Abstract

Near-wellbore damage can cause severe reduction in effective permeability and production. A typical solution for near-wellbore damage removal involves wellbore cleanout and squeezing the treatment fluids into the formation through perforation with a conventional jetting-nozzle run on coiled tubing. However, there are numerous old wells in North Africa oil fields that have been completed with a slotted or preperforated liner and require an effective near-wellbore stimulation to remove the damage and restore the near-wellbore permeability and production.

A fluid-oscillation technique created by a fluidic-oscillator (FO) tool was applied successfully in conjunction with stimulation treatments, such as matrix acidizing, salt, and asphaltene treatment. The results from using this tool instead of the conventional jetting tool were significant. The post-stimulation production improved over previous stimulation gains when performed on the same wells. Recently, the fluid-oscillation technique was also applied effectively for near-wellbore stimulation treatments in horizontal wells without requiring matrix squeezing. Results from using this technique have been promising and have simplified the near-wellbore damage treatments. Several wells in this field were treated using this near-wellbore stimulation treatment, resulting in significant production gains. Using the matrix and near-wellbore stimulation in conjunction with the FO tool has become the preferred method to enhance the effectiveness of treatments.

The FO tool creates pressure waves within the wellbore and formation fluids that break up near-wellbore damage to restore and enhance the permeability of the near-wellbore area. As the damage is removed and the original permeability is restored, the pressure waves can penetrate deeper into the formation matrix for more complete damage removal. The direct comparative results from using conventional jetting nozzles and FO tools for several wells in a North Africa oil field are quite evident and are presented in this paper. This technique should help other operators enhance the effectiveness of near-wellbore treatments to achieve similar benefits.

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