Viscoelastic surfactant for high-temperature self-diverting acid and its preparation method and application

Abstract

The invention discloses a viscoelastic surfactant for high-temperature self-diverting acid. The structural formula of the viscoelastic surfactant is as shown in the specification, wherein n refers tosaturated alkane with 2-8 carbon atoms, R1 refers to saturated or unsaturated alkane with 18-28 carbon atoms, R2 and R3 refer to independent methyl, ethyl and hydrogen atoms and can be the same or different, and X refers to optional one of Cl<->, Br<->, F<->, CO3<2->, SO4<2->, HCOO<-> and CH3COO<->. The preparation method includes subjecting aliphatic acid and organic amine to acid and amine condensation reaction to obtain an intermediate product, subjecting the intermediate product to reaction with metallic oxide to obtain aliphatic amine, adding in acid solution to perform protonation, so asto obtain the very-long viscoelastic cation surfactant. The invention further provides the application of using the surfactant as a thickening diverter of self-diverting acid. The self-diverting acidutilizing the surfactant as the thickening diverter can be used at the temperature of 150 DEG C, and has the advantages of stable structure, thickened acid, uniform acidification, automatic divertingand the like.

Description

technical field [0001] The invention relates to the field of oil and gas exploitation, in particular to a viscoelastic surfactant for high-temperature self-steering acid, a preparation method and application. Background technique [0002] In order to restore and increase the production of low-permeability oil and gas wells, acid liquid (usually 20% concentration of hydrochloric acid) is often injected into the reservoir, through which the acid liquid acts on rock cement (cement mostly contains carbonates and clay) or formation pores, Dissolution and corrosion of blockages in fractures, restore reservoir permeability, and expand oil and gas seepage channels (K.M.Bartko, F.F.Chang, L.A.Behrmann, I.C.Walton. Effective matrix acidizing in carbonate reservoir-Does perforating matter? Paper presented at SPE Middle East Oil and Gas Show and Conference, MEOS, Proceedings, Bahrain, 250-259, 2007). But for a long time, there have been two problems in the conventional acid system: (1)...

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Problems solved by technology

However, for a long time, there have been two problems in the conventional acid system: (1) The reaction speed with the reservoir rock is fast, resulting in too short acidizing distance, making it difficult to realize deep acidizing

(2) Due to the heterogeneity of the reservoir, after the acid fluid is injected into the formation, following the principle of least resistance, it preferentially enters the high-permeability area rather than the low-permeability area that needs acid treatment most; moreover, the subsequent injection The acid liquid will flow along the reacted large pores with less resistance, which will over-acidify the high-permeability area, while the medium-low permeability area will not be effectively improved by plugging removal, which will eventually lead to further increase of interlayer heterogeneity (F. Chang, Q. Qu, W. Frenier. A novel self-diverting-acid developed for matrix stimulation of carbonate reservoirs. Paper SPE65033 presented at the SPE International Symposium on Oilfield Chemistry held in Houston, Texas, 13–16 February 2001)

U.S. Patent No. 4,695,389 discloses a VDA system based on N,N-dihydroxyethyl fatty amine acetate surfactant. The initial viscosity of the system is low, but as the acid-rock reaction proceeds, the viscosity of the system increases, making it The increased flow resistance forces the subsequent acid liquid to enter the low-permeability area, which can achieve the purpose of uniform acidification. However, the viscosity of the system is as low as 5 mPa s at 80 °C, which makes it difficult to achieve the function of reducing the acid-rock reaction rate.

U.S. Patent No. 7,119,050 discloses a VDA system based on alkyl betaine amphoteric surfactants. As the acid-rock reaction proceeds, the viscosity first increases and then decreases. Active agent usage as high as 8%, resulting in high operating costs

[0007] (2) Most of the VES used in the current VDA system are cationic and zwitterionic surfactants, especially alkyl betaine amphoteric surfactants, amine oxide amphoteric surfactants, etc. Most of these VES molecular structures contain easily hydrolyzed surfactants. The weak bonds (amide bonds, ester bonds, ether bonds, etc.) of VES are easily broken in high temperature and strong acid environment, so it is difficult for VES to maintain a stable chemical structure during acidification operations, and it is easy to deteriorate and decompose (Z.Y.Zhao, G.C Lv, Y.H.Zhang, S.J.Lian,N.Tian.Performance of EDAB-HCl acid blended system as fracturing fluids in oil fields.Chinese J.Chem.Engin.,2014,22,202)

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