Matrix acid stimulation: What are the gaps to bridge from lab to field?

Abstract

Acidizing core flooding experiments in carbonates are typically performed in the laboratory in order to observe different physical phenomena and to design acid stimulation jobs in the field. The experiments are usually well defined in terms of mineralogy, permeability, porosity, pressure, temperature and salinity. During the tests, key parameters are analyzed such as the pore volume of acid needed to create wormholes and breakthrough as well as pressure and permeability time-evolution. In reality, the result of an acid stimulation in the field is difficult to predict because of the heterogeneous nature of carbonate formations, complexity of such reactive transport phenomenon, and more importantly the uncertainties related to subsurface well conditions. Stimulation models and numerical tools can help bridge the gap between the laboratory observations and real field applications. We utilize selected core flooding results obtained from the QP - TOTAL collaboration on acid stimulation and use these measurements as input for different acid stimulation software. Subsequently, a benchmarking of commercial and academic acid stimulation software at the well scale is performed. The main criteria for this comparison are the capacity of modeling improved acid stimulation under constant or varying pumping rates, the capability of modeling complex fluids such as chemical diverters and relative permeability modifiers and the ability to simulate different well configurations. Then, a sensitivity analysis on selected key parameters such as the dissolution model, pore volume to breakthrough and solute velocities is conducted. Finally, predictions from numerical models are compared to acid stimulation field results from literature, for Middle Eastern carbonate. We try to history match the results and we identify main areas of improvement for future development of acid stimulation software.