scholarly journals Synthesis and Characterization of Surfactant for Retarding Acid–Rock Reaction Rate in Acid Fracturing

2021 ◽  
Vol 9 ◽  
Author(s):  
Fuli Yan ◽  
Yongmin Shi ◽  
Yu Tian

Acid fracturing is an effective method to develop ultra-low permeability reservoirs. However, the fast reaction rate reduces the effect of the acid fracturing and increases the near-well collapse risk. Therefore, it is necessary to retard the acid–rock reaction rate. In this work, we synthesized an acid-resistant Gemini zwitterionic viscoelastic surfactant (named VES-c), which has good performances such as temperature resistance, salt resistance, and shear resistance. Besides, a low concentration of VES-c increases the viscosity of the acid solution. The CO2 drainage method was used to measure the reaction rate between the dibasic acid and dolomite/broken core. We find that the dibasic acid containing 0.3% VES-c retards the dolomite reaction rate of 3.22 times compared with only dibasic acid. Furthermore, the dibasic acid containing 0.3% VES-c exhibits uniform distribution and is not easy to adhere to the solid surface. The VES-c also is favorable to reduce the formation of amorphous calcium carbonate. Retarding the rate of acid–rock reaction and enhancing the acidification are mainly attributed to VES-c's salt-tolerance, anti-adsorption, and the property of increasing the viscosity of the solution. Hopefully, this kind of surfactant retarding reaction rate is applied to other acid–rock reactions.

2021 ◽  
Author(s):  
Jun Yan ◽  
Mingyue Cui ◽  
Anle He ◽  
Ning Qi ◽  
Weixiang Cui ◽  
...  

Abstract The understanding of acid rock reaction kinetics is the basis for the proposal of carbonate rock acidizing and acid fracturing. So far, the study of acid rock reaction kinetics in carbonate reservoirs is mostly focused on limestone reservoirs. The difference in acid rock reaction characteristics between limestone and dolomite reservoirs is obvious. In order to clarify the boundaries of control models and mechanisms of acid rock reaction in dolomite reservoirs, to guide the optimization of acidizing and acid fracturing proposal for carbonate reservoirs with different dolomite contents. The experimental study of acid rock reaction kinetics was completed with carbonate cores with different dolomite mass fraction, and the difference of acid corrosion mechanism between limestone and dolomite was analyzed by scanning electron microscope. The dolomite acid rock reaction kinetics equation under the control of different factors was established, and it was clarified that the temperature 90°C and the rotation speed 500r/min are the boundary of the surface reaction and mass transfer control mode. The study found that under the same experimental conditions, the acid rock reaction rate of dolomite is much lower than that of limestone; as the dolomite mass fraction increases, the acid rock reaction rate decreases rapidly, when the dolomite content exceeds 75%, the reaction rate of acid rock is reduced to the lowest and tends to be stable. Limestone is dominated by surface dissolution, with good dissolution effect, fast dissolution rate; dolomite is dominated by point dissolution, with holes on the surface, poor dissolution effect and low dissolution rate. Compared with limestone, the particle size of dolomite crystal is much larger, and the specific surface area is small, which is also the reaction rate of acid rock in dolomite is slower than limestone, this is also a main reason why the reaction rate of dolomite acid rocks is slower than that of limestone. So the acidizing or acid fracturing methodology of the dolomite reservoir is different from that of the limestone reservoir. The acid rock reaction rate and hydrochloric acid concentration should be appropriately increased within the allowable range to improve the uneven etching of the fracture wall, thereby increasing increase the conductivity of acid fracture.


1990 ◽  
Vol 10 (1) ◽  
pp. 235-242
Author(s):  
L Meyer-Leon ◽  
R B Inman ◽  
M M Cox

Holliday structures are formed in the course of FLP protein-promoted site-specific recombination. Here, we demonstrate that Holliday structures are formed in reactions involving wild-type substrates and that they are kinetically competent with respect to the overall reaction rate. Together with a previous demonstration of chemical competence (L. Meyer-Leon, L.-C. Huang, S. W. Umlauf, M. M. Cox, and R. B. Inman, Mol. Cell. Biol. 8:3784-3796, 1988), Holliday structures therefore meet all criteria necessary to establish that they are obligate reaction intermediates in FLP-mediated site-specific recombination. In addition, kinetic evidence suggests that two distinct forms of the Holliday intermediate are present in the reaction pathway, interconverted in an isomerization process that is rate limiting at 0 degree C.


