A Novel Cost-Effective Stimulation Workflow Unlocks New Perspectives for Matrix Acidizing in Fractured Carbonate Reservoir – A Case Study from Egypt

Abstract Matrix acidizing can effectively stimulate carbonate reservoirs, often resulting in skin factors on the order of –3 to –4. Wormholes can effectively connect the well with the reservoir. However, if the carbonate reservoir is naturally fractured, it will be difficult to generate dominant wormholes using conventional matrix acidizing. Hence, an effective acidizing technique is crucial to handle such heterogeneous carbonate rock, especially if the permeability contrast is vast between the matrix and fracture. This paper exhibits a novel workflow developed by a multidomain team to reveal the true potential of the fractured carbonate reservoir in a heterogeneous complex basin in the Eastern Desert in Egypt called the GoS basin. The new logging program uses high-resolution wellbore imaging, nuclear magnetic resonance (NMR), and casedhole pulsed neutron logging technology and processing algorithms to record capture and inelastic elemental spectroscopy for matrix parameters, detailed mineralogy, and oil saturation. The output of this characterization portrayed complex challenges that prevent having defined acid distribution between the flow zones of the natural fractures and the unfractured matrix due to the permeability contrast of 130:1. The key to success in dealing with such stimulation jobs is choosing the optimal chemical diversion, main acid treatment, pumping placement, and establishing a fit-for-purpose pumping schedule. Many experimental and laboratory tests were performed to prepare a viscous pill to be utilized as temporary isolation for the fracture or the fissures network prior to starting the full acid treatment. In addition to that, employing a passive diverter instead of an active acid-based diverter was a seamless technique to divert the acid away from each zone after pumping. The results of this novel workflow and the new acid technique indicate a sixfold increase in well productivity. The falloff analysis followed by the viscous pill reinforces the potency of the temporary isolation; this aids in treating the lower-permeability layers, which are the candidates for matrix acidizing. The applications of this novel workflow unlock the true potential of the lower-permeability reservoirs and maximize the estimated ultimate recovery. This paper showcases our experiences with the use of this unique recipe in fractured carbonate reservoirs, and in reservoir characterization and provides lessons learned to fill knowledge gaps in this area and provide a complete workflow that can be utilized everywhere worldwide.