Abstract
In planning successful development of any field, one of the key objectives is to determine the remaining infield potential. In conventional reservoirs, this is usually performed by using decline curve reserves coupled with volumetric recovery. There exist two disparities when the same methodology is applied in ultra low permeability reservoirs such as shale formations. First, production data used in decline curve analysis may be governed by infinite acting rather than boundary dominated flow regime. The prolonged infinite acting production reduces volumetric recovery efficiency to half of what is obtained in conventional reservoirs in situations where spacing exceeds the drainage area during a life of the well. Secondly, in these tight reservoirs, hydraulic stimulation generates the necessary conduit for hydrocarbons to flow at commercial rates, and may also interconnect individual wells into a flow network. Interference among wells in the same flow network must be accounted for to accurately assess remaining infield potential. This study addresses these issues by developing a new evaluation system to assess field maturity.
Production data from 40 wells of core area Barnett shale were analyzed in this study. Based on infinite acting flow behavior exhibited by these wells, new methodologies are presented to estimate reserves and recovery. These methodologies are applicable to the cases where flow over the life of a well is governed by an interconnected yet infinite acting flow system.
A new reservoir management tool is presented which serves as an aid in assessing field development maturity. It is developed by utilizing a correlation between cumulative stimulation treatment volume and reserves which are adjusted for interference and restimulation. Stimulation treatment volume was selected owing to the mixed presence of vertical and horizontal wells found in the investigated reservoir - the Barnett shale. Due to the straightforward nature of this evaluation system, it can be applied to other shale or ultra tight formations as well as to conventional reservoirs.
