An Integrated Modeling Work Flow With Hydraulic Fracturing, Reservoir Simulation, and Uncertainty Analysis for Unconventional-Reservoir Development

Summary It is important to determine several key parameters, such as well spacing, completions design, landing strategy, and pad sequence, for a successful full-field development of the unconventional reservoir that involves multiple wells and pads in a given area of interest. Those parameters are normally considered individually through small and simple models. In this paper, focusing on developing the whole area effectively, we provided a systematic work flow to handle such challenges together: We first recommended a top-down concept that better represents actual field development and illustrates the importance of the 3D Earth model for the unconventional reservoir; we then proposed an integrated modeling that is an iterative loop consisting of the 3D Earth model, hydraulic-fracture modeling, reservoir simulation, and uncertainty analysis. It is uncommon to build a 3D Earth model for the unconventional reservoir mainly because of the lack of data and software capability. In this paper, we provided a cost-effective approach for the first time on the basis of a large amount of existing vertical wells, newly drilled horizontal wells, and all the data available. A 3D Earth model using information from approximately 1,100 vertical wells from the Midland Basin was presented. Such a model has a high resolution conditioned by high well density, and has an advantage of capturing heterogeneities and interactions more than a simplified model created either from one well or low-resolution seismic interpretation. The model was fed into hydraulic-fracture modeling with the consideration of natural-fracture network and stress shadow, followed by reservoir simulation. The in-house uncertainty-analysis package that functions by experimental-design philosophy is linked to the Earth model, hydraulic-fracture modeling, and reservoir simulation. For the first time, the impacts of all the parameters together were evaluated through the final production performance. In our example, we considered completions design, discrete-fracture-network (DFN) characterization and generation, unpropped hydraulic-fracture properties, fracture compaction, and matrix permeability. The result indicated that DFN characterization is the most important parameter affecting production performance. We applied our model and work flow to field development. Well spacing and pad sequence were studied in this paper as two examples. We demonstrated that it is important to properly consider complex interactions among multiple clusters, stages, and wells to evaluate the impacts on well spacing, completions, and development sequence.