Effect of fiber on the rheological properties of gelled acid

Abstract

Degradable fiber is widely used to assist gelled acid diversion and reduce acid leak-off in the acid stimulation of carbonate hydrocarbon reservoirs in Sichuan Basin of China. The rheological properties of an acid system will affect the geometry of the acid-etching fracture. However, the effect of fiber on the rheological properties of gelled acid is not yet clear. This paper investigates the rheological properties of gelled acid with various fiber concentrations at different temperatures. The results show that when the temperature is less than the degradable temperature of the fiber, the apparent viscosity of gelled acid rises gradually with an increase in fiber concentration, while the fiber has no significant effect on the viscosity of gelled acid at the degradable temperature. The dissolution process of fiber in gelled acid experiences none-dissolution, surface dissolution, dissolution and fining, and a complete dissolution stage from low to high temperatures, which all have different effects on gelled acid viscosity. The fiber links more gelling agent molecules of gelled acid together to form a quasi-network structure between the fiber and fiber and the fiber and polymer, which results in a rise in the viscosity of gelled acid. The acid system also shows a strong shear thinning property under different temperatures and fiber concentrations. However, the power-law index n of this acid system always maintains a steady average value of about 0.181, while the change pattern of consistency index K is similar to the change in viscosity with varying fiber concentrations and temperatures. The research results are useful for acid fracturing treatment design in carbonate reservoir.

Research and Application of Segmented Acid Fracturing by Temporary Plugging in Ultradeep Carbonate Reservoirs

“…Fiber and granule are common temporary plugging materials . In this paper, we use a three-dimensional fracture sealing ability tester to evaluate the bearing capacity of the sealing layer formed by a single material and a composite material.…”

“…Fiber and granule are common temporary plugging materials. 21 In this paper, we use a three-dimensional fracture sealing ability tester to evaluate the bearing capacity of the sealing layer formed by a single material and a composite material. We place the fibers and particles in clean water in a certain proportion, use a precision pressure pump to displace the temporary plugging material into the simulated fracture at a constant speed, and observe the change of displacement pressure after the temporary plugging material enters the simulated fracture.…”

Experimental and Modeling Investigation on Artificial Fracture Conductivity for Hybrid Fracturing in a Deep Carbonate Reservoir Using an Acid and a Proppant

“…Therefore, it was based on the Reynolds number similarity principle when acid flowed in hydraulic fractures. The acid injection rate at the engineering scale is scaled down the laboratory scale according to the following formula; q l = q f h l 2 h f true( w normalf w normall true) 2 n − 2 2 − n where q l is the laboratory scale acid pumping rate, m 3 /s; q f is the engineering scale acid pumping rate, m 3 /s; w f is the fracture width in formation, m; h f is the fracture height in formation, m; w l is the width of experimental fracture, m; h l is the slab width, m; n is the flow regime index, dimensionless, which is determined by conducting rheological testing using a high temperature rheometer at various shear rates . The acid pumping rate at laboratory-scale obtained from Equation is 300 mL/min, as shown in Table .…”

Experimental Study on the Autogenic Acid Fluid System of a High-Temperature Carbonate Reservoir by Acid Fracturing

“…Thickened acid can form wide cracks, small filtration loss, and low friction and show good performance of suspended solid particles in the process of acid pressing. 16 − 18 Autogenic acid is an acid product produced in situ by chemical dissociation or reaction of fluid injected into the formation. It has no acidity or weak acidity on the surface, but acid is produced gradually at the bottom of the hole temperature, and acid production is carried out gradually, which can effectively reduce the acid rock reaction rate, prolong the acid action distance, and reduce the corrosion effect on the underground pipe string.…”

“…Emulsified acid is widely used in repeated acid pressure or high sulfur gas well acid pressure, and the use of emulsified acid in matrix acidification is also significantly increased. − Gelled acid can reduce the filtration loss of acid solution, form a colloidal network structure, and reduce the diffusion of H + . Thickened acid can form wide cracks, small filtration loss, and low friction and show good performance of suspended solid particles in the process of acid pressing. − Autogenic acid is an acid product produced in situ by chemical dissociation or reaction of fluid injected into the formation. It has no acidity or weak acidity on the surface, but acid is produced gradually at the bottom of the hole temperature, and acid production is carried out gradually, which can effectively reduce the acid rock reaction rate, prolong the acid action distance, and reduce the corrosion effect on the underground pipe string. − …”