This study examined the relationship between the early production data and the long-term performance of shale gas wells, including the estimated ultimate recovery (EUR) and economics. The investigated early production data are peak gas production rate, 3-, 6-, 12-, 18-, and 24-month cumulative gas production (CGP). Based on production data analysis of 485 reservoir simulation datasets, CGP at 12 months (CGP_12m) was selected as a key input parameter to predict a long-term shale gas well’s performance in terms of the EUR and net present value (NPV) for a given well. The developed prediction models were then validated using the field production data from 164 wells which have more than 10 years of production history in Barnett Shale, USA. The validation results showed strong correlations between the predicted data and field data. This suggests that the proposed models can predict the shale gas production and economics reliably in Barnett shale area. Only a short history of production (one year) can be used to estimate the EUR and NPV of various production periods for a gas well. Moreover, the proposed prediction models are consistently applied for young wells with short production histories and lack of reservoir and hydraulic fracturing data.

Steam and gas push (SAGP) reduces greenhouse gas emissions by co-injecting non-condensable gas (NCG) with steam, preventing heat loss to thief zones and maintaining steam chamber pressure and temperature. However, NCG can hinder steam chamber growth, reducing oil production than steam-assisted gravity drainage (SAGD). Additionally, determining the type, concentration, and injection timing of NCG based on the given reservoir conditions can be challenging. Nitrogen and methane are commonly used NCGs due to their low solubility in oil, but concentrations above 3 mol% typically decreases SAGP efficiency. To prevent NCG interference with steam chamber, an injection pressure of 0.95–1.1 times reservoir pressure and an NCG injection between 0 and 0.6 times total production period are recommended. Numerical simulations showed that injecting NCG after 0.125, 0.25, and 0.375 times total 8-year production period increased cumulative oil production by 18.6%, 163.7%, and 218.6% respectively, compared to injection from the start. Sensitivity ranges for reservoir parameters include thief zone thickness of aquifer (0–0.5 times reservoir thickness), ratio of vertical to horizontal permeability for sandstone (0.3–0.65), and oil viscosity based on major oil sands regions in Canada (2,000,000 cp. for Athabasca, 200,000 cp. for Peace River, and 60,000 cp. for Cold Lake at 12 °C). Thicker thief zones increase heat loss and higher vertical permeability accelerates steam chamber rise, requiring earlier NCG injection. Additionally, lower oil viscosity regions are more suitable for SAGP. Field application of Suncor Firebag project that NCG reduced cumulative steam-oil ratio from 3.14 to 2.76, demonstrating SAGP’s effectiveness.

This study developed a production-forecasting model to replace the numerical simulation and the decline curve analysis using reservoir and hydraulic fracture data in Montney shale gas reservoir, Canada. A shale-gas production curve can be generated if some of the decline parameters such as a peak rate, a decline rate, and a decline exponent are properly estimated based on reservoir and hydraulic fracturing parameters. The production-forecasting model was developed to estimate five decline parameters of a modified hyperbolic decline by using significant reservoir and hydraulic fracture parameters which are derived through the simulation experiments designed by design of experiments and statistical analysis: (1) initial peak rate (), (2) hyperbolic decline rate (), (3) hyperbolic decline exponent (), (4) transition time (), and (5) exponential decline rate (). Total eight reservoir and hydraulic fracture parameters were selected as significant parameters on five decline parameters from the results of multivariate analysis of variance among 11 reservoir and hydraulic fracture parameters. The models based on the significant parameters had high predicted values on the cumulative production. The validation results on the 1-, 5-, 10-, and 30-year cumulative production data obtained by the simulation showed a good agreement: . The developed production-forecasting model can be also applied for the history matching. The mean absolute percentage error on history matching was 5.28% and 6.23% for the forecasting model and numerical simulator, respectively. Therefore, the results from this study can be applied to substitute numerical simulations for the shale reservoirs which have similar properties with the Montney shale gas reservoir.