Jet Cleaning Processes in the Plug and Abandonment of Oil and Gas Wells: An Experimental Study on Horizontal Miscible Jets

The plug and abandonment (P&A) operation is considered as one of the essential stages during life cycle of oil and gas wells. During the P&A operation, each well needs to go through the specific steps; these may include accessing behind the casing (i.e. annulus), cleaning the target area (i.e. inside and outside the casing), and installing the cement plug barriers in the target area. The jetting process is one of the efficient approaches in the cleaning step of P&A operation, where an injection fluid pushes and removes unwanted fluids/materials. To achieve an efficient jet cleaning process, studies on the effects of different parameters (e.g. operational parameters, fluid properties, and geometrical parameters) seem crucial. In this paper, we experimentally study the characteristics of horizontal miscible jets, to develop an understanding about fundamental aspects of the jet cleaning process in P&A operation. We analyze the effects of the injection velocity, the perforation diameter, and the rheological parameters on jet characteristics, such as the laminar length and the mixing index. Based on our results, increasing the injection velocity leads to a decrease in the laminar length. Also, the mixing index before the perforated wall increases by decreasing the perforation diameter. In addition, using a non-Newtonian ambient fluid results in decreasing the mixing index.