2014 ◽  
Vol 1042 ◽  
pp. 44-51
Author(s):  
Jia Nye Mou ◽  
Mao Tang Yao ◽  
Ke Xiang Zheng

Acid fracture conductivity is a key parameter in acid fracturing designs and production performance prediction. It depends on the fracture surface etching pattern, rock mechanical properties, and closure stress. The fracture surfaces undergo creep deformation under closure stress during production. Preservation of fracture conductivity becomes a challenge at elevated closure stress. In this paper, we investigated acid fracture conductivity behavior of Tahe deep carbonate reservoir with high closure stress and high temperature. A series of acid fracture conductivity experiment was conducted in a laboratory facility designed to perform acid fracture conductivity. Gelled acid and cross linked acid with different acid-rock contact times were tested for analyzing the effect of acid type and acid-rock contact time on the resulting conductivity. Closure stress up to 100MPa was tested to verify the feasibility of acid fracturing for elevated closure stress. Long-term conductivity up to 7-day was tested to determine the capability of conductivity retaining after creep deformation. Composite conductivity of acid fracture with prop pant was also carried out. The study shows that the fracture retained enough conductivity even under effective closure stress of 70MPa. The gelled acid has a much higher conductivity than the cross linked acid for the same contact time. For the gelled acid, contact time above 60-minute does not lead to conductivity increase. Acid fracture with prop pant has a lower conductivity at low closure stress and a higher conductivity at high closure stress than the acid fracture, which shows composite conductivity is a feasible way to raise conductivity at high closure stress. The long-term conductivity tests show that the acid fracture conductivity decreases fast within the first 48-hour and then levels off. The conductivity keeps stable after 120-hour. An acid fracture conductivity correlation was also developed for this reservoir.


2019 ◽  
Vol 54 (16) ◽  
pp. 11243-11253 ◽  
Author(s):  
Chaohui Rao ◽  
Xia Guo ◽  
Min Li ◽  
Xiaoqing Sun ◽  
Xiaojie Lian ◽  
...  

2018 ◽  
Vol 42 (9) ◽  
pp. 6636-6639 ◽  
Author(s):  
Manli Han ◽  
Qingsheng Fan ◽  
Yi Zhang ◽  
Lida Xu ◽  
Changyuan Yu ◽  
...  

A novel strand displacement triggered by the non-classical hydrogen bond between cyanuric acid and adenine exhibits a fast reaction rate.


1980 ◽  
Vol 20 (06) ◽  
pp. 501-507 ◽  
Author(s):  
M.H. Lee ◽  
L.D. Roberts

Abstract In a fracture acidizing treatment the acid reacts with the fracture faces. This acid/rock reaction generates heat that causes the acid temperature itself to increase. To predict accurately the temperature profile and acid spending rate of acid traveling down a hydraulically created fracture, this heat must be considered.Since the heat generated by reaction depends on the reaction rate, the thermal energy equation must be coupled with the acid spending equation. A model has been developed that, for the first time, examines the effect of the heat of reaction on fluid temperature and acid penetration in a fracture. Some sample calculations have also been made to illustrate the effects of the most important parameters on acid penetration in a fracture. Introduction Acid hydraulic fracturing is a common method of stimulating a reservoir. Acid selectively reacts with, and dissolves, portions of the fracture wall so that a finite fluid conductivity remains when the well is returned to production. An important aim in designing such fracturing treatments is determining the distance that live acid will penetrate down the hydraulically induced fracture. This distance is usually called the acid penetration distance and is essential to estimate the production improvement from a given treatment.Because of its importance in predicting stimulation ratio, acid penetration in fractures has been studied by numerous investigators. They assumed the temperature in the fracture was uniform. In real fractures, however, the temperature will vary from the wellbore to the tip of the fracture. Therefore, the assumption of constant temperature seems to be an oversimplification.Whitsitt and Dysart were among the first to study the temperature distribution in a fracture. They constructed a model but it could be applied only to a nonreacting fluid flowing in a fracture because the heat generated by an acid/rock reaction was not considered. In a fracture acidizing treatment, the acid is reacting with the rock walls. This acid/rock reaction generates heat, which causes the acid temperature itself to increase. To predict accurately the temperature profile along the fracture, this heat also must be considered. A model has been developed that, for the first time, examines the effect of the heat of reaction on fluid temperature and acid penetration distance. Mathematical Development The mathematical model is a modification of that introduced by Whitsitt and Dysart to allow for the heat of reaction in the energy-balance equation. Since the heat generated by the acid reaction also depends on the reaction rate, the thermal-energy equation is coupled with the mass-balance equation. These two equations must be solved simultaneously .The model for acid spending in a fractures is illustrated in Fig. 1. The fluid leakoff velocity Vw is assumed constant over the fracture length. Assuming steady-state flow in a vertical fracture and constant fluid properties, the mass-balance equation for acid flowing in a fracture is ................(1) SPEJ P. 501^


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