As people has the deepening research and understanding of acid/rock reaction mechanism in the acidification process, especially the late 1990s, the U.S. oil services company Haliburton and other research units by means of nuclear magnetic resonance, induction coupling, scanning electron microscopy, X diffraction and other advanced testing methods  basically recognize the chemical behavior of hydrofluoric acid and mineral reactions in the sandstone matrix acidizing process, put forwards the three reaction kinetics of HF and aluminum silicate, point out the conventional hydrochloric and mud acid caused very serious damage for the formation, but organic acid system has a unique solution to reduce the damage of acidification effect on reservoir, and therefore in nineties the research and application of non-hydrochloric acid is greatly concerned by the acidification researchers, wherein the organic acid system become the focus of development applications.  The non-hydrochloric acid / mud acid system is developed on the basis of reference to foreign patents and fraternal units on, and has been applied in the field, also achieved good results.

1. The compare between organic system and hydrochloric acid/ mud acid system:

(1) The organic acid system is low corrosive, in 90℃the corrosion rate is generally 3g/m²•h, but the hydrochloric acid/mud acid system is 5~10g/m²•h.

(2) Organic acid system is faintly acid and has weaker sensitive to formation, help to protect the stratum, but hydrochloric acid is  strong acid, could easily lead to the stratum sensitive.

(3) Organic acids dissociate H⁺slower , difficult to produce acid residue with crude oil, the hydrochloric acid/mud acid dissociation H⁺ faster, charge concentrationand easy to produce acid residue when reacting with crude oil , causing permanent damage to the formatin.

(4) Organic acids react slower with formation components, difficult to produce a large number of particles, and therefore difficult to produce particle migration block theformation and also not easy to produce excessive particles stabilize the oil/acid emulsion. The hydrochloric acid/mud acid system react faster, could easily lead to particle migration, form secondary damage.

2. Organic Acid System

2.1 Composition

By organic acid/hydrofluoric acid composition, adding different types of additives.

2.2 Performance

(1) Appearance: red brown transparent liquid.

_{(2) Density: 1.05~1.10g/cm³}

(3) Dispersion: miscrible in water in any proportion, and transparent.

(4) Calcium carbonate retarder capacity of 5 to 12 times. (with the consuming time 15% HCL reduce to 1.5% HCL, as standard comparation)

(5) Corrosion rate: 90℃, atmospheric 4 hours less than 4g/m²•h. (inhibitor concentration less 1/2than the hydrochloric acid / soil acid)

(6) Anti-sludge: does not produce acid residue.

(7) Interfacial tension: ≤3dy/m

2.3 Usage:

(1) Pretreatment fluid: 1:4 dilution  2.5m³/m

(2) Treatment fluid: 1:4 dilution  2.5m³/m

(3) Post-treatment fluid: conventional acidification.

3. Organic retarded acid system

3.1 Composition

It is composed by H⁺ ions organic acids with several inorganic salts and organic matter.

The system reacts at 60℃ and produces acid, with H+ consumption continues to produce acid, which add different types of additives.

3.2 Performance

(1) Appearance: red brown transparent liquid.

(2) Density: 1.03~1.08 g/cm³

(3) Dispersion: miscible in water in any proportion, and transparent

(4) Calcium carbonate retarder capacity 2 to 5 times. (Condition same with organic acid system)

(5) Buffer capacity on SiO₂ 3~6 times (SiO₂ dissolved by3% HF solution, dissolution rate per hour is 1)

(6) Interfacial tension: ≤3 dy/m

(7) Demulsification capacity: water output ratio ≥95%

(8) Corrosion rate: 90℃ atmospheric pressure 4 hours less than 4g/m²•h.

3.3 Usage:

(1) Pretreatment fluid: 1:3 dilution  2.5m³/m

(2) Treatment fluid: 1:3 dilution  2.5m³/m

(3) Post-treatment fluid: conventional acidification.

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