In Russia many operators are challenged with the goal to increase production on oil and gas fields by drilling new wells or by using enhanced completion designs in the old ones. The latter is significantly less expensive, hence is preferable. The transition from completion to production on new and workover wells requires optimal clean up and the removal of the perforation damage to achieve maximum productivity.
Perforating in the low formation pressure West Salym field has historically been performed overbalanced using wireline or with static underbalance using tubing conveyed perforating (TCP) with immediate well kill to remove guns. These perforating techniques, do not provide sufficient cleanup of the perforation tunnels and leave out significant perforation skin. A novel tubing conveyed perforating (TCP) technique using the dynamic underbalance effect combined with an afterperforation inflow testing was applied in the West Salym field. The goal was to achieve maximum productivity and to record the pressure transient. Deep penetrating charges were also used to bypass near wellbore damage and maximize potential results.
A customized TCP test string was designed for 7 in. (178mm) casing that had two sets of gauges installed at different depths, and a production valve for the in-flow surge. The test string allowed to conduct a perforation inflow test to estimate post perforation skin, productive zone permeability and reservoir pressure.
The operations were performed on 10 wells (5 workover wells and 5 new wells). Inflow pressure data on 5 wells, which allowed us to make conclusive estimates of skin, showed negative values. Improved productivity exceeded expected values by 10% on average.
Dynamic underbalanced perforating has enabled us to obtain clean perforation tunnels and resulted in an average 50% production increase in comparison to the average field production.