WorldWide Drilling Resource

Drilling Fluid Updates by Ray McLarty Drilling Fluids & Grouts Questions & Answers Question I read your article in the January 2015 edition of WWDR on grouting using the various products HOLEPLUG ® , BENSEAL ® , E-Z MUD ® , etc. I am cur- rently working on a geotechnical project in South Carolina. The specs call for a cement grout with 6% bentonite added to reduce shrinkage. The grout will be pumped via tremie pipe from the top 20 feet to the surface. The holes are 4-inch and average 125 to 150 feet. We placed HOLEPLUG ® in the bottom of the holes, hydrated it, and then backfilled up to 20 feet of the surface. We are using a ChemGrout ® mixing unit to mix and pump the grout into place. We are having a problem with excessive shrinkage, up to 9 inches per hole. I think part of the prob- lem is I can’t shear the powdered material at a high rate without having a lot of spill from the mix tank, resulting in a thin- ner grout mix, which results in shrinkage. Would BENSEAL ® granular work better with the cement? Would it thicken up the grout and reduce shrinkage as well as cement and powder bentonite? Do you have any other suggestions? Thanks, Stan Answer First of all, thanks for your e-mail sent to me via WWDR , and thanks for reading my article and WWDR . As I told you in our phone conversation, I have never been a big fan of mixing ben- tonite with cement for grouting. However, there are a lot of people who swear by it, and a lot of places require its use in their regulations. Myself, I think you would be better off to pour in 20 feet of HOLEPLUG ® rather than grouting the top 20 feet on top of a backfill. It is eas- ier, quicker, and eliminates the need for special equipment such as a grouter. As far as your mixers and/or grouter go, I have used ChemGrout ® equipment numerous times over the years mixing various types of grouts, and I always had great success with them. It sounds like part of your problem might have been solved if you had a unit with a larger mixing hopper to reduce spillage, or else you mixed smaller batches. As far as using granular bentonite with port- land cement, I think it would be fine, although I don’t know how much it will reduce shrinkage of the cement column. The addition of bentonite to cement according to the Halliburton cement RedBook ® (the bible of well cementing), is to every 94-pound bag of portland, use 5.2 gallons of mix water. For every 2% of bentonite added to the slurry, add an additional .65 to .69 gallons of mix water. I double-checked this information with David Roberts with Baroid IDP. David has over 40 years of experience in the drilling and grouting of all types and depths of wells. David thought it was worth a try using BENSEAL ® and portland at a rate of 9 pounds of granular bentonite to a 94-pound bag of cement and 10 gallons of mix water. David also suggested I send you info on BARAD-658™ cement additive. I was not too familiar with this product or its performance, having never used it, but according to David and the spec- ification sheet he sent me, it might be a product you want to consider for future usage. BARAD-658™ spec sheet states the product, when mixed with portland cement (94 pounds) at a recommended 15.6 pounds per gallon slurry, will provide an easily pumped slurry with lower vis- cosity than typical high-density cements. It remains fluid in mixing equipment longer than typical high-density cements; helps control filtration rates in perme- able zones; delivers high compression strength development within 24 hours; works well in both freshwater and salt- water, etc. Note: Stan switched from powder bentonite to BENSEAL ® granular mixed at the above suggested rate. This solved his mixing problem and reduced shrink- age from9 inches to 1 inch or less per hole. HOLEPLUG ® , BENSEAL ® , E-Z MUD ® , and BARAD-658™ are all Baroid IDP products. Similar products would be Wyo- Ben ENVIROPLUG ® , ENVIROPLUG ® NO. 16, NO. 20 , and WYO-VIS ® ; CETCO ® CHIPS, CRUMBLES, and INSTA-VIS™ . The statements and comments in this article are my own and are based on information and references believed to be true and factual. If you have a question or comment on this article, or on bentonite drilling muds, polymers, grouts, or additives, please forward them to me in care of WWDR . Ray michele@ worldwidedrillingresource.com WorldWide Drilling Resource ® 16 APRIL 2015 4< /*2'3* "& > > > > ,'< ? /2+ '6* /3+6 /3+6 ')1/3- " " !8=2+ /7843 4* 4* ')1/3- !+8 5)7 !8'3*'6* $'2:+ 9((+6 6':+2 $'2:+ 9((+6 !+'87 9((+6 $'2:+ 37+687 #6+8.'3+ $'2:+ 37+687 $'2:+ !56/3- ! ! $'2:+ 4:+6 '71+8 ? !;/:+2 ')1/3- ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 < /3+6 < /3+6 < /3+6 < /3+6 < /3+6 6/)+7 !9(0+)8 "4 .'3-+ %/8.498 48/)+ !@ @ < < < < < WWDR ’s June issue is coming soon. Deadlines: Space Reservation - April 25 th Display & Classified Ad Copy - May 1 st