Solvent Selection Criteria and Optimal Application Conditions for Heavy-Oil/Bitumen Recovery at Elevated Temperatures: A Review and Comparative Analysis

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Khosrow Naderi ◽  
Tayfun Babadagli
Keyword(s):  
Comparative Analysis ◽  
Oil Recovery ◽  
Heavy Oil ◽  
Selection Criteria ◽  
Elevated Temperatures ◽  
Fractured Reservoirs ◽  
Solvent Type ◽  
Wide Range ◽  
Cost Efficient ◽  
Fractured Carbonates

Sole thermal or solvent methods for heavy-oil recovery are not effective enough to deliver cost efficient processes. Hybrid applications of those two techniques have been proposed to take advantage of each and a wide range of investigations have been recently performed focusing on extreme conditions such as bitumen containing sands and carbonates, deep reservoirs, and oil-wet fractured carbonates. What is critically important in these applications is to determine the best performing solvent for a particular application and optimal application conditions for a given solvent at high temperature conditions. In this study, the results from various reported works on the hybrid applications of thermal (mainly steam) and solvent methods were complied, analyzed, and compared. Attention was given to a comparative analysis of steam-over-solvent injection in fractured reservoirs (SOS-FR) method. Steam/solvent methods show a promising outcome in general, while specific modifications must be taken into account for different application situations. These were discussed and specified, especially from proper solvent type and optimal application conditions for alternate injection of steam and solvent in different reservoir types.

An Experimental Investigation of In Situ Combustion in High Permeability Contrast Systems

2021 ◽  
pp. 1-13
Author(s):  
Melek Deniz Paker ◽  
Murat Cinar
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Combustion Front ◽  
Fractured Reservoirs ◽  
Front Propagation ◽  
High Permeability ◽  
Vertical Orientation ◽  
In Situ Combustion ◽  
Horizontal Orientation

Abstract A significant portion of world oil reserves reside in naturally fractured reservoirs and a considerable amount of these resources includes heavy oil and bitumen. Thermal enhanced oil recovery methods (EOR) are mostly applied in heavy oil reservoirs to improve oil recovery. In situ combustion (/SC) is one of the thermal EOR methods that could be applicable in a variety of reservoirs. Unlike steam, heat is generated in situ due to the injection of air or oxygen enriched air into a reservoir. Energy is provided by multi-step reactions between oxygen and the fuel at particular temperatures underground. This method upgrades the oil in situ while the heaviest fraction of the oil is burned during the process. The application of /SC in fractured reservoirs is challenging since the injected air would flow through the fracture and a small portion of oil in the/near fracture would react with the injected air. Only a few researchers have studied /SC in fractured or high permeability contrast systems experimentally. For in situ combustion to be applied in fractured systems in an efficient way, the underlying mechanism needs to be understood. In this study, the major focus is permeability variation that is the most prominent feature of fractured systems. The effect of orientation and width of the region with higher permeability on the sustainability of front propagation are studied. The contrast in permeability was experimentally simulated with sand of different particle size. These higher permeability regions are analogous to fractures within a naturally fractured rock. Several /SC tests with sand-pack were carried out to obtain a better understanding of the effect of horizontal vertical, and combined (both vertical and horizontal) orientation of the high permeability region with respect to airflow to investigate the conditions that are required for a self-sustained front propagation and to understand the fundamental behavior. Within the experimental conditions of the study, the test results showed that combustion front propagated faster in the higher permeability region. In addition, horizontal orientation almost had no effect on the sustainability of the front; however, it affected oxygen consumption, temperature, and velocity of the front. On the contrary, the vertical orientation of the higher permeability region had a profound effect on the sustainability of the combustion front. The combustion behavior was poorer for the tests with vertical orientation, yet the produced oil AP/ gravity was higher. Based on the experimental results a mechanism has been proposed to explain the behavior of combustion front in systems with high permeability contrast.

