How do they slant a "vertical" bore?
Many HA wells have slanted "verticals." i.e. the perforation point is not directly under the surface well location. How do they do this?
Do they tilt the drilling rig or the pipe above the ground and aim for the top of the curve? i.e. if you put a level against the pipe where it goes into the ground? i.e. if you held a plumb bob next to the pipe, would the pipe above the ground be vertical?
Do they drill "vertically" where they enter the ground and then use "directional drilling" techniques to steer the bore to the side where they want it to go?
It seems you'd have to actively steer the pipe for the vertical even if you want a true vertical bore. I can't conceive a 10,000 foot long "drill bit" following a straight course on its own without some kind of active steering.
(BTW, is "vertical" the correct term for the well bore from the surface to the top of the turn?)
Do they tilt the drilling rig or the pipe above the ground and aim for the top of the curve? i.e. if you put a level against the pipe where it goes into the ground? i.e. if you held a plumb bob next to the pipe, would the pipe above the ground be vertical?
Do they drill "vertically" where they enter the ground and then use "directional drilling" techniques to steer the bore to the side where they want it to go?
It seems you'd have to actively steer the pipe for the vertical even if you want a true vertical bore. I can't conceive a 10,000 foot long "drill bit" following a straight course on its own without some kind of active steering.
(BTW, is "vertical" the correct term for the well bore from the surface to the top of the turn?)
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Replies to This Discussion
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Permalink Reply by Mac Davis on
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Skip mentioned MWD, but would the "normal" process be to pull the drill string and run gyroscopic instruments down the bore to map out the location of the bore?
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Permalink Reply by Walter Phillips on -
MWD(Measured While Drilling) records log curves while a well is drilling. Often the tools will be set up to record a gamma ray curve and a resistivity curve for geologic correlation to nearby well logs. They have some capability to measure the inclination and bearing of the well bore, but not to the same degree of detail that a gyro survey does.
The gyro survey is also part of the state well permit requirements for a directionally drilled well and has to be filed with the state...look in SONRIS under Office Of Conservation in the WELL ENGINEERING/MECHANICAL category and you can usually find them there not long after a well has reached TD.
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Permalink Reply by Mac Davis on
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Thanks Walter. Does the gyro survey involve running a gyroscopic instrument for a quick trip down and up the well bore? Either a separate trip just for a gyro survey after the final depth is reached or in combination with some other equipment for a quick trip up or down the well bore?
I'm thinking the gyros would drift if you didn't run them down the well bore relatively quickly.
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Permalink Reply by Walter Phillips on
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Mac, The gyro survey could be done as either a separate trip or combined with a logging run. Either way it would probably be run into and out of the hole at standard wireline logging speeds of around 3,600 ft/hr. There would not be enough drift in the time frame of a logging run to cause any problems with accuracy.
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Permalink Reply by drilltheshale on
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Just want to thank you guys for the discussion. I learn something new nearly every time I visit.
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