Geology And Geophysics

What is Slant Drilling



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The U.S. Department of Energy has a brochure on directional drilling,  It says, “…Oil and gas at depths recently considered unreachable can now be tapped.  Smaller accumulations once thought to be uneconomic can now be produced profitably.  Fields under wetlands or cities can be accessed without disruption of the surface.”

Directional drilling – is also known as “horizontal”, “Deviated” or “Slant” drilling is describing a method of drilling in an indirect approach to get to the reservoir of oil.  This technique was first introduced in 1939.  It was not feasible at that time because the short lateral extension did not have the capacity to go far enough.  The newer technology allows the drill to make a transitional curve to 90 degrees in less than 100 feet in the earth.

Horizontal or slant drilling helps gather more oil reservoirs.  The following reservoir types are examples the benefits of  horizontal drilling.

Thin reservoirs are when the hydrocarbon deposits are wide and not particularly thick.  Vertical drilling would get a small amount of the oil that was available only around the wellbore (a hole drilled for exploration).  Horizontal would go sideways into the reservoir with its longer lateral arms and extract more oil.

Natural vertical fracture reservoirs are when the hydrocarbons are able to flow through the fractures. The drill bit can be manuevered to come in perpendicular to the wellbore. This method makes drilling productive.

Overlooked or isolated reservoirs are the ones that could not be reached vertically.  The horizontal can reenter the old fields and find  reservoirs.

Reservoirs in environmentally sanctioned areas are under a building, below a lake, or a wildlife habitat.  The horizontal drill can explore for oil without touching the surface.

In 2000, Sandia National Laboratories developed a new technology that combines horizontal drilling with and Environmental Measurement While Drilling (EMWD).  The combination of both makes it possible to detect soil contamination while drilling.

In normal horizontal drilling the bit needs drilling fluid,  made of “mud”.  The fluid and soil removed from the borehole are contaminated and must be discarded.

This novel method pushes the casings with the drill bit into the earth and instead of removal of excess soil by pumping out the fluids, it pushes the soil to the side.  It does away with the drilling fluid when digging and drilling in the ground.

Another exciting part of this new system is that it has a location sensor as well as a gamma ray spectrometer (GRS). GRS analyzes soil through a sensor.  It saves time and gives a measure of security because it reveals contamination and non-contaminated fields.  It can also reveal hydrocarbon reservoirs.  The sensor, placed right behind the drill bit, sends information to a computer.  The computer analyzes the soil in real time.  As with all technology, there are problems.  One of the problems is that the sensor can get clogged and be unable to transmit information.

This innovative technology is tremendously exciting as an environmental safeguard for the future. 

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