RU2103496C1 - Method for increasing injectivity of terrigenous clay-bearing bed - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: this is aimed at increasing efficiency of treating terrigonous clay-bearing bed, reducing bed treating period and cutting amount of complexing agent used. According to method, injected into bed at first stage are hydrofluoboric acid and complexing agent, and injected at second stage are mixtures of acidic hydrochloric acid, hydrofluoric acid, and complexing agent. Interval between first and second stages, amounts and concentration of components are sufficient for proper reaction with bed. Used as complexing agent is nitriloacetic acid or acidic diaminopropanol. EFFECT: high efficiency. 1 cl, 1 tbl

Description

 The invention relates to a technology for well development and stimulation of oil flow from a reservoir.

A known method of treating a terrigenous clayey formation with 15% hydrofluoric acid with a volume of 1.5 - 2.5 m ³ per 1 m of the thickness of the formation and holding the well for a reaction of 18 hours. It is recommended to use fresh water as a squeezing fluid, and in winter conditions a solution calcium chloride.

The disadvantage of this method is the precipitation of sparingly soluble salts of CaF ₂ , Na ₂ SiF ₆ , K ₂ SiF ₆ , Si (OH) ₄ , which complicates the removal of reaction products [1 and 2].

 The closest to the invention in technical essence and the achieved result is a method of acid treatment of the formation by preliminary injection into the formation of a 12% aqueous solution of hydrofluoric acid followed by treatment of the formation with an aqueous solution of clay acid (12% hydrochloric acid + 3% hydrofluoric acid solution) [ 3].

 However, the prototype method does not effectively increase the permeability of terrigenous clayey formation.

 The purpose of the invention is achieved in that in a method comprising injecting into the formation in the first stage hydrofluoric acid and a chemical additive, and in the second stage, a mixture of hydrochloric and hydrofluoric acids and chemical additives with a time interval between the first and second stages and a concentration of components sufficient for reactions with the reservoir, a carboxyl-containing complexone (for example, nitrilotriacetic acid or diaminopropanol acetic acid) is used as a chemical additive.

 In the oil industry, chemical additives with carboxyl units in the molecule are used as additives in polymer solutions before injection into the formation in order to reduce their fluidity [4].

 Hydrofluoric acid in a mixture with a chemical additive that includes carboxyl groups in the molecule allows, significantly, in a shorter time and at a lower consumption of the chemical additive, to increase the permeability of the terrigenous clay formation compared with the prototype.

 After a short break for 1 h, the injection of mud acid (HCl + HF) in the presence of a chemical additive (nitrilotriacetic acid or diaminopropanol acetic acid) further increases the permeability of the formation.

The volume of injection into the reservoir of composite material is 1.5 m ³ per 1 m of reservoir power. The injection pressure should not exceed the fracture pressure.

 An example implementation of the method. A cylinder with a diameter of 30 mm and a height of 50 mm is made from the core sample under study. At the UNPK-1M installation, the initial permeability of the samples is determined. Then, an aqueous solution containing 9% borofluoric acid and 0.1% nitrilotriacetic acid (NTU) is pumped through the samples. The volume of pumped composite material is 14 pore volumes (experiment No. 6).

 After that, 5 pore volumes of a mixture containing 10% hydrochloric acid are pumped through the same core. 1% fluoric acid and 0.05% nitrilotriacetic acid (NTU).

 The permeability of the sample before and after treatment with the composite composition is determined in a known manner.

 The table shows the comparative results of measuring the permeability after its processing, according to this method, the prototype method, the compositions of the individual stages and the ingredients included in them.

 From the data presented in the table, it follows that the proposed method significantly exceeds the prototype method and other technical solutions.

So, with an initial core permeability of 0.02 - 0.03 μm ² and a pressure drop of 1.8 to 6.0 MPa, this method allows you to increase the permeability of a clay formation using nitrilotriacetic acid (NTU) 16-20 times (experiments 4 - 6), while according to the prototype method, permeability increases only 2.2 - 6.0 times (experiments 1-3).

 Thus, the objective of the invention is fully realized, namely, the permeability of the terrigenous clay layer is increased.

Sources of information
1. Yuzhaninov P. M. Research on the use of sulfamic and hydrofluoric acid for treating the bottom-hole zone of wells. Abstract. dis. Cand. tech. sciences. Ufa, 1982, 20 p.

 2. Giyazova V. M., Trakhtman G. I. Improving the intensification of oil inflow to the bottom of the wells by acid treatments. Overview information. VNIIOENG. Series "Oilfield business", 1985.

 3. US Patent N 4,151,878, cl. E 21 B 43/27, prototype.

 4. Copyright certificate of the USSR N 791943, cl. E 21 B 43/27, BI. N 48, 1980.

Claims (2)

 1. A method of increasing the injectivity of a terrigenous clayey formation by injecting boro-hydrofluoric acid and a chemical additive into the formation in the first stage and a mixture of hydrochloric and hydrofluoric and chemical additives in the second stage with a time interval between the first and second stages and a concentration of components sufficient for the reaction to proceed with formation, characterized in that a carboxyl-containing complexon is used as a chemical additive.  2. The method according to claim 1, characterized in that nitrilotriacetic acid or diaminopropanol acetic are used as the carboxyl-containing complexone.

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