Gilsonite usage in drilling fluid is as high-temperature, high-pressure filtration control additives in drilling mud. This mineral can be used in all oil based mud and all temperatures. Also, mixed Gilsonite is used effectively in water-based mud systems.
Gilsonite powder reduce API and HPHT fluid loss in all oil-base muds. It has the ability to stabilize drilling mud and thus prevent erosion of pit. It helps improve the overall emulsion stability, Thermal stability and suspension characteristics of most oil-base formulations. Gilsonite also increase viscosity, especially at lower temperatures due to its partial solubility and reduces torque and drag.
Mud with Gilsonite creates a narrow and strong wall inside the wells. It is used to control lost circulation in drilling formations.
Specification of using Gilsonite in drilling
Normal concentration of Gilsonite range from 2 to 8 lb/bbl (5.7 to 23 kg/m3), with occasional daily additions in the 0.25 to 0.5 lb/bbl (0.71 to 1.43 kg/m3). High-temperature situation and special applications require higher concentrations, as much as 10 lb/bbl (29 kg/m3).
When used in initial formation, it is recommended to add Gilsonite last. For existing systems, the product can be added at any time, mixed slowly during at least one complete circulation. Monitor solids control equipment for several circulations to ensure product is not discarded.
Gilsonite powder used in drilling mud have particle size of 45-75 µ, ash content 5-10%, softening point of 185-220ºC and specific gravity between 1.4 to 1.06.
Application of Gilsonite in lost fluid circulation
Another application of Gilsonite is as an additive in controlling and preventing waste on drilling fluids, which is called lost fluid circulation control. This material is added to the drilling mud and melts after entering the well by absorbing heat. Heat absorption cools the drill bit as well as lubricates it. Gilsonite lubrication capability prevents drilling bit from being trapped due to the accumulation of materials and sediments in the well.
Weak or fractured zone can result in lost circulation. During drilling, if areas in the well are loose or lose their resistance due to pressure and circulation, fluid enters that area. The larger the area or the less strength in the walls, the more fluid is lost. Even this can cause the well to collapse and stop the process. In this situation Gilsonite, by forming a thin layer can strengthens the well and prevents drilling fluids from escaping.
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Application of Gilsonite in Oil Industry
Gilsonite is used in cementing wells in oil industry. It is also used to to move drilling debris to ground surface by the rotation of the drill and the rotational motion created in the particles.
Adding Gilsonite to drilling mud has many benefits, including reducing the composition of the mud and increasing the strength of the well. This material shows high resistance to dissolution with oil and prevents pellets or agglomerates of rocky soil compounds. Gilsonite polishes the surfaces of drilling wells by removing excess mud.
Advantages of using Gilsonite in drilling industry
The use of Gilsonite in the drilling industry has the following advantages:
The resulting mixture has a low density without adding a large volume of water
This material is compatible with other additives and is resistant to acidic, alkaline and corrosive substances
Wide range of temperature (high softening point between 175 to 235 ° C)
It resists moderate pressures due to dehydration, but is soft enough to deform under pressure
It does not clump due to pressure
It is resistant to dissolution in oil
it causes the seams and cracks of the wells to close during cementing the walls
Prevent damage to drill bits
Polishing the surfaces of drilling wells and removing excess drilling mud
Reduces the weight of drilling fluid
Related Article: Gilsonite in cementing oil well
Use of hydrophilic Gilsonite nanoparticles in drilling mud
Recent developments in nanofluids show that the addition of nanoparticles to water-based drilling mud can solve many drilling problems, including instability, lost circulation, torque and tension, drill string, shale swelling, and reduction of drilling speed. In this section, hydrophilic Gilsonite nanoparticles are produced from the reaction of natural Gilsonite with a mixture of sulfuric acid and nitric acid. The properties of hydrophilic Gilsonite are different from the properties of natural Gilsonite. Examination of the rheological properties of drilling mud with these nanoparticles shows that the addition of 10 gr of hydrophilic Gilsonite (in 350 ml drilling mud) to the base mud and reducing the starch concentration to half the initial amount, leads to the best combination for water-based drilling mud efficiency.
After hot roll process, the plastic viscosity (PV) is improved and the yield point (YP) is significantly maintained. Also in mud containing hydrophilic Gilsonite nanoparticles, drilling mud drop under standard conditions and thickness of mud cake in high temperature-high pressure conditions after hot roll process is reduced. In addition, after the hot roller, the amount of lubrication and the percentage of torque are reduced.
Experimental results show that hydrophilic Gilsonite nanoparticles as a low cost, non-toxic and effective additive have good potential in improving the performance of water-based drilling fluid at high temperatures.
