Abstract
Perforations provide the communication between wellbore and formation resulting in a communication path both for injected and produced fluids from the reservoir. Many perforation parameters such as shot phasing, charges size, shot density, type of gun and length of interval play an important role in the correct execution of a fracturing job. Those parameters have to be engineered to guarantee easy formation breakdown, minimize near wellbore restrictions (or tortuosity) and be big enough to prevent proppant bridging while considering fracture treatment size, proppant concentration, proppant size and treatment flow rate. Ideal fracture initiation perforations would create a minimum injection pressure initiating a single fracture (not for shale gas reservoirs) and generate a fracture with minimum tortuosity at an achievable fracture initiation pressure. Best perforation practices are important during the decisional and designing phase but have to be confirmed by field experience even in well known reservoir where formation heterogenity, well deviation, local stress anomalies, cement bound and many other factors can result in unexpected behaviors that could compromise the success of the stimulation treatment.
In the following paper a briefly description of perforating theories and different field experiences are reported showing test results executed for a better perforation strategy. Unexpected deviations both from theory recommendations and from field analogies were analyzed as well as successful and unsuccessful remedial solutions in cases of injectivity issues.
