Multilateral Junction Connectivity Discussion and Analysis

Abstract Multilateral junction connectivity failures have been identified as a recurring risk when deploying junctions featuring casing windows in unstable formations. Connectivity has previously been described as a property defining general mechanical attributes such as resistance to formation loads of the constructed junction. When a junction experiences a connectivity problem, usually because unstable formations induce mechanical loads, solids can intrude and expected junction geometry can deteriorate. This paper explores the main connectivity issues and redefines the functional and technical requirements. An analysis of potential solutions illustrates that casing is not a suitable structural component when a full-size window is created. Our design introduces a structural layer internal to the parent casing, composed of two main prefabricated parts that create a lateral junction. A template braces the parent bore adjacent to the window, and a lateral connector interlocks with the template in such a way that it effectively supports axial and radial mechanical loads while creating a barrier against migration of formation solids. Case histories and laboratory testing confirm the structural integrity of our simple, two-trip junction construction method.