Abstract
Perforating multiple zones in a single deep-water well, where the zonal pressures between reservoirs differ significantly, at times in excess of 2000 psi, presents substantial challenges in developing and maintaining sufficient dynamic underbalance for effective perforation cleanout across the zones. The principal objective of this study is the development of recommended design practices for perforating deep-water, extended reach, step-out wells that present such challenges.
Design practices were evaluated through the perforation strategy optimization of four multi-zone, deep-water wells situated in the Jubilee Field, off the coast of Ghana. The sensitivity of dynamic underbalance generation and perforation cleanout performance to changes in readily modifiable gun system characteristics was studied. This includes charge loading, string positioning and management of gun free volume. Multi-physics simulation was used to resolve the fluid and structural dynamic responses of the system during perforation. The applied methodology provides enhanced visualization and resolution of the system-wide dynamics during this highly energetic event. It accounts for the complexity of the material interactions and the resulting 3-dimensional loading on the string from charge detonation, casing fragmentation and high-speed fluid flows [Glenn, 2014]. To build confidence in this analytical approach, pressure data recorded downhole was used to close the loop on the process and calibrate the simulations against their respective job histories.
