초록 ▼

A downhole drilling tractor for moving within a borehole comprises a tractor body, two packerfeet, two aft propulsion cylinders, and two forward propulsion cylinders. The body comprises aft and forward shafts and a central control assembly. The packerfeet and propulsion cylinders are slidably engage

A downhole drilling tractor for moving within a borehole comprises a tractor body, two packerfeet, two aft propulsion cylinders, and two forward propulsion cylinders. The body comprises aft and forward shafts and a central control assembly. The packerfeet and propulsion cylinders are slidably engaged with the tractor body. Drilling fluid can be delivered to the packerfeet to cause the packerfeet to grip onto the borehole wall. Drilling fluid can be delivered to the propulsion cylinders to selectively provide downhole or uphole hydraulic thrust to the tractor body. The tractor receives drilling fluid from a drill string extending to the surface. A system of spool valves in the control assembly controls the distribution of drilling fluid to the packerfeet and cylinders. The valve positions are controlled by motors. A programmable electronic logic component on the tractor receives control signals from the surface and feedback signals from various sensors on the tool. The feedback signals may include pressure, position, and load signals. The logic component also generates and transmits command signals to the motors, to electronically sequence the valves. Advantageously, the logic component operates according to a control algorithm for intelligently sequencing the valves to control the speed, thrust, and direction of the tractor.

대표청구항 ▼

1. A tractor for moving within a borehole, comprising:a tractor body sized and shaped to move within a borehole; a valve on said tractor body, said valve positioned along a flowpath between a source of fluid and a thrust-receiving portion of said body, said valve comprising: a fluid port; and a flow

1. A tractor for moving within a borehole, comprising:a tractor body sized and shaped to move within a borehole; a valve on said tractor body, said valve positioned along a flowpath between a source of fluid and a thrust-receiving portion of said body, said valve comprising: a fluid port; and a flow restrictor having a first position in which said restrictor completely blocks fluid flow through said fluid port, a range of second positions in which said restrictor permits a first level of fluid flow through said fluid port, a third position in which said restrictor permits a second level of fluid flow through said fluid port, said second level of fluid flow being greater than said first level of fluid flow; a motor on said tractor body; and a coupler connecting said motor and said flow restrictor, such that movement of said motor causes said restrictor to move between said first position, said range of second positions, and said third position, said restrictor being movable by said motor such that the net thrust received by said thrust receiving portion can be altered by 100 pounds within 0.5 seconds.