Drawdown-Management and Fracture-Spacing Optimization in the Meramec Formation: Numerical- and Economics-Based Approach

Abstract

Summary Optimal spacing between fracture clusters has eluded reservoir and completions engineers since the inception of multistage hydraulic fracturing. Very small fracture spacing could result in fracture to fracture (intrawell) interference and a higher completion cost, whereas very large fracture spacing could lead to inefficient hydrocarbon recovery, which is detrimental to the well economics. Meramec Formation has moved to full-field development, and multiple wells are put on production in a relatively short time. Depending on the desired economic metric, net present value (NPV), or rate of return (ROR), the magnitude of intrawell interference can be optimized by adjusting fracture spacing. For instance, if the objective is to maximize ROR, then tighter fracture spacing can be accepted. Furthermore, petroleum economics are often ignored in simulation studies, particularly the concepts of time value of money and oil-price sensitivity. This has led to a knowledge gap in identifying optimal drawdown procedure and fracture spacing from numerical models. This study proposes a framework that integrates petroleum economics with simulation results to optimize a horizontal well from the Meramec Formation. On the basis of this framework, we identified optimal drawdown procedure and fracture spacing. Then, oil-pricing sensitivity analysis was conducted to illustrate the effect of oil-price volatility on design parameters. Moreover, this study investigates the relative contribution of reservoir and completions characteristics with regard to short- and long-term well performance. These characteristics include drawdown management, fracture spacing, pressure-dependent permeability, critical gas saturation, and petrophysical properties. Available geologic data were integrated to construct a geologic model that is used to history match a well from the Meramec Formation. The geologic model covers an area of 640 acres that encompasses a multistage hydraulically fractured horizontal well. The well is unique because it is unbounded and has more than 2 years of continuous production without being disturbed by offset operations. Findings suggest that the drawdown strategy (aggressive vs. conservative) has more effect on short-term oil productivity than fracture spacing. Drawdown strategy even has more of an effect on short-term oil recovery than does a 20% error in porosity, or water saturation. Furthermore, the profile of the producing-gas/oil ratio (GOR) depends on completions efficiency, and it has been interpreted using linear-flow theory.