Abstract
Based on the equivalent permeability tensor theory, a novel carbonate acidizing mathematical model is developed, which can be adopted to simulate the simulation process for carbonate matrix-acidizing and vuggy carbonate acidizing. Wormhole-channel in the core BC21 and BC10 was simulated based on the Omer Izgec experimental data. The comparative result between the experiment and the simulation shows that the two dominating wormhole-channels, the variation of pressure-drop curve and the pressure values at the inlet of the core are almost the same. The acid-flowing channel is significantly influenced by mineral distribution heterogeneity and macropore distribution pattern in the core. The acid breakthrough volume is defined as 1.5 PV divided by pore volume of core (PV is the acid volume consumed to form the dominating wormhole channel.). If the acid is injected continuously while the wormhole has completely broken through the core, the wormhole shape only changes a little, but the end-face dissolution will be formed at the end of the core. And the conclusion could be used to optimize the acid consumption volume.
Highlights
It is crucial for vuggy carbonate formation to enhance near wellbore permeability to connect formation, release damage and improve productivity
1) In this paper, a novel numerical model for carbonate formation and vuggy carbonate formation acidizing is deduced based on equivalent permeability, which avoids distractions of pressure field and seepage variation between fracture-vuggy and matrix
2) According to the experimental and simulation results, the acid flow channel is depended on the rock, minerals and the macropores distribution
Summary
It is crucial for vuggy carbonate formation to enhance near wellbore permeability to connect formation, release damage and improve productivity. R [8] [9] (2005) researched matrix acidizing in carbonate formation by combining the simulation and laboratory experiment results. The acid-etched wormhole can be formed only with appropriate acid injection volume, which will connect formation and improve permeability. Vemuri Balakotaiah [10] established a radial numerical model for wormhole based on fractal geometry. In the formation of vuggy carbonate, acid flow in the vug system is described by Navier-Stokes equation, while that in matrix is described by Darcy law. Omer Izgec [11] deduced pressure field and acidizing models for vuggy carbonate formation according to the above theory. A numerical model for vuggy carbonate formation is deduced based on equivalent permeability, which avoids distractions of pressure field and seepage variation between fracture-vug and matrix. The simulation result provides an important guidance to optimize the operation parameters of matrix acidizing in carbonate formation
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