Reservoir characterization: Evaluation for the channel deposits sequence – Upper part using scanning electron microscope (SEM) and mercury injection (MICP): Case of tight reservoirs (North Sea)

Abstract

Textural and structural facies analysis in the Buchan Field (North Sea) has provided an important potential database for the assessment of parameters controlling the reservoir quality. Nowadays, significant research effort in oilfield reservoirs focused on pore-scale petrophysics, grain distribution, pore geometry and distribution besides the fluid flow circulation. The investigation, we are conducting, is aimed to determine the reservoir type, based on qualitative and quantitative evaluation. This study deals with the upper part of the defined upward channel sequence in the Buchan oilfield (North Sea). In this view, determination of pore geometry and pore aperture sizes which are related to grain size, sorting and packing becomes essential. The pore geometry size and distribution are present but at a microscopical-scale. They constitute the main petrophysical properties of the studied reservoir, since these selected parts of the reservoirs can be qualified as tight or unconventional material type. These investigated deposits are characterized by very low permeability with the presence of reduced pores leading to the probable existence of important interfacial tension forces as well as high capillary pressure. These properties are directly affecting fluid circulation by trapping considerable amount of residual oil leading to a lesser reservoir recovery. In the case study, examination and assessment of this type of reservoirs and their characteristics, responsible for the H/C accumulations and circulation can only be accomplished by the use of very refined equipments such as the Micro-CT or the SEM. Support for this investigation can be credited to the Autopore use.Accordingly, this paper presents the results of a combination of reservoir characteristics determination, the use of the SEM. petrographical investigation for the purpose of detailed examination as well as the MICP application for the physical properties appraisal. The overall will lead to better understanding of the studied section coupled to other reservoir attributes identification.