Abstract
In shale gas formations, imbibition is significant since the tight pore structure causes a strong capillary suction pressure. After hydraulic fracturing, imbibition during the period of shut-in affects the water recovery of flowback. Although there have been many studies investigating imbibition in shale formations, few papers have studied the relationship between gas production and shut-in time under the influence of imbibition. This paper developed a numerical model to investigate the effect of imbibition on gas production to optimize the shut-in time after hydraulic fracturing. This numerical model is a 2-D two-phase (gas and water) imbibition model for simulating an imbibed fluid flow and its effect on permeability, flowback, and water recovery. The experimental and field data from the Woodford shale formation were matched by the model to properly configure and calibrate the model parameters. The experimental data consisted of the relationship between the imbibed fluid volume and permeability change, the relative permeability, and the capillary pressure for the Woodford shale samples. The Woodford field data included the gas production and flowback volume. The modeling results indicate that imbibition can be a beneficial factor for gas production, since it can increase rock permeability. However, the gas production would be reduced when excessive fluid is imbibed by the shale matrix. Therefore, the shut-in time after hydraulic fracturing, when the imbibition happens in shale, could be optimized to maximize the gas production.
Highlights
Hydraulic fracturing is a method to improve gas production in shale formations
Almulhim et al found that the gas production peak and cumulative gas production could be higher when the shut-in time was longer in some shale gas formations, which had strong water-wet characteristics [1]
We introduce a numerical model which considers imbibition to simulate the fluid flow from porous media into hydraulic fractures
Summary
Hydraulic fracturing is a method to improve gas production in shale formations. Well shut-in is one of the necessary steps during the hydraulic fracturing operation to calm down the formation and prepare the flow back. The recovery in in shale gasgas formations is that a longer shut-in timetime can can result in fluid flow from fracture faces to deep inside the rock matrix [4]. The highlight of this study time based on this relationship to achieve the best gas production performance The highlight of this is to quantitatively combine the imbibition with the gas-water flow model. The experimental and field data of the Woodford shale formation were considered thethe model to study thethe effect of imbibition on gas production and and shut-in timetime optimization. The included the imbibition volume, rock permeability change, relative permeability, capillary pressure, data included the imbibition volume, rock permeability change, relative permeability, capillary daily flowback rate and volume, gas production, which were matched by the model achieve pressure, daily flowback rate and and volume, and gas production, which were matched by thetomodel to the parameters for simulating.
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