Decline curves (production vs time) were drawn and evaluated in an effort to determine the results of restimulation work performed in the Silurian Clinton Sand Formation, east central Ohio area.
A total of seventy-one oil wells were hydraulically fractured between 1972 and 1975. Of these wells, seven had to be plugged and abandoned due to problems resulting from the restimulation work.
The average increase production due to restimulation was 4,000 bbls per well.
This paper concerns itself with an evaluation of seventy-one oil wells restimulated by hydrofracing. The type of wells restimulated consisted of uncemented, shot wells, uncemented, fractured wells and cemented, fractured wells. The Oxford oil Company did this work between the years 1972 and 1975.
In this paper four case studies are used to evaluate the results by the different types of frac jobs. In selecting a particular well for case study examination, several factors must be considered. They are (1) volume of water injected; (2) type of completion; (3) type of initial stimulation; (4) past production history; and (5) geographic location. The wells in the case studies are classified according to the volume of water used in the restimulation.
Less than 1,000 bbls
1,000 bbls—2,500 bbls
2,500 bbls—5,000 bbls
5,000 bbls—10,000 bbls
Decline curves (production vs time) were drawn and analyzed to determine the ultimate recovery and economic limit of each reworked well.
For a successful rework, several factors must be completed.
Clean out wellbore
Protect casing against high pressure (if necessary)
Increase fracture size and length
Wellbore must be clean before tubing run