Crude oil recovery system

A crude oil recovery system installed in a borehole in an earth formation that passes through an oil production zone, said recovery system comprising:

• a length of production tubing positioned in the borehole;
• a downhole pump carried by the production tubing and positioned in the borehole, said pump comprising a pump inlet and a pump outlet, said pump outlet in fluid communication with a pump column defined by the production tubing;
• an extension extending downwardly from the pump inlet, said extension being free of openings between the pump inlet and the extension inlet such that oil pumped by the downhole pump is drawn upwardly from the extension inlet to the pump inlet before entering the pump;
• a reciprocating rod disposed in the pump column and coupled with the downhole pump to power the downhole pump;
• said borehole comprising a borehole annulus extending around the downhole pump, wherein the borehole annulus comprises a quantity of oil of density D gm/cm3 and a gas above the oil of pressure P gm/cm2, wherein the extension inlet is vertically spaced below the pump outlet by a minimum vertical distance H cm, and wherein H is greater than P/D such that the downhole pump is prevented by the extension from pumping oil at a rate sufficient to draw down the oil in the borehole annulus to a level that permits the gas to enter the extension inlet, thereby preventing a substantial volume of the gas from flowing into the pump inlet and the pump column.

A crude oil recovery system installed in a borehole in an earth formation that passes through an oil production zone, said recovery system comprising:

• a length of production tubing positioned in the borehole;
• a downhole pump carried by the production tubing and positioned in the borehole, said pump comprising a pump inlet and a pump outlet, said pump outlet in fluid communication with a pump column defined by the production tubing;
• an extension extending downwardly from the pump inlet, said extension comprising an extension inlet and being free of openings between the pump inlet and the extension inlet such that oil pumped by the downhole pump is drawn upwardly from the extension inlet to the pump inlet before entering the pump;
• said extension inlet positioned entirely below a level L1;
• said downhole pump operative to draw down the oil in the annulus to a lowest level L2, wherein L2 is above L1 such that the downhole pump is prevented by the extension from pumping oil at a rate sufficient to permit a substantial volume of gas to enter the extension inlet, thereby preventing a substantial volume of gas from flowing into the pump inlet and the pump column.