Study of Various Water Alternating Gas Injection Methods in 4- and 5-Spot Injection Patterns in an Iranian Fractured Reservoir
- Mohammad Javad Darvishnezhad (Islamic Azad University) | Babak Moradi (Iranian Central Oil Field Company) | Ghassem Zargar (National Iranian Oil Co.) | Afshin Jannatrostami (National Iranian Oil Co.) | Gholam Hossein Montazeri (Iranian Central Oil Field Company)
- Document ID
- Society of Petroleum Engineers
- Trinidad and Tobago Energy Resources Conference, 27-30 June, Port of Spain, Trinidad
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 5.7.2 Recovery Factors, 5.4.2 Gas Injection Methods, 5.1.5 Geologic Modeling, 5.4.6 Thermal Methods, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.3.4 Reduction of Residual Oil Saturation, 4.1.5 Processing Equipment, 5.4 Enhanced Recovery, 5.2 Reservoir Fluid Dynamics, 5.2.1 Phase Behavior and PVT Measurements, 6.5.2 Water use, produced water discharge and disposal, 5.3.2 Multiphase Flow, 4.1.2 Separation and Treating
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In the common methods of water and gas injection, high and unsuitable mobility ratio within the injected fluid and the oil in the reservoir, leads to viscose fingering and reduction of sweep efficiency. It was originally intended to improve sweep efficiency during gas flooding, with alternating slugs of water and gas (WAG injection) designed by and large to follow the same route through the reservoir.
WAG injection has been widely applied since the late 1950s. The typical improved oil recovery (IOR) potential for WAG injection when compared with water injection is quoted in the literature at 5-10%. In this method, injection of water slugs followed by gas, leads to triple region, increase the contact level of injected fluid and reservoir, stable the movement front, and finally increase the recovery. However, depend on the conditions, type and pattern of injection, improvement of recovery is variable and different. WAG injection in five methods, immiscible, miscible, hybrid, simultaneous and selective simultaneous.
In this work, scenarios of WAG injection such as Immiscible WAG (IWAG), Hybrid WAG (HWAG), Simultaneous WAG (SWAG) and Selective Simultaneous WAG (SSWAG) and water and gas injection are compared to specify the appropriate injection method. Then ultimate oil recovery, residual oil saturation, daily and total oil production are compared in these scenarios. Also these scenarios in four and five spot injection patterns were compared.
Results indicated that, SSWAG injection has the higher oil production and lowest residual oil saturation. In addition, among these scenarios, SSWAG in 4-spot pattern had the highest recovery and daily oil production. 4-spot pattern had the higher recovery and lower residual oil saturation than 5-spot pattern, so adding the number of wells could not raise the recovery.
Enhancing the recovery of an oil reservoir is one of the major roles of any oil company. This is achieved by development of the oilfields by employing different techniques such as water injection, gas injection, WAG injection, chemical flooding and even thermal methods. These enhanced oil recovery (EOR) techniques are implemented on mature oil fields to recover additional reserves after primary recovery methods have run their course . By increasing production efficiency, EOR methods can increase the economic life of older fields by as much as 30 years .
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