Abstract

For unconventional reservoir development, it is critical to understand the impact of well spacing, completion designs, formation pressure depletion, and parent-child interference, etc. The comprehensive diagnostic dataset acquired in the Hydraulic Fracturing Test Site 2 (HFTS-2) project in the Delaware Basin provided a unique opportunity to develop a comprehensive modeling workflow for accelerating development optimization by building and calibrating integrated fracture and reservoir models.

Full well models were constructed in this work to better capture the nonuniform depletion effect along the lateral by calibration with actual parent-child wells. The fracture model was calibrated with key observations from the HFTS-2 diagnostic dataset, which included fiber optic, microseismic, and downhole pressure data, along with hydraulic fracture and proppant descriptions and DFIT and image logs (presented in Part I of the study). The production data, pressure gauge data, and observations of well interference tests were then honored through history matching of the reservoir model. Finally, the fully calibrated model was employed to perform sensitivity analysis and to optimize completion design and field development. A simplified, fit-for-purpose workflow, as both a supplementary and a complementary modeling approach, was also introduced to provide quick initial guidance for the integrated workflow. 

Model calibration: The integrated fracture and reservoir models were fully calibrated with the comprehensive HFTS-2 diagnostic dataset that included fracture and production data and matched with DFIT and pressure gauge data. The prediction capability of the calibrated model was validated using other methods, such as decline curve analysis, rate transient analysis, and pressure-normalized rate analysis. 

Parent-child effect: Diagnostics and calibrated subsurface models both showed asymmetric fracture geometries for stages in child wells that overlapped parent wells due to the depletion effect. Further analysis quantitatively revealed strong communication between parent and child wells. 

Completion design optimization: Sensitivity studies were conducted to optimize completion designs, including various proppant and fluid loading intensities and fluid types. Short- and long-term production forecasts were compared using the various designs. 

The HFTS-2 comprehensive diagnostic dataset resulted in a well-calibrated integrated model with high confidence in its predictions and helped to verify the accuracy, completeness, and adequacy of all the modeling components. The integrated workflow demonstrated how well spacing, completion design optimization, and parent-child interference can be resolved effectively, and it provided unique insights for making key capital decisions in the unconventional resource development. Furthermore, the calibrated fitfor-purpose workflow would be very valuable for unconventional field development, especially when limited diagnostic data are available.