Packer weighted and pressure differential method and apparatus for Big Hole drilling

A packer weighted and pressure differential tool for big hole well bore drilling through earth formation having a pore pressure opposed by hydrostatic fluid pressure, and including;

• a dual tube stem for coupled engagement with a dual drill pipe and operation through a large diameter well bore and with concentric passages isolating the pressured supply and discharge flow of circulating fluid therethrough, there being a well bore annulus surrounding the dual drill pipe,
• a drill bit carried by the stem for rotation and formation engagement at a bit-to-bore bottom interface,
• a packer means rotatably carried over the dual tube stem to seal with and slide down the well bore immediate to and above the drill bit and separating said well bore into a drilling zone and a hydrostatic head of fluid supported by the packer means,
• the drill bit being comprised of a large diameter body carrying cutters having coextensive bore bottom engagement, and means responsive to release of circulating fluid under pressure from one of the dual stem passages and reducing fluid pressure in the drilling zone at the bit-to-bore bottom interface for flushing fluid to remove cuttings from said bore bottom and discharge through the other one of the dual stem passages,
• and anti-friction axial thrust bearing means operable between the packer means and drill bit body for transferring the weight of the hydrostatic head of fluid supported by the packer means into the drill bit body as said packer means is sliding down the well bore.

A packer weighted and pressure differential pressure set tool for big hole well bore drilling through earth formation having a pore pressure opposed by hydrostatic fluid pressure, and including;

• a dual tube stem for coupled engagement with a dual drill pipe and operation through a large diameter well bore and with concentric passages isolating the pressured supply and discharge flow of circulating fluid therethrough, there being a well bore annulus surrounding the dual drill pipe, and a by-pass passage extending longitudinally through a peripheral wall of the dual tube stem and in open communication with fluid standing in the well bore annulus for downward flow therethrough,
• a drill bit carried by the stem for rotation and formation engagement at a bit-to-bore bottom interface, and having a chamber in open communication with the by-pass,
• a packer means rotatably carried over the dual stem to seal with and set by fluid pressure to slide down the well bore immediate to and above the drill bit and separating said well bore into a drilling zone and a hydrostatic head of fluid supported by the packer means,
• the drill bit being comprised of a large diameter body carrying cutters having coextensive bore bottom engagement, and carrying bit jets exhausting into the drilling zone, and means responsive to release of circulating fluid under pressure from one of the dual stem passages and comprised of a jet pump with an intake plenum open into and reducing fluid pressure in the drilling zone at the bit-to-bore bottom interface for flushing fluid to remove cuttings from said bore bottom and discharge through the other one of the dual stem passages,
• and anti-friction axial thrust bearing means operable between the packer means and drill bit body for transferring the weight of the hydrostatic head of fluid supported by the packer means into the drill bit body as said packer means is sliding down the well bore.

A packer weighted and pressure differential weight set tool for big hole well bore drilling through earth formation having a pore pressure opposed by hydrostatic fluid pressure, and including;

• a dual tube stem for coupled engagement with a dual drill pipe and operation through a large diameter well bore and with concentric passages isolating the pressured supply and discharge flow of circulating fluid therethrough, there being a well bore annulus surrounding the dual drill pipe, and a by-pass passage extending longitudinally through a peripheral wall of the dual tube stem and in open communication with fluid standing in the well bore annulus for downward flow therethrough,
• a drill bit shiftably carried by the stem with a splined coupling to the dual drill pipe for rotation of the bit and its formation engagement at a bit-to-bore bottom interface, and having a chamber in open communication with the by-pass,
• a packer means rotatably carried over the dual stem and responsive to shifting of the dual drill pipe downwardly thereto to seal with and set by weight of the dual drill pipe to slide down the well bore immediate to and above the drill bit and separating said well bore into a drilling zone and a hydrostatic head of fluid supported by the packer means,
• the drill bit being comprised of a large diameter body carrying cutters having coextensive bore bottom engagement, and carrying bit jets exhausting into the drilling zone, and means responsive to release of circulating fluid under pressure from one of the dual stem passages and comprised of a jet pump with an intake plenum open into and reducing fluid pressure in the drilling zone at the bit-to-bore bottom interface for flushing fluid to remove cuttings from said bore bottom and discharge through the other one of the dual stem passages,
• and anti-friction axial thrust bearing means operable between the packer means and drill bit body for transferring the weight of the hydrostatic head of fluid supported by the packer means into the drill bit body as said packer means is sliding down the well bore.