Light-Oil Steamflooding: A Laboratory Study
- Partha S. Sarathi (Natl. Inst. for Petroleum and Energy Research) | S. Doug Roark (Natl. Inst. for Petroleum and Energy Research) | Arden R. Stryker (Natl. Inst. for Petroleum and Energy Research)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Engineering
- Publication Date
- May 1990
- Document Type
- Journal Paper
- 177 - 184
- 1990. Society of Petroleum Engineers
- 5.3.4 Reduction of Residual Oil Saturation, 5.7.2 Recovery Factors, 5.1.1 Exploration, Development, Structural Geology, 5.4.6 Thermal Methods, 5.8.5 Oil Sand, Oil Shale, Bitumen, 5.4.1 Waterflooding, 4.1.5 Processing Equipment, 1.6.9 Coring, Fishing, 5.5.2 Core Analysis, 1.2.3 Rock properties, 2.4.3 Sand/Solids Control, 5.2.1 Phase Behavior and PVT Measurements, 4.3.4 Scale, 5.4.2 Gas Injection Methods
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Experiments were conducted in a 2D elemental model to determine the response of light crudes to steam injection and to verify reported numerical simulation results. The results showed that light-oil steamfloods are typified by an early production response to steam injection and that recovery efficiencies are strongly influenced by the chemical nature of the crude. The data also indicated that gravity override of steam remains a potential problem in light-oil steamflooding and that as much as 65% of oil in place (OOIP) can be recovered economically by steamflooding light oils.
Steamdrive, the most commonly used EOR process, has been used commercially for more than 2 decades to recover heavy oil from shallow reservoirs. In recent years, a great deal of interest in extending this technology to light-oil reservoirs has been evidenced by reports of several pilot projects and laboratory and computer simulation studies. Results of these studies indicate that light-oil steamflooding is a viable process and that steam distillation during steamflooding is the principal recovery mechanism. Numerical simulation studies indicate that gravity override of steam is expected to be minimal for light-oil reservoirs and that good sweep efficiencies are possible in homogeneous production zones. Despite the promise shown by these studies, no full-scale light-oil steamfloods have been undertaken. One reason for this is the scarcity of quantitative information on various process variables that affect the economics of the process. Most of the previous experimental studies focused on generating crude oil steam distillation data and correlating steam distillation yields with crude gravity. Other studies focused on the overall recovery and the temperature distribution in linear models. Effects on the process of such important variables as rock properties, nature of the crude, steam injection rate, and degree of gravity override were not addressed. Reported simulation studies made allowances for only a few components, and the assumptions built into these reservoir models limited their predictive ability. To make light-oil steamflooding a fully proven method, the key economic and technical risks associated with the process must be identified and addressed. This requires an understanding of the process variables. The goal of this project was to identify factors that have a direct bearing on the success of the process. Some of these factors are rock properties, crude oil composition, degree of steam override, sweep efficiency, steam quality, and steam injection rate. Previous studies investigated the effects of oil and rock properties on the performance of light-oil steamfloods. Findings of these studies, conducted primarily to check fluid/rock interactions under field conditions, are summarized later. This investigation was undertaken to obtain information on the importance of gravity override in a light-oil steamflood process and to ascertain crude oil composition changes and their influence on recovery. Data obtained in this study were also used to verify reported numerical simulation findings.
Previous Studies. Strycker and Sarathi presented a critical review of previous light-oil steamflood studies, including field projects, research projects, and simulation studies. Here, we summarize our earlier findings. Our first study in 1984 investigated the effects of rock and fluid properties on the performance of light-oil steamfloods. Tests were conducted under simulated in-situ field conditions of pressure, temperature, and overburden pressure in 1.5-in. [3.8-cm] -diameter 26-in. [66-cm] -long fired Berea sandstone cores. Two kinds of experiments were performed: waterflooded cores were used to simulate tertiary recovery and non-waterflooded cores were used to simulate primary recovery. Madden and Sarathi reported the details of the investigation, which included the following findings. 1. Ultimate recovery as high as 86% original OOIP is possible. 2. Residual oil saturation (ROS) is relatively independent of initial oil and water saturations, but premature steam breakthrough may result if the initial water saturation is high. 3. The chemical nature of the crude affects ultimate oil recovery; the presence of large amounts of polar compounds in the crude lowers the ultimate oil recovery. 4. The ultimate oil recovery is relatively independent of injected steam quality and steam injection rate. Oil can be recovered faster, however, by injecting higher-quality steam or by using a higher injection rate. 5. While variations in core permeabilities had a negligible effect on experimental ultimate oil recoveries, the use of lower-permeability cores resulted in greater heat losses because of slow steam-front progress.
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