Document qa584ykyogdYjykBqNMbYzz7x

FILE NAME: Union Carbide (UC) DATE: 1970 DOC#: UC373 DOCUMENT DESCRIPTION: Trade Journal Article - Presheared Asbestos Muds Help Cut Costs, Rotating Time OL&GAS JOURNAL Presbearecf asbestos muds heio cut costs, rotating time J ohn !.. Ki.vnpmv Drilling Editor Rcpriniod li5 ,une !), 1070 otiil'.oi' Cor>Mmcr*<s ci A E S-02879 Presheared asbestos mods help cot costs, rotating time J ohn L. KwiNBDY Drilling Editor RESULTS of drilling in widely sep arated areas indicate that the use of presheared asbestos in drilling fluids can help reduce mud costs and rotat ing time. These drilling fluids are designed as tow-solids muds and ap pear to bo (lading increased applica tion. In one o[ these instances, presheared asbestos was used with bentonite and results were compared to drilling re sults using a straight bentonite system on an adjacent well. In this Okfuskee County, Okla., comparison, mud costs for the preuliearod asbestos-bentonite system were 47.3f/ft while the straight bentonite system cost 58.2(7it- These two wells, located 6EQ It apart, were drilled by the same op erator using the same contractor and the same rig, the same mud company and the same mud engineer. Total depth of the two wells was slightly over -1,01 ft and mud-up depth was around 2,700 ft. Casing string in both wells was 8%-in. A significant savings in drilling time resolted from using the presheared a s b e s to s -b e n to n ite mud over the straight bentonite system. The well using the combination fluid was drilled in 99 rig hr, compared to 140 hr to drill Hie well en which the straight bentonite system was used. The bentonite-drilled well required six bits compared to live for the well drilled with the presheared asbestos- bcmonSte mud, in Libya, a similar system proved to be competitive with straight bentonite fluids that had been used previously. And this particular well was drilled without any lost-circulation problems, something that had given operators considerable trouble in the past in this area. . The Libya wall was drilled to a total depth of 10,068 ft with mud weights varying from 8.7 to 8.3 ib/gal. Afler an ts^j-in. surface string was set, 13%- in. was run to 3.272 ft and a tt'A-w- production string set at TD. The p re s h e a re d asbestos-bentonite low-solids mud system was built in a ratio of 1 lb of prcshcarcd asbestos to 2 lb of bentonite. But plans for the next well included using a drilling iittid built in a l / l ratio of these materials. In this Instance, a luld-lciss control agent was used and the properties of the mud system included a plastic viscosity of 8; yield value of 4; funnel viscosity of 40 sec; and 4-7% solids. For North Slops drilling, a preshearod asbestos-bentonite e x ten d ed system has been recommended from surface to total depth. In this case, this procedure applies: 1. Initial surface volume is prepared using freshwater treated with pro-' sheared asbestos and bentonite in. a 50-50 ratio. 2. Surface volume is then treated with salt to lower the freezing point to the necessary level. 3. The system Is then used to drill through the permafrost to the surface casing point. During this interval, presheared asbestos can be added directly to the system for viscosity and hole cleaning when needed. Bentonite can be prehydrated and added to the system when required, and nitration control can be obtained with salt-water fluid-loss agents. 4. Do not discard this fluid after drilling permafrost and setting surface casing--simply discontinue the addi tion of salt to the mud system and use freshwater for makeup. 5. This same system is used out from under surface to approximately 3.099 ft where casing is again set. Since no sail was added during this second Interval and freshwater make up was used, the system will be fresh enough to allow mixing o! bentonite directly, fo r maximum yield, 50-50 w8. i Apparent viscosity comparison Fig. 1 Synergistic effect of Super Visbestos V Pifi.3 Shear thinning characteristics r ~ ~ ~ ------------------------------------------------------- ^ I v__ - ____ ________ ' Fie-5 concentrations of preshreadcd asbestos and bentonite arc used. G. From tccond casing point to TO, the drilling fluid system is essentially a freshwater. low-solids, presheared asboslos-benionite