State-of-the-Art Review of Steamflood Field Projects

Abstract

Summary Based on reservoir data from 28 selected steamflood projects, a new screening guide has been developed. Two projects, a new screening guide has been developed. Two regression equations that will allow the prediction of steam/oil ratio (SOR) using known reservoir characteristics were developed. Reported values of other performance variables, such as sweep efficiency, displacement performance variables, such as sweep efficiency, displacement efficiency, and oil recovery, are discussed. Industry experience on project design with numerical and physical models is reviewed. Special well completions needed for steamflood are reviewed, together with surface facilities and monitoring devices. Also discussed are operational problems plaguing the steamflood projects, including problems plaguing the steamflood projects, including steam-related problems, sanding, hot-well productivity, emulsion, the production of acid gas and solids, and mechanical failures. Remedies for these problems are outlined. Introduction Comprehensive reviews of steam-injection field projects, including both steamfloods and steam-stimulation projects. have been given by Farouq Ali and Farouq Ali and projects. have been given by Farouq Ali and Farouq Ali and Meldau. This review covers only steamfloods, specifically screening guides, reservoir performance predictions, project design, well completions, surface facilities and project design, well completions, surface facilities and monitoring devices, and operational problems and their remedies. Screening Guides When dealing with oil prospects, the very first step is to find out whether the field in question can be produced by certain recovery methods. Screening guides are useful for this purpose. Screening guides for steamflooding have been proposed by various authors, including Farouq Ali, Geffen, Lewin and Assocs., and Iyoho (Table 1). A new set of screening guides appears as the last entry in Table 1. The approach used for developing this new screening guide is similar to that used by Chu in developing a screening guide for fireflood field projects. As the data base for the development of the new screening guide, 28 steamflood projects were selected. The reservoir characteristics of these projects are listed in Table 2. Project design, operating variables, and reservoir performance of these projects are given in Table 3. Because the economic feasibility of a steamflood project is related to the steam consumption needed for producing the oil, an SOR of 10.0 was used as the criterion to differentiate between successful and unsuccessful projects. As seen in Table 3, 23 projects have an SOR less than 10.0. These are positive projects. The other five projects, with an SOR of 10.0 projects. The other five projects, with an SOR of 10.0 or greater, are negative projects. The frequency distributions of the various key reservoir characteristics for the positive and negative projects are given in Fig. 1. For example, Fig. 1a shows that there are four positive projects that have a value of So in an interval 0.16 to 0.18 and one negative project in the same interval, resulting in three net positive projects for this interval. Similarly, for the interval 0.08 to 0.10, there is one positive project and one negative project, giving a zero net project for this interval. Following this procedure for the whole range of values for phi So, procedure for the whole range of values for phi So, frequency profiles for the net number of projects are obtained, as given in Fig. 1a. Because negative projects predominate in the interval below phi So=0.08, it is concluded that the values of So should be greater than 0.08 to avoid unfavorable results. The same process was followed regarding other key reservoir characteristics (Fig. 1), resulting in a screening guide that specifies desirable ranges for phi So, phi, So, degrees API, h, and D. No specification was phi So, phi, So, degrees API, h, and D. No specification was made for the other variables because no definite trend can be detected in their frequency profiles for the net number of projects. A perusal of the various screening guides listed in Table 1 shows that some of the earlier screening guides were quite restrictive when used to select oil prospects. Such a guide minimizes the risk of including some undesirable prospects. In so doing, it increases the risk of missing prospects. In so doing, it increases the risk of missing some desirable prospects. Recent changes in the price structure of crude oil and improved steamflood technology helped widen the range of applicability for the steamflood process. This is reflected in the less restrictive screening guide developed in this work. However, in minimizing erroneous rejection, the current guide may possibly increase erroneous acceptance. This should be possibly increase erroneous acceptance. This should be remembered when one applies this screening guide to the oil prospects. Reservoir Performance Predictions After an oil prospect passes the preliminary screening, the next step is to predict reservoir performance a priori under steamflood. This information will help in the preliminary design and evaluation of the project. preliminary design and evaluation of the project. SOR. The SOR is the most important factor characterizing the success or failure of a steamflood project. Its reciprocal, the oil/steam ratio (OSR) is commonly used also. JPT P. 1887