Loading...

Experimental Investigation to Determine the Main Parameters for Viscoelastic Surfactant (VES) Injection for Acid Diversion in Reservoirs and Improving Their Design Conditions

Habibi, Reza | 2018

693 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 50562 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ayatollahi, Shahab; Bazargan, Mohammad
  7. Abstract:
  8. The success of matrix acid production operations and its proper efficiency is one of the main challenges for oil and gas companies. The heterogeneity of the reservoir formation (especially the permeability difference) in the area around the well due to the presence of different reservoir layers results in the non-uniform distribution of acid among them and adds acidizing challenges. In order to improve production conditions, stimulation fluid transfer to the low permeability layer, which is the main target of acidizing. In this study, a new generation of chemical diverter, called Viscoelastic Surfactant, has been used. These materials have two components of elastic and viscous behavior, and have complex properties to describe them. The focus of this research is to study the complex behavior of these surfactants in order to determine the highest performance and best condition for injection diverters. Determining the properties associated with the elastic behavior of these types of surfactants will help you to choose the right fluid, as well as the correct and optimum use of them. In this study, the effect of various operating parameters including the surfactant concentration, pH, initial acid concentration (subsequently spent acid salt), frequency or shear rate, temperature, and the presence of acid additive (corrosion inhibitor and iron control agent) on the elastic behavior of diversion materials that has been mentioned to obtain the proper fluid composition. The results showed that elastic behavior is dominant in viscoelastic surfactants, and the fluid behaves like a viscoelastic solid. Therefore, the main consideration in order to optimize their condition should be on this property. The results showed that the concentration of 8 vol% VES create most suitable elastic behavior for acid diversion. Also, with increasing pH, the elastic modulus was continuously increased, but the viscose modulus was fixed after a small increase. As the temperature increases, the elastic and viscous properties of the material are increasing, but the increase in the elastic modulus is higher than viscosity. Salt produced from the reaction of hydrochloric acid at a concentration of 15 wt% provide the best rheological properties for diversion. By controlling the injection rate, it can also be avoided from being positioned in the elastic modulus reduction area where the diversion ability is low. Based on previous work, additives had a significant impact on viscosity changes, here also had the greatest effect on the viscous modulus, but their effect on the elastic modulus is negligible. Considering the operational requirement to reduce the viscosity of these materials at the end of acidizing and the production of wells, the degree of viscosity reduction of the gel material with different fluids such as water, oil and mutual solvent in different concentrations was investigated. It was observed that a mutual solvent with a concentration of 10 and 15 vol% and petroleum well disrupted the material to facilitate flow and not damage. In order to confirm the rheology behavior of the surfactant in the reservoir condition, injection tests were conducted to sandstone core to investigate the effect of elasticity and the pressure required to displace the viscoelastic gel in different pH was investigated. At pH 0.5 and 1.5 with the same apparent viscosity but different elasticity, the water pushes the viscoelastic gel up to 15 and 20 times the initial pressure difference, respectively. Also, at pH 1.5 and 3 with the same viscous modulus but different elasticity, the pressure that water required to move the viscoelastic gel is 20 and 29 times the initial pressure difference respectively. The higher pressure that water needed to move the viscoelastic gel is due to the elastic component of the viscoelastic surfactant. Therefore, it was concluded that the main role of acid deviation is in the elastic component, and the viscose section is used to facilitate its flow
  9. Keywords:
  10. Rheology ; Viscoelastic Surfactant (VES) ; Acid Divertor ; Elastic Behavior ; Heterogeneous Reservoirs ; Viscose Behavior

 Digital Object List

 Bookmark

No TOC