type. Filtration is controlled wiUi a freshwater Iluid-toss additive, and shale can be controlled using this same system but with the addition of powdered asphalt mater ials. A typical system, A mud system like the one used in Libya is usually bmll ;n<nni-l It-7t |b/kltl ol pu-sheaicd A 50-50 mix usually gives the best hole-cleaning results, but a higher pro portion of bentonite is usually recom mended when hole stability is a prob lem. Using Super Visbesios, a presheared asbestos distributed by Monielio, Inc., Sand Springs, Okla.. a cost comparison indicates that such a fluid would nm in the neighborhood of 52.5<7bbl com pared to a straight bentonite system a i nbnul Gil 5>7bbl. These costs were based on tlie use of 2 ll)/l)hi of ptc-V ared tisl)<-*ief combination system, and 25 ib/bbl of bentonkefor ibe other fluid. In addition to a lowet initial Cost, manufacturers of the preslieared as bestos additives cite olher passible savings including lower mixing costs; lower hauling costs; less water re quirements; reduced chemical treat ment cost; and highet penetration cates. Prcsbettred asbestos-ljemomte sys tems will usually givt some bale stabilization and a small amotini of tluid-loss i outlet. then il neu ssary. to lower loss to required levels. Such a system is applicable in any area. To get proper cleaning, a drilling fluid's yield point and plastic viscosity are Important properties. Table 1 in dicates the effect of those variables on the sealing time of solids in a flocculated solids settling lesl. Another important consideration in transport is annulus flow profile, it this profile ts turbulent, cuttings slip page is increased and cuttings can fail faster than the average annular rate causing a hole-cleaning ptobiem. If hole cleaning is critical and an adjustment of annulus (low does not help, yield value can be raised with asbestos. Montello recommends, how ever. when using their product that before raising the yield value too high the hole should he (lushed clean uitn a JS-50-hbl slurry containing 3 Ib/bbt of presheared nsbestos. Or it can e done by adding 75-100 lb of the ma terial directly into the mud system the mud hopper. This flushing Table t S e t t l i n g tests Density of flee Y/eielit lb/gal 13 in.4 S3 10.4 8.3 104 8.3 104 8J3 10.4 8.3 10.4 9.0 11.0 5.0 1UD 10.0 U S 10.0 11.8 Settling time for M % ,, seflis seltling h fP tmin/ft) 1.0- 0 14 2.0 Utb 1 2.U 1.0 2 2.U 2.0 8 4M 4.0 V K.U B.O S3 4.0 4.0 30 s.o 8.0 9? 4.0 4.0 34 S.0 8.0 112 operation o n be repealed as needed with frequency ranging from once a day to twice a lour. And it should be done just before making a trip, accord ing to Montello. Of course, good solids removal techniques are essential to the per formance of low-solids systems. Both chemical and mechanical means can be used to accomplish this. Some properties. Presheared asbes- los has grown in use recently. Us ad vantages stemming from the fact that the carefully controlled shearing process at the point of manufacture provides a high degree of fiber sep aration quickly at the well (OGJ, O ct 28, 1963). Properties of presheared asbestos compared with those of other mud-system additives are shown hi SUPER VSSBESTOS A message of special interest to drilling superintendents and those responsible for writing drilling nmd pro gram s, distributed courtesy of Montf.-lio, tnc. For-more information and extra copies of the reprint, write Montello at P-O. Drawer 130. Sand Springs, OKla, 7-1063. : i L ;? fciU ..- \il : ..S,' Vi . -81 A 2 REGULAR ASBESTOS (Dry Processed) SUPER VISBESTOS (Wet Processed-Presheared Asbestos) fAOMTEUO. INC. n o MAWis tuo x iutn seiiiN-r.s O '1AtJ.OiVA- / 1 G exclusively for Montello. Inc., by chemically and erV isb esfo s is prodcceo ex^ lv A , o;ile a sb e sto s, through a unique, raulicaify sh earin g a )P s grr^ esCsh pf0duces a high degree of asbestos prietary, wet-process. Tins process n :r separation. pr0vided alm ost instantly with he S to achieve U5inS A eU' a r dry Pr CeSSed aSbeSi S ^ n af e r days o( circulation and m,x,ne . L V y t data below rcvea.s the a d v a n c e s of Super Visbasfos. (T ests W ere Run By A Major University) ABS-0287S SUPER VISBESTOS VS. REGULAR ASBESTOS FannVG Met6* Apparent Viscosity Plastic Viscocily Yield Point K itti ' 1/- G U 7 . TBSST 7 6 2