Oil Sector

Oil Sector

Drilling Fluids

The Use of Gilsonite® in Drilling Fluids

For many years, Gilsonite has been used in the oilfield as an additive in drilling fluids. Gilsonite, in various grades and formulations, has been used to combat borehole instability problems, provide lubricity, especially in highly deviated holes, and more recently as a bridging agent to combat differential pressure sticking and provide a low invasion coring fluid. It has been well documented that appropriately formulated Gilsonite products can minimize hole collapse in formations containing water-sensitive, sloughing shales and reduce stuck pipe problems by forming a thin wall cake and an inter-matrix filter cake.

The causes of borehole instability are numerous. The reasons for the instability can be mechanical, chemical or physical in nature. Mechanical problems include borehole erosion by high annular velocities, adverse hydraulic stresses due to high annular pressures, hole collapse from high swab and surge pressures due to excessive wall cake, and stress erosion due to drill string movement. Chemical alteration problems include hydration, dispersion, and disintegration of shales due to the interaction of clays with the mud filtrate. Physical instability problems include the spalling and rock bursts of shales due to abnormal pressure or overpressure relationships of hydrostatic and formation pressures. Fracture and slippage along bedding planes of hard, brittle shales and the collapse of fractured shales above deviated holes are also physical problems encountered while drilling troublesome shales. This problem also occurs in non-deviated holes while drilling over-pressured shales.

Borehole instability problems are often referred to as sloughing, heaving, spalling, or over-pressured shales, mud balls, mud rings, and many other descriptive names. There are many solutions to these problems. The use of additives to inhibit or partially inhibit the swelling of shales has been well documented. Gilsonite products play a key role in addressing these problems.

Gilsonite products are currently being widely used in water based, oil based, and synthetic based mud systems worldwide. Blended Gilsonite has proved to be very effective in all water-based systems, with the flagship product in this line being Bore-Plate(R) Shale Stabilizer.

Bore-Plate® Shale Stabilizer

Bore-Plate Shale Stabilizer is a proven, unique composition of Gilsonite grades and dispersants, blended to provide optimum performance in water based drilling fluids. Bore-Plate is effective in low and high-temperature wells, stable in the presence of mud contaminants, and tolerant to additions of diesel oil. It can replace or complement sulphonated asphalts at a much lower cost, while providing additional properties that sulphonated asphalts lack.

Please contact us with your specific need and we will be delighted to assist you.

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Provides low slurry density without addition of large water volumes. Compressive strengths are higher due to addition of solid particles rather than water.
Compatible with other additives since the solid hydrocarbon is chemically inert.
Protects against premature slurry dehydration since Gilsonite is impermeable and nonporous.
Resists the effects of corrosive waters as well as acidic and alkaline solutions.
Is strong enough to withstand moderate squeeze pressures, but soft enough to permit pressure deformation, thus providing an effective seal. This gives Gilsonite® an advantage over ground coal, which does not compress and does not have pressure deformation characteristics.
Effective to bottomhole temperatures of 350°F.
Resistant to dissolution by crude oils.
Scours uncirculated drilling mud and filter cake from borehole walls during slurry placement.

Six cases were cited in the paper which illustrated the before and after effects of the use of Gilsonite in cementing operations. Successful squeeze jobs, prevention of cement fallback, and full or almost full fillup during a cement operation were obtained. These cases cited success in squeeze jobs after 15 unsuccessful attempts, successful cementing in shallow wells with severe lost circulation, reestablishment of lost circulation in wells used for a waterflooding program, squeezing off corrosive damage in oil casing, and successfully cementing in severely pressured depleted wells.