Additives For Oil Cement

Since Gilsonite, a solid hydrocarbon, was introduced to the oil industry in August 1957 as a cement additive, several thousands of jobs have been performed using the material. These operations have included primary cementing through lost-circulation zones of surface, intermediate, and production pipe in both single and multiple stages as well as various remedial jobs such as squeezing, re-cementing above inadequate fill-up, and plugging back to reestablish drilling-fluid circulation. Designed primarily as a combination low-density lost-circulation slurry, Gilsonite has yielded excellent results in areas of incompetent formations as well as in other types of lost-circulation zones. Field results generally show that fill-up of 80 to 90 percent can be obtained in areas where only 50 to 60 percent fill-up was possible with other types of slurries.
Source of Gilsonite
Gilsonite is a unique additive for the oil industry's use to combat lost circulation conditions. This material is a solid hydrocarbon that occurs in the Uintah Basin of Utah and Colorado. It was discovered in 1885 by Captain Samuel Gilson, hence the name of the material, Gilsonite. It has been generally grouped as a form of native asphalt, but its unusual properties make it markedly different from the bitumens or asphalts which may range from liquid to definite solid form whether native or processed. Gilsonite is mineralogically classified as an asphaltite. This material was deposited in roughly parallel lines running from a northwest to a southeast direction and it occurs in vertical fissures rather than in beds, pools, or lakes where the bitumens and asphalts are found. Gilsonite also has many uses other than those being discussed here. Its properties make it valuable for both heat and electrical insulation applications, floor tile, roofing materials, acid-resisting paints, electrical-insulating varnish, battery boxes, and brake and clutch linings. It is used in underbody coatings for cars, printing ink, and other items where its black color can be used to advantage.
Laboratory Investigations

Gilsonite was first evaluated as a density-reducing additive for cementing slurries because of its low specific gravity (1.07) . Laboratory testing was set up to establish an optimum particle size for these applications with three primary points being considered:

1. Maximum size to permit pumping through down-hole cementing equipment such as float collars and multiple-stage collars .
2. Minimum size to provide excellent control of lost circulation zones .
3. Proper particle size distribution to obtain the two preceding objectives and to also allow slurry preparation with a minimum amount of mixing water.

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