Synthetic-based aphrons: Correlation between properties and filtrate reduction performance

Experimental Investigation on the Impacts of Fracture Roughness and Fluid Composition on the Formation of Bubble Bridges through the Microbubble Fluid Flow

The colloidal gas Aphron (CGA) drilling fluids are an alternative to ordinary drilling mud to minimize formation damage by blocking rock pores with microbubbles in low-pressure or depleted reservoirs. Fractured formations usually have different characteristics and behavior in contrast to conventional ones and need to be investigated for Aphron applications. In this research, a series of core flood tests were conducted to understand the factors controlling the pore-blocking mechanisms of microbubbles in fractured formations. For the first time, a synthetic metal plug was used to simulate the fracture walls and eliminate the formation matrix effect. This study analyzed the effects of three fluid compositions, considering the polymer and surfactant concentrations at reservoir conditions, including temperature and overburden pressure. Additionally, fracture surface roughness as one of the parameters affecting the microbubble fluid penetration through the fracture path and bubble blockage were studied. The results indicated that microbubble fluid composition would not affect the bubble size or blockage probability. The different stable microbubble fluids resulted in the same pattern and conditions. Besides, fluid penetration would be more challenging if the fracture roughness decreased. Due to the accumulation of bubbles and the fact that some of them were trapped in the fracture's rough surface, the blockage possibility increased. According to the range of roughness for the steel core in previous studies and compared with the roughness of carbonate reservoir rocks, the roughness of fractured reservoir rocks is much higher than that of the steel surface. Accordingly, the observed trend in the experiments showed that when it is possible to form a bubble bridge in steel cores, then in carbonate rocks, we will definitely see blockage with any roughness, provided that other parameters are acceptable.

Mechanistic Study of Micro-bubble Fluid Infiltration through the Fractured Medium

Drilling in depleted reservoirs has many challenges due to the overbalance pressure. Another trouble associated with overbalance drilling is differential sticking and formation damage. Low-density drilling fluid is an advanced method for drilling these depleted reservoirs and pay zones with different pressures to balance the formation pore pressure and hydrostatic drilling fluid pressure. This study investigated the infiltration of a micro-bubble fluid as an underbalanced drilling method in fractured reservoirs. A novel method has been presented for drilling permeable formations and depleted reservoirs, leading to an impressive reduction in costs, high-tech facilities, and drilling mud invasion. It also reduces mud loss, formation damages, and skin effects during the drilling operation. This paper studied micro-bubble fluid infiltration in a single fracture, and a synthetic metal plug investigated the bridging phenomenon through the fractured medium. Moreover, the effects of fracture size, bubble size, and a pressure differential of fracture ends have been thoroughly analyzed, considering the polymer and surfactant concentrations at reservoir conditions, including the temperature and overburden pressure. In this study, nine experimental tests were designed using the design of experiment, Taguchi method. The results indicated that higher micro-bubble fluid mixing speed values make smaller bubbles with lower blocking ability in fracture (decrease the chance of blocking more than two times). On the other hand, a smaller fracture width increases the probability of bubble bridges in the fracture but is not as crucial as bubble size. As a result, drilling fluid infiltration in fractures and formation damages decreases in the condition of overbalanced drilling pressure differences of about 200 psi.

Using Fe(III)-coagulant-modified colloidal gas aphrons to remove bio-recalcitrant dissolved organic matter and colorants from cassava distillery wastewater

Efficient removal of bio-recalcitrant dissolved organic matter (DOM) and colorants is essential for discharging or reusing the distillery wastewater. The present work adopted a novel microbubble system - Fe(III)-coagulant-modified colloidal gas aphrons (CGAs) in flotation as tertiary treatment of the bio-chemically treated cassava distillery wastewater. Approximately 93% of bio-recalcitrant color and around 79% of dissolved organic carbon (DOC) were removed at the initial pH of 9.0 and 7.1, individually. The modified CGAs exhibited strong ability of complexation and electrostatic attraction of the polyanions of DOM and colorants. But the 1-10 kDa DOM was found to be resistant to the CGA capture. Compared with directly dosing coagulant, the Fe(III)-coagulant-modified CGAs consumed ∼47% and ∼21% less coagulant to achieve the optimum decoloration efficiency and DOC removal, respectively. In the flotation with Fe(III)-coagulant-modified CGAs, the coagulant-dosing system could be omitted while the coagulant utilization was improved.