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Investigation of Formation Damage with Oil-Based Mud (Invert Emulsion) Using Microfluidic Method

Madanchi, Parham | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55414 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Mahani, Hassan
  7. Abstract:
  8. Formation damage is one of the most important challneges in hydrocarbon production; drilling mud invasion is one of its common types. This damage is caused by the penetration of the drilling fluid into the porous media, which its filtrate and solid pareticles block the pores and cause permeability reduction. The main purpose of this thesis is to investigate the pore-scale mechanisms of the formation damage induced by invert-emulsion drilling fluid and to investigate the effect of adding nanoparticles to the drilling fluid on the severity of the damage using microfluidic technique. According to the latest published articles, there has not been any research conducted at the pore-scale with invert-emulsion drilling fluid and most of the studies have been performed at the core and well scale.For conducting the experminets, first the micromodel was completely saturated with oil, and then the drilling fluid circulated at the inlet at constant rate and entered the porous media. Next, for simulation of the well cleaning and production stages, first hydrochloric acid was injected as a stimulation fluid and then the oil was flowed back from the opposite side of the micromodel to simualte the oil production stage after acidizing.For the design of the experiments, the effect of four nanoparticles including, silica and surface modified silica –by applying silane coupling aganets on their surfaces (new nanoparticles)- including GPTS, DGPTS and PGPTS which were made by applying ethyl silane, double amount of ethyl silane and propyl silane on nanosilica, respectively, at three different concentrations has been studied to improve rheological properties of the drilling fluid and the possibility of formation damage control.According to the results obtained from the rheology tests of the invert-emulsion drilling fluid, the critical nanoparticle size was determined to be 15 nm. Also, the mutual relationship between the nanoparticle and its concentration was investigated, which shows that the more hydrophobic the nanoparticle is, the better its efficiency at the lowest concentrations and vice-versa. According to the results and observations obtained from the micromodel tests, the most important mechanism of formation damage by inverst-emulsion drilling fluid is the instability of the fluid due to its contact with the oil inside of the micromodel. Due to the non-polar nature of the continuous phase of the drilling fluid, the partial dissolution of the oil into the mud causes an increase in the oil-to-water ratio and as a result the stability of the fluid is lost, and the separated water droplets cause a decrease in permeability by blocking the pore throats. Also, in the use of nanoparticles for the control of this damage, the results are in line with the rheology tests results, that the most hydrophobic nanoparticle at the lowest concentration has the best performance in terms of fluid stability and degree of formation damage, which indicates that surface chemistry has a greater effect than the concentration of the nanoparticles on mud stability. In the stages acid cleaning and production, emulsions are formed that block the porous medium and reduce its permeability. Also, acid sludge is formed within the unstable internal mudcake, which indicates the presence of oil in the structure of the drilling fluid and its partial dissolution in the invert-emulsion drilling fluid. The mentioned damages are highly dependent on the stability of the drilling fluid and its related primary damages. In other words, the more stable the invert-emulsion drilling fluid is, the less the possible damages would be during the life span of the well.According to the obtained results, 0.5% wt PGPTS and 0.5% wt SiO2 nanofluids with 48.1% and 79.6% penetration depth and 42.1% and70.1% reduction in permeability have caused the lowest and highest amount of formation damage, respecively
  9. Keywords:
  10. Formation Damage ; Silica Nanoparticles ; Micromodel ; Surface Modification ; Invert-Emulsion Drilling Fluid ; Pore-Scale Model ; Drilling Fluid

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