RIASSUNTO
Abstract
This paper describes a novel improved hydrocarbon recovery (IHR) screening methodology capable of (1) screening and prioritizing a large number of reservoirs for various IHR processes and (2) generating preliminary flowstreams through generic sector modeling and proxy simulation. This methodology enables quick screening for a variety of EOR techniques using reservoir rock/fluid properties and technical/economic screening criteria, and quantitatively ranks the EOR options. It also provides the means to complete a first-pass estimate of reservoir performance by applying case-specific performance curves to run facility level simulations. It has been thoroughly tested for various fields where different EOR strategies were or are being implemented, and the results are in good agreement with published data. This methodology helps identify potential IHR opportunities, enabling operators to quickly test the validity and relative merits of IHR for any field or reservoir.
1. Introduction
With the maturity of conventional oil resources increasing and limited volumes of new conventional oil discoveries to replace production, improved hydrocarbon recovery (IHR) will play a key role in any oil company's ability to grow its reserves base. Therefore, it is vital to develop the necessary tools and methodologies required to effectively screen and prioritize assets for IHR opportunities. In addition to merely identifying the most appropriate IHR process, it is of equal importance to be able to predict reservoir performance of an IHR project. IHR encompasses both improved oil recovery (IOR-waterflooding and immiscible hydrocarbon gas injection), and enhanced oil recovery (EOR-miscible gas, chemical, and thermal processes).
The IHR evaluation workflow used by ExxonMobil is presented in Fig. 1 (Selamat et al. 2008). The first step is to identify the most promising injection type and processes for a given reservoir and to complete preliminary screening economics to ensure feasibility. This initial screening step is followed by a more in-depth investigation (i.e. laboratory studies, mechanistic simulations, additional data gathering, etc.) into the most promising processes. When a proposed project demonstrates potential for field implementation, pilot tests may be conducted to resolve any key uncertainties. Additional simulations or laboratory studies may be required after pilot test completion, as indicated by the feedback loop in Fig. 1. The final steps consist of developing the commercial project plan and implementing the necessary surveillance program. This work presents a complete methodology to satisfy the first step of the process described in Fig. 1.
Numerous EOR screening studies have been published with scopes varying from compiling screening criteria for EOR processes to completing a comprehensive prioritization of a country's EOR potential. Over the past two decades, many researchers have used laboratory and field data to develop detailed economic and technical screening criteria for different EOR processes (Taber et al. 1997; Strycker et al. 1999; Henson et al. 2002). These criteria have been used in the development of qualitative screening methods of varying complexities, ranging from simple binary pass/fail tests (Al-Bahar et al. 2004; Yee et al. 2007) to more sophisticated logic algorithms which incorporate uncertainty and risk management (Goodyear and Gregory 1994). In recent years, there has been progress made from merely identifying the most appropriate EOR processes to quantifying its potential through the use of fractional-flow based simulation models (Al-Bahar et al. 2004).