Gilsonite Cementing is the process of introducing cement to the annular space between the wellbore. A wellbore means it is a hole that is drilled to aid in the exploration and recovery of natural resources, including oil, gas, or water. A wellbore is the actual hole that forms the well. A wellbore can be encased by materials such as steel and cement, or it may be uncased. The motivation for drilling a wellbore is usually to extract oil or gas for a protracted period of time.
Gilsonite Cementing is used in bonding slurries (Slurry means, it is a mixture of solids denser than water suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids, the liquid being a carrier that is pumped on a device such as a centrifugal pump. The size of solid particles may vary from 1 micron up to hundreds of millimeters) to provide density control. It is also 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 stricter around the world. The nature of Gilsonite allows this material to act as a binder. Gilsonite also plays the role to fill the cracks made in the wellbore casing, causing better bonding and avoiding isolation in different zones.
The Gilsonite which needs to be applied in oil well cementing is standard quality lump grade Gilsonite. Basically, when an oil well is finished off, a mixture of cement and rock aggregate is pumped down the well to encase the oil pipe into the formation. Pumping such a heavy mix down into a well and pulling it back up again is a very expensive process. Replacing a great extent of the heavy rock with light–weight Gilsonite particles reduces the pumping costs dramatically. Therefore applying Gilsonite in Oil Well Cementing is simply a “rock replacement.”
As the challenges presented by today’s wellbore configurations increase, a properly designed cementing process is critical to keeping the wellbore isolated, protected and environmentally sound. For more than 50 years, the industry has depended on Gilsonite as a lost circulation material and a critical component for primary cementing operations in some of the world’s toughest drilling environments. Adding Gilsonite during cementing operations enhances the characteristics that are critical to effectively cementing the casing, isolating hydrocarbon formations and preventing annular gas flow. With its unique physical and chemical properties, Gilsonite provides a range of important benefits in the slurry and set cement that is unmatched by any other single additive.
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 the 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 re-establish 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% – 90% can be obtained in areas where only 50% – 60% fill up was possible with other types of slurries. The unique properties of Gilsonite such as low specific gravity, particle size distribution, and impermeability, resistance to corrosive fluids, chemical inertness, and low water requirements result in a slurry having 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.
Advantages of using Gilsonite in oil well cementing:
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 the 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 1500/Kg/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 Glisonite are most important.
Cement slurry:
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 pump able 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, 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
Cementing of oil well:
An oil well is made primary to the final well which will be filled later on and also needs to be encased during the primary works. For cementing an oil well, different ways can be used while several include applying of Gilsonite. The material should be pumped into the well for to encase the piping, therefore applying Gilsonite as a soft rock decreases the material density.
Gilsonite eliminates the problems of free water:
By controlling free water, Gilsonite helps stabilize slurry and eliminates the need for–and cost of–additional free–water–control agents. As a lost circulation material, it also improves zonal isolation by preventing water channeling on the upper side of the wellbore.
Self–healing properties help maintain zonal isolation:
The properties of Gilsonite are (1) Flexible, (2) Deformable, (3) Swell–able, (4) Impermeable and (5) Non–Porous. These characteristics give Gilsonite self–healing properties that can plug induced micro fissures in the cement sheath.
Gilsonite properties that create the ideal cement additive:
- Low specific gravity (1.04–06 @ 77 °F)
- High softening points (>340 °F)
- Semi–Polymeric behavior
- Low moisture content (<5%)
- Does not impact thickening time
- Hard to fuse (no re–massing)
- Compatible with paraffin, Resins, Oils, Asphalts, and Elastomers
- Compatible with other cement additives
- High purity
- Cost effective
- Consistent quality
- Multipurpose
Cementing is vital to environmental and financial responsibility:
The extraordinary properties of Gilsonite offer the reliability that the cementing job is the basis of reliability, adaptability, and long–term production with minimal adverse environmental effects.
- Zonal isolation for the life of the well
- Eradication of fluid cross flow
- Avoidance of gas migration to the surface
- Safeguarding fresh water aquifers