Abstract
The use of water-based fracturing fluids during fracturing treatment can be a problem in water-sensitive formations due to the permeability damage hazard caused by clay minerals swelling. The article includes laboratory tests, analyses and simulations for nitrogen foamed fracturing fluids. The rheology and filtration coefficients of foamed fracturing fluids were examined and compared to the properties of conventional water-based fracturing fluid. Laboratory results provided the input for numerical simulation of the fractures geometry for water-based fracturing fluids and 50% N2 foamed fluids, with addition of natural, fast hydrating guar gum. The results show that the foamed fluids were able to create shorter and thinner fractures compared to the fractures induced by the non-foamed fluid. The simulation proved that the concentration of proppant in the fracture and its conductivity are similar or slightly higher when using the foamed fluid. The foamed fluids, when injected to the reservoir, provide additional energy that allows for more effective flowback, and maintain the proper fracture geometry and proppant placing. The results of laboratory work in combination with the 3D simulation showed that the foamed fluids have suitable viscosity which allows opening the fracture, and transport the proppant into the fracture, providing successful fracturing operation. The analysis of laboratory data and the performed computer simulations indicated that fracturing fluids foamed by nitrogen are a good alternative to non-foamed fluids. The N2-foamed fluids exhibit good rheological parameters and proppant-carrying capacity. Simulated fracture of water-based fracturing fluid is slightly longer and higher compared to foamed fluid. At the same time, when using a fluid with a gas additive, the water content in fracturing fluid is reduced which means the minimization of the negative results of the clay minerals swelling.
Highlights
Considering the continuing depletion of energy resources in the world [1,2], the extraction of natural gas has become a priority and it is believed to be a more ecological solution than the extraction of high-emission solid fossils
Fracturing fluids based on polymers such as guar and guar derivatives have been widely used for fracturing treatments, but polymer based fluids could cause serious formation damages and may cause numerous environmental problems [4,5,6], which is why alternative solutions are tested, among which the use of foamed fluid is a relatively new but effective technique [7]
Rheological parameters are of key significance for fracturing fluids, since they largely decide about the geometry of the created fracture and transport properties for proppant materials during fracturing process
Summary
Considering the continuing depletion of energy resources in the world [1,2], the extraction of natural gas has become a priority and it is believed to be a more ecological solution than the extraction of high-emission solid fossils. The process of hydraulic fracturing of unconventional deposits, especially those which are characterized by low reservoir pressures, and sensitive to contact with water, is performed very frequently with the use of foams or energized fluids [16,17]. The selection of the foam quality, liquid phase and gas types depends on economic aspects and reservoir conditions (rock permeability and porosity, water availability, reservoir temperature, pressure, clay content, etc.). This is why foams are recommended in the case of deposits sensitive to contact with water due to water absorption into the clay minerals structure. This model is used to simulate fracture growth behavior for this research because layered tight gas sands have been shown to exhibit this behavior [33]
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