General abstract Gilsonite Cement Additive
Since Gilsonite, a solid hydrocarbon, was Introduced to the Oil Industry in August 1957 as a cement additive, over 200 jobs have been performed using the material. Designed primarily as a combination low-density, lost-circulation slurry, Gilsonite cement additive 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.
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 borehole, 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.
Introduction of Gilsonite Cement additive
As the oil-producing industry has continued to grow, the need for a low-density cementing slurry possessing lost-circulation control characteristics has become more and more evident. This is especially so in primary cementing because of the different types of formations being encountered and the need to reduce remedial cementing operations. Lost-circulation zones encountered during drilling operations may produce many problems in the normal course of completing a well. Increased expenditures can result from reduced drilling rates, fishing jobs, and other mechanical difficulties as well as from loss of large volumes of drilling fluid. Sometimes severe lost-circulation problems may even cause abandonment of a well. Lost circulation during cementing operations will often be reflected by inadequate fill-up in the annulus and the consequent displacement of slurry into formations away from the wellbore.
Attempts have been made to restore circulation while cementing, using many types of materials. Sometimes sufficiently good results have been obtained simply by reducing the slurry density whereas other instances have occurred where bridging materials were found to be most helpful, but they’re still remained zones of loss which would not react satisfactorily to either of these methods. Combinations of these two approaches have also been utilized, but it has been difficult to obtain optimum bridging and density without sacrificing other desirable slurry properties such as strength and resistance to corrosive fluids. Some of the more commonly used additives in this application should be mentioned briefly.
Actually even these two materials do reduce the strength of cement, they will generally provide adequate strength for normal cementing operations and their prevalent disadvantage for use in lost-circulation zones is the lack of coarse bridging particles. Incorporation of coarse additives into these slurries is possible, but may further reduce the compressive strength beyond that which is desired when sufficient quantities are used to effectively control lost returns in relatively severe areas. Materials such as ground nutshells, granulated plastics, and cellophane flakes have been used as bridging agents with excellent results where lost circulation problems were of a relatively minor nature, but they have not been too successful where major difficulties were encountered.
Moderate slurry weight reduction can be attained by the use of pozzolanic additives with cement. Because a pozzolan reacts with the hydrated lime from tile cement to yield cementitious compounds, relatively good strengths are realized and bridging materials may be used with this type of slurry to provide additional benefits. Expanded perlites have been used in the oil industry since 1951 for both lost circulation control and moderately light slurry weight, although in order to have a pumpable slurry extra mixing water is required.
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.
Application of cementing additive in oil & gas
- Increasing cement function
- The weight of Slurry would be very lower
- prevent from spread of free waters
- will reduce water quantity of slurry
- reducing the mud quantity
- improving scours of wellbore
- preventing from wellbore rheology
Advantages of Gilsonite cementing additive
Gilsonite should be realized that there are various classes with respect to melting points. The lower the melting point, the faster the Gilsonite will dissolve in a solvent therefore or soften under conditions of heat. Therefore, the use of gilsonite in an oil & gas well-cementing composition affords an opportunity to select a class of that material that best serves the particular purpose. The heat softening characteristic of Gilsonite becomes of particular importance in instances of relatively high bottom-hole temperatures, where there is a tendency for the Gilsonite to soften and diffuse into the surrounding cement.
The blending of Gilsonite with other drilling mud additives increase performance in cementing and drilling fluids in a way no other single additive can. gilsonite, the recognized industry standard for filtration control, is equally effective at controlling lost circulation and improving wellbore stability.
