Perforation is the process of creating holes through casing, cement, and into the formation to establish communication between the reservoir and wellbore. Shaped charge explosives generate high-velocity metal jets that penetrate these barriers, creating flow paths for hydrocarbon production.
Shaped Charge Types
Deep penetrating charges achieve 1-30+ inches formation penetration with 10-12mm entrance holes. These use 40-60° conical liners and are preferred for low-permeability formations where reservoir contact is critical.
Big hole charges create entrance holes up to 30mm (~1 inch) with shorter penetration, using 70-90° parabolic liners. These are suited for high-permeability formations and gravel pack completions.
Shot Density Optimization
Shot density significantly impacts productivity. Research shows 4 shots per foot (SPF) with 90° phasing equals openhole productivity. Industry recommendations specify 8 SPF minimum for homogeneous formations and 12-16 SPF for weak formations with sand production risk (SPE 15029).
Perforation Damage
The high-energy jet creates a crushed zone around each tunnel where permeability can be reduced to just 5% of original formation permeability. Studies using downhole video recording show approximately 50% of perforations are actually open to flow (SPE 15029). API RP 19B provides standardized testing protocols.
Why It Matters
Perforation design directly controls well productivity. Poor perforation strategies create permanent skin damage that restricts flow throughout the well's producing life.