Proper lateral and vertical well spacing is extremely critical to efficiently develop unconventional reservoirs. Much research has focused on lateral well spacing, but little on vertical spacing, which is important and challenging for those stacked-bench plays like Permian Basin. Following the previously successful single well study (SPE 189855), we have performed a seven-well case study by applying the latest complex fracture modeling and reservoir simulation technologies. Those seven wells are located at the same section but also are vertically placed in 4 different zones in the Wolfcamp formation.

With the latest modeling technologies, we first built a 3-D geological and geomechanical model, and full wellbore fracturing propagation model for those seven wells, and then calibrated the model with multi-stage fracturing pumping history of each well. The resulting model was then converted into an unstructured grid-based reservoir simulation model, which was then calibrated with production history.

Based upon the understandings on the local geomechanical characterization, as well as confidence on the capacity of those models from our previous study, we conducted experiments in fracturing modeling to study the impact by different completion design parameters on fracture propagation, including cluster spacing, frac-fluid viscosity, cluster pumping rate, and fluid and proppant intensities. With the statistical distributions of fracture length and height from different completion designs, we then optimized the completion design, studied lateral and vertical well spacings, further investigated frac-hit possibility assisted by Monte Carlo simulation, and estimated stimulated reservoir volume.

The modeling results show: (1) both the length and height of those fractures initiated from perforation clusters are in log-normal distributions depending on completion designs, which provide crucial insights to well interference and furthermore on well spacing; (2) the hydraulic fracture length, height, and network complexity mainly depend on discrete fracture network (DFN), stress and its anisotropy, and frac-fluid viscosity; (3) the key completion design parameters, which impact the fracture length and height distributions, include cluster spacing, clusters per stage, the fluid and proppant intensities, and fluid viscosity and proppant concentration; (4) the implication of frac-hit probability on well spacing and completion design on the well spacing decision and furthermore on recovery and value.

Therefore, we can reasonably model complicated fracturing propagation and well performance with the latest modeling technologies, and optimize both lateral and vertical well spacings, and the corresponding completion designs. The application of those technologies could help operators save significant time and money on well completion and spacing piloting projects, and thus speed up field development decision.

In addition to the detailed modeling process, techniques, and results, the paper will demonstrate our novel workflow to optimize completion design and lateral and vertical well spacings by integrating advanced multi-stage fracture modeling with reservoir simulation in unconventional reservoirs.

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