Performance Quantification of Enhanced Oil Recovery Methods in Fractured Reservoirs

Kharrat, Riyaz; Zallaghi, Mehdi; Ott, Holger

doi:10.3390/en14164739

Cited by 14 publications

(8 citation statements)

References 41 publications

(60 reference statements)

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“…Analyzing fractured reservoirs, especially in the context of hydrocarbon production mechanisms, is particularly difficult [1,2]. The type and orientation of fractures notably impact enhanced oil recovery methods, especially in gas and thermal applications, significantly influencing production mechanisms [3][4][5]. A significant complicating factor arises from the fact that the permeability of carbonates is influenced either by secondary dissolution porosity or by fractures that serve as pathways for fluid flow.…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Investigation of the Relationship between Fractures and Oil Production in a Giant Fractured Carbonate Field

Kharrat,

Kadkhodaie,

Azizmohammadi

et al. 2024

Processes

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This study examines the connections between various fracture indicators and production data with an example from one of the giant fields in the Middle East producing complex fractured carbonate lithologies. The field under study hosts two reservoirs with a long development and production history, including carbonates from the Asmari and Bangestan Formations. A fracture intensity map was generated based on the interpretation of image logs from 28 wells drilled within the field. Mud loss data were collected and mapped based on the geostatistical Gaussian Random Function Simulation (GRFS) algorithm. Maximum curvature maps were generated based on Asmari structural surface maps. Comparing the results shows a good agreement between the curvature map, fault distribution model, mud loss map, fracture intensity map, and productivity index. The results of image log interpretations led to the identification of four classes of open fractures, including major open fractures, medium open fractures, minor open fractures, and hairline fractures. Using the azimuth and dip data of the four fracture sets mentioned above, the fracture intensity log was generated as a continuous log for each well with available image log data. For this purpose, the fracture intensity log and a continuous fracture network (CFN) model were generated. The continuous fracture network model was used to generate a 3D discrete fracture network (DFN) for the Asmari Formation. Finally, a 3D upscaled model of fracture dip and azimuth, fracture porosity, fracture permeability, fracture length, fracture aperture, and the sigma parameter (the connectivity index between matrix and fracture) were obtained. The results of this study can illuminate the modeling of intricate reservoirs and the associated production challenges, providing insights not only during the initial production phase but also in the application of advanced oil recovery methods, such as thermal recovery.

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Section: Introductionmentioning

confidence: 99%

A Comprehensive Investigation of the Relationship between Fractures and Oil Production in a Giant Fractured Carbonate Field

Kharrat,

Kadkhodaie,

Azizmohammadi

et al. 2024

Processes

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“…Increasingly, NFR recoveries ensure a steady supply of resources to international oil markets. Consequently, redevelopment of currently producing fractured reservoirs requires maintaining the supply Energies 2023, 16, 6364 2 of 19 but with adequate fracture characterization and modeling [10]. Therefore proper fracture identification and characterization are essential for understanding fluid displacements, especially for improved and enhanced oil recovery [11,12].…”

Section: Introductionmentioning

confidence: 99%

Assessing the Influence of Fracture Networks on Gas-Based Enhanced Oil Recovery Methods

Kharrat,

Alalim,

Ott

2023

Energies

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Numerous reservoirs that play a significant role in worldwide petroleum production and reserves contain fractures. Typically, the fractures must form a connected network for a reservoir to be classified as naturally fractured. Characterizing the reservoir with a focus on its fracture network is crucial for modeling and predicting production performance. To simplify the solution, dual-continuum modeling techniques are commonly employed. However, to use continuum-scale approaches, properties such as the average aperture, permeability, and matrix fracture interaction parameters must be assigned, making it necessary to improve the fracture depiction and modeling methods. This study investigated a fractured reservoir with a low matrix permeability and a well-connected fracture network. The focus was on the impact of the hierarchical fracture network on the production performance of gas-based enhanced oil recovery methods. The discrete fracture network (DFN) model was utilized to create comprehensive two-dimensional models for three processes: gas injection (GI), water alternating gas (WAG), and foam-assisted water alternating gas (FAWAG). Moreover, dimensionless numbers were employed to establish connections between properties across the entire fracture hierarchy, spanning from minor to major fractures and encompassing the fracture intensity. The results indicate that the FAWAG process was more sensitive to fracture types and networks than the WAG and GI processes. Hence, the sensitivity of the individual EOR method to the fracture network requires a respective depth of description of the fracture network. However, other factors, such as reservoir fluid properties and fracture properties, might influence the recovery when the minor fracture networks are excluded. This study determined that among the enhanced oil recovery (EOR) techniques examined, the significance of the hierarchical depth of fracture networks diminished as the ratio of major (primary fracture) aperture to the aperture of medium and minor fractures increased. Additionally, the impact of the assisted-gravity drainage method was greater with increased reservoir height; however, as the intensity ratio increased, the relative importance of the medium and minor fracture networks decreased.

