Tight Reservoir: Characterization, Modeling, and Development Feasibility

Abstract

The distribution of reservoir quality in tight carbonates depends primarily upon how diagenetic processes have modified the rock microstructure, leading to significant heterogeneity and anisotropy. The size and connectivity of the pore network may be enhanced by dissolution or reduced by cementation and compaction. Consequently, a clear understanding of the diagenetic process that responsible for the reservoir tightness would offer vital assurance on the spatial property distribution and future field development plan. In this paper, we have examined the factors which affect the distribution of porosity, permeability and reservoir quality in the Thamama Group, which is a prospective low permeability carbonate reservoir rock in Onshore Abu Dhabi. The dataset includes regional stratigraphy, well logs and core material from a number of wells, a suite of laboratory petrophysical measurements, seismic attributes, geomechanics, fracture study, and production history. Dataset analysis and interpretation suggested that the reservoir was deposited in shallow to deep marine low energy environment which led to deposition of fine to very fine grains (lime-mud supported) types of sediments. This, in turn, would produce poor reservoirs during compaction and finally leads to tightness. Because of the low permeability nature of this tight reservoir, it is quite challenging to obtain their complete reservoir properties and dynamic behavior. As in many other tight reservoir projects, a considerable area of the reservoir must be effectively stimulated during the hydraulic fracturing process to achieve economic productivity. In addition, development of tight reservoirs often faces challenges, for example, low initial production rates and high declining rate. This paper aims to frame all possible optimum development practices for tight reservoir in the studied field that should be considered for future development plan. We also investigated the application of new technology to enhance the poor oil recovery within the pool including horizontal drilling and multi-stage fracture completion technology. Furthermore, this paper also discusses well orientation relative to the far field principal stresses, hydraulic fractures treatment, fracture fluid selection, and nano-technology application. This, in turn, would provide valuable information on how to optimally develop this previously considered marginal and uneconomic reservoir.