Gilsonite In Cementing
Gilsonite is used in cementing slurries to provide density control, scouring action for mud removal, and to support compressive strength development. It has a unique reaction with shale that improves cement bond development and strength.The wellbore is the primary hole on which the final well will be made. Also, wellbores can be encased by steel or cement or in some cases, depending on the situation, may not be encased.In oil wells, it is necessary to encase the wellbore by cement. Adding the Gilsonite material during oil well cementing enhances the isolation characteristics while decreasing the vertiginous Gas flows. These characteristics can result in more effective mud removal which also enhances the environmental factors. Drilling environmental regulations are getting more and stricter around the world.
Gilsonite in Oil Well Cementing Advantages
Gilsonite significantly improves cement properties, cuts cost, and difficulty of consuming several additives. Gilsonite guarantees zonal isolation, diminishes environmental hazard, enhances ultimate recovery, and lowers total cost of ownership for the life of a well. Cement integrity and wellbore architecture are considered vital to performance and total recovery of wells. Thanks to its distinctive chemical properties and physical appearances, Gilsonite is the supreme cement additive for a wide range of wellbore configurations.
Gilsonite is a soft rock with the specific gravity of 1.04. So it can act simply as an easy rock to be pumped down the well.
Gilsonite Application will decrease the return of the gasses to the surface. The Nature of Gilsonite is adaptable with Oil matters including resins used in cement. While using High Softening Point Gilsonite (above 180) shall avoid softening of the sand pumping down and keeps the thickening intact.
Cementing with Gilsonite significantly decreases the cost of water agents caused by loss of free water. A cement produced by Gilsonite is suitable for blocking or plugging an abandoned pipeline or backfilling a mine shaft, tunnel or excavations contains Portland cement or a mixture of at least two components selected from Portland cement, A cementitious slurry, formulated from the cement mix, may have a density less than or equal to 1500kg/m3, and exhibits good compressive strength.
In the formulation of the cementing composition of the invention, it is preferable to employ gilsonite in an amount ranging from approximately one-half to approximately ten times by volume the amount of the cement utilized, depending upon the particular result desired.
The lower range is employed where maximum strength is important; the higher range where the various qualities imparted by the gilsonite are most important.
Particle size and particle size distribution of the Gilsonite determine the strength and porosity-permeability characteristics of the set cement for any given mix ratio.
Where maximum strength is desirable, a coarse gilsonite Where lightest weight and lowest porosity-permeability are important and strength is to be sacrificed or is of little importance, an aggregate of minus 50 mesh or finer may be used.
Conditions are often encountered in the field requiring various combinations of particle size and particle size distribution. The above examples represent extremes. The mix must, however, always pumpable through the system from the mixing point to the final point of placement of the cement slurry. The coarser the aggregate, the less that may be present in any given slurry without impeding pump ability.
For example, a cement-Gilsonite ration of 1:4, using the coarse aggregate specified above, is difficult to pump and is likely to plug restricted passages in the system, whereas the same mix, using the fine aggregate specified above, will never plug if the water-cement ratio is high enough.
An amount of a petroleum solvent which depends upon the amount of Gilsonite present, may be added to the wet or dry mix for wetting the surface of the Gilsonite particles and causing them to form an intimate bond with casing and earth formations of the bore hole, thus preventing corrosion and minimizing pulling away of the cement from the casing and/or borehole wall by reason of the shrinkage normal to setting of the cement.
Instead of adding the solvent directly to the mix, it may be pumped through the casing and into the cementing zone in advance of the Gilsonite-cement slurry.
Set Cement Benefits
- Maintains compressive strength, unlike coal or fly ash
- Increases flexibility
- Reduces cracking
- Heals micro fissures
- Reduces permeability
- Strengthens bond to the formation and the casing
- Reduces environmental risk
- Assures zonal isolation
Cement Slurry Benefits
- Increases yield
- Reduces slurry weight
- Controls free water
- Lowers slurry water ratio
- Promotes favorable rheologies resulting in lower ECDs
- Prevents lost circulation
- Scours wellbore/enhances mud removal