Aproximación práctica para estimar la presión promedia del yacimiento de pruebas multitasas en pozos horizontales largos

If good pressure-time well data during pseudosteady-state flow are available, then a simple material balance that accounts for rate history would give us the value of average reservoir pressure. On the other hand, pressure buildup analysis is the most popular methodology to obtain this value. However, pressure buildup testing involves a negative economic impact caused by shutting-in the well during the test. Moreover, either in low permeability or very large size reservoirs, a test conducted in a horizontal well hardly reaches the pseudorradial flow regime. Since buildup tests are the most particular case of multi-rate tests, therefore, they can also be used for estimation of the average reservoir pressure. Conventional methods for determination of the average reservoir pressure may also be extended to multi-rate tests once the test time is converted to equivalent time by using the superposition principle.In this paper, an easy and practical approximation for determining average reservoir pressure from a multi-rate test run in a long horizontal is presented. The methodology which is applied to anisotropic reservoirs uses a normalized pressure and pressure derivative point read at any arbitrary point on the pseudosteady-state flow regime. This point is then used into a simple equation which readily provides the average reservoir pressure value. Obviously, another limitation appears when the pressure derivative is so noisy.The method has been verified by comparing the results from analyzing several synthetic tests that were obtained from a commercial well testing software. The estimated values of average reservoir pressure by using the proposed methodology agree quite well with those estimated from the commercial software. This methodology is useful when a commercial software is unavailable. Si se dispone de buenos datos de presión-tiempo durante estado pseudoestable, es posible determinar la presión promedia de un yacimiento utilizando simplemente balance de materia que considere la historia de caudales. De otro lado, la metodología más usada para este fin es el uso de pruebas de restauración de presión. Éstas, por su parte, introducen un impacto económico negativo producto del cierre del pozo durante la prueba. Aunado a ello, es incluso difícil el desarrollo del régimen de flujo pseudorradial durante una prueba de presión en un pozo horizontal, cuando existen formaciones de poca permeabilidad o yacimientos muy grandes. Puesto que las pruebas de restauració