This paper presents a closed-loop reservoir study in tight gas fluvial sands of the giant Jonah gas field located in the northwestern part of the Greater Green River Basin, Wyoming. It produces gas from the micro-darcy fluvial channel sandstones of the Upper Cretaceous Lance Formation after multistage hydraulic fracturing. Single sand body pay zones would not be commercially attractive.
Rigorous reservoir modeling and simulation workflows were employed to build a 3D flow model from geology, geophysics, petrophysics and engineering data and interpretation. The stacked, multi-pay, tight gas sandstone reservoirs and their overpressured conditions were modeled and the hydraulic fractures properties were derived from matching initial well performance. The model was calibrated with well and field performance data through 2006. The calibrated model was used to forecast well performance, estimate reserves; investigate optimal well spacing and infill-well patterns.
Production for old wells and infill wells completed during 2007 and 2008 which was not included in the model calibration is compared with our previously forecasted results. The comparison shows that the actual well production of most of the wells is close to our forecasted results. The production-validated results of this closed-loop study clearly demonstrate that well production and field performance can be forecasted using reservoir modeling and simulation in a highly heterogeneous reservoir. Rigorously-constructed reservoir model(s) help us test and determine optimal production techniques to maximize field production goals. It can be confidently used to reduce field development risk and maximize profits.