| dc.description.abstract | Successful exploitation of unconventional resource plays relies on the massive hydraulic fractures which provide high conductive paths and large contact area between formation and wellbore. The pursuit of efficiency and cost savings drives the industry to implement the strategies that utilize more closely spaced hydraulic fractures, as well as multiple horizontal wells with reduced spacing, to maximize the production from unconventional reservoirs with ultra-low permeability. One rising challenge from this trend is to find the optimized spacing between fracture clusters, fracture stages, and fractured horizontal wells so that the potential fracture interference could be minimized. This interference could occur at different scales within lifecycle of exploration, from stress interference in completion stage to pressure interference in production stage. Thus, to systematically study these issues, both geomechanical model and reservoir model are required. In this dissertation, a finite element based geomechanical model and a fast marching based reservoir model are customized to address these emerging problems in unconventional reservoir development.
First, we present a comprehensive study of various factors that affect the performance of refracturing operation, such as fracturing spacing, permeability, proppants and refracturing time, by using a cohesive zone finite element based model that can capture the effect of depletion on fracture propagation. The well performance are evaluated under two different refracturing designs: refracturing new or existing perforations. Based on the simulation results, their respective suitability have been concluded.
Second, we integrate fracture propagation, reservoir flow and wellbore hydraulics to evaluate the stress shadow effect and efficiency of limited entry perforations during multiple simultaneous fracture propagation within a single fracture stage. Simulation results provide insights to the selection of operational parameters such as cluster spacing, number of clusters and perforations, which can be modified accordingly to deal with the fracture interference and thus promote the uniform stimulation in the formation.
Last, to study the production interference between wells, on top of current fast marching based reservoir simulation workflow, we proposed an approach to extend its applicability from transient to boundary-dominated flow regime, as well as a new partition method to identify the respective drainage volume of individual well. This partition criterion utilizes asymptotic pressure solution and results in a good approximation to the conventional streamline tracing method. The supremacy of numerical efficiency has been further demonstrated with numerical experiments. | en |
