Method for making gravel filters in oil wells

Abstract

A method for making gravel filters in oil well bores by ascertaining the location of a producing formation adjacent to a cemented casing in a well bore. Water formation may exist between oil formations. The next step involves cutting a portion of the casing adjacent to the producing formation. A section mill equipment is used to cut, continuously, the cemented casing. The bore adjacent to the producing formation is enlarged. An underreamer is utilized to remove the surrounding cemented space and enlarge the oil well diameter. Then a sufficient amount of gravel is deposited in the enlarged portion of the bore to create an effective filter for a producing tube with a screen at its distal end positioned adjacent to the cemented bottom of the well bore.

1 . A method for making gravel filters in oil wells having a casing coaxially mounted within a well bore and defining a space between said bore and said casing that is cemented to keep said casing in place, comprising the steps of:
 A) ascertaining the location, at the cemented casing in an oil well bore, adjacent to a producing formation where a gravel filter is to be built;   B) cutting a continuous portion of said casing adjacent to said producing formation;   C) enlarging said bore's diameter where said portion was cut to create an enlarged annular space by removing the cemented space adjacent to said portion and beyond the bore's initial diameter;   D) lowering and installing a producing tube having a distal end with an intake screen and being coaxially disposed within said casing and positioning said intake screen substantially adjacent to said casing portion which was removed;   E) depositing an effective amount of gravel in said enlarged annular space; and   F) sealing said space between said bore and said casing at a predetermined distance above said portion.   
     
     
         2 . The method set forth in  claim 1  wherein the steps of cutting said casing and enlarging said bore's diameter is performed with a section mill and an underreamer. 
     
     
         3 . The method set forth in  claim 2  wherein the gravel is selected for predetermined diameters in accordance with the characteristics of said producing formation.