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Investigation of Formation Damage and its Remediation Caused by Wellbore Fluids by Using Micromodel

Khanzadeh, Ahmad | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52897 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Mahani, Hassan
  7. Abstract:
  8. Various methods have been developed to improve the production capacity of hydrocarbon wells, one of the most successful method is hydraulic fracture. This method, despite improving well production and increasing production levels in a reservoir, causes secondary damages such as water blockage, which is a result of the leakage of fracturing fluid into the fracture matrix and the deformation of the reservoir. This damage can reduce the production rate of a well. Studies prior to this study have mainly examined the damages caused by the leakage of fracturing fluids on a core scale. In most of these studies, damages has been studied only by measuring the pressure and changes in the permeability of the core, and theories have been proposed to explain how this damage happened and justify how to eliminate the damage.In this research, the visual inspection of this damage has been investigated by using glass micromodel system. The purpose of this study is to investigate this phenomenon more accurately in order to identify the mechanisms that causes damage at pore scale and how to eliminate it. These studies can interpret the behavior of damages at higher scales. In order to achieve this important goal in this study, in addition to investigating the known affecting damage factors such as the amount of fluid leaked into the porous environment and the duration of process, other factors had been investigated for the role of variables affecting dynamic factors such as heterogeneity and hole structure. And salinity effect of leaked water and its changes and the effect of surface tension reducers in micromodel experiments have been studied.Numerous experiments in micromodel systems have shown that the water blockage phenomenon in pore scale occurs as an emulsion, and the addition of interfacial tensile reduction agents to water-base fluids can, in addition to reducing the saturation of water-based fluids, Porous environment reduces the number of residual emulsions in the pore scale. According to research in this study, using the ethyl alcohol as an interfacial tension reducing agent compared to methyl alcohol is more inappropriate performance. Also, increasing the amount of interfacial tension reducers at high concentrations of reducing materials will have less effect on the saturation of the remaining fluids.On the other hand, studies in this research show that in contrast to the behavior of pure paraffin fluids that have been studied in previous studies as reservoir fluids, salinity changes in fluid leakage can have a significant effect on remaining water saturation in the pores and the number and size of formed emulsions. This trend has been such that the use of Persian Gulf water as a fluid pad can have close results to the use of 1.% volume of methyl alcohol as an interfacial tension agent . The main reason for this effect can be due to the reduction of interfacial tension caused by the polar activation of polar compounds in crude oil. This can be used as an alternative or complementary method due to easy and low cost access to the fluid source.Also, studies in this study suggest that reducing interfacial tension may not necessarily reduce remaining fluid saturation in the pores. As an example, the two times diluted Persian Gulf's water, despite its low level of interfacial tension, shows poor performance in cleaning procedure. According to experiments conducted in this study, the changes in surface wetness increase the surface's tendency to absorb water compare to oil due to the use of these fluids. This could be the cause of this problem. This modification increases the change in saturation and capillary pressure of the porous medium, which manifests itself as an increase in the saturation of the water remaining in the porous medium.Based on this study findings, reduction of interfacial tension is not the only factor affecting the amount of water saturation and it is necessary to consider other factors such as surface deformation due to the influence of these fluids. This study provides a good overview on the reality of water blockage process. Study of the water blockage phenomenon on the pore scale could improves the knowledge in larger scales. Based on this, the findings of this study can be useful for understanding the process of reducing water blockages in porous environments
  9. Keywords:
  10. Formation Damage ; Water Blockage ; Micromodel ; Simulation Fluid ; Water-in-oil Emulsion ; Pore Scale Simulation of Fluid Flow ; Damage in Porous Media

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