An Innovative Fluid Technology and Advanced Digital Workflow Set a New Standard for Carbonate Matrix Stimulation in High-Temperature Extended-Reach Wells: An Exceeding Expectations Story from the UAE

Abstract Designing acid stimulation in extended-reach wells is challenging. This study adopts a digital workflow that integrates data from previous treatments, lab experiments, and production performance to design and optimize acid treatments in carbonate formations. The wells under study are horizontal and completed as open holes. The laterals are over 13,000 ft. long, and the average formation permeability is 4 mD. The formation temperature is 270°F. An advanced acid placement simulator and production analysis software evaluated a previous treatment involving emulsified acid in the same field. The evaluation of the previous treatment was a blind test where only pre-stimulation production data and acid treatment data were provided. The acid placement simulator used the inputs from the operator as an initial guess to match actual treatment pressures. Measured wellhead pressures and bottomhole pressures were used to adjust the fluid's friction multiplier. In agreement with the operator, initial skin and some other parameters were modified to achieve an accurate pressure match. The post-stimulation skin from the simulator was then used in production analysis software to predict the post-stimulation drawdown. The reduction in actual drawdown before and after the treatment, as well as the simulated reduction, was found to be within 10%. This demonstrates the accuracy of the acid placement simulator in modeling the carbonate acidizing process in long laterals. Core flow experiments were conducted to evaluate the performance of emulsified acid and polymer-free delayed acid on outcrop and reservoir cores. The experimental data were utilized to fine-tune the acid performance curves in the simulator. A validated upscaling scheme was implemented to compare the performance of the two acids at the field scale. The simulations showcased that polymer-free delayed acid consistently outperformed emulsified acid, in terms of placement, friction, and acid penetration in this specific application. The design for the well treatments involved conducting numerous runs on the acid placement simulator. The runs were ranked based on acid coverage and skin distribution along the lateral. The post-stimulation skin distributions were then input into the production analysis software to predict drawdown and improvements in PI. Treatment decisions were based on optimum dosage rates/economics, PI without compromising target skin reductions. The results from eight stimulated wells reveal that predicted pressures from the simulator closely match gauge pressures. This integrated digital workflow facilitates accurate engineered solutions and economics-driven optimization of carbonate acidizing stimulation. It also highlights how full engagement/collaboration between the operator and service company enhances performance and optimum design. In this stimulation campaign, continuous integration and engagement translated to a 30% reduction in acid volume, a 65% increase in injection rate, a 100% improvement in post-stimulation PI, and 560 metric tons less CO2 emitted compared to previous well treatments in the same field.