This paper provides a methodology that is practical and logical in its approach to provide answers involving the evaluation and development of unconventional reservoirs. Multiple sources of data are analyzed to estimate the effectively stimulated volume of reservoir for horizontal wells in the Wolfcamp formation in the Midland Basin of west Texas. Estimating this volume is critical in determining optimum spacing and stacking of horizontal wellbores in unconventional reservoirs.
Stimulated Reservoir Volume (SRV), as determined from microseismic, locates seismic events due to rock failure but does not necessarily represent the reservoir volume contributing to production. The reduced volume contributing to production is defined as the Contributing Reservoir Volume (CRV). This paper presents a workflow of using three methods - interpreted microseismic, proppant material balance, and calibrated hydraulic fracture modeling - to collectively estimate the CRV in hydraulically fractured horizontal Wolfcamp wells.
Microseismic data is interpreted both by applying a discount factor based on industry studies and by analyzing locations and concentrations of events. Then a method of proppant material balance is used to estimate the maximum propped dimensions based on the mass of sand that is placed in each cluster of perforations. Finally, a calibrated geomechanical hydraulic fracturing model is used to model the CRV of 25 wells drilled in the Wolfcamp throughout the study area.
The Wolfcamp formation of the southern Midland Basin has been a popular target for vertical well production for many years (Fig. 1). The Wolfcamp is organically rich and well within the maturity window for oil. It is 1,500 to 2,500 ft thick throughout the heart of the basin and is broken down into four main subsections, labeled A, B, C, and D from top to bottom (see Fig. 2). Recently, horizontal wells in the Wolfcamp have been shown by multiple operators to have significant economic profitability in many areas of the Midland Basin.