Abstract
Unconventional gas and tight oil reservoirs require cost-effective fracturing technologies to optimize cost versus productivity and ensure viable commercial development. Horizontal wells together with completion techniques to initiate transverse fractures have been the key to unlocking these vast resources. Variables in the completion design for fracture stimulation in a horizontal well include injection rate, fluid properties, solid loading, well spacing, cluster spacing, and the sequence and timing of pumping stages between wells in a multi-well pad.
An optimized design is critical to improve hydrocarbon production and to reduce the cost. However in current practice, multi-cluster and multi-well design is primarily based on progressive experience and is typically of standardized design in a given area (e.g. the clusters and wells are evenly distributed). This is due in part by the limitations of existing hydraulic fracturing simulators, including: 1. An assumption of planar fractures; 2. Fracture interference within and among stages and adjacent wells is ignored; and 3. Numerical instability when modeling systems with large dimensionless toughness e.g. slick water injection into high-toughness rock.
This paper describes an emerging non-planar 3D fracturing software package with the capability to simulate interference between hydraulic fractures propagating from multiple clusters and multiple wells. Thus, both simultaneous and sequential multiple fracture propagation can be modeled. Furthermore, numerical instability with large dimensionless toughness is solved and makes it possible to predict the fracture geometry equally well for slick water fluids. The case study in this paper shows how fracture interference and proppant distribution occurs within a stage as well as between well and stages. The simulated fracture patterns can be matched with field microseismic data and the simulated pressure trend is in agreement with field operational data. Using this approach, multi-cluster and multi-well designs can be optimized in a manner not previously possible.
