Oil Based MudOil based muds & Synthetic-Based muds:
Through this memo, we expect:
-To present the materials oil-based muds (OBMs) or synthetic-based muds (SBMs) are made of (most of the time,such muds are water-in-oil, invert, emulsions),
-To give information and field habits to effectively solve formulating problems.
Same of these information are also included in an XL-based program (currently under development) to design drilling fluids.
Specification of Gilsonite in oil well drilling fluidng FLC natural asphaltSoftening Point (ASTM E28-92) 365-400°F
Ash (ASTM D271-70M) <= 3.0%
Moisture (AGC Method) <= 1.0%
Penetration (25°C, 100 gm, 5 sec.) = 0
Specific Gravity = 1.06 (=/- 0.01)
Color in Mass =Black
Flash Point (COC) = 600 F
Sulfur <= 0.3%
Typical Particle Sizing (ASTM E11-70) % Retained (Cumulative)
Pulverized + 10 mesh --
+ 35 mesh = 0
+ 65 mesh <= 1
+ 100 mesh <= 5
+ 200 mesh <= 20
1-Applications Of OBMs.
OBM offers many advantages over water muds. Cost and environmental disposals can be factors in not selecting this type of mud system.
2-OBMs Basic Chemistry.
Invert emulsions (the most common OBMs)are formulated to contain moderate to high concentrations of water (up to 60% in extreme ocnditions).
Special emulsifiers are added to emulsify the water as the internal phase and prevent the water from breaking out and coalescing into larger droplets.
These water droplets,if not tightly emulsified, can water-wet the already oil-wet solids and ddramatically affect the emulsion stability.
The balanced activity concept is shortly described in annex 1.Shale swelling is a required notion to expain the need of this concept : it is briefly explained in annex 2.
BHT=bottom Hole Temperature
Oil muds require special products to ensure that the emulsion is extremely stable and can withstand conditions of HT and contaminants. Every single product must be dispersible in the external oil phase.
3-Synthetic-Based Fluids For Oil Muds Replacement.
The first use of oil as a drilling fluid is not know. It is likely,however, that someone thought of using produced crude to drill the well, assuming that would eliminate wellbore damage that can occur with water contact.
Crude oils were difficult to use as drilling fluids, so refined oils and processed asphalts replaced them .A number of mud products came into ,being to control the normal mud properties of viscosity and fluid loss and to emulsify water.
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