Optimisation of Perforation Techniques for Deep, HP Stringer Wells Located in the South of Oman

摘要

The intra-salt carbonate stringers represent a new oil province located in the south of Oman. To date, over 60 wells have been drilled in and around these reservoirs that in general are high pressure, deep and sour. Fluids within the fields range from a retrograde gas condensate to light oil. The stringers are geologically heterogeneous and commonly have low permeability. They are being developed in a phased manner that will involve miscible gas injection. This paper describes the strategy that was developed by Petroleum Development Oman to optimize perforation techniques. Perforations were required to by-pass the drilling induced impaired zone to enable effective stimulation of the reservoir and enhanced inflow performance. It was planned to perforate under-balanced, to apply the highest perforation phasing, to leave minimum gun debris in hole and to pull guns to surface to verify charges had fired and that the reservoir was amenable to future reservoir management activities. Simulations were carried out to predict penetration depths in the formation using newly developed in-house software and the results were compared with those from an industry-recognised package of a major Service Provider. In addition, the performance of commercial shaped charge perforators in full bore Harweel core was evaluated under pseudo downhole conditions. A series of tests with agreed procedures were carried out to compare perforation performance in actual core compared to that from industry recognized API RP19B Section 1 tests in cement. The paper will provide an assessment of the predictive capabilities of the software packages in light of these laboratory tests on Harweel core samples as well as a comparison of the actual perforation performance of the evaluated charges.