Tool and method for gravel packing a well

Claim 1

In a tool for use in gravel packing an annulus in a well casing between the casing and a liner with upper and lower sand screen sections therein separated by an annular seal acting between the inside of the liner and the outside of a wash pipe which is telescoped into the liner for returning liquid from a gravel slurry pumped into the annulus and filtered at least initially through the lower sand screen before entering the wash pipe for return to the head of the well, wherein the improvement in said tool comprises, a port formed through the wash pipe above the seal, a differential area piston sleeve telescoped onto said wash pipe and being movable from a first position closing said port and toward a second position opening said port in response to a differential pressure of a preselected magnitude existing between the inside and outside of said wash pipe, and means for urging said sleeve into its closing position when said pressures inside and outside wash pipe approach equality.

Claim 8

A method for gravel packing an annulus in a well casing between the casing and a sand screen liner having upper and lower sand screen sections sealed from each other and a wash pipe extending therebetween for returning liquid from a gravel slurry pumped into the well, said method comprising: pumping a gravel slurry down the well and into the annulus between the well casing and the sand screen liner, initially filtering the slurry through the lower sand screen section to cause the gravel therein to collect in the annulus, directing the liquid filtered from the slurry into the wash pipe from beneath the seal between the upper and lower sand screen sections and back to the top of the well, thereafter opening communication from the annulus into said wash pipe through the upper sand screen section automatically when the pressure drop across the gravel collected in the annulus exceeds a preselected magnitude so as to filter the slurry primarily through the upper sand screen section, and directing the liquid filtered through the upper sand screen section into and through the wash pipe above the seal between the sand screen sections and back toward the head of the well.

Claim 9

A method for gravel packing an annulus in a well casing between the casing and a sand screen liner having upper and lower sand screen sections sealed from each other and a wash pipe extending therebetween for returning liquid from a gravel slurry pumped into the well, said method comprising: pumping a gravel slurry down the well and into the annulus between the well casing and the sand screen liner, initially filtering the slurry through the lower sand screen section to cause the gravel therein to collect in the annulus, directing the liquid filtered from the slurry into the wash pipe from beneath the seal between the upper and lower sand screen sections and back to the top of the well, thereafter opening communication from the annulus into said wash pipe through the upper sand screen section automatically when the pressure drop across the gravel collected in the annulus exceeds a preselected magnitude so as to filter the slurry primarily through the upper sand screen section, and directing the liquid filtered through the upper sand screen section into and through the wash pipe above the seal between the sand screen sections and back toward the head of the well.