Radial Multi-Branch Sidetracking Technology for Low Permeability Carbonate Reservoir Stimulation

Abstract To achieve economic and efficient utilization of marginal oil zones and remaining oil zones in low-permeability reservoirs, a directional wellbore stimulation technology with strong targeting and controllability is proposed. This technology integrates drilling, completion, and stimulation functions. For low-permeability carbonate reservoirs, hydraulic fracturing or acid fracturing are necessary to achieve economically viable development. However, for reservoirs with multiple layers, thin single layers, or those close to edge or bottom water, hydraulic fracturing lacks advantages in targeted and economical modifications and poses significant risks of connecting water channels. A technology is needed that can achieve targeted modifications for multiple layers, with fully controllable modification scope and good economics, integrating drilling, completion, and stimulation. Radial multi-branch sidetracking technology is a drilling-based technique for increasing oil well production. This technology utilizes magnetic positioning-natural gamma logging tools and gyroscopic inclinometers to determine the depth of casing perforation for radial direction of jet holes. Subsequently, a milling bit is used to create a hole approximately 1 inch in diameter on the casing of the target layer. High-pressure hoses and nozzles are then inserted through continuous tubing, and drilling fluid or acid fluid is injected through a 0.5-inch jet bit. With the hydraulic rock-breaking action of high-speed jets and the dissolution reaction of acid on rocks, multiple radial holes with diameters of 1-3 inches and lengths exceeding 50 meters are drilled in different directions within the reservoir. During implementation, multiple radial holes can be drilled in the same or different layers according to the actual reservoir distribution and production enhancement requirements. This technology offers advantages such as deep-scale damage removal, layered stimulation, three-dimensional digging, physical directional drilling, and avoiding direct connection with edge and bottom water. Moreover, compared to hydraulic fracturing or acid fracturing, it saves significant costs on fluids, equipment, and operations, demonstrating favorable economics. Field applications have shown that the milling and jetting time for a single branch is only about 1.5 hours, with operation depths exceeding 50 meters. The single branches are distributed in a 60° phase, and the liquid usage for a single branch is only about 10 cubic meters, greatly reducing operational costs. Radial multi-branch sidetracking technology is primarily suitable for oil and gas reservoirs with poor permeability and thin effective thickness, as well as for directed utilization of remaining oil in mature fields and development of marginal oil and gas reservoirs.