Mullibranch wells offer a means to contact more reservoir per wellhead or platform slot. Optimal well plans must begin with a concept of the trajectories of the lateral branches within the productive reservoir zones These can be vertical, inclined or horizontal, as can the main trunk of the well. This paper provides criteria for deciding the lateral branch trajectories depending on reservoir properties, rock stress regime and the geometries of the productive reservoir units. Because production from several lateral wells can be commingled in a common main trunk, this may permit more holes to be drilled in the reservoir than would have been feasible with conventional wells.
The reservoir model used for planning a multibranch well must capture the delineations of the hydrocarbon-bearing zones, the major axes of the stress regime and the first order controls on fluid flow in the reservoir. This paper illustrates the representation of the three-dimensional visualization of the main reservoir bodies showing the gas, oil and water zones along with the proposed well path. Finally, the reservoir model provides properties of the productive zones to be completed along the well trajectory enabling a forecast of the well productivity for economic analysis.
Once a set of well branches has been envisioned, the well plan proceeds from the reservoir to the surface. For a multibranch well, the main trunk should have a simple trajectory to ensure successful drilling and completion and to enable future access to the branches. From the main trunk the well plan projects an optimal path to the wellhead location. Alternatively, the well plan may accommodate a sidetrack trajectory to a planned branch from an existing well.