Analysis of pressure and pressure derivative without type-curve matching, 5. Horizontal well tests in naturally fractured reservoirs

Pressure transient analysis of horizontal wells penetrating naturally fractured reservoirs is a complicated and arduous task. That is, results from type-curve matching frequently suffer from nonuniqueness. Specialized plots (semilog or square root) are accurate but require individual plots for each identifiable flow regime. Subsequently, a new approach, known as direct synthesis, is proposed to overcome these problems. ethod couples the characteristic points and lines from a log-log plot of pressure and pressure derivative data with the exact, analytical solution, resulting in simple equations to solve for the desired reservoir parameters. Two key naturally fractured parameters, storage coefficient (ω) and interporosity flow parameter (λ) are sought from the technique. Parametric analysis in dimensionless space illustrates the behavior of ω and λ and provides the basis for newly developed expressions relating these parameters to field data. igations show the timing of the transition period with respect to horizontal well flow regimes to be critical in the determination of the naturally fractured parameters. Several alternatives are illustrated along with the associated procedures for analysis. As a result of this work, direct synthesis simplifies evaluation of pressure tests in horizontal wells penetrating naturally fractured reservoirs, eliminates the trial-and-error approach of type-curve matching and has the advantages of being easily verifiable and applicable to incomplete pressure data. Examples are given to demonstrate the technique and accuracy.