A case study in the Uinta Basin integrated multiple diagnostic measurements to understand the interaction between mechanical stratigraphy, fracture geometry and effective drainage for horizontal wells landed within different benches. In the center of a planned development cube of horizontal wells, a new vertical observation well was instrumented with permanent fiber, isolated external casing pressure gauges and a vertical geophone array to map hydraulic fracture growth during the completion of the stacked cube. After the wells were completed, pressure interference and a high-resolution geochemical analysis of the produced hydrocarbons was used to assess how different formations in the reservoir were draining throughout time. The diagnostics showed consistent hydraulic geometries between wells and that some fracture stimulations were contained within specific landing zones while other landing zones interfered with each other to varying degrees. In the isolated zones, production allocation results from the geochemical fingerprinting and pressure interference generally agreed with the fracture diagnostics. By investigating changes with well spacing, we were able to get a clearer picture of how drainage between zones was impacted and how fracture heights differ within the mechanical stratigraphy. Understanding the mechanical stratigraphic controls on hydraulic fracture height growth relative to the reservoir drainage is a key to making informed decisions on wine-rack configurations for optimal reservoir drainage.
Economic production from intrinsically impermeable, unconventional reservoirs requires effective hydraulic fracture growth into the hydrocarbon bearing layers to induce flow. However, geomechanical property changes within stratigraphically layered systems can control the hydraulic fracture geometry and potential contact within different hydrocarbon producing layers in a stacked reservoir system. Moreover, only a portion of the hydraulic fracture system will retain enhanced permeability and effectively drain during production, depending on proppant placement during the hydraulic fracture stimulation. Ultimately, the efficient and uniform drainage of a reservoir unit depends on the combined effective enhanced permeability systems interacting between hydraulic fractures from multiple wells.