Dimensional Analysis of the Criteria for Steam Injection
Authors: Donaldson A.B. , Donaldson Jed E. 
Published: December 2007

A review of the empirical screening criteria for steam stimulation and steam drive was undertaken in order to obtain dimensionless groupings of the listed parameters in conjunction with operator determined recovery choices. To insure a complete set of important parameters, the simple analytic models were considered in combination with the published screening criteria. Correlations with field operations summaries were then used to determine the influence of each individual dimensional parameter, and next the group influence was determined. The utility of a dimensionless screening set is to relax limits on individual parameters and instead, identify contribution of each to the composite or group value.

Introduction

In order for steam stimulation or steam drive to be successful, several factors need to be favorable for economic recovery. These factors can generally be grouped into reservoir parameters, oil parameters and parameters which can be controlled by the operator, such as injection rate and development spacing. Before an investment is made in the conversion of a primary producing field to EOR, some sort of evaluation will be made to predict the probability of economic success. Frequently, this evaluation progresses through several stages, beginning with a rough screening, perhaps based on a table representing composite properties of past successes, followed by analysis with approximate analytic models. If the property development still appears to be promising, then core flow testing might be done to simulate the response of the oil saturated formation matrix to steam. If these results appear promising, a high fidelity three-dimensional computer model can be utilized, which may account for several variations of development strategy. Each of these examinations may cost progressively more in time, manpower and money. Because the costs of the development of a field by steam are quite high, the costs for preliminary studies are justified. This is particularly true when considering the large expenditures for EOR which is made by major oil producers with substantial heavy oil reserves. This consideration is not necessarily the case for smaller oil companies and independents who are more likely to be dealing with marginal properties. In their circumstances, it could be possible that an actual field test might be lower cost than a detailed simulation study. In this latter case, it is may be that one of the rough screening guides is as much analysis as will be done.

The process of using the performance of past projects and bench top core flow experiments as a guide can be termed the empirical approach. The process of predicting performance by calculation based on first principles can be called the analytic approach. Both the empirical and the analytic approach rely on each other to some extent. In the analytic approach, data from thermal and fluid flow tests is generally necessary to provide the required parameters for input to the analytic model. Similarly, the empirical approach requires scaling rules to be known in order to conduct the appropriate core flow experiments.

A number of screening criteria have appeared in the literature. One of the better known and referenced is published by the National Petroleum Council. Others with slightly different entries have been published and will also be discussed later. Presumably, these tables were developed by examining the physical parameters and the results of a large number of field operations and associating a set of these with the success of each project. Some authors have attached a value judgment for each of the standard reservoir and oil screening criteria. Schmidt ranks the depth (shallow) and net pay as the most important factors, followed by porosity, the product of oil saturation and porosity, and permeability. Chu analyzed the performance of 28 field operations to arrive at an empirical correlation and specified the influence factors which should be applied to each of the customary physical parameters to arrive at a prediction of oil/steam ratio at the end of project life. His results show the initial oil saturation to be the most important factor.

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