Patent ID: 6347674
Filing Date: 2002-02-19
Classification: E21B

Abstract:
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.