A ground drilling device comprising a housing, a lengthwise movable drilling head tip arranged in the housing, and a bearing for supporting the drilling head tip in the housing during its lengthwise movement.

A separator for separating gas from a fluid mixture in a production stream of a well. The separator includes an outer tube and an inner tube positioned concentrically with the outer tube. The production stream is directed through the outer tube and into a space between a well casing of the well and the outer tube where gas in the production stream can separate from fluid in the production stream. The separated fluid is then directed through the inner tube to a pump.

Provided is a two-piston hydraulic striking device that has stable operatively. This two-piston hydraulic striking device includes two striking mechanisms for striking one transfer member. Each striking mechanism has a pressure receiving area ratio between the front and rear of a piston thereof set in such a way that the two striking mechanisms have the same cycle time.

Provided is a two-piston hydraulic striking device that has stable operatively. This two-piston hydraulic striking device includes two striking mechanisms for striking one transfer member. Each striking mechanism has a pressure receiving area ratio between the front and rear of a piston thereof set in such a way that the two striking mechanisms have the same cycle time.

A method for maintaining a penetration rate of a drilling operation, where the drilling operation is carried out by a drilling rig having a hammer drill apparatus. A reference penetration rate for the hammer drill bit is chosen. A starting depth of cut is computed from the reference penetration rate, the measured hammer frequency, and the drill bit parameters. The system measures the actual penetration rate of the drill bit and computes an actual depth of cut. From the actual depth of cut a target bit rotation speed is computed. The target rotation speed is compared to the actual rotation speed, and the rotation speed is adjusted up or down to set the bit rotation speed at a value that will maintain the target rotation speed, notwithstanding changes in hammer frequency or ground conditions.

A method for maintaining a penetration rate of a drilling operation, where the drilling operation is carried out by a drilling rig having a hammer drill apparatus. A reference penetration rate for the hammer drill bit is chosen. A starting depth of cut is computed from the reference penetration rate, the measured hammer frequency, and the drill bit parameters. The system measures the actual penetration rate of the drill bit and computes an actual depth of cut. From the actual depth of cut a target bit rotation speed is computed. The target rotation speed is compared to the actual rotation speed, and the rotation speed is adjusted up or down to set the bit rotation speed at a value that will maintain the target rotation speed, notwithstanding changes in hammer frequency or ground conditions.

A hydraulic percussion device comprising a piston mounted for reciprocal motion within a cylinder to impact a percussion bit and a control valve to control reciprocation of the piston. A valve pilot line is arranged to switch the control valve based on the position of the piston within the cylinder, wherein the valve pilot line is alternately connected, by the reciprocal movement of the piston, to high and low pressure lines (P, T) via an undercut in the piston. The undercut is located at a portion of the piston having a diameter less than the maximum sealing diameter of the piston.

A hydraulic percussion device comprising a piston mounted for reciprocal motion within a cylinder to impact a percussion bit and a control valve to control reciprocation of the piston. A valve pilot line is arranged to switch the control valve based on the position of the piston within the cylinder, wherein the valve pilot line is alternately connected, by the reciprocal movement of the piston, to high and low pressure lines (P, T) via an undercut in the piston. The undercut is located at a portion of the piston having a diameter less than the maximum sealing diameter of the piston.

A drilling apparatus for drilling a lateral bore to main bore, comprises a casing in the main bore, having at least one window, at least one lateral tube, including a bit or other soil penetrator, the lateral tube which engages with an aperture in the casing, the outer diameter of lateral tube flush with aperture, such that the lateral tube is forced through the casing aperture into the formation when a sufficient pressure differential between the inside of the casing and the outside of the casing and a plurality of packers disposed at intervals along the outside of the casing, capable of sealing the annulus to the passage of fluids.

A drilling apparatus for drilling a lateral bore to main bore, comprises a casing in the main bore, having at least one window, at least one lateral tube, including a bit or other soil penetrator, the lateral tube which engages with an aperture in the casing, the outer diameter of lateral tube flush with aperture, such that the lateral tube is forced through the casing aperture into the formation when a sufficient pressure differential between the inside of the casing and the outside of the casing and a plurality of packers disposed at intervals along the outside of the casing, capable of sealing the annulus to the passage of fluids.