Analysis of Water Flowback Data in Gas Shale Reservoirs

Properties of both shale gas reservoirs and hydraulic fractures are usually estimated by analyzing hydrocarbon production data while water data is typically ignored. This study introduces a new method to estimate the effective fracture volume in shale gas wells using water production data instead of the hydrocarbon production data.

The main objective of this study is to verify and improve Alkouh?s method of estimating the effective fracture volume using water production data through testing it at different reservoir conditions. For this purpose, several simulation cases were run. The results of the simulation runs were compared with the production data from several Fayetteville gas wells. Different conclusions were obtained from these comparisons that emphasize the importance of using water production data in the production data analysis. A better evaluation for fracture-stimulation jobs can be acquired through the estimation of the effective fracture volume from early water production data.

The main outcome of this study is a new method (modification ofAlkouh?s method) for analyzing water production data in shale gas wells. The new method gave very good estimation to the actual effective fracture volume in all simulation cases while Alkouh?s method overestimated the volume in all cases. In addition, the new method considered the effect of changing initial reservoir pressure (different reservoirs) and flowing bottom-hole pressure. In addition, the new method showed very good estimation of the effective fracture volume when applied on field data. The data of the first 10-15 days of production (early production data) was used to evaluate the fracture job using the new method and it only underestimated the actual volume (after few years of water production) by around 10%.