The Tchendo oil field, located 18 miles off the coast of the Republic of Congo has been operated since 1991, by Total E&P Congo in approximately 100 meters of water.

The wells are deviated (more than 60 degree), completed with production casing as large as 9 5/8", and partially to extensively perforated, with poor to unknown cement quality.

The wells are produced by electrical submersible pumps.

One of the three reservoirs, the Sénonien reservoir, is an intercalation of metric carbonate layers with thicker (20 to 30 meters) but poorer quality sandstones. (0.1 to 10 mD). It is shallow (450 mVSS) and depleted (0.37 psi/ft).

Various attempts to enhance productivity were tested since initial production, including selective or extensive perforation, acid treatments on carbonate layers, and one open hole horizontal well.

However, a large part of the original oil in place still remains in the reservoir.

Therefore, it was decided to evaluate the potential of hydraulic fracturing stimulation treatments to rejuvenate the existing wells.

The well characteristics made conventional methods of hydraulic fracturing either cost prohibitive or impossible.

A first test of the hydrajet propped fracturing technique was performed in 2008, followed in 2010 by two other pilot treatments.

This paper details the lessons learned in using this innovative technique to stimulate the three wells and demonstrates limitations of the technique associated with the existing wellbore conditions. This paper will serve as a guide for revitalizing the Tchendo field and possibly other mature oil fields with low to moderate permeability.

You can access this article if you purchase or spend a download.