(24a) Data Requirements for Heavy Oil Production - A Reservoir Fluid Perspective

There is a spectrum of methods available for the production and transportation of heavy oils from a variety of different environments (e.g. arctic, onshore, offshore, urban). The production methods may be grouped into one of three main categories; primary methods such as CHOPS, thermal methods including combustion and steam injection, and non-thermal methods such as VAPEX. These methods may be used on their own in or in combination, such as solvent assisted steam injection processes. In each of these cases, some level of understanding of the reservoir fluids is required to select and optimize the production process. As a general rule of thumb, techniques requiring alteration of the fluid properties during production require a greater understanding of the fluid properties.

From an industry perspective, there are a few key challenges that are common to understanding the heavy oil phase behavior and fluid properties for all production processes. The first challenge is deciding what samples to collect. The choice of sampling is determined to some extent on the type of processes (and the related data requirements) under consideration for a particular reservoir. In addition, there is a growing awareness that heavy oil fields often involve fluids with a range of fluid properties, where the variation in properties may be both vertical and aerial. Therefore, there is a need to develop new sample selection approaches that provide the necessary samples that meet the data generation requirements of the production processes of interest as well as to allow identification and quantification of potential fluid properties variations within a heavy oil field.

After selection of sampling locations, there is the challenge of actually acquiring the fluid samples. Ideally, samples would be acquired directly from the reservoir using fluid sampling tools. Unfortunately, due to the low mobility of heavy oil fluids in a reservoir, such tools are often ineffective and most fluid samples must be acquired at the surface when the wells are already flowing or through extraction of a small volume of fluid from a limited number of cores. As a result, thermodynamic models for reservoir simulation or transport will be developed using estimated fluid properties since key data may be not be measurable with the available samples, the data may not provided in time, or there is simply a lack of representative samples.

Once in the laboratory, there are challenges related to the handling of the samples and subsequent measurements. It most case the fluid samples contain some level of contamination, which may include drilling mud, fine solids, and emulsified water, that can alter the measured fluid properties. While there are options available to remove such contaminates, there is no reliable standard approach for ?cleaning' that ensures the samples remain representative. Thus, there is a need to develop a standard method or suite of standard methods for preparing ?representative' fluid samples for measurement. The final challenge is the ability to routinely and consistently characterize heavy oil fluids. While some data can be readily generated using existing standard methods, either directly or through minor modifications to conventional oil procedures, there are a number of key data needs where there is no ?standard' methodology. A simple example is the whole oil composition for heavy oils, where the options are often limited to methods that do not offer enough detail about the composition (e.g. SARA) or cannot resolve a significant portion of the composition (e.g. GC-based methods). A more detailed knowledge of the heavier components is needed for fluid modeling. A solution to this example may be a suite of standardized compositional approaches that address the requirements of each type of production process.

This presentation will provide a brief overview of the types of data required by different production processes and attempt to identify areas of potential technology development in the selection, acquisition, handling, and analysis of heavy oils.