Acid-etching fracture morphology and conductivity for alternate stages of self-generating acid and gelled acid during acid-fracturing

Gou, Bo; Guan, Chencheng; Xiao, Li; Ren, Jun; Zeng, Jie; Wu, Lin; Guo, Jianchun

doi:10.1016/j.petrol.2021.108358

Cited by 38 publications

(23 citation statements)

References 12 publications

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“…This paper developed high-temperature-resistant authigenic acid using the principle that organic esters can be hydrolyzed in water to form acids, , and an authigenic acid thickener with hyperbranched fraction structure was synthesized. With the aid of the acid produced by organic ester hydrolysis, the rock is dissolved, and the fracture conductivity is improved . At the same time, using zirconia chloride, citric acid, diethanolamine, glycerol, polyhydroxyalcoholamine, and other materials as the main raw materials, a citric acid polyhydroxyalcoholamine organic zirconium cross-linking agent was synthesized.…”

Section: Resultsmentioning

confidence: 99%

“…With the aid of the acid produced by organic ester hydrolysis, the rock is dissolved, and the fracture conductivity is improved. 25 At the same time, using zirconia chloride, citric acid, diethanolamine, glycerol, polyhydroxyalcoholamine, and other materials as the main raw materials, a citric acid polyhydroxyalcoholamine organic zirconium cross-linking agent was synthesized. The viscosity of authigenic acid can be higher than 150 mPa s after shearing for 60 min at 160 °C and 170 s −1 , and the highest acid generation concentration is 4.05 mol/L.…”

Section: Temporary Plugging Segmented Fracturing Technology the Hole ...mentioning

confidence: 99%

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

Wang¹,

Fan²,

Zhou³

et al. 2021

ACS Omega

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The ultradeep carbonate reservoir in Sichuan Basin is characterized by deep burial depth, high temperature, and strong heterogeneity. In the early stage of production, the vertical well acid fracturing is the main reservoir stimulation method, and the horizontal well stimulation technology is not mature enough to release the production capacity of gas wells. Segmented acid fracturing of the ultradeep horizontal wells currently faces the following problems: the strong heterogeneity of reservoir leads to the difficulty of fine segmentation; the high reservoir temperature requires higher performance of working fluid; the reaction rate between acid and rock is fast and the action distance of acid is short, and there is low fracture conductivity under high closure stress. In view of the above problems, the fine segmented design method was studied, and the high-temperature-resistant authigenic acid and gelling acid systems were developed. The viscosity of authigenic acid is greater than 150 mPa s after shearing at 160 °C and 170 s −1 for 50 min, and the highest acid generation concentration is 4.05 mol/L. The gelling acid system has both the properties of high-temperature resistance and low friction resistance; not only canit meet the requirements of the retarding rate and the corrosion inhibition ability when the reservoir temperature is 160 °C but also the resistance reduction rate is up to more than 70%. By alternating injection of authigenic acid and gelling acid, the acid-etched fracture length and conductivity were, respectively, increased by 80% and 45%. The application of this technology in the horizontal well of the ultradeep carbonate reservoir in Sichuan Basin can increase the productivity by 3 times when compared with the vertical well acid fracturing, and a better stimulation effect has been achieved.

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Section: Resultsmentioning

confidence: 99%

Section: Temporary Plugging Segmented Fracturing Technology the Hole ...mentioning

confidence: 99%

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

Wang¹,

Fan²,

Zhou³

et al. 2021

ACS Omega

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“…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. 19 − 23 …”

Section: Introductionmentioning

confidence: 99%

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

Guo

Liu

et al. 2022

ACS Omega

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As an important part of the acid fracturing process of carbonate reservoir, the performance of acid fracturing working fluid directly affects the stimulation effect of oil wells. In this paper, formaldehyde (agent A) and ammonium chloride (agent B) were used as the matrix. Several aldehydes with different volume ratios were prepared. The acid ratio with the highest acid yield was selected by the sodium hydroxide titration experiment. The results show that when the volume ratio of agent A to agent B is 1:1.3, the acid production capacity is the strongest. The pH values at several time points in the process of acid reaction were measured by a pen pH meter. The relationship curve between acid production capacity and time was obtained. The acid production capacity increased with time. It tends to be stable after a certain time. The experiment of acid rock reaction kinetics shows that the reaction rate between acid and rock decreases with the extension of time. The reaction time can reach 6 h. The reaction rate of autogenic acid under different temperatures and concentrations ranges from 6.61 × 10 –7 to 9.49 × 10 –7 mol/(s·cm 2 ) within 6 h. Therefore, it indicates that the reaction time between autogenic acid and carbonate rock is long and the reaction rate is low. It is beneficial to improve the acid treatment effect of the carbonate reservoir. The conductivity experiments show that at different temperatures, with the increase of sealing pressure, the etching ability of autogenic acid decreases. The etching effect is better at 338 K. After etching, the permeability and conductivity of the rock slab of 5 MPa closure pressure are 227 D and 72.62 D·cm, respectively. To sum up, this autogenic acid is an effective working fluid in the acid fracturing process of the carbonate reservoir. It can obviously reduce the reaction rate of acid rock and has certain conductivity.

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“…Because the natural fracture is easily connected and etched by gelled acid for creating complex fracture network, gelled acid is widely used in the acid stimulation of marine carbonate reservoirs in Sichuan Basin (Gou et al 2021a, b). To improve the performance of acid distribution and reduce acid leak-off in the acid stimulation process, degradable fiber is used to temporarily block natural fractures and acid-etching wormholes, which makes acid divert to another un-stimulated area to create new fractures and assists in controlling acid leak-off (Guo et al 2015a;Zhang et al 2020;Jauregui et al 2011;Quevedo et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…To improve the performance of acid distribution and reduce acid leak-off in the acid stimulation process, degradable fiber is used to temporarily block natural fractures and acid-etching wormholes, which makes acid divert to another un-stimulated area to create new fractures and assists in controlling acid leak-off (Guo et al 2015a;Zhang et al 2020;Jauregui et al 2011;Quevedo et al 2012). Acid rheological properties have a large influence on fracture morphology, acid-rock reaction rate and the effective penetration distance of living acid, etching morphology and fracture conductivity, and acid leak-off (Gou et al 2021a(Gou et al , 2021bDong et al 2018;Rui et al 2018;Mou et al 2012). Therefore, it is necessary to understand the impact of fiber on the rheological properties of gelled acid.…”

Section: Introductionmentioning

confidence: 99%

Effect of fiber on the rheological properties of gelled acid

Gou

Zeng

Wang

et al. 2021

J Petrol Explor Prod Technol

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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.

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Acid-etching fracture morphology and conductivity for alternate stages of self-generating acid and gelled acid during acid-fracturing

Cited by 38 publications

References 12 publications

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

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

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

Effect of fiber on the rheological properties of gelled acid

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