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<p>Carbonate rocks are generally characterized by small pore throats and poor permeability. During the drilling and completion process, the reservoir is extremely susceptible to being contaminated by drilling fluids, and the contamination is difficult to be removed. The purpose of removing contamination can be achieved by wellbore acidizing through chemical dissolution. To deeply study the damage process and acidizing plug-removal process of carbonate reservoirs, a numerical model of wellbore contamination and acidizing plug-removal in carbonate rocks was established based on the mathematical models of drilling fluid invasion and acidizing plug-removal. The finite-element method was utilized for solving. The contamination conditions and plug-removal effects under different porosities, drilling fluid leakage amounts, injected acid concentrations, and the presence of fractures were investigated. It is shown by the results that with the increase of the original formation porosity and the drilling fluid leakage amount, the decline range of porosity and permeability after being contaminated by the drilling fluid is larger, and the contamination is more serious. At the same time, with the aggravation of the contamination degree, the acidizing plug-removal range around the wellbore is smaller. When the drilling fluid leakage amount is increased from 100 m<sup>3</sup> to 300 m<sup>3</sup>, the plug-removal range is decreased from 22.8% to 8.9%. With the increase of the injected acid concentration, wormholes can communicate with the original formation more rapidly, but the plug-removal range around the wellbore is decreased. When fractures exist, the position and angle of the fractures have a significant influence on the acidizing plug-removal effect. When the fracture is close to the wellbore and the fracture angle is small, the fracture becomes the dominant flow channel, and the expansion of wormholes in other directions is affected, thus reducing the plug-removal range in the contaminated area. The research results are provided to offer theoretical guidance and reference for the contamination evaluation of drilling fluids and the analysis of wellbore acidizing plug-removal effects.</p>

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Study on Carbonate Reservoir Pollution and Acidizing Deblocking Via Numerical Simulation

  • 期刊论文

  • 发表日期：

    2025年11月1日

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  • Liang Wenlong,
  • Chen Fuhu,
  • Li Xiaoming,
  • Ou Yanghui,
  • Li Qin

摘要

Carbonate rocks are generally characterized by small pore throats and poor permeability. During the drilling and completion process, the reservoir is extremely susceptible to being contaminated by drilling fluids, and the contamination is difficult to be removed. The purpose of removing contamination can be achieved by wellbore acidizing through chemical dissolution. To deeply study the damage process and acidizing plug-removal process of carbonate reservoirs, a numerical model of wellbore contamination and acidizing plug-removal in carbonate rocks was established based on the mathematical models of drilling fluid invasion and acidizing plug-removal. The finite-element method was utilized for solving. The contamination conditions and plug-removal effects under different porosities, drilling fluid leakage amounts, injected acid concentrations, and the presence of fractures were investigated. It is shown by the results that with the increase of the original formation porosity and the drilling fluid leakage amount, the decline range of porosity and permeability after being contaminated by the drilling fluid is larger, and the contamination is more serious. At the same time, with the aggravation of the contamination degree, the acidizing plug-removal range around the wellbore is smaller. When the drilling fluid leakage amount is increased from 100 m3 to 300 m3, the plug-removal range is decreased from 22.8% to 8.9%. With the increase of the injected acid concentration, wormholes can communicate with the original formation more rapidly, but the plug-removal range around the wellbore is decreased. When fractures exist, the position and angle of the fractures have a significant influence on the acidizing plug-removal effect. When the fracture is close to the wellbore and the fracture angle is small, the fracture becomes the dominant flow channel, and the expansion of wormholes in other directions is affected, thus reducing the plug-removal range in the contaminated area. The research results are provided to offer theoretical guidance and reference for the contamination evaluation of drilling fluids and the analysis of wellbore acidizing plug-removal effects.