In shale plays, as with all reservoirs, it is desirable to achieve the optimal development strategies, particularly well spacing, as early as possible, without overdrilling. This paper documents a new technology that can aid in determining optimal development strategies in shale reservoirs. We integrate a decline-curve-based reservoir model with a decision model that incorporates uncertainty in production forecasts. Our work extends previous work by not only correlating well spacing and other completion parameters with performance indicators, but also developing an integrated model that can forecast production probabilistically and determine the impact of development decisions on long-term production.

A public data set of 64 horizontal wells in the Barnett shale play in Cooke, Montague and Wise Counties, Texas, was used to construct the integrated model. This part of the Barnett shale is in the oil window and wells produce significant volumes of hydrocarbon liquids. The data set includes directional surveys, completion and stimulation data, and oil and gas production data. Completion and stimulation parameters, such as perforated interval, fluid volume, proppant mass, and well spacing, were correlated with decline curve parameters, such as initial oil rate and a proxy for the initial decline rate, the ratio of cumulative production at 6 months to 1 month (CP6to1), using linear regression. In addition, a GOR model was developed based on thermal maturity and average GOR versus time. Thousands of oil and gas production forecasts were generated from linear regression and GOR models using Monte Carlo simulation, which serve as the input to the decision model. The decision model then determines the impact of well spacing and other completion/stimulation decisions on long-term production performance.

The technology introduced in this paper can be used to help operators in unconventional reservoirs reach optimal spacing and completion strategies earlier in the lives of these reservoirs, which could accelerate production and increase reserves.

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