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Characterization of Formation Damage Induced by Oil-Based Drilling Fluid and Proposing its Optimized Remedy

Ahmadi, Amir | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56086 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Masihi, Mohsen; Tahmasbi, Koroush; Kalhor, Mojtaba
  7. Abstract:
  8. During all operations in hydrocarbon reservoirs, there is a possibility of formation damage. These damages can reduce the production of fluids from reservoir. One of the major damages that can seriously affect the performance of a reservoir is the damage caused by drilling fluid. The main purpose of this research is to study the main mechanisms of formation damages when using oil-based drilling fluids and fixing or preventing these damages. Once the mechanisms are identified, it is tried to cure the damages but without acid-washing. The alternative method is surfactant-washing which is a surfactant-brine injection. This injection has been done for the first time. This study helps to industry to avoid the risk of acidizing and additional costs. Three surfactants were used to prevent damage and cure it. The first nonionic surfactant is Cedar leaf powder and the other two are anionic surfactants (A and B) have been made by Pars Drilling Fluids (PDF) Company in order to obtain a new surfactant-solution for washing downhole tools and formation layer. To investigate the effect of these surfactants on the properties of mud, these three surfactants were added to mud. Rheology, electrical stability, filtration and emulsion stability tests were performed on the mud and it was found that two surfactants Cedar and A did not have any adverse effect on the mud rheology and even caused mud stability. The contact angle test for aged carbonated thin sections in the filtrate containing these surfactants was also done. The results of these tests showed that the aged thin sections in the filtrate containing cedar was able to reduce the oil-wetting. This bio-surfactant has the ability to be used in Oil-Based Muds as a preventive agent. The contact angle tests with aged carbonate sections in salt water solution containing surfactant was also repeated and it was found that cedar surfactant can change the wettability of carbonate rock from hydrophobic to hydrophilic. Interfacial tension tests showed that this surfactant can reduce the interfacial tension between crude oil and water. By using core-flood tests, the damage caused by oil-based mud on the carbonate core was simulated. The relative permeability of oil decreased from 0.729 mD to 0.23 mD for this carbonate core. After injecting the cedar surfactant solution into the core, the relative permeability of oil increased to 0.63 mD and 75% of the remaining oil in the core was produced. The results of core-flooding tests showed that Cedar as a cheap bio-surfactant can reduce and cure the formation damage. This surfactant can be called as detergent surfactant. Considering amount of produced remaining oil, Cedar is useful in cases of enhanced oil recovery
  9. Keywords:
  10. Drilling Fluid ; Formation Damage ; Core Flooding ; Wettability ; Permeability ; Surfactants ; Cedar Tree

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