Stimulation of Packerless Wells for Enhanced Oil Recovery

Abstract

Four methods are described for inducing high differential pressures across perforations in wells traversing earth formations. Nitrogen, N 2 , or another inert gas is introduced into the well under pressure (via the annulus and/or the tubing), thereby lowering the fluid column and setting up conditions for lowering the hydrostatic pressure above the formation. The formation is then subjected to sudden exposure to the lowered hydrostatic pressure, either through use of a pressure-actuated surge valve or through sudden bleed-off of the N 2 gas. In both cases, a sudden release of well fluid pressure into the tubing string and/or annulus produces an implosion force and surges the perforations.

We claim: 
     
         1 . A method for the stimulation of packerless wells for enhanced oil recovery, the method comprising the steps of:
 (a) removing the sucker rod and pump if the well is a beam pumping well;   (b) applying nitrogen pressure to the tubing column and bleeding off any fluid that exits through the annulus;   (c) introducing a through-tubing surge valve into the well and setting it;   (d) gradually bleeding off the nitrogen; and   (e) surging the well when the pressure-actuated valve opens.