WorldWide Drilling Resource

Foam is to Help Get Me Out of Trouble! by John Christ J.C.’s Drilling Consultant This is a false statement I have heard more than I care to think about. I check a drilling posting board daily. It seems someone drilling with air gets stuck on a regular basis. The first response is to use foam to help get unstuck. There is a good chance it may work. There are suggestions to stiffen it or add bentonite to it, again all good ideas and may work. What is happening down there that causes the problem? A large blast of air is injected down a tube and comes out a bit or hammer, depending on the formation being drilled. If you are in rock from the get-go all you have to worry about are the cuttings created. You can use enough air to clean the hole because, except for cuttings, the hole is pretty solid. What if you went through a section of overburden before the rock? Now what happens to the air in that area? You don’t have anything to create a filter cake and keep the air in the hole, so air is going out in that part of the formation. Most rigs don’t have a graduated dial valve to turn air on and off. It’s either on or off. So, you pressure up that part of the formation, then turn the air off, which sends the air back into the borehole. There is a chance the formation will lose stability. Now, not only do you have the cuttings to deal with, you possibly have some of the formation falling in. Once it becomes unstable it will constantly want to keep falling in. So, what can we do to improve this situation? How about running foam from the beginning? The main reason I heard is running foam the whole time creates a mess. There is no doubt the foam needs to be contained. You never want to let foam get into a waterway, since it will take the oxygen out of the water and kill the fish. You will also get to save money on fuel because it will take less air to clean the borehole. Every time you thicken the air column, you have to reduce the air volume. There are three phases to enhanced air drilling: air, cuttings, and water. You need to have the right volume of air to carry the cuttings and water. If not, you have a blast of cuttings or water come through the air column. You need all three working in harmony. Next thing to consider is the progression of air drilling. First is straight air, which is most likely why we can get in trouble because we are in “get-r-done” mode. Like I said before, best if in solid rock from the get-go. Not my recommendation. Next is injecting water - mainly for dust suppression. Be aware this can cause booting or balling of the cuttings. It may activate clay swelling if you hit a section of it. Then there is foam drilling. Again, reduce the air. We have to thicken the air column for a second time. Now you will have increased lifting capacity and a little more borehole stability. Foam with cutting entrained in it will not enter unconsolidated for- mations as with dry air. There is stiff foam I would consider when encountering more clay stringers. You would mix a PHPA (partially-hydrolyzed polyacrylamide) polymer in the pretreated water, then blend in the foam. Reduce the air because, again, we have thickened the air column. This increases your carrying capacity over regular foam by tightening the foam, basically going from a dish soap consistency to shaving cream. If you are going to be drilling a fair amount of unconsolidated formation with air, I sure hope you are now considering gel foam. It’s just what it sounds like, a bentonite and PAC (polyanionic cellulose) polymer system with foam blended in after the gel is mixed. This helps to create the filter cake necessary to give the hole stability and carrying capacity. It will also help sus- pend the cuttings during the time it takes to make a connection. So for this month, I’m going to just say foam was never to get you out of trouble, it was to enhance the differing formations you will encounter in a bore- hole. We will get more in depth with this subject in the near future. And as a friend of mine used to say, “Air is for breathing and mud is for drilling!” R.I.P. Carl Mason! The statements and comments in this article are based on information and references believed to be true and factual. If you have any questions or comments, please forward them to me in care of WWDR . John John Christ may be contacted via e-mail to michele@ worldwidedrillingresource.com 52 NOVEMBER 2016 WorldWide Drilling Resource ®