Fractures can be first-order controls on fluid flow in hydrocarbon reservoirs. Understanding the characteristics of fractures such as their aperture, density, distribution, conductivity, connectivity, etc, is key for reservoir engineering and production analysis. Well testing plays a key role in the the characterisation of fractured reservoirs, especially. New advances in the Pressure Transient Analysis (PTA) have enabled the interpretation of production data in a way where the resulting geological scenarios are in better agreement with fracture patterns observed in outcrop analogues. Traditionally, Drill Stem Test (DST) data have been the primay source of information for well testing. However, we hypothesise that wireline conveyed tools designed for Interval Pressure Transient Testing (IPTT) could yield a more throrough description of the near-wellbore heterogeneities, including fractures. Hence, we investigate the applicability of IPTT for characterising fractured reservoirs using detailed numerical simulations models with accurate wellbore representation to generate synthetic IPTT responses that can obtained through a next-generation wireline testing tool called SATURN. We particularly focus on cases where fractures are present in the near-wellbore region but do not intersect the wellbore. The study included parameters such as fracture densities and conductivities, distance between fractures and wellbore and the vertical extension of the fractures across geological beds. The impact of the different fracture scenarios on the pressure transient tests was recorded as characteristic signatures on diagnostic plots (pressure derivative curves). We have called these curves "IPTT-Geotypes"; they can be used to assist the interpretation process of IPTT responses. To the best of our knowledge, this is the first time pressure derivative type curves for IPTT in fractured reservoirs are presented in the literature. A field example of an IPTT case was analysed using the concept of geological well testing. We integrated the information from petrophysical logs and the IPTT-Geotypes to assist the calibration of a reservoir model developed to represent the geological setting of the tested reservoir interval. The results provided a sound interpretation of the reservoir geology and quantitative estimation of the matrix and fracture parameters.@en

The estimation of permeabilities is a key objective of a well test. In Naturally Fractured Reservoirs (NFRs), this is particularly important because the permeability derived from pressure transient analysis can yield quantitatve information about the characteristics of both, the fractured and matrix system. In this study, we present new insights that enable us to understand the nature of the permeability values obtained from well testing in NFRs. We considered cases that are little explored in the literature like the impact of varying apertures along the fracture planes or disconnected fractures on the effective permeability of the fracture-matrix system. We showed that if only 5% of the fracture connections are closed, the fracture network no longer percolates, that is the fractures begin to act as isolated features and the effective total permeability of the fracture-matrix system is reduced significantly. We propose a way forward for distinguishing between connected and unconnected fracture networks, which uses the ratio of well test-derived permeability and the average core permeability. We suggest that if this ratio is larger than 10, the fracture network is likely to be connected while values below 10 likely correspond to either disconnected, poorly connected or very low-conductivity fracture networks.@en