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Abstract With a recent trend in increased infill well development in the Midland basin and other unconventional plays, it has been shown that depletion has a significant impact on hydraulic fracture propagation. This is largely because production drawdown causes in-situ stress changes, resulting in asymmetric fracture growth toward the depleted regions. In turn, this can have a negative impact on production capacity. For the initial part of this study, an infill child well was drilled and completed adjacent to a parent well that had been producing for two years. Due to drilling difficulties, the child well was steered to a new target zone located 125 feet above the original target. However, relative to the original target, treatment data from the new zone indicated abnormal treatment responses leading to a study to evaluate the source of these variations and subsequent mitigation. The initial study was conducted using a pore pressure estimation derived from drill bit geomechanics data to investigate depletion effects on the infill child well. The pore pressure results were compared to the child well treatment responses and bottom hole pressure measurements in the parent well. Following the initial study, additional hydraulic fracture modeling studies were conducted on a separate pad to investigate depletion around the infill wells, determine optimal well spacing for future wells given the level of depletion, and optimize treatment designs for future wells in similar depletion scenarios. A depletion model workflow was implemented based on integrating hydraulic fracture modeling and reservoir analytics for future infill pad development. The geomechanical properties were calibrated by DFIT results and pressure matching of the parent well treatments for the in-situ virgin conditions. Parent well fracture geometries were used in an RTA for an analytical approach of estimating drainage area of the parent wells. These were then applied to a depletion profile in the hydraulic fracture model for well spacing analysis and treatment design sensitivities. Results of the initial study indicated that stages in the new, higher interval had higher breakdown pressures than the lower interval. Additionally, the child well drilled in the lower interval had normal breakdown pressures in line with the parent well treatments. This suggests that treatment differences in the wells were ultimately due to depletion of the offset parent well. Based on the modeling efforts, optimal infill well spacing was determined based on the on-production time of the parent wells. The optimal treatment designs were also determined under the same conditions to minimize offset frac hits and unnecessary completion costs. This case study presents the use of a multi-disciplinary approach for well spacing and treatment optimization. The integration of a novel method of estimating pore pressure and depletion modeling workflows were used in an inventive way to understand depletion effects on future development.
Abstract In a multiwell environment, the formula for improving the recovery efficiency per rock volume depends on the well spacing, stacking, and the completion strategy. Operators in the multi-benched Permian basin have been actively pursuing various trials of different combinations of vertical and horizontal spacing and completions of the wellbores. The study presented in this paper tries to achieve a prescription for successful exploitation of the cube of the unconventional reservoir rock through cloud-based multivariate simulation modeling. A multilayer Wolfcamp earth model was calibrated. Reservoir characterization for petrophysical and geomechanical properties and discrete natural fracture network (DFN) were the fundamental steps to build the calibrated earth model. The tools used to derive the optimal solution space included over 500 multithreaded streamlined cloud-based complex hydraulic fracture simulations, use of unstructured gridding, fine-resolution numerical simulations, and finite-element geomechanical simulations. Optimal well landing was achieved by using a full-3D hydraulic fracture simulator. The effects of varying proppant-per-foot design (1,000 lbm/ft to 5,000 lbm/ft.); cluster spacing, stage spacing, and various well spacing (300 ft to 1,500 ft) configurations; and vertically stacked and staggered configurations are studied. From the study, it is demonstrated that there are four elements that contribute to maximizing the recovery factor: optimal well landing, optimal well completion, optimal well spacing, and optimal time of completion. The parent-to-child relationship impairs production by up to 18% in 1 year, which is exemplified though finite-element simulations capturing the stress magnitude and direction reorientation. Stimulation sequences such as zippering and non-zippering the wellbores for completion were also found to be critical. Multiple sensitivities have therefore allowed us to define the envelope for optimal strategy of asset development in the reservoir volume. With cloud computing serving as the enabler, the methodology discussed in the case study provides an integrated workflow to optimize the completion strategy in a multilayered unconventional formation such as in the Permian basin. The workflow helps to derive a structured approach to minimize the development cost, increase well completion effectiveness, and minimize the bypassed leftover hydrocarbon in the reservoir.