What is an unconsolidated formation?
A sediment that is loosely arranged or unstratified (not in layers) or whose particles are not cemented together (soft rock); occurring either at the ground surface or at a depth below the surface. Also see consolidated formation.
What are the three drilling muds?
There are three main types of drilling mud: water-based, oil-based and synthetic-based.
What type of mud should be used for shale rock formations?
Most conventional oil-based mud (OBM) systems are formulated with calcium chloride brine, which appears to offer the best inhibition properties for most shales. The ratio of the oil percentage to the water percentage in the liquid phase of an oil-based system is called its oil/water ratio.
What are consolidated formations?
A geologic material whose particles are stratified (layered), cemented, or firmly packed together (hard rock); usually occurring at a depth below the ground surface.
What is the definition of unconsolidated?
Definition of unconsolidated : loosely arranged unconsolidated subsidiaries especially : not stratified unconsolidated soil.
What does drilling mud consist of?
Drilling muds are traditionally based on water, either fresh water, seawater, naturally occurring brines, or prepared brines. Many muds are oil-based, using direct products of petroleum refining such as diesel oil or mineral oil as the fluid matrix.
Why is bentonite used for drilling mud?
The most common use of bentonite is in drilling fluids. The bentonite in the flush fluid lubricates and cools the cutting tools whilst protecting against corrosion. As the drilling fluid generates hydrostatic pressure in the borehole, it hinders fluid and gas penetration.
What is the difference between consolidated and unconsolidated rock?
Geologic materials can be classified as consolidated rock or unconsolidated (loose) sediment. Consolidated rock may consist of such materials as sandstone, shale, granite, and basalt. Unconsolidated sediment contains granular material such as sand, gravel, silt, and clay.
What does unconsolidated mean in geography?
Unconsolidated material. A sediment that is loosely arranged or unstratified, or whose particles are not cemented together, found either at the surface or at depth.
How do you reduce friction in a borehole?
In many cases the casing size is progressively decreased as a hole is deepened, thereby reducing friction and also the weight of the drilling tools. Friction between the borehole wall and casing can be reduced by the addition of drilling fluid slurry around the outside of the casing during driving.
What happens when you drill with a drill bit?
The drill bit breaks or crushes consolidated rock into small fragments, whereas the bit primarily loosens the material when drilling unconsolidated formations. In both instances, the reciprocating action of the tools mixes the crushed or loosened particles with water to form a slurry or sludge at the bottom of the borehole.
How did the ancient Chinese drill their wells?
Using Tools constructed of bamboo, the early Chinese could drill wells to a depth of 3000 ft although construction took two to three generations. Cable tool drilling machines, also called percussion or spudder rigs, operate by repeatedly lifting and dropping a heavy string of drilling tools into the borehole.