Cementing Gilsonit – Since Gilsonit, 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 all 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, Gilsonit 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 80-90% can obtained in areas where only 50-60% fill-up was possible with other slurry types.
Low chemical inertness.
Resistance to corrosive fluids.
Light specific gravity.
Low water requirements cause a slurry containing exceptional bridging properties.
Low slurry weight.
Compatibility with other slurry additives and relatively high compressive strength when compared to other slurries of the same weight.
Gilsonit Cementing Grade has a light specific gravity, is non-porous, and impermeable. The addition of Gilsonit to cement slurries reduces the slurry weight without requiring large additions of water. As a result, superior lightweight slurry have good compressive ability, especially suited for cementing weak formations and controlling lost circulation.
As oil-producing industry has incessant grow, necessity for a low-density cementing Slurry possessing lost-circulation control specs becomes more Introduction of Gilsonit.
Especially in primal cementing due to the need to reduce remedial cementing operations and the different types of formations existence encountered.
These problematic formations may range from either porous or cavernous formations to very weak formations. This makes supporting hydrostatic head unable, while is necessary for drilling and well supplementation. This recent type of formation will often break down or fracture under hydrostatic loading, terminating in partial or complete loss of flow.
A cement produced by Gilsonit is suitable for blocking or plugging an abandoned pipeline or back filling a mine shaft, tunnel or excavations contains Portland cement or a mixture of at least two components selected from Portland cement, A cementation slurry, formulated from the cement mix, may have a density less than or equal to 1500 kg/m3, and exhibits good compressive strength.
In formulation of cementing composition, it`s preferable to employ Gilsonit in an amount ranging from approximately 1.5 to approximately 10 times. By volume the amount of cement utilized, depending upon the particular result desired.
Lower range is employed where maximum strength is important. Higher range where various qualities imparted by Gilsonit is important.
Particle size and distribution of Gilsonit determine strength and porosity-permeability characteristics of cement for any given mix ratio.
Where maximum strength is favor, a coarse Gilsonit with lightest weight and lowest porosity-permeability are important. The strength has little importance. Mass of minus 50 mesh or finer may used.
Field often require various combinations of particle size and particle size distribution. Also mixture must be pumpable through the system from mixing point to final point of cement slurry placement.
An amount of petroleum solvent which depends upon the amount of Gilsonite present, may be added to wet/dry mixture, wetting surface of Gilsonit particles, causing them to form an intimate bond with casing. Also needs earth formations of bore hole. Thus preventing corrosion and minimizing pulling away of cement from casing and/or bore hole wall by reason of shrinkage normal to cement setting.
By adding solvent directly to mixture, it may pumped through casing and to Cementing zone in advance of Gilsonite-cement slurry.