Accurate Simulation of Acidizing Operations
StimBR accurately simulates matrix acidizing operations, including wormhole propagation and acid injection dynamics, optimizing the stimulation process.
The simulator combines advanced finite element models with wormhole propagation formulations. It is capable of simulating the injection of strong acids (HCl) and weak acids (acetic acid), self-diverting acids, viscoelastic, emulsified, and solid divergent. The pumping schedule with dozens of alternating fluid stages is simulated. The results allow for quantifying the removal of drilling-induced damage and the stimulation achieved through wormholes.
The dissolution of the porous matrix is a very unstable process that leads to the formation of preferential flow channels called in the literature as wormholes. These branched channels, which can be from pore size to a few millimeters, are the result of instabilities generated by the coupling of rock dissolution and flow. The acid in contact with the rock formation reacts with the solid, increasing the local permeability of the rock and, consequently, increasing the mass transfer and the dissolution reaction itself. This process is quite complex and depends on several factors, such as:
Wormhole propagation is a complex phenomenon to model. There are academic models available, but they often lack practical application due to high computational costs or inherent uncertainties. There are also models based on the PVBt curve (pore-volume to breakthrough). Laboratory tests allow for quantifying the volume of acid required for wormholes to traverse the entire core sample. Figure 1 shows a typical injection pressure behavior during the test. From this, the wormhole propagation speed can be defined. By repeating the tests at different injection flow rates, the PVBt curve is obtained, as shown in Figure 2. This reveals that there is an optimal injection rate. Figure 3 presents the rock dissolution patterns for different flow rates.
The PVBt curve represents the interaction behavior between an acid and a reservoir rock. It can be determined in the laboratory or through back-analysis simulations of past operations. StimBR includes a back-analysis module.
Leveraging Simworx’s expertise in well–reservoir coupling simulation, StimBR combines wormhole propagation formulations with Darcy flow in the reservoir, coupled to the flow in the lower well completion (screen, annulus, and valves).
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StimBR accurately simulates matrix acidizing operations, including wormhole propagation and acid injection dynamics, optimizing the stimulation process.
The simulator manages complex pumping schedules and fluid stage alternations, improving the efficiency of acid treatments and maximizing operage coverage.
StimBR’s integration of rock dissolution and flow modeling provides detailed insights into wormhole formation and its impact on reservoir permeability.
StimBR’s use of the PVBt curve ensures precise modeling of wormhole propagation, accounting for different flow rates and injection behaviors.
By simulating the acidizing operation and predicting wormhole propagation, StimBR helps enhance overall well performance, leading to increased production efficiency and reduced operational costs.