RU1774004C - Method of blocking critical zone - Google Patents

Abstract

SUBSTANCE: aqueous solutions of calcium chloride and carbonic acid salts are sequentially pumped into the formation. Preliminarily, the VