Improving oil mechanism of polymer gel fracturing fluid based on filtration displacement

In contrast to the field effect of guar gum fracturing fluid, the polymer gel fracturing fluid causes a different production phenomenon. There is a lag between fracturing and the occurrence of oil production; however, the period of higher oil production is extended. In this study, the filtration displacement of the polymer gel fracturing fluid improves the fracturing effect was put forward. The claim is verified by comparing the difference in the mechanism by which the polymer gel and guar gum fracturing fluids increase oil production. Experiments were conducted to determine the influence of permeability and filtration pressure on the filtration volume of the polymer gel fracturing fluid and the remaining oil saturation in the filtration displacement area. The field effect of the polymer gel fracturing fluid was analyzed. The results indicated that the filtration displacement of the polymer gel fracturing fluid can help improve the remaining oil distribution in reservoirs in the upper, lower, and front areas of the fracture, which may help extract the remaining oil under the pressure difference of the subsequent production and displacement function of flooding agents. The filtration pressure difference was controlled according to the permeabilities of fracturing reservoirs to ensure that the oil displaced by polymer gel fracturing fluid could flow back to the fracture after being displaced. A new method of injecting the pre-displacement agent before fracturing the reservoir, namely the “fracturing after displacement”, was proposed. This method can help further exploit the remaining oil in the reservoir near the well production end, thereby improving the fracturing effect. Field applications also show that the fracture construction effect of the polymer gel is better than that of the guar gum fracturing fluid, owing to better filtration performance.