Defining the Ideal Range for Reducing Oil Viscosity and the Optimal Rate of Steam Injection for a Heavy Oil Field

Introduction

Thermal Enhanced Oil Recovery (EOR) methods, also known as thermal recovery techniques, are a category of EOR processes that involve the application of heat to increase the mobility of heavy or viscous crude oil, making it easier to extract from underground reservoirs. These methods are particularly effective in heavy oil, bitumen, and certain types of oil sands reservoirs, to reduce the viscosity of oil, the thermal recovery process involves heating the reservoir. Thermal enhanced oil recovery (EOR) accounts for more than 50% of the EOR market share, with steam injection being the most widely adopted technique within this category. Another method is in-situ combustion, where a high-oxygen gas mixture is injected into the reservoir, igniting, and creating a combustion front. Steam injection is primarily employed in shallow reservoirs containing highly viscous, often heavy, crude oil. Notable examples include the oil sands in Alberta, Canada, and those in California’s San Joaquin Valley [1]. Here are some of the most common thermal EOR methods.

Methodology

After conducting multiple simulation runs. The optimal steam injection rate range for this field has been identified as 1500 km3. Beyond this value any further increase in the steam injection rate does not have a significant impact on oil production.

Determining the optimal oil viscosity reduction range and steam injection rate for a heavy oil field is a critical aspect of designing an effective thermal Enhanced Oil Recovery (EOR) project. The following steps are typically involved in this process: Reservoir Characterization: The first step is to thoroughly characterize the heavy oil reservoir. This includes assessing factors such as reservoir depth. Temperature, permeability, porosity and the nature of the heavy oil. Understanding the reservoir’s properties is crucial in determining the appropriate EOR method and parameters. Laboratory Testing: Laboratory experiments can be conducted to determine the oil’s response to temperature changes and the effect of steam injection. These tests can provide data on how oil viscosity changes at different temperatures and the impact of steam [8]. Reservoir Simulation: Using specialized reservoir simulation software. Engineers model the reservoir and the proposed EOR process. This simulation helps determine the optimal injection rates, steam temperatures and well spacing required to achieve the desired oil viscosity reduction and production rates. Sensitivity Analysis: Engineers perform sensitivity analyses to assess how variations in injection rates, steam quality and other parameters affect the project’s performance. This helps in identifying the range of optimal values [9]. Field Pilot Testing: Field pilot projects are often conducted to validate the findings from laboratory testing and simulations. These pilots involve actual steam injection and monitoring of oil production and reservoir behavior. Data Analysis: The data collected from laboratory testing, simulation and field pilots are analyzed to determine the optimal range for reducing oil viscosity and the steam injection rate that maximizes production [10].

Economic Evaluation: A cost-benefit analysis is crucial to assess the economic feasibility of the EOR project. Factors such as the cost of steam generation, equipment installation and the expected increase in oil production are considered. Environmental and Regulatory Considerations: Compliance with environmental regulations and the responsible use of resources, including water for steam generation are important considerations. Implementation and Monitoring: If the project is deemed economically viable and environmentally responsible. It is implemented and performance is continually monitored and adjusted as needed [11].

In this project, heavy oil field was modeled in Tempest software. Oil viscosity multiplier was defined based on previous experiences. Sensitivity analysis was done based on various viscosity multiplier for oil. Optimal oil viscosity multiplier was determined based on this research. Then, sensitivity analysis made based on different steam injection volumes, optimal steam injection volume was obtained.

The Experimental Part

The experimental phase of this research project was carried out in the West (Qarbi) Absheron field, known for its heavy oil characteristics with oil viscosity ranging between 20-28 cP, Thermal enhanced oil recovery methods are particularly suitable for heavy oil fields. The study focused on determining the optimal range for reducing oil viscosity and the suitable steam injection rate for this specific field (Table 1 & Figure 2).

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According to the research, optimum oil viscosity was achieved in case of 0.102 oil viscosity reduction multiplier. Total oil production was 960.583 km3 in the beginning of 2045 year.

Based on different simulation runs. It has been defined the optimum oil viscosity reduction range for this field. It is 0.102 (Table 2 & Figure 3).

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In this stage of research, sensitivity analysis was done in different volumes of steam injection. Based on this sensitivity analysis, daily 1500 m3 volume of steam injection is the optimal volume. After this volume, increase in steam injection doesn’t increase total oil production than 1500 m3 volume of steam injection.

Conclusion

In conclusion the selection of an enhanced oil recovery method for a specific field is of utmost importance and is primarily determined by screening criteria. Thermal enhanced oil recovery methods are particularly well- suited for heavy oil fields. This study primarily focused on determining the optimal oil viscosity reduction multiplier, which was found to be 0.102 after several cases. Additionally, it was established that 1500 km3 of steam injection serves as a critical threshold for this field. Beyond this point, increasing the volume of steam injection does not lead to a significant improvement in oil production.