The oil and gas industry has been developing various technologies to increase the productivity and recovery of hydrocarbons from conventional and unconventional reservoirs. Reservoir stimulation is an essential operation used to enhance production in many fields around the world. Hydraulic fracturing and acid treatments are the main stimulation methods. Reservoir tunneling concepts are used to drill branched channels in the formation from the main wellbore. With thousands of tunnels drilled to date, it is a viable technique that can improve the recovery of selected reservoirs.

This paper reviews the recent developments in reservoir tunneling technologies and their current applications. These tunneling methods can be categorized mainly into water jetting, abrasive jetting, reactive jetting (acid), and needle and mechanical tunneling (radial drilling). The paper includes reviewing and analyzing these techniques based on documented literature results that include simulation studies, lab and yard experiments, field implementation, candidate selection, operational requirements, technology enhancements, advantages, limitations, and challenges of each technique.

The paper provides a comprehensive summary of different tunneling techniques focusing on the operational practices, tunneling mechanisms, tunneling depth, and recent advancements available in the market. The most effective applications of the tunneling techniques are in stimulating low permeability, depleted and thin reservoirs, layers close to water zones, and bypassing near wellbore formation damage. The efficiency of creating tunnels is affected by many factors such as reservoir properties, nozzle, and fluid types, etc. The tunnel shape and trajectory are affected by reservoir geological properties. The combination of the tunneling with other stimulation techniques can result in more effective treatments, which enhance the methods of current stimulation. Reservoir tunneling technologies can pave the way to improve hydrocarbon recovery and enable access to unstimulated formations.

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