Drawdown management optimization in overpressured formations is recognized as challenging by reservoir engineers. Well flowback operational procedures can vary widely and have an impact not only in the first months of production but on the long term performance as well. In this study, the results of choke management in more than a hundred horizontal wells in Loma Campana block, located in Vaca Muerta Shale Oil window, will be evaluated to investigate the potential impact on estimated ultimate recovery (EUR) and net present value (NPV). Using different flowback strategies, production data of wells in the same interval within Vaca Muerta Fm. have been analyzed using diagnostic plots commonly applied in unconventional reservoirs to identify early flow regimes. The evolution of stress over hydraulic fractures have been evaluated as well, which may contribute to a permanent conductivity loss due to hysteresis effects. Several forecasts have been created using Rate Transient Analysis (RTA) to quantify EUR loss due to aggressive choke management and to establish a relationship between drawdown and productivity degradation. The study found out that an aggressive choke management may cause a reduction in EUR of up to 20%. This can be attributed to a loss in fracture conductivity as a result of geomechanical-related factors. Therefore, an aggressive drawdown management is prone to minimize value, but understanding the tradeoff between the financial benefit due to production acceleration versus loss in reserves (as a result of fracture degradation) is the key issue that will be investigated in this paper. Furthermore, the proposed methodology used to integrate production performance analysis with the economic evaluation has allowed defining an optimum drawdown management for Vaca Muerta wells. Therefore, a standard procedure based on best practices is proposed for managing new wells put on production. As summary, this work provides evidence of production dependence on drawdown based on empirical data of horizontal wells in Loma Campana Oilfield. Complementing the study with RTA analysis has allowed quantifying the loss in EUR, estimating the effect of fracture degradation and verifying the economic impact. Finally, a workflow is proposed to accomplish optimum pressure decline with the right choke selection over time to optimize well performance.

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Well spacing and stimulation design are amongst the highest impact design variables which can dictate the economics of an unconventional development. The objective of this paper is to showcase a numerical simulation workflow, with emphasis on the hydraulic fracture simulation methodology, which optimizes well spacing and completion design simultaneously. The workflow is deployed using Cloud Computing functionality, a step-change over past simulation methods. Workflow showcased in this paper covers the whole cycle of 1) petrophysical and geomechanical modeling, 2) hydraulic fracture simulations and 3) reservoir simulation modeling, followed by 4) design optimization using advanced non-linear methods. The focus of this paper is to discuss the hydraulic fracture simulation methods which are an integral part of this workflow. The workflow is deployed on a dataset from a multi-well pad completed in late 2018 targeting two landing zones in the Vaca Muerta shale play. On calibrated petrophysical and geomechanical model, hydraulic fracture simulations are conducted to map the stimulated rock around the wellbores. Finely gridded base model is utilized to capture the property variation between layers to estimate fracture height. The 3d discrete fracture network (DFN) built for the acreage is utilized to pick the natural fracture characteristics of the layers intersected by the wellbores. The methodology highlights advances over the past modeling approaches by including the variation of discrete fracture network between layers. The hydraulic fracture model in conjunction with reservoir flow simulation is used for history matching the production data. On the history matched model, a design of experiments (DOE) simulation study is conducted to quantify the impact of a wide range of well spacing and stimulation design variables. These simulations are facilitated by the recent deployments of cloud computing. Cloud computing allows parallel running of hundreds of hydraulic fracturing and reservoir simulations, thereby allowing testing of many combinations of stimulation deigns and well spacing and reducing the effective run time from 3 months on a local machine to 1 week on the cloud. Output from the parallel simulations are fitted with a proxy model to finally select the well spacing and stimulation design variables that offer the minimum unit development cost i.e. capital cost-$ per EUR-bbl. The workflow illustrates that stimulation design and well spacing are interlinked to each other and need to be optimized simultaneously to maximize the economics of an unconventional asset. Using the workflow, the team identified development designs which increase EUR of a development area by 50-100% and reduce the unit development cost ($/bbl-EUR) by 10-30%.