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“…Waterflooding is generally not an effective recovery method in naturally fractured carbonate reservoirs, especially in oil-wet/mixed-wet reservoirs, in addition to the negative effects of scaling [7] and early water breakthrough [8]. The WAG method in NFR might be feasible because gas prefers to flow in the high permeability fractures, resulting in gravity drainage.…”

Section: Introductionmentioning

confidence: 99%

“…For the WAG process, high-permeability fractures and low-permeability matrices are important for a successful application [9]. Recently, the effect of driving forces on oil recovery for gas injection, foam injection, water-alternating gas injection, and foam-assisted water-alternating gas injection was analyzed for fractured reservoirs using dimensionless numbers and a surface response model [8]. The foam and FAWAG injection methods were more sensitive to permeability contrast, density, and matrix block highs than WAG injection.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Gas-Based EOR Methods in Gas-Invaded Zones of Fractured Carbonate Reservoir

et al. 2022

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More than half of all recoverable oil reserves are found in carbonate rocks. Most of these fields are highly fractured and develop different zonations during primary and secondary recovery stages; therefore, they require a different developmental approach than conventional reservoirs. Experimental results for water-alternating gas injection [WAG] and foam-assisted water-alternating gas [FAWAG] injection under secondary and tertiary recovery conditions were used to investigate these enhanced oil recovery [EOR] methods in gas-invaded reservoirs. The relative permeability curves of the cores and the fitting foam parameters were derived from these experiments through history matching. These findings were then used in a quarter five-spot, cross-sectional, and a sector model of a carbonate reservoir where a double five-spot setup was implemented. The fracture and matrix properties’ impact on the recovery was illustrated through the cross-sectional model. The gas mobility reduction effect of the FAWAG was more noticeable than that of WAG. The apparent viscosity of the gas was increased due to the foam presence, which caused a diversion of the gas from the fractures into the matrix blocks. This greatly enhanced the sweep efficiency and led to higher oil recovery. The gas front was much sharper, and gravity overrides by the gas were much less of a concern. The properties of the fracture network also had a significant effect on the recovery. Oil recovery was found to be most sensitive to fracture permeability. At the same time, sweep efficiency increased substantially, improving the recovery rate in the early injection stages, and differed slightly at the ultimate recovery. However, a lower fracture permeability facilitated gas entry into the matrix blocks. The results of the reservoir sector model were similar to the core and pilot. However, the WAG injection recovered more of the uppermost layers, whereas significant portions of the lowest layer were not effectively recovered. In contrast, FAWAG was more effective in the lowest layer of the reservoir. The FAWAG was a beneficial aid in the recovery of gas-invaded fractured reservoirs, increasing the oil recovery factor with respect to WAG.

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Performance Quantification of Enhanced Oil Recovery Methods in Fractured Reservoirs

Cited by 14 publications

References 41 publications

A Comprehensive Investigation of the Relationship between Fractures and Oil Production in a Giant Fractured Carbonate Field

A Comprehensive Investigation of the Relationship between Fractures and Oil Production in a Giant Fractured Carbonate Field

Assessing the Influence of Fracture Networks on Gas-Based Enhanced Oil Recovery Methods

Evaluation of Gas-Based EOR Methods in Gas-Invaded Zones of Fractured Carbonate Reservoir

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