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These micrographs show the difference A | BTypical Candian asbestos-fiber structure Typical Caiidria asbestos fibers C DDry-processed asbestos fibers Wet-processed Caiidria asbestos fibrils pared to an average mud cost for the other welts of about 515,870, These average figures are broken down into individual well data in Table 2. An additional characteristic of the test wells drilled with the presheared asbestos was the reduction in lost circulation troubles. Lost circulation occurred from 3 to 11 times in each of the wells drilled with other asbestos products. Circu lation was lost in only two of the wells drilled with the presheared as bestos, and then only once in each well. Makers of the presheared asbestos attribute much of its drilling cost savings to the need for less material, less mixing time, less supervision, and ease of storage and handling. Reprinted from OIL&CAS JOURNAL UCC 014974 A078 31 October 28, 1968 Edition Preshearing, pelletizing improves asbestos fibers for drilling mud Asbestos materials used as drilling mud additives provide one method of increasing the carrying capacity and suspending ability of clear fluids, without sacrificing the high penetra tion rates possible when using dear water. But asbestos products have pre sented two main problems in the past--high bulk and slow yield. An improved asbestos material is now available which eliminates these two problems and reduces the cost of using asbestos as an additive. By chemically and hydraulically shearing a top-grade chrysotile as bestos in a wet process, a high de gree of fiber separation is achieved. Then for convenience, this presheared material is pelletized. The process for shearing the as bestos was developed by Union Car bide Corp. and is still proprietary. But the presheared asbestos distributed as Super Visbesto by Montello, Inc., Sand Springs, Okla., is said to have these advantages over asbestos ma terials now being used in drilling muds: It has only about one-half the bulk. The material is compressed into pellets about Vi-in. long and 14-in. diameter and a given volume con tains approximately twice the amount of asbestos as other products now available. It yields 8-10 times faster. Until now, asbestos products have been sheared on the location using special pumps or shearing equipment. This sometimes requires from several hours up to several days. It is more effective on a poundper-pound basis. Lab and field tests indicate that the presheared material gives much better mud properties than other asbestos products. The need for a low-solids, lowviscosity, and high-carrying capacity fluid will offer good possibilities for use of this material. And it will find application in shallow holes where mixing time and money are critical. The difference. The electron micro graphs in Fig. 1 show why the new material has provided some favorable results. Typical Canadian chrysotile ore (A) is linear in structure and made up of bundles of asbestos fibers that are straight and tightly bonded. This ore John L. Kennedy Drilling Editor usually assays about 7-15% asbestos and the rest is generally serpentine rock. California chrysotile (B) is a unique formation in which the as bestos fibers are arranged in a random pattern. The bonding is basically on a pointto-point contact, and the ore assays about 50% asbestos with some de posits going as high as 60%. The higher purity and less tightly held bond of this ore makes it very suitable for a hydraulic separation process. Micrograph (C) represents the fiber structure of California asbestos addi tives that have been dry processed with conventional methods. It ' still contains fiber bundles and maintains a considerable amount of linear con tact. Micrograph (D) shows the pre sheared asbestos of extremely high purity with up to 98% of the fibers being liberated. Since the fibers are the material that does the work in a drilling mud additive, this material is more efficient and economical. After the separation of the fibers to the point shown in (D), the pre sheared asbestos is pelletized for stor age and handling convenience. Lab and field tests. In lab tests made to evaluate the effectiveness of the presheared asbestos each material was tested following the same pro cedure. Five g of the material was added to 350 cc's of distilled water contain ing 3.5 g of common salt. The mix ture was stirred for 10 min and then tested in a Fann v-g meter. Labora tory results are shown in Table 1. Comparison field tests were also also made on six wells--three using the presheared material and three using a regular asbestos product--in the Texas Panhandle. These 7,100-ft wells in the Perryton, Tex. area usually encounter a geologic column something like this: down to 3,000-4,000 ft are redbeds, (silty) dolomite and hydrates, and shale; at approximately 4,000 ft is the Wolfcamp dolomite; and from there to total depth--about 7,200 ft--sheets of shale, lime, and sand are found. Completions are usually made in limestone that exhibits varying de grees of fracture. In the three wells that were drilled with the presheared material, average rotating time per well was 186 hr compared to a 242-hr average for the wells in which regular asbestos products were used. The average number of bits used on the wells using the regular asbes tos-bentonite mud was 18, compared to 12.33 bits per well on the wells in which the presheared material was added to the bentonite mud system. As far as the mud costs were con cerned, the wells using the presheared additive averaged about $4,220 com- Table 1 Lab test results Un Prod Pre- sheared uct sheared (regular) F Apparent viscosity 14.5 8 7 Fann V-G meter 600 rpm . 29 16 14 Fann V-g meter 300 rpm . 18 98 Plastic viscos ity (centi- poises) ... 11 76 Yield point (lb per 100 sqft) 7 22 Initial gel (lb per 100 sqft) 5 33 Here's how field comparison turned out Table 2 Well No. 1 2 34 5G Hours rotating Number bits .... Mud cost......... Days on location Depth in ft ... 209,75 19 $14,586.31 14 7,475 251.75 21 $25,474.82 27 7,160 267.25 14 $7,544.23 15 7,202 175.5 13 $3,573.06 13 7,200 180.25 13 $4,232.98 12 7,142 203.5 11 $4,861.65 11 7,300 UCC 014975 A07S3C