Control Over the Fracture in Carbonate Reservoirs as a Result of an Integrated Digital Stimulation Approach to Core Testing and Modeling

Abstract

The oilfield industry is rapidly changing towards reduced CO2 emissions and sustainability. Although hydrocarbons are expected to remain the leading source for global energy, costs to produce them may become prohibitive unless new breakthrough in technology is established. Fortunately, the digital revolution in the IT industry continues at an accelerating pace. A digital stimulation approach for tight formations is presented, using the achievements of one industry to solve the challenges of another. The fracture hydrodynamics and in-situ kinetics model is incorporated in the advanced simulator together with the detailed multiphysics models based on acid systems digitization, including rheology and fluid- carbonate interactions data obtained from the laboratory experiments. Digitization of fluid-rock interaction and fluid leakoff was performed using a coreflooding setup that allowed pumping concentrated acids in core samples at high-pressure/high-temperature (HP/HT) conditions. Varying the testing parameters across a broad range allowed refining the model coefficients in the simulator to obtain high accuracy in the predicted results. The digital slot concept was used to validate physical models in an iterative experimental approach. The software proved efficient at providing validation of multiphysics models used together with advanced slurry transport in the simulator. The fine computational grid allowed accurate predictions of the fracture geometry, etched width, and channel conductivity, resulting in realistic well productivity anticipations. Since multiple fluid systems of the acid stimulation portfolio were digitized and incorporated into the simulator, it was possible to optimize complex acid fracturing designs in the real field operations that included retarded single-phase and multiphase acid systems, self-diverting viscoelastic acids, and fiber- based diverting systems. Several case studies from multiple areas and reservoirs from Caspian and Middle East areas have demonstrated extremely positive oil and gas production results with reduced acid volumes with the digital stimulation workflow compared to conventionally stimulated offset wells. The digital stimulation workflow brings a new approach to acid fracturing optimization based on an integrated cycle in which high-resolution data from several sources are processed by powerful computing capacities. Starting from digitizing acid reactions with the core samples, through digitized rheology and particle transport in multiphysics models, an advanced numerical simulator tailors an optimum design from a number of acid system options, pumping rates, additive concentrations, and stage volumes to achieve best geometry of etched channels inside a fracture.