On-The-Fly Mixing Skid Mounted Technology Allows Cost-Effective Stimulation Jobs on Rigs with Limited Deck Space in Brazil Offshore

Abstract

Abstract While pre salt carbonate reservoirs are the main source of hydrocarbon production in Brazil (Jardim et. Al 2020), offshore mature fields located on post salt and sandstone reservoirs are still relevant. Cost effective solutions and treatment optimization are required to maximize return on investment. This paper introduces a new method to perform these jobs economically and efficiently. An overview of the operations performed on Brazilian mature fields and contingency operations for pre-salt carbonate wells including methods, strategies and benefits are reviewed. A compacted and versatile on-the-fly stimulation plant is deployed to perform acid stimulation jobs for sandstone and carbonate offshore formations. The use of this system provides the flexibility to mix several types of acidizing fluids in reduced areas, for both carbonates and sandstones, providing similar capabilities than a costly stimulation vessel, or an offshore rig with limited deck area. Concentrations of the stimulation chemicals are modified in real time, using various systems without stopping the pumping operation. This compact on-the-fly stimulation method shows many benefits, saving rig time, allowing the pumping of several chemicals, and making feasible operations that were possible only with stimulation vessel due to limited deck space of the rig. In some scenarios, large acid volumes are pumped without the need of additional acid tanks with pre-mixed acid solutions. Higher pumping rates are attained, leading to large zonal coverage treatments and rig time savings. This method has been used very successfully in Brazil since 2018 using several acidizing systems, including HCl, Mud Acid, polymeric diversion system and other acid-based technologies. Over eleven wells were treated using this on-the-fly stimulation method. Such operations take a maximum of 15 days from mobilization until demobilization. Assembly skid mounted vessels can take double or triple of the time and can increase the costs three times, which can make some projects unfeasible. This solution is switchable for low-cost projects on mature wells and workovers. The novelty is the introduction of a compact on-the-fly stimulation plant that provides with more efficient and cost-effective acid stimulation and pumping treatment allowing real-time acid concentration modification and the capability to use various acidizing technologies.