Experimental Analysis of the Effects of Varying Temperature and Viscosities on Foamy Oil Production

2021 ◽  
Author(s):  
Jasmine Shivani Medina ◽  
Iomi Dhanielle Medina ◽  
Gao Zhang
Keyword(s):  
Oil Recovery ◽  
Heavy Oil ◽  
Elevated Temperatures ◽  
Oil Production ◽  
Oil Reservoirs ◽  
Oil Viscosity ◽  
Gas Recovery ◽  
Foamy Oil ◽  
Heavy Oil Reservoirs ◽  
Pressure Depletion

Abstract The phenomenon of higher than expected production rates and recovery factors in heavy oil reservoirs captured the term "foamy oil," by researchers. This is mainly due to the bubble filled chocolate mousse appearance found at wellheads where this phenomenon occurs. Foamy oil flow is barely understood up to this day. Understanding why this unusual occurrence exists can aid in the transfer of principles to low recovery heavy oil reservoirs globally. This study focused mainly on how varying the viscosity and temperature via pressure depletion lab tests affected the performance of foamy oil production. Six different lab-scaled experiments were conducted, four with varying temperatures and two with varying viscosities. All experiments were conducted using lab-scaled sand pack pressure depletion tests with the same initial gas oil ratio (GOR). The first series of experiments with varying temperatures showed that the oil recovery was inversely proportional to elevated temperatures, however there was a directly proportional relationship between gas recovery and elevation in temperature. A unique observation was also made, during late-stage production, foamy oil recovery reappeared with temperatures in the 45-55°C range. With respect to the viscosities, a non-linear relationship existed, however there was an optimal region in which the live-oil viscosity and foamy oil production seem to be harmonious.

Effects of Rate, Temperature, and Solvent Type on Vapor/Oil Gravity Drainage (VOGD) in Fractured Reservoirs

SPE Journal ◽  
2019 ◽  
Vol 24 (03) ◽  
pp. 973-987 ◽  
Author(s):  
Neha Anand ◽  
Brandon Tang ◽  
Bradley (Duong) Nguyen ◽  
Chao-yu Sie ◽  
Marco Verlaan ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Molecular Diffusion ◽  
Operating Temperature ◽  
Fractured Reservoirs ◽  
Viscosity Reduction ◽  
Gravity Drainage ◽  
Asphaltene Precipitation ◽  
Solvent Vapor ◽  
Solvent Type ◽  
High Fluid

Summary Application of thermal and solvent enhanced-oil-recovery (EOR) technologies for viscous heavy-oil recovery in naturally fractured reservoirs is generally challenging because of low permeability, unfavorable wettability and mobility, and considerable heat losses. Vapor/oil gravity drainage (VOGD) is a modified solvent-only injection technology, targeted at improving viscous oil recovery in fractured reservoirs. It uses high fluid conductivity in vertical fractures to rapidly establish a large solvent/oil contact area and eliminates the need for massive energy and water inputs, compared with thermal processes, by operating at significantly lower temperatures with no water requirement. An investigation of the effects of solvent-injection rate, temperature, and solvent type [n-butane and dichloromethane (DCM)] on the recovery profile was performed on a single-fracture core model. This work combines the knowledge obtained from experimental investigation and analytical modeling using the Butler correlation (Das and Butler 1999) with validated fluid-property models to understand the relative importance of various recovery mechanisms behind VOGD—namely, molecular diffusion, asphaltene precipitation and deposition, capillarity, and viscosity reduction. Experimental and analytical model studies indicated that molecular diffusion, convective dispersion, viscosity reduction by means of solvent dissolution, and gravity drainage are dominant phenomena in the recovery process. Material-balance analysis indicated limited asphaltene precipitation. High fluid transmissibility in the fracture along with gravity drainage led to early solvent breakthroughs and oil recoveries as high as 75% of original oil in place (OOIP). Injecting butane at a higher rate and operating temperature enhanced the solvent-vapor rate inside the core, leading to the highest ultimate recovery. Increasing the operating temperature alone did not improve ultimate recovery because of decreased solvent solubility in the oil. Although with DCM, lower asphaltene precipitation should maximize the oil-recovery rate, its higher solvent (vapor)/oil interfacial tension (IFT) resulted in lower ultimate recovery than butane. Ideal density and nonideal double-log viscosity-mixing rules along with molecular diffusivity as a power function of oil viscosity were used to obtain an accurate physical description of the fluids for modeling solvent/oil behavior. With critical phenomena such as capillarity and asphaltene precipitation missing, the Butler analytical model underpredicts recovery rates by as much as 70%.

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