Tese e Dissertação

Tese: Study and Application of Controlled Sodium Silicate Gelation through Encapsulation of Hydrochloric Acid for Fracture Sealing

Enhanced oil recovery methods (EOR) are applied to mitigate non-uniform oil sweep. Gel treatment in the injection wells is one of these methods. It consists of blocking off the high permeability path with a polymeric gel to divert subsequently injected water into lesspermeable, oil-bearing pores. Fractures in reservoirs create preferential paths for the injected water and compromise the efficiency of the liquid displacement process. Sodium silicate gels could be injected to seal fractures and force the aqueous phase to flow through unswept regions. However, in this case, because the polymeric solution is injected with its cross-linker the gelation time is not predictable. As a result, it becomes difficult to control the depth at which the chemicals penetrate the fracture before solidifying, thus hindering the sealing of long fractures. Alternatively, microcapsules set a way to mitigate this problem, encapsulating the gelation activator making it possible to fill the fracture before activating the gelation. It allows controlling the timing and location of the content release. The microcapsules must be mechanically stable and impermeable to the encapsulated material during storage. Polydimethylsiloxane (PDMS) was used to encapsulate the hydrochloric acid (HCl), which is the activator of sodium silicate gelation, making it possible to better control the gelation reaction to reach deeper locations of fractured reservoirs. PDMS microcapsules were produced using a microfluidic device that combines co-flow and flow-focusing in coaxial glass capillaries. Fluorescent dyes were used in the inner and middle phases to enable microcapsule characterization. HCl release in hypotonic media (water) evaluation was made through pH measurement. Due to the osmotic difference, microcapsules swelled until burst. We discussed the effects of the mechanical properties of capsules on the HCl release process. Results show that the release time can be controlled by changing the eccentricity and stiffness of the capsules. A 3D device printed in white resin of a fractured porous medium was designed for our tests. Results show that the release time of HCl and the subsequent sodium silicate gelation can be controlled by adjusting the capsules’ shell material, thickness, stiffness, and eccentricity. PDMS microcapsules were injected alongside the sodium silicate solution. The device permeability was measured, before and after the gelation process, resulting in a considerable reduction in the device’s permeability.

Link da defesa

https://puc-rio.zoom.us/j/92846828910?pwd=5bRKJkfhGv3tpf5d6D0Jf9mmODaIg4.1

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