Enabling Synthetic PLT Through Integration of Brittleness Indicator and Porosity-Independent Permeability to Improve Understanding of Expected Flow Profile in an Unconventional Reservoir: Case Study from Kuwait

Abstract

Mauddud carbonates in the Bahrah Field of Kuwait, with their low permeability, are often considered as unconventional reservoirs, which require multi-stage hydraulic fracturing stimulation. Optimal stage distribution is one of the key elements in this type of completion design. This paper presents the forecasting methodology for estimating the production performance of each stage which can later help to optimize stage placement in long horizontal sections. High-resolution micro-resistivity imaging and an azimuthal sonic tool, in combination with conventional triple-combo logs and formation pressure testing, were run in a 6.125-in. section to help develop an effective and sustainable production plan, based on the petrophysical and geomechanical properties of the heterogeneous tight carbonate reservoir. The use of image data helped to evaluate the permeability distribution close to the borehole wall more accurately than conventional porosity-based permeability relationships, which showed marginal correlation with actual permeability. Sonic and density logs helped to estimate rock mechanical properties. Mobilities derived from the formation pressure build-up curve were used to normalize permeability indicators. The porosity-independent image permeability indicator, which was developed specifically for carbonate formations and is based on the electrical conductivity distribution around the circumference of the borehole, showed fair correlation with the brittleness indicator. The brittleness indicator, on the other hand, exhibited a high degree of correlation in all completion stages with the production logging (PLT) data. The good correlation of production information with the brittleness indicator, derived from Poisson's ratio and Young's modulus, is in line with the main inputs for hydraulic fracture design, which use these mechanical properties. Both brittleness and image permeability indicators were used to improve well placement in the sweet part of the reservoir and played an important role in the success of this complex process. This process also enables the potential for synthetic PLT derivation, which can help to improve understanding of the expected flow profiles from different frac stages. The case study presented in this paper demonstrates the promising benefits of integration of open-hole logs to derive synthetic PLT data that can improve completion design and enhance production forecasting in an unconventional reservoir. The availability of several years of production and formation pressure dynamics data also helped to extend the application of the methodology to forecast future production stability for the field.