Drilling Fluid: Stuck Pipe Stuck drill pipe is an expensive and unproductive operation. All to often the blame is placed at the feet of the mud engineer when really we should be looking in other directions. Unfortunately the drilling industry is somewhat slow at working out cost and cost effectiveness and would sooner spend time and money attempting to free stuck pipe than on prevention. Forget all the hype about engineering, the major cause of pipe becoming stuck is human error and as long as you have untrained people running the show expect to join the ranks of companies that spend almost as much freeing the string as they do drilling the hole. It is impossible to cover the subject of stuck pipe in just a few pages. It is a subject that needs training and discussion but most of all it needs understanding. There are tool that monitor the progress of the operation day and night but can not normally be seen from the office. Computers mounted in the office are ok but take time to react. The chart in the mud loggers shack is far better for this and also shows the trend.  Trends are very important in drilling. and providing you translate the information they store it can often help solve many problems. It is impossible to dictate what a bit will do or where it will go but by looking back over what its done you can build up an opinion and from that make judgment and decide on what might be the best move   A trip to the mud logger before going on tour will give more information than a man that has spent the past 12 hours standing on a cold break or running around a wet rig floor. The driller can do lot to avoid the problem of stuck pipe (in fact it is all down to the driller). Providing he has the information on what has been going on. In many instances of stuck pipe, the difficulty arises while circulation is stopped. But such condition would have been noted on connection where the drag had picked up.  How often do you see drillers chain the break down and make out the pipe book then walk around the back and add the number to the chart all to often. It only take a minute or two but a string can become stuck in seconds. How often do you see a string of casing being run and there a discrepancy in the tally. What happen, the break is chained down while the driller walk over and count what's left on the cat walk, if there are a lot of joint that could mean two or three count. The most important thing any person on the break needs to do in open hole is to keep the pipe moving as long as its moving it's not stuck Unstable hole is usually blamed for stuck pipe. Junk in the hole, balled-up bit, hole collapse because of loss of circulation, settling and packing off cuttings of heavy minerals, and thick filter cake are other causes. Differential-pressure is the major cause of stuck pipe and the characteristics of differential-pressure sticking are (1) bit off bottom and pipe immovable, (2) permeable formations exposed in the hole, (3) circulating rate and pressure normal after drill string sticks. The mechanism of wall-sticking. If the drill pipe stops moving while it is touching a permeable formation, the area of filter cake between the pipe and the hole wall is isolated from the rest of the drilling fluid. With the pump shut off, filtration continues because of the difference in pressure between the mud and the fluid in the porous rock. The pressure which had been carried by the isolated filter cake is transmitted to an equivalent area of the drill pipe. As filtration proceeds, more and more area of the drill pipe is pressed against the filter cake and stuck to it. The ratio of pipe-to-hole diameters affects the area of pipe isolated from the hydrostatic pressure and also the relative increase in isolated area as filtration continues. The rate of filter cake build-up is an important factor. The amount of friction between the pipe and the filter cake significantly affects the effort to release the stuck pipe. From the what you have read of the mechanism of wall-sticking, certain practices in mud control obviously help avoid stuck pipe. These are (1) minimum mud weight for least pressure differential and to assure low solids content for thin wall-cake, (2) low filtration rate for slowest build-up of cake when circulation is stopped, and (3) minimum friction between the wall-cake and the pipe. Least friction will be assured by keeping the mud free, and by adding a lubricating agent  A long string with a heavy BHA will have quite a bit of stretch and it is possible the bit will not leave bottom. Recognition of pending problem such as tight hole. Not conditioning the hole as you go. Fast drilling in lose and unconsolidated formation. Slow reaction. Not being prepared, all add up to getting stuck So what can we do (1) Keep pipe moving with sitting time kept to a minimum. (2) condition the hole as we go the time spent ream a tight connection is well spent. (3) slow the penetration rate down when drilling lose sands. (4) un cock the jars before pulling from the hole and running in. (5)If a hole start to pack off pull up to safety and give yourself room to work. (6) Never stay on bottom if the is a pending problem. (7)know your formation and how to react. (8) Have the chemical needed on the rig so as you can pump what is needed. The longer you take to react the worse the problem will become. (9) have a contingence plan jacking of on stuck pipe for days on end is without doubt a waste of money. The force required to free the stuck pipe depends on (1) the area of contact, (2) the magnitude of the pressure differential, and (3) the friction between the pipe and the mud cake. The usual treatment to release wall-stuck pipe is to place oil in the hole. Oil, because it is lighter than water or mud, reduces the differential pressure. Displacement of mud by oil also stops the build-up of filter cake. The ability of the oil to penetrate between the pipe and the filter cake is enhanced by adding a surfactant to promote oil-wetting of the steel. As soon as the pipe is found to be stuck, displace the mud from the annulus with a pipe freeing agent and spot it around the bha leaving enough to move it after a given time. There are many lubricants on the market for this. some work on a 1 to 100 base other on different ratios   If oil is objectionable (e.g., in water wells), there are lubricant, alone or diluted with an equal volume of water, should be placed in the hole over the section of pipe thought to be stuck. Additional lubricant solution should be pumped into the hole at intervals while the pipe is being worked. Spotting the lubricant promptly when pipe becomes stuck is extremely important. Several drums of lubricant should be kept at the rig site at all times for use if needed. Jarring on pipe is not always the answer some time just maintaining weight while the lubricant goes to work will free up the string this will often happen in salt when fresh water is pumped so in area where large salt formation are common have plenty of fresh water on hand It does wonders when it come to freeing up the pipe If salt is a problem consider having a direct feed from the fresh water to the rig pump. I have seen pipe come lose within seconds of the fresh water getting to it If the Bit get stuck on bottom don't just pull on it. Fire the jars into it then fire on the way up especially if you have a near bit stabilizer in the hole it possible it may be the stabilizer hanging up It is quite a common practice to use acid to free stuck pipe in limestone formation, the idea being to dissolving Calcium Carbonate in Hydrochloric Acid. Drilling bent or horizontal wells in carbonate reservoirs and getting stuck can be freed up with 15% HCI if you are using a normal drilling assembly or if working with coiled tubing, 28% HCI would seem to do the trick In open hole condition the acid must make contact with the formation, it is therefore a good practice to pump a wash ahead of the acid , in order to remove as much of the filter cake as possible. More so when working with an OBM the success ratio of using acid is extremely low, if you don't use a wash train to water wet the formation. The all important point being to recognize how you are stuck. If the string has been pulled into tight hole then say so. Know the problem is knowing the answer. Treating pipe for differential sticking when it has been pulled into tight hole will only make matters worse. Lowering the drilling fluid weight could very well add more problems. Most pipe string are lost simple due to the fact the truth was not told at the beginning and things got out of hand   While working in the middle East a scraper was in the string while drilling out cement unfortunately the pump went down and allowed the cement to full back in the hole trapping the scrapper. by the time the pump was restarted the cement had all but packed off around the scraper fortunately the rig could still circulate, No amount of circulating would move the cement and the pipe was held fast Acid ( 15% HCl) was spotted and the scraper was allowed to pickle after an hour or so It just pop free very much like putting fresh water around pipe when it is stuck in salt. Had we not been able to circulate the scraper would have gone the same way as other and still be in the hole.  And before someone writes to me on the effect acid has on the mud and the pipe , remember, there are times when to junk the pipe and leave it there cost not only a new BHA but a re-drill. I have always lived by the policy the drilled hole is paid for and will do what is necessary to keep it. This works as long as you can circulate Taking everything into account the action on what to do will be made taking all conditions into account and the use of acid is an option. Stuck pipe and lost circulation are two of the biggest problems we face. So as the boy scout say "be prepared" Anticipation and fast reaction can often save a lot of down time. Back around the early 90 I read some very interesting reports on stuck pipe from an oil company who shall remain nameless. What grabbed my attention was how one of the problems was solve. in one of the report they ran the contractor's toolpusher off as he was on the break at the time. What amazed me about the report were the witness's The Drilling Manager, Drilling Superintendent and Company man were on the floor as this was going on. The reports went on to say that of the 16 stuck pipe incident that year 12 lost the string. I wonder why.  I have been very fortunate over the years I have work with the best. The two things they all had in common was, training their people to do the job and tell the truth, this often meant they took the static. Never passed the buck providing the truth was told, they would set about curing the problem. As one old timer once told me. Son having the pipe stuck is not our problem ? our problem is how do we get it free. Possibly some of the best advise I have ever been given. We work in an industry that is rampant with hindsight buffed by science, prone to bull shit and allow pride to get in the way of common sense and good oilfield practice. Most stuck pipe problems can be avoided providing you use bit of common sense and patients.  By keeping the pipe on the move and reacting fast there is no need to leave the string in the hole. If you must use the phone then tell the base what you intend to do or are doing about a problem. Holding meeting that produce no result are an expensive waste of time. However they do allow you to spread the buck. The course Stuck Pipe for Supervisor is a 3 day insight and very informative course that looks at the subject of stuck pipe from every angle and has been design to provide crew with the knowledge to enable them to prevent pipe from becoming stuck