Patent ID: 6675909
Filing Date: 2004-01-13
Classification: E21B

Abstract:
A bidirectional hydraulic jar comprising:an outer assembly comprising: a tubular body with first and second ends, wherein the tubular body defines an inner wall, and wherein the first end comprises a connecting portion; a first impact surface on the tubular body to transmit force in a first direction; and a second impact surface on the tubular body longitudinally spaced from the first impact surface to transmit force in a second direction opposite the first direction; an inner assembly comprising: an elongate body having a portion telescopically receivable within the outer assembly, the elongate body defining an outer wall and having first and second ends, and wherein the second end comprises a connecting portion; a first impact surface on the elongate body adapted to engage the first impact surface on the tubular body of the outer assembly; a second impact surface on the elongate body longitudinally spaced a distance from the second impact surface on the elongate body and adapted to engage the second impact surface on the tubular body of the outer assembly; an annular elongate fluid chamber formed between the outer wall of the elongate body of the inner assembly and the inner wall of the tubular body of the outer assembly, the fluid chamber comprising first and second portions and a restrictor portion therebetween, the restrictor portion having a smaller radial dimension than the first and second portions; and a valve assembly supported in the fluid chamber and fixed to one of the outer wall of the elongate body of the inner assembly and the inner wall of the tubular body of the outer assembly, wherein the valve assembly is sized for reciprocal movement in the restrictor portion, and is adapted to obstruct fluid flow through the restrictor portion except for a bleed passage therethrough to create a delay as the valve assembly moves through the restrictor portion and accelerated movement as the valve assembly exits the restrictor portion into the first and second portions of the fluid chamber, and wherein the valve assembly comprises: a first valve ring comprising first and second ends with a body therebetween, the first end defining a metering face; a second valve ring comprising first and second ends with a body therebetween, the first end defining a metering face adjacent the metering face of the first ring and forming therewith a metering space between the first and second valve rings, the metering space forming part of the bleed passage; wherein at least one of the first and second valve rings is sized for sealing engagement with the restrictor passage and comprises a pass-though opening continuous with the metering space and forming part of the bleed passage; and wherein the size of the metering space is adjustable by moving at least one of the first and second valve rings relative to the other to vary the size of the bleed passage; whereby movement of a selected one of the outer assembly and inner assembly relative to the other one in a first direction causes jarring impacts between the first impact surfaces of the outer and inner assemblies to thrust the jar in a first direction, and movement of the selected one of the outer assembly and inner assembly relative to the other one in a second direction causes jarring impacts between the second impact surfaces of the outer and inner assemblies to thrust the jar in a second direction; and whereby adjusting the size of the metering space between the first and second valve rings varies the force and speed of the jarring impacts.