In the gas and oil industry, Gilsonite is used for oil well cementing. It is used to perform a diversity of operations that influence the drilling rapidity, efficiency, safety and the cost of drilling operator. An important characteristic of Gilsonite that makes it noteworthy for drilling fluid usages is its softening point temperature. There are many types of drilling fluid systems available such as water base muds (Refer Fig: 1), oil base muds, stable foam muds, air or gas base muds from which the right system may be chosen. In water–based muds, it is used as a shale–stabilizing additive and is difficult to evaluate unless tested at or above its softening point. In oil–base muds, it is used as a fluid–loss control agent.
Main drilling mud additives include viscosifying factors, fluid loss control agents, corrosion inhibitors and drilling fluid dispersant cement additives (Cement additives are the additives to be used and their concentration shall be decided by the Cement Contractor, after testing the slurry using representative samples of cement, additives and mixwater despatched from the rig. This has to be then approved by the Operations Engineer and Superintendent.) are considered to be critical inputs in the supplementation of any oil and gas well.
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 (A Wellbore is a borehole or a hole drilled in the earth’s surface so as to carry out exploration and extraction of natural resources like water, oil or gas) 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 (Refer to fig: 2). 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 is a generic name widely used for a black, lustrous, carbonaceous resin classified as an Asphaltite. Its proper name is Uintaite, and it is found in Utah, USA. An important characteristic of Gilsonite is its softening–point temperature. In oil–base muds, it is used as a fluid–loss control agent. Being a hydrocarbon, it is naturally wetted by the oil. In water–base muds, it is used as a shale–stabilizing additive and is difficult to evaluate unless tested at or above its softening point. As a hydrocarbon, the powder must be coupled with water by using a Ethylene glycol with the formula (CH2OH)2 or similar water–wetter, the recognized industry standard for filtration control. It is equally effective at controlling lost circulation and improving wellbore stability. Gilsonite is naturally better.
This versatile, multi–purpose additive is a naturally occurring hydrocarbon resin found only in North Eastern Utah. Gilsonite has significant health, safety and environmental advantages over synthetic products.
Material Safety Data Sheets classify Gilsonite as:
Gilsonite requires only standard PPE safety measures.
Strengthens cement bonds to shales and sands
Reduces cement slurry density
Prevents lost circulation
Supports compressive strength development
Drilling fluids benefits:
Provides superior shale stabilization
Prevents differential sticking
Reduces or eliminates lost circulation
Provides wellbore strengthening matrix
Gilsonite in Oil & Gas:
With unmatched benefits in cementing and drilling fluids, Gilsonite is proven under pressure. With a unique blend of strength, flexibility, bonding and high–temperature capability, Gilsonite adds properties that 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.
Gilsonite in oil and gas well cementing is a highly developed technology. Cement–water slurries, with or without various additives, have been used for many years in cementing procedures carried out from time to time during the drilling of the productive life of a well. Cementing is often applied during drilling and completion procedures in connection with the protection of production zones, isolation and confinement of water zones, support of borehole wall, anchorage of the casing, and control of lost circulation not overcome by methods associated with the circulation of drilling mud. Such cementing procedures by Gilsonite additives are ordinarily regarded as being of the primary character.
Gilsonite is used in drilling mud fluids and oil well cementing. Gilsonite, in a range of softening points and particle sizes, is a standard ingredient in oil–based drilling muds used in shales and other difficult geological formations. The addition of specially treated Gilsonite to water based drilling fluids helps minimize whole washout by stabilizing troublesome shales and seals off highly permeable sands while reducing torque and drag. The addition of Gilsonite to oil well cement reduces slurry weight without loss of compressive strength and acts as an effective bridging and plugging agent to seal fractures in weak formations while cementing. Also, Gilsonite use in Mud drilling according to FLC “Filtrate Loss Control” or “Fluid Loss Control” in oil base mud.
Gilsonite is effective at sealing off permeable formations even when drilling such zones at a highly over–balanced pressure differential. In this manner, Gilsonite helps prevent the occurrence of stuck pipe and stuck logging tools across these zones.
Gilsonite is used in cementing slurries to provide (1) Density control, (2) Scouring action for mud removal, and to (3) Support compressive strength development. It has a unique reaction with shale that improves cement bond development and strength.
All the common varieties of Gilsonite are substantially incompressible and have a specific gravity sufficiently near to that of water that properly sized granules of the Gilsonite can be readily suspended in the aqueous liquid carrier. Thus, Gilsonite is used for this purpose in powder. Pellet size is variable according to the characteristic of the wellbore. The softening point is very important, as Gilsonite must soften at a temperature above the temperature of the well formation. The recommended softening point is from 150 ºC (302 ºF) to 180 °C (356 ºF) and pellet from 4 ºC to 100 ºC. Actually, with more technological devices, the most commonly used is 200/200 (Softening Point/Pellet).
Usage cementing additive in oil & gas:
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 which best serves the particular purpose. The heat softening characteristic of Gilsonite becomes of particular importance in instances of relatively high bottom whole temperatures, where there is a tendency for the Gilsonite to soften and diffuse into the surrounding cement.
With 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.
In order to keep wellbore isolated and protected, having well–designed cement process is a must.
Natural Bitumen helps in preventing annular gas flow, isolation of hydrocarbon formations, mud removal density control, and compressive strength.
Benefits of natural bitumen in cementing:
Filtration control, Natural Bitumen is a product that simultaneously controls loss circulation and strengthens the wellbore.
Due to exceptional reaction with shale, it strengthens cement bonds to shale and sand. It also strengthens cementing bonds to the formation and the casing.
No compromising compressive strengths and density control unlike fly ash or coal additives.
Low specific gravity to reduce cement slurry weight and high softening points >176 ºC (>350 ºF).
Lowering the cost, with Natural Bitumen as is controls free water, hence no additional free water control agent is required.
Superior bonding improving zonal isolation.
Particle size of cementing additive in oil and gas:
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, coarse natural asphalt where lightest weight and lowest porosity permeability are important and strength is to be sacrificed or is of little importance, an aggregate of –50 mesh or finer may be used.
Application of Gilsonite in Oil & Gas–Gilsonite drilling fluid as fluid loss control additives, shale inhibitor, filtration:
The physical shape of Gilsonite and coal is same but the specification and analyze is quite a difference. The main differences are in softening point and solubility also ash content. Gilsonite in powder or lump form is hydrocarbon with softening point between 150 ºC (302 ºF) to 250 °C (482 ºF) and coal is carbon with high softening point starting from 300 °C (572 ºF).
Benefits of natural bitumen in drilling fluids:
Adding Natural Bitumen will create premium quality, multifunctional drilling fluid additive while reducing cost compare to other additives.
Suitable to any environment especially the ones with High Temperature (HT) and zones with High Pressures (HP). It prevents stuck pipe and stuck logging tolls from happening in those zones by sealing permeable formation.
Natural Bitumen in oil based drilling fluids as a fluid–loss control agent. Softening points (Softening Point 176 ºC (350 ºF) to 203 ºC (399 ºF).
Natural Bitumen in water–based drilling fluids when pretreated with surfactant to stabilize the shale and to prevent circulation, (softening point 176 ºC (350 ºF) to 203 ºC (399 ºF).
It minimizes differential sticking and it also passes deep–water Environmental Planning and Assessment Regulation (EPAR).