Pressure and Pressure Derivative Analysis without Type-Curve Matching for Triple Porosity Reservoirs

Abstract

Proposal Currently, the study of naturally fractured reservoirs represents a constant-growing technology because of the high amount of this type of behavior in many reservoirs worldwide. Therefore, for an efficient exploitation is necessary to adequately model them, so a more realistic fracture-matrix flow behavior can be obtained and identified. However, by inspecting some well pressure tests, anomalous slope changes during a matrix-controlled flow period are observed. This behavior does not follow the one described by a dual porosity model. Throughout the years, the pressure transient behavior of naturally fractured reservoirs has been extensively studied. Customary, dual porosity models have been widely utilized to describe the flow behavior taking place in the fracture/matrix system of naturally fractured reservoirs. However, a remarkable flaw of these models is their assumption of homogeneous matrix properties through the whole system. Recently, pseudosteady-state and transient-state triple porosity models have been introduced to take into account the existence of two domains in the matrix with different properties and one domain in the fracture net. There is no flow between the two matrix domains. On a semilog plot of pressure versus time, three parallel straight lines are observed when one domain has lower storativity and higher interporosity flow coefficient. Well pressure analysis for such systems was conducted using the conventional method or semilog type-curve matching. In this study, pressure derivative is applied to triple porosity reservoirs so their typical characteristics and fingerprints are reported. A technique to analyze pressure and pressure derivative data without using type-curve matching is also provided. This technique uses characteristics lines, characteristics points and features found on the pressure and pressure derivative plot to obtain analytical expressions for a practical estimation of permeability, skin and the fundamental parameters of such systems. The proposed methodology was successfully verified by its application to field data cases and simulated pressure data.