A Comprehensive EOR Study of a Highly Fractured Matured Field-Case Study

Kharrat, Riyaz; Mahdavi, Sedigheh; Ghorbani, Davood

doi:10.2118/153311-ms

Cited by 11 publications

(5 citation statements)

References 10 publications

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“…This study was based on the experimental work conducted by Kharrat and his team [17][18][19][20][21], wherein they studied the effects of carbon dioxide injection, WAG, and FAWAG injection into cores from the matrix of the naturally fractured carbonate reservoir as a secondary and tertiary recovery method. The experiments were conducted using live oil, brine with 5000 ppm of salts (4000 ppm NaCl, 500 ppm CaCl 2 and MgCl 2 ), and sodium lauryl sulfate as the anionic surfactant and foaming agent.…”

Section: Overview Of Utilized Experimental Datamentioning

confidence: 99%

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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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Section: Overview Of Utilized Experimental Datamentioning

confidence: 99%

“…The core models need to be set up with the acquired PVT data. The runs are based on the experiments conducted by [17,18]. Roughly 1.6 pore volumes were injected into the core.…”

Section: History Matchingmentioning

confidence: 99%

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

et al. 2022

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“…In contrast, the rock matrix serves as the hydrocarbon source [2]. These reservoirs are well known for having poorer recoveries than their counterpart clastic reservoirs due to their production characteristics and geological heterogeneities [3][4][5][6][7][8]. Furthermore, the channeling and fingering of the injected fluid may be due to the complexity of the natural fracture networks [9].…”

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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“…In this method, by stabilizing the injection front, the remaining oil saturation of the formation decreases. In addition, gas injection reduces the oil saturation in bigger pores, whereas water ooding reduces the oil saturation in smaller pores [8]. Thus, WAG ooding can squeeze more volume of hydrocarbon out of a reservoir by combining factors including better mobility control, sweeping un-swept zones (i.e., macroscopic displacement), and improved microscopic displacement e ciency [9,10].…”

Section: Introductionmentioning

confidence: 99%

Simulation Optimization of Water Alternating Gas (WAG) Process under Operational Constraints: A Case Study in the Persian Gulf

2019

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The optimization of the e ciency of Water Alternating Gas (WAG) ooding projects can guarantee the success of these projects. Many operational constraints can indirectly a ect ooding e ciency. Their e ects are not normally considered during routine optimizations. The main aim of this study is to determine the in uence of these constraints (e.g., maximum water-cut, maximum Gas-Oil Ratio (GOR), and minimum Bottom Hole Pressure (BHP) during the WAG process). Implementing a reservoir simulator coupled with Simulating-Annealing (SA) enables us to discover the e ects of these constraints during simulation optimization. The developed optimizer is applied to a case study from an Iranian formation located in the Persian Gulf. The recovery factor of WAG ooding is compared with that of the conventional water ooding and gas injection. Moreover, the optimization of individual and simultaneous WAG parameters is analyzed. Results indicate that: (a) Operational constraints can not only alter the production mechanism but also directly a ect the ultimate recovery factor; (b) The recovery factor of simultaneous optimization of all WAG parameters is higher than that of individual parameter optimization; (c) Irrespective of the approach to parameter optimization, WAG ratio (or the volume fraction of injected water to gas) remains almost constant during all optimizations, showing the in uence of this parameter during WAG ooding scenarios.

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A Comprehensive EOR Study of a Highly Fractured Matured Field-Case Study

Cited by 11 publications

References 10 publications

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

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

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

Simulation Optimization of Water Alternating Gas (WAG) Process under Operational Constraints: A Case Study in the Persian Gulf

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