34 Tight Plays and Unconventional Reservoirs

Friday, 28 May 2010
1:30 PM - 5:00 PM
Platinum 7

APPLICATION OF ADVANCED RESERVOIR SIMULATION WORK FLOW IN TIGHT GAS RESERVOIRS

Paper number: 34-6
Program: Theme Sessions
Time: 4:00 PM – 4:30 PM

Authors

Abstract

As demand for natural gas is increasing yearly, full field reservoir studies are becoming more important to optimize recovery of tight gas fields. However, there are several challenges in tight gas reservoir simulation studies. Since most wells are hydraulically fractured, appropriate representation of hydraulic fractures in a coarse grid is a key to overcome an impractical number of grid blocks resulted using explicit gridding. During history matching fast updating hydraulic fracture parameters is necessary since it may be time consuming when large number of wells and fracture stages are involved. For tight gas reservoirs, shut‑in and initial well bottomhole pressures are important for individual well matches and even fieldwide match, so accurately simulating observed bottom‑hole pressures controls history match quality. In this paper we developed a practical workflow to address the above challenges. First, hydraulic treatments were analyzed to estimate fracture geometries (half‑length, height growth). Then hydraulic fractures were represented by increasing transmissibilities of gridblocks that contain the fractures both in x and y direction. To match initial well bottomhole pressure, bottomhole pressures were simulated by artificially completing wells earlier with negligible production rates and disabling wellbore cross‑flow. The process was automated using a VBA program, so updating the fracture model can be done in a very short time. The workflow was applied in a fluvial tight gas field in Canada. History matching was done by adjusting rock properties and hydraulic fracture parameters. Good history matches were achieved for most wells, despite the complexity of this fluvial reservoir system. The calibrated mode was then used to predict future performance for different development scenarios and evaluate infill locations. The chief technical contribution is the presentation of a workflow to model tight gas reservoirs more efficiently. The workflow described can be applied to any tight gas reservoirs.