A Novel Multiphase Workflow for Tight Unconventionals, with Eagle Ford Well Example

Abstract The goal of unconventional reservoir characterization is to forecast production based on historical well performance. This has been historically achieved using three main categories of modeling (1) decline curve analysis (DCA), (2) rate transient analysis (RTA), and (3) finite-difference numerical modeling. In the past 4 years, new technologies have emerged that, when used together, allow maximum consistency in production forecasting between these modeling approaches. The objective of this paper is to present a novel multiphase workflow integrating the most recent developments in unconventional reservoir characterization, and applying the workflow to an Eagle Ford well example provided in the SPE Data Repository. The unconventional reservoir characterization workflow presented in this paper can be divided into 6 main steps. (1) PVT to correctly describe the fluid behavior and fluid properties using flowback data (Younus et al. 2019, Carlsen et al. 2020); (2) bottomhole pressures, to measure or estimate the flowing bottomhole pressure of each well; (3) multiphase flowing material balance, to estimate the contacted pore volume and contacted OOIP / OGIP (Thompson & Ruddick 2022); (4) numerical RTA, to quantify early time well performance using the linear flow parameter (LFP) (Bowie & Ewert 2020, Carlsen et al. 2021); (5) numerical modeling & forecasting; to estimate the EUR with different bottomhole pressure forecasts; and (6) decline curve analysis; to input DCA parameters into economic evaluation workflows. Common challenges and best practices are provided for each of the 6 steps of the workflow, resulting in a comprehensive workflow that can be readily applied consistently by any reservoir engineer working with unconventional reservoirs. The proposed workflow has been used on many hundreds of wells covering all the ultra-tight unconventional / shale basins in North America. In this paper, the workflow is specifically applied to a well in the Eagle Ford, yielding (but not limited to) initial fluids in place, reservoir rock properties, PVT, well completion factors, fracture area and conductivity, and definition of infinite-acting and boundary-dominated flow regimes. The most relevant characteristics of the proposed workflow are (1) it can be automated and would require less than 30 minutes of engineering analysis per well; (2) it results in a full physics numerical model (finite difference) that can readily be used for any further studies. The proposed workflow is rigorous, complete, and practical, the first of its kind – (1) rigorous, leveraging existing and proven technologies, (2) complete, including every key engineeringstep from the PVT to production forecast and (3) practical, being used currently for more than a thousand wells in several North American basins.