Integrated Core Analysis for Fractured Reservoirs: Quantification of the Storage and Flow Capacity of Matrix, Vugs, and Fractures

摘要

Answering general questions such as "Where is the oil?," "How much oil is there?," and "Can we extract it?" is a challenging task for a large fractured field in southern Italy. Various studies were conducted to gain more insight into the way oil is distributed in the rock and the producibility of the different structures observable on the cores (matrix, vugs, and fissures). These included the cryogenic scanning electron microscope (CryoSEM) and gas chromatography (GC)-pyrolysis, pore-size-distribution measurements, SEM analysis on thin sections, and a number of nonconventional techniques that were designed specifically for that type of rock. Nuclear magnetic resonance (NMR) imaging was conducted on several whole core samples and the different porosity contributions (microporosity, vugs, and fissures) defined on a 3D basis. An analytical approach based on the percolation theory was used to separate the permeability contributions and define the conditions under which vugs and fissures may form a conducting system. The inputs were distributions of pore throats, throat length, coordination number, fissure orientation, and porosities. Wettability is a key parameter for production estimates, and we used a technique for measuring it in both microporosity and fissures, which makes use of dielectric constant measurements. All the data contributed to our current understanding of the reservoir.