In production, the amount of oil recovered is very important to assess the profitability of a field, so one of the major goals of the oil industry is to maximize it, but after a period of operation, we see a significant drop in the rate of production.
An improved oil recovery process whereby water injection and gas injection are carried out alternately for periods of time to provide better sweep efficiency and reduce gas channeling from injector to producer. This process is used mostly in CO2 floods to improve hydrocarbon contact time and sweep efficiency of the CO2. What do you think it is? Of course it is: water alternating gas (WAG). So what is The WAG? What are its types? What are its advantages?
DEFINITION OF WAG
WAG is one of the most widely techniques used in the petroleum field for low-hanging tanks, injecting gas and water alternating cycles. It is applied as an enhanced oil recovery method meaning that the oil field was in production for a certain period of time, and underwent a primary depletion as well as a normal water injection. The fields examined reported in most cases a good recovery, and in almost all cases, WAG proved a success.
TYPES OF WAG
This process contains several chaps, like the WAG miscible made in onshore and rarely applied in offshore, its technique is based on depressurization to reduce the tank pressure above the minimum miscibility pressure (MMP), which allows us to increase the recovery rate by 9,7%.
the immiscible WAG that applies in tanks with a stable density, and that is made to improve the stability of the forehead or to ensure contact between areas that are not swept, also causes improvement inmicroscopic efficiency and decreases macroscopic due to high miscibility, and generally with this technique there is an increase in the recovery rate of 6,4%, the hybrid WAG which injects a large gas cap followed by a number of small caps of water and gas, we also have the SWAG which is the simultaneous WAG tried the first time in 1962 on the field of SEELINGTON, the latter is carried out with double simultaneous injection columns, one for gas and one for water.
ADVANTAGES OF WAG
Among the advantages of this technique, there is a reduction in the volume of gas injected from water injection, the decrease in the volume of gas produced which decreases the GOR, which is the ratio between the quantity of gas produced and the quantity of oil, also causes improved scanning efficiency and increased oil recovery. Each tank has a special technique for its treatment.
The WAG injection analysis is one of these techniques which is an Enhanced Oil Recovery process developed to mitigate the technical and economic disadvantages of gas injection. Thus it can be concluded that the WAG is a salvage factor that maintains the production rate of a tank over a longer period.