Reservoirs Fracturinghelps maximize production from unconventional gas reservoir. The primary goal of fracturing is to create a pathway for hydrocarbons to flow from the reservoir to the wellbore. Recently, we have introduced technology that enables achieving and maintaining a highly conductive fracture for improved long-term production. through ongoing research also learned how the fracturing process can damage the formation in the vicinity of the fracture face resulting in reduced gas production and increased water production .when the fracturing fluid initiates and extends fracture and then carries proppant into the fracture, water is drawn into the formation , sometimes several feet into the rock porosity. This movement of water into the formation is due to the capillary effect. The mineral grains in the formation are randomly sized and shaped. This results in voids of pores between the grains. These pores act just like a straw or capillary tube but on a microscopic scale.
When fluids flow into the pore spaces, they are held there by capillary pressure and surface tension and can block formation gases from passing into the wellbore. Here is an actual video of fluid trapped in the porosity of formation rock. The fluid is under pressure but the capillary pressure exceeds the pumping pressure. It's clear that not much gas will be able to flow through this porosity. This is even more pronounced in unconventional gas reservoirs with the lower permeability result in increased capillary pressure. How serious is the problem? Water imbibed into the formation matrix can result in greatly decreased gas production and increased water production.
There is a mathematical simulation of water saturation in a non-damaged formation. Note that during 30 days of production, water saturation decreased dramatically, gas production was high, and water production was low. Here's a simulation of water saturation with 99% damage. Note that during 30 days of production, gas production was low and water production was high. Water saturation remained at almost 100% along a large portion of the fracture. The conclusions is that if the reservoir adjacent to the fracture face is filled with water, gas production will be greatly reduced and water production we'll be enhanced. It's clear that to maximize gas production, the water needs to be removed from the fracture face region. Unfortunately, reservoir pressure in ultra-low permeability formations usually is not sufficient.
This microscopic video shows phase trapping in which water and condensate phases are trapped in this pore network. Even with pressure applied, the imbibed water and gas bubbles cannot be removed. The combination of surface tension and capillary pressure is just too much for the formation pressure to overcome. After applying the new research results, this microscopic video was taken at the same conditions as the previous video. Note that the water and previously trapped phases pass easily through the porosity, leaving a clear pathway for gas production.
R&D Engineers role in fracturing stimulation process:
- Helps reduce damage due to phase trapping.
- Enhances mobilization of liquid hydrocarbon including condensate.
- Helps increase regained permeability to the gas following treatment.
- Improves load recovery.
- Replaces methanol for water block applications.
- Improves environmental and safety performance over existing alternatives.
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