SUBSURFACE FORMATION PLUGGING

• US 3,814,187 A
• Filed: 05/14/1973
• Issued: 06/04/1974
• Est. Priority Date: 05/14/1973
• Status: Expired due to Term

• Current Assignee: George B. Holman
• Original Assignee: George B. Holman
• Inventors: Holman, George B.
• Primary Examiner(s): Brown, David H.
• Application Number:
  US05/360,222
• Time in Patent Office: 386 Days
• Field of Search: 166/281,292,271
• US Class Current: 166/281
• CPC Class Codes: E21B 33/138 Plastering the borehole wall; Injecting into the formation
• CPC Class Codes: E21B 43/261 Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking the formation

Abstract

This invention concerns a method of selectively plugging fractures in an underground formation without permanently plugging the '"'"''"'"''"'"''"'"'secondary porosity,'"'"''"'"''"'"''"'"' e.g., vugs, etc., which may be in communication with the wellbore. A slurry of finely divided limestone is first pumped through the well to fill the secondary porosity. Then a second slurry of finely divided solids, such as flyash, which is not soluble in most acids, is injected into the well to plug the interwell fracture system. Thereafter, to aid injectivity, the well is given a low pressure acid treatment to remove the limestone from the secondary porosity.

Claims

2. A method as defined in claim 1 in which the slurry of limestone particles is injected at a pressure in the range of the fracture opening pressure to below the pressure required to create a fracture therein and in which the acid flush is applied at a pressure less than the fracture opening pressure.

3. A method as defined in claim 1 in which the finely divided particles of step b) are flyash.

4. A method as defined in claim 3 in which the flyash slurry includes water as a carrier fluid, containing about 18 to 26 lbs of flyash per gallon of water.