The Hole Problem: Sloughing shale

some mechanical occurrances that causing stuck pipe

I’m glad when the drilling process runs well and fast. No drilling problem or accident occurs. So far, loss and kick are things that I’m still worried about. It’s so damn tiring! I used to work like crazy at that time. When dealing with loss, I tired of making a lot of LCM, pumped it down, mixing it again, and so on. The stressful thing at that time was mud level in thanks was getting down and down. Sure I cannot let it be as the worst problem possible come when hydrostatic pressure is less than the formation pressure: Kick and Blow out. Oh God, it’s so nightmare! That’s why I called the well which susceptible to get loss as the wild well. So with the kick,  I was sick of it because I have to raise MW in very limited time. Well, I thought these are the only hazard that possibly happed in drilling an oil well. Apparently not. There’s any problem that should be keeping an eye of, the sloughing shale.

first time got BHA stuck then seeing cutting size in shaker. Oh God, I was shock!

Actually, I Love drilling the shale formation as it commonly drill down much faster than any other formation. It is soft. In a day I could have reached like 200 meter even more. But still keep in mind that all mud properties must be on allowable range particularly the mud weight. But, I’ve work in shale formation with no excitement at all coz at that time it turns to be another horrible problem: Pack off due to The Sloghing Shale! Oh,,all problem was just the same, it’s stressful. Simply, sloughing shale happened when there’s no adequate mud weight to control subsurface pressure or too bad mud salinity that cause undesirable osmotic pressure. It causes borehole collapse then stuck the drill pipe or BHA . The sloughing shale is one of the mechanical occurrences that causing the stuck pipe.

Operators worldwide lose billions of dollars every year — sometimes millions in a single well — due to such of drilling problem. Stuck pipe increase NPT, lose expensive tools in the hole (mud motor, bit, collar, NMDC, MWD tool, etc) and forced to make undesirable sidetrack. Oh, it so nightmare! The sloughing always happened in clay-rich shale formations. A combination of stress and pore pressure conditions around the well bore, related in part to incorrect drilling fluid salinity and type and improper mud weight.

I was working in a well where the sloughing shale was happened. I drilled shale formation with high ROP. I used a mud weigh as per program. Everything went so normal, no anomaly or something like that. After reaching casing point, we put Hi-Visc Mud down there to suspend cutting when we do short trip to casing Shoe. When run in hole back, it stuck in certain depth. Oh God I feel so guilty. I was questioning about that. Was that the mud fault? But I have used the proper mud properties during drilling that hole particularly the mud weight. But then, my senior said that I don’t to worry about that. We’re working in a team. Nobody knows what really happened in the subsurface, right? Although you have applied the mud program, but the kind of formation being drilled will possibly different. I was trying to free it by circulation. And apparently, I was shocked as I found a lot of cutting coming out in shaker in horrible size. That was first time I see that kind of cutting size,. Really abnormal!

cutting evidence when normal and abnormal condition.

I raised mud weight gradually in attempt to cure it. Oh, it’s a tiring time. Yes, I was not lifting all chemical sack but I was tired of asking a lot of people to help it (crane operator, the mud boy, etc.). I’ve heard the term “bomp-ing” to help curing it quickly. It means I raised mud weight quite drastically. It’s been work in several well, my senior said. The kind of shale I was dealing it is the brittle one which has micro fracture in it. Raising mud weight gradually didn’t work well. But at the time, the company men didn’t accept the offer. He worried about getting worst which causing loss of circulation. After raising almost 6 times (it takes 3 days ) then it’s getting better. We used some chemical to help curing it: the asphaltic material. It called shale stabilizer commonly. Every company has its own name for it. Use Hi-concentration to make it take effect.

The 3 days I’ve passed through was the stressful days. U know, the BHA got stuck, can be moved vertically and rotated. I was worried about unable to free it and have to use fishing service. But then, it solved. Yeahhhh….I learned how to deal with it. What a precious experience 🙂