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

Abstract

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.

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

“…Aphron fluid has been investigated in different aspects, such as microbubble fluid rheology and filtration in various polymer and surfactant concentrations. 10 Besides, the fluid stability, bubble size distribution, impacts of water-based or oil-based muds, flow rate, rheological models, rock wettability, permeability, temperature, and pressure effects, and drainage rate were scrutinized by Arabloo and Shahri 10b and Mirabbasi et al 11 In the latest research, Baseli Zadeh et al 12 studied the effects of fracture width, mixing speed, and pressure difference on microbubble infiltration in a single-fracture medium. They observed that when the mixing speed (RPM 1 ) and pressure difference increase, the diameter of the bubbles decreases, and consequently, the chances of blockage are reduced.…”