1. n. [Well Testing]
Families of the paired pressure change and its derivative computed from a model. The model is usually generated from an analytical solution of the diffusion equation with boundary conditions strategically defined to enable observation of theoretical trends in the pressure-transient response. The boundary conditions that can be defined near the well include constant or variable wellbore storage, limited entry (partial penetration), radial composite (damage skin due to permeability alteration), and a fracture extending the cylindrical wellbore to a extended plane. The borehole trajectory can be vertical, angled, or horizontal. The distant boundary conditions include a sealing or partially sealing planar boundary (fault), intersecting faults and rectangular boundaries (sealing or constant pressure). Further, the diffusion equation can be adjusted to accommodate reservoir heterogeneity in the form of dual porosity or layering. Finally, when generated with computer assistance, the type-curve family can account for superposition in time due to flow-rate variations before and even during the transient data acquisition. Originally, type-curve families were printed on specialized (usually log-log) coordinates with dimensionless parameters defining the x and y axes. Today, commercial software can generate the type-curve families on the computer screen, enabling a much more flexible and user-friendly analysis. Further, automated regression (usually least squares) permits an optimized match between the acquired data and a selected model. Type curves have greatly enriched the ability of interpreters to extract potential explanations for transient data trends that differ from the radial-flow behavior required for conventional semilog (Horner buildup) analysis.
