Finally, I’ve worked in the last section of drilling phase here; the 6″ section. This is a production zone. It is a small hole and is susceptible of getting some drilling hazard such as stuck pipe, loss circulation and kick. How does it sounds? interesting, huh? 🙂
I was working in a development well in West Java, Indonesia. I never thought that a place called Bekasi has that pretty big oil reserve. It’s been drilled for the seventh. I’ve worked in well xxxx, the eighth well that was drilled. Historical data shows us that this field was really susceptible to get loss of circulation (hereafter it called as “loss”). Things that was happened in field A, from 4 well that have been drilled, most of them got a serious loss. Just heard from the crew, that there’s one well that was discontinue drilling because of serious loss on it. wow! can’t imagine how severe it is! It was stopped because of economic consideration. A company man have told me that the first well is also got losses seriously, however it produce really big oil afterward (I don’t know how much it actually is) and could covered the cost for the dry hole that have been drilled before in that area. Hmm,,, sounds amazing, right? Well, just heard an information from my senior, the well that’s got losses on drilling is most likely to get a good oil production (or may be contain oil at least)…It’s almost 90 % that this kind of well has that characteristics. I think It’s just a gossip . Hmmm,,,I have no idea regarding to that. Oh I need to learn hard and got a lot of experience before write down that opinion. So, anybody know?
Well, I need to explain what’s actually a loss of circulation is. It can be one of the more serious problems that can arise during the drilling of an oil well or gas well. Circulation is said to be lost when the drilling fluid, known commonly as “mud”, flows into one or more geological formations instead of returning up the annulus. . It is the loss of whole fluid, not simply filtrate, to the formation. Losses can result from either natural or induced causes and can range from a couple of barrels per hour to hundreds of barrels in minutes. Lost circulation is one of drilling’s biggest expenses in terms of rig time and safety. Uncontrolled lost circulation can result in a dangerous pressure control situation and loss of the well.
The drilling of 6-inch section here is so so risky. Mud properties has a big deal and play a vital role on it, particularly the carrying capacity. Therefore, The YP (yield point) and the funnel viscosity (actually it just indicates a changes in viscosity) must be on spec. As the historical data in the previous well that susceptible to get loss, we need to prepare in mud tank an LCM and Kill mud in adequate amount. Other important things is making sure that the stock of LCM and weighting materials (e.g barite) in the field must be enough. The more stock, the better it is.
I was really lucky to have a field training here as it planed to have a coring program in this well. Seems like need a separate chapter to tell since it rare and expensive to be applied. Basically, the coring has an aim to take a rock sample in the prospective zone. It is going to be use as a complete evaluation of that reservoir. The depth that was targeted is defined by the wellsite geologist. After the rock sample was capture, it’s then evaluated either in Lemigas. Hmm,,,it must be interesting to be learned.
Working on losses is not easy things especially for “a baby engineer” like me . It’s my first time working in this section and the loss has just occurred. OMG! 😥 Almost for 2 weeks I was working there like crazy. I was really really panic and suddenly forgot what I was supposed to do. Haha. The rate of loss was reached 5 barrels per minute or more than 100 bbls per hour ( Oh my god, just realized that a severe lost!). More than 10.000 barrels mud have been made was lost to formation and more than 600 bbls of Loss circulation materials (hereafter it called “LCM”, and commonly it called like that) was spotted and doesn’t take effect unless just a little. It getting worst when there’s no return at all ( Oh my god, That total loss! 😥 ) but fortunately it was happened just a couple minutes and not in my shift time,,,yuhuuu. Don’t know what would be happened in me when got that things. May be I’ll be super duper panic! Haha. But, that’s normal anyway.. Things that make me more stressed in dealling with the loss is the material stock. That makes me more more panic. More than 5 times, I have asked well next to mine to transfer some materials (barite, LCM, etc) because of its shipping from Jakarta warehouse was delayed and found some problem.
Actually, at the first time there’s a discourse to have a cement plug if the LCM doesn’t work properly. But then, the wellsite geologist doesn’t allow to do that as problem in the previous well which become a dry hole because of it. He was suspicious on cement plug has an effect on production at that well although the cement itself is actually production friendly such as carbonate cement, etc. Again, I don’t know what’s really happened at that time. But for sure, a mud engineer now have to be working hard to cure the loss. They just rely on LCM due to fears of using cement plug.
Making mud in the situation of loss is tend to be incorrect. We mixed mud like crazy. Yup, every body knows that we worked with limited time to fill up the annulus. It’s emergency! So, the mud properties that being our concern at that time just mud weight and the carrying capacity ( although just by a funnel viscosity). If we didn’t keep the hole filled by mud, the hidrostatic pressure will be gradually down as the mud level in the annulus is getting down as well. Consequently, when the hidrostatic pressure reached a point that lower than the reservoir pressure then The Kick will be occurred which possibly create a blow out. Hmm,,could be so nightmare! I made 100 bbls of mud for 30 minutes, whereas the optimum mud mixing for that volume is around 2 hours. The mixing of some polymers that need 15-25 minutes per sack is now blended at once without any fears of getting fish eyes. Concequently, when the loss is getting small and the mud pump line doesn’t use, the barite was settled and causing pressured drop . so, we need a long time before use the pump.
The losss was start getting slow when I spotted a higher consentration of LCM (100 ppb) including the KWIK-Seal. That’s getting better when the mud weight is decresed from 1.24 SG to 1.08 SG gradually. As higher LCM used, the MWD tool need to be lay down due to the max consentration can be accapted was 50 ppb. So, the POOH is a must. Yeahhhh..rest for a while? Of course not! Coz I attempt to fill the hole with mud with same rate of loss. oh,,what a day! after spotting the higher LCM. It’s really work. Yeahhhh. To minimise the loss I added LCM (CaCO3) continously to active system. Surprisingly, it’s getting lower and lower until it reached 0.04 bpm or almost nothing. Yuhuuu. But then, as the more depth being drilled, the loss is again getting higher, but fortunately still in the attemtable range. Finallyyyy, drilling section 6 inch was finished in the depth of 2975 meters. But, unfortunately, there’s a sudden crew change at 2950 depth drilling. And I need to go home 😦 but, I feel better although sometimes feel upset. why don’t they let me work here till the completion..
Though I was so stressed this drilling section, there’s a benefit I had. First, I’m getting close with all rig crew from rig floor to rostabout. Really! I miss that moment again 🙂 .And then, I’m getting used to the same problem. I don’t feel panic again when hearing the term “loss”. Ups, I forgot that I spent a lot of money and various brands of cigarettes just to entertain the crew . I still remember when dealing with high loss, the tool pusher just tell me “be patient dude, that’s really hard for a green engineer like you”. Almost all people and gathered up in the tank to help me mixed thousands barrel of mud, some of them help me to check the mud weight periodically, another else helped me load and discharge anykinds of mud material. Even the company man stayed up in the tank and gives some instruction to help me. Hmmm,,,to be honest, that’s really a interesting experience 🙂 .