Effect of Heterogeneity in a Horizontal Well With Multiple Fractures on the Long-Term Forecast in Shale Gas Reservoirs

Abstract

Abstract Shale gas reservoirs have become a significant source of gas supply in North America owing to the advancement of drilling and stimulation techniques to enable commercial development. The most popular method for exploiting shale gas reservoirs today is the use of long horizontal wells completed with multiple-fracturing stages (MFHW). The stimulation process may result in bi-wing fractures or a complex hydraulic fracture network. However, there is no way to differentiate between these two scenarios using production data analysis alone, making accurate forecasting difficult. For simplicity, often hydraulic fractures are considered bi-wing when analyzing production data. A conceptual model that is often used for analyzing MFHWs is that of a homogeneous completion; in which all fractures have the same length. However, fracture lengths that are equal in length are rarely if ever seen (Ambrose et al., 2011). In this paper, production data from heterogeneous MFHW (i.e., all fracture lengths are not the same) drilled in extremely low permeability reservoirs is studied. First, the simplified forecasting method of Nobakht et al. (2010) developed for homogeneous completions is extended to heterogeneous completions. For one specific case, the Arps decline exponent is correlated to the heterogeneity of the completion. It is found that Arps’ decline exponent to be used after the end of linear flow increases with the heterogeneity of the completion. Finally, it is shown that ignoring the heterogeneity of the completion can have a great effect on the long-term forecast of these wells.