TY - THES

T1 - Wettability Changes due to Nanomaterials and Alkali in Spontaneous Imbibition Experiments

AU - Saleh, Samhar

N1 - embargoed until null

PY - 2020

Y1 - 2020

N2 - Nanomaterials gained a lot of attention in the past few years. Recent studies revealed that silica nanomaterials can be a very promising agent in enhanced oil recovery (EOR) operations. Previous researches discussed the potential synergy between nanomaterials and other EOR agents like surfactants or polymers and substantial impact on key EOR mechanisms like emulsion stabilization and wettability alteration. In this work, the usage of silica nanomaterials and alkali in enhanced oil recovery was investigated through spontaneous imbibition tests, IFT measurements and phase behavior. The additional recovery was assessed for different rock/oil systems. The main goal was to evaluate the wettability alteration induced by the synergy between nanomaterials and alkali. Moreover, numerical analysis of the results by the means of inverse Bond number and capillary diffusion coefficient was carried out. In the experimental part, two types of nanomaterials with different surface modification were tested. The influence of rock type on the recovery process was investigated by using Berea and Keuper outcrop materials. The influence of oil composition was examined by using two crude oil samples with different total acid numbers (TAN). Sodium carbonate (Na2CO3) was used as an alkaline agent and two types of synthetic brine were utilized in order to investigate the effect of brine composition on the recovery. Interfacial tension (IFT) measurements showed that nanomaterials are very effective in terms of IFT reduction. The surface charge of the nanomaterials plays an important role in this process. A good synergy with alkali lead to very low IFT values (0.039 mN/m). This effect was also seen in the phase behavior tests, where brine/oil systems with lower IFT exhibited better emulsification. Nanomaterials contribution to the phase behavior was mainly the stabilization of the emulsion mid-phase. The influence of TAN number on the IFT and the phase behavior was very prominent, especially when combined with alkali. Rock-fluid interactions were assessed using Amott tests which rely on spontaneous imbibition mechanism. This mechanism is very sensitive to wettability changes. The enhancements observed within fluid-fluid interactions - especially IFT reduction - resulted in additional recovery ranging from 4 to 50% on top of the baseline under spontaneous imbibition, which was confirmed by inverse Bond number analysis. Promising results (97.7% of OOIP) were achieved using novel EOR formulations of alkali and nanomaterials. These values were attributed to wettability alteration that accelerated the imbibition kinetics as shown in capillary diffusion coefficient analysis. Rock-fluid interactions are very complex and require a deeper understanding for the initial wettability state of each rock-oil system. This opens the door for future investigation, which might include contact angle measurements and forced imbibition.

AB - Nanomaterials gained a lot of attention in the past few years. Recent studies revealed that silica nanomaterials can be a very promising agent in enhanced oil recovery (EOR) operations. Previous researches discussed the potential synergy between nanomaterials and other EOR agents like surfactants or polymers and substantial impact on key EOR mechanisms like emulsion stabilization and wettability alteration. In this work, the usage of silica nanomaterials and alkali in enhanced oil recovery was investigated through spontaneous imbibition tests, IFT measurements and phase behavior. The additional recovery was assessed for different rock/oil systems. The main goal was to evaluate the wettability alteration induced by the synergy between nanomaterials and alkali. Moreover, numerical analysis of the results by the means of inverse Bond number and capillary diffusion coefficient was carried out. In the experimental part, two types of nanomaterials with different surface modification were tested. The influence of rock type on the recovery process was investigated by using Berea and Keuper outcrop materials. The influence of oil composition was examined by using two crude oil samples with different total acid numbers (TAN). Sodium carbonate (Na2CO3) was used as an alkaline agent and two types of synthetic brine were utilized in order to investigate the effect of brine composition on the recovery. Interfacial tension (IFT) measurements showed that nanomaterials are very effective in terms of IFT reduction. The surface charge of the nanomaterials plays an important role in this process. A good synergy with alkali lead to very low IFT values (0.039 mN/m). This effect was also seen in the phase behavior tests, where brine/oil systems with lower IFT exhibited better emulsification. Nanomaterials contribution to the phase behavior was mainly the stabilization of the emulsion mid-phase. The influence of TAN number on the IFT and the phase behavior was very prominent, especially when combined with alkali. Rock-fluid interactions were assessed using Amott tests which rely on spontaneous imbibition mechanism. This mechanism is very sensitive to wettability changes. The enhancements observed within fluid-fluid interactions - especially IFT reduction - resulted in additional recovery ranging from 4 to 50% on top of the baseline under spontaneous imbibition, which was confirmed by inverse Bond number analysis. Promising results (97.7% of OOIP) were achieved using novel EOR formulations of alkali and nanomaterials. These values were attributed to wettability alteration that accelerated the imbibition kinetics as shown in capillary diffusion coefficient analysis. Rock-fluid interactions are very complex and require a deeper understanding for the initial wettability state of each rock-oil system. This opens the door for future investigation, which might include contact angle measurements and forced imbibition.

KW - Nanotechnologie

KW - EOR

KW - spontane Imbibition

KW - Alkali

KW - Nanopartikeln

KW - Berea

KW - Keuper

KW - Benetzbarkeit

KW - IFT

KW - Emulsion

KW - nanomaterials

KW - EOR

KW - Alkali flooding

KW - nanotechnology

KW - spontaneous imbibition

KW - Berea

KW - Keuper

KW - nanoparticles

KW - silica

KW - IFT

KW - emulsion

M3 - Master's Thesis

ER -