacement).
Secondly, you’ll need to figure out how far the level of mud in the riser or casing will drop per stand as each stand of drill pipe is pulled out (since you’re losing the metal displacement volume and the internal capacity volume of the pipe, the mud level in the casing or riser will drop).
Finally, you’ll need to calculate what the resultant pressure drop is per stand due to the dropping fluid level in the riser or casing. For example, a 10 ft drop in fluid level means a ten ft loss of hydrostatic pressure.
The good news is the formula sheet provided to you during the IWCF exam combines all three of these calculations into one simple formula. The bad news is if you don’t understand what is actually going on in the formula there is a good chance that you won’t be able to adapt when a question is asked that isn’t exactly addressed by one of the specific formulas (which happens quite a bit on the IWCF exam).
Understanding U-Tube, Bottom Hole and Formation Pressure:
Another fundamental concept you’ll need to master to do well on the IWCF exam is understanding U-Tube balance, formation pressure and bottom hole pressure.
Formation Pressure vs. Bottom Hole Pressure: Remember, formation pressure is the actual pressure of the formation you are drilling into. Bottom hole pressure is the pressure at the bottom of the well that is created by the hydrostatic weight of the mud in the well plus any additional forces created by annular friction from circulating mud through the well. The goal is to maintain bottom hole pressure above formation pressure to prevent formation fluids from entering the well (i.e. taking a kick or influx). On the flipside, if too much bottom hole pressure is applied to the formation you could fracture the well which could allow drilling fluids to enter the formation (lost circulation). In turn, this would cause the mud level in your well to drop which could eventually lead to a drop in hydrostatic pressure which could allow a larger influx into the wellbore.
U-Tube: You need to understand how the u-tube is always balanced even though you may see different pressure readings on the drill pipe and pressure gauges. In almost every IWCF well control situation, the casing gauge reads higher than the drill pipe pressure. This is because the lighter “influx” (formation fluid) on the casing side of the U-Tube is lighter and therefore exerting less pressure down on the bottom hole than the “clean” drilling mud that is in the drill pipe side of the U-Tube. This loss of hydrostatic pressure is compensated by the increase in casing pressure.
In the example to the right, you can see that the drill string is full of clean drilling mud even through there is an influx in the well. Because you have a known column of fluid in the drill pipe you can figure out the formation pressure by simply adding the drill pipe reading to the hydrostatic pressure of the drilling mud in the drill pipe. You can’t do this with the casing gauge because you don’t know the density of the influx in the annulus of the well (but it will almost always be less than the drilling mud). The additional 200 psi on the casing gauge is the additional pressure needed to keep the U-Tube balanced between the casing side and the drill pipe pressure side.
Understanding this concept is very beneficial when you start studying the practice questions. It is especially helpful when determining what happens to casing pressure, drill pipe pressure and bottom hole pressure when hydraulic changes are made when circulating out a kick (plugged bit, change in pump speed, washed out choke, plugged choke, etc.). It is equally helpful for P&P questions such as calculating the pressure at the casing shoe when there are several different layers of fluid in the hydrostatic column. As I mentioned with the formulas above, the more you can think your way through a problem and understand what is being asked, the easier it will be for you to answer the question.
Mastering IWCF Gauge Problems:
Another area where you can score huge points on the IWCF exam is on the gauge problems. I had probably 10 of these problems on my IWCF Level 4 exam and they made up a very large percentage of my final score. When I first started practicing them, most of them made very little sense to me what so ever. As I continued to review the IWCF Study Pack Workbook and gained a better idea of the equipment and the relationships of bottom hole pressure, formation pressure and the U-Tube, the gauge problems started to become easier and easier.
Here are some IWCF gauge problem tips that will help you master the gauge problems on your IWCF exam.
When answering a gauge problem, you’ll need to look at all of the information that is provided to you in the question. While you may get a stand alone gauge question, in most cases you’ll get a series of gauge questions that are all connected together in sequence in which you are given a completed kill sheet and corresponding well data to help interpret the gauges. You probably won’t do any better than I did at first when you start going through these questions, however, once you start going through some of the sample IWCF questions and do a few kill sheets, it all starts to come together.
IWCF Gauge Problem Tips:
1) Pump Rate: Always look at the mud pump rate. If you’re supposed to be pumping at 30 SPM and the gauge shows that you are pumping above or below that, you’re pretty much guaranteed that the answer to the question is to either speed up or slow down the pump speed to the speed used in the kill sheet calculations.
2) Pressure too High: On the IWCF exam, your drill pipe pressure gauges are considered to be too “high” if they are 70 psi above what they’re supposed to be for that particular situation. For example, if you’re starting to circulate out a kick in the well and your “actual” initial circulating pressure is 71 psi more than your calculated ICP then the correct answer is most likely going to be to open the choke slightly to bring the drill pipe pressure back down to range.
3) Pressure too Low: On the other hand, if at anytime your drill pipe pressure is below where it is supposed to be (even by 1 psi), the correct answer is most likely to close the choke slightly to bring your drill pipe and/or casing pressures back up. For example, if you’ve pumped 700 strokes and your pressure chart says you’re supposed to be at 1010 psi on the drill pipe gauge but your actual drill pipe pressure gauge reads 1009 psi, you should close the choke ever so slightly to bring the pressure back up.
4) “Dramatic” Key Words: If the gauge question includes verbiage such as “hoses begin shaking violently” or “jumping wildly”, etc. then the correct answer is likely to shut the well in and reassess.
5) Everything is “OK”: There are also many instances when the correct answer is “everything is OK”. This occurs when the pump rate, casing pressure, drill pipe pressure, etc. are all were they are supposed to be. On my test, 3 of the 10 correct answers on my IWCF Level 4 exam where “everything is OK”.
General Theory and Knowledge Questions:
Another large component of the P&P exam is general theory and knowledge questions about well control. These could be questions ranging from the difference between the various well kill methods (Drillers, Weight and Wait, Volumetric, Lubricate and Bleed, Bullheading, etc.) to what could cause formations to become abnormally pressurized.
As with the equipment questions, the best way I’ve found to prepare for theory questions is to keep reviewing the various sample IWCF questions in the IWCF Study Pack Workbook. As I’ve already mentioned a couple of times, once you review the questions a couple times the questions start to connect and then you can make educated guesses on the next batch of questions based on what you’ve learned from the previous questions. On test day, I had a ton of theory questions that I had never seen before. However, because I had learned so much from studying the other questions (and asking questions from people during the class about things I didn’t quite understand) I was able to correctly guess what the answer was to the questions on the exam.
As mentioned above, there are three exams that you’ll take as part of your IWCF Level 3 and/or Level 4 certification (Simulator, Equipment, and P&P).
If you’ve worked your way through my IWCF Study Workbook, then you should be in really good shape by the first day of class.
If you arrive to class unprepared (especially if this is your first IWCF well control course) you’re going to be struggling to keep up. The instructor has a lot of material to cover in the week leading up to the exam and you’re going to fall behind very quickly to stay on top of the material.
Remember, the more you prepare, the less stressful the examination process will be!
Good luck with your IWCF exam, I hope this guide has been helpful!
Ask your specific well control exam questions in the comments below!
Remember, you can download this complete article as a PDF complete with an Appendix of over 400 sample questions, IWCF equipment diagrams and worked out IWCF formula problems with explanations.
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IWCF Formula Sheet Explained with Worked Out Problems
IWCF Study Material