Integrated Resource Estimation and Field Development Workflow for Unconventional Reservoirs Using Reservoir Simulation and Economic Analysis Tools: A Case Study from a Shale Well in Saudi Arabia

Abstract

Abstract Unlike conventional reservoirs, unconventional shale reservoirs have significantly lower permeabilities and therefore exhibit transient behavior for longer periods of time, creating uncertainty in reservoir parameters during simulation. Currently, there is no standard industry technique to assess gas deliverability in unconventional reservoirs. The aim of this paper is to present a workflow to calculate Estimated Ultimate Recovery (EUR) and optimize field development that was applied for a multistage fractured horizontal well in a shale play in Saudi Arabia. The workflow starts with using a combination of Decline Curve Analysis (DCA) and Rate Transient Analysis (RTA) methods performed with reservoir simulation software. To achieve an initial estimate of the EUR, we employed the following decline curve models: Stretched Exponential and Duong. After establishing a range of EUR values, a history match was carried out by varying porosity, permeability, stage number, fracture half-length, lateral length, and the Stimulated Reservoir Volume (SRV). We then performed a numerical simulation, where reservoir properties and compeletion pamaters were altered until the simulated data matched the production data. We then performed a sensitivity analysis on the results where the reservoir and well parameters were changed and compared against the cumulative gas production to assess the influence of each parameter on well deliverability while considering the economics of such sensitivities. The economic analysis was carried out by calculating the Net Present Value (NPV), which is dependent on the gas rate, shrinkage, and price, and stimulation and operation costs. The economic evaluation was then carried out by sensitizing different completion parameters, which were then determined for subsequent wells in the area. The results of the sensitivity analysis indicate that increasing the fracture half-length has the most significant impact on the gas production when compared to other completion parameters such as the number of fractured stages. The proposed workflow can be used to determine the EUR and the optimum field development plan for an unconventional shale well in Saudi Arabia to maximize gas production while reducing costs. The workflow can be also used, through the suggested tools, to improve our understanding of the behavior of unconventional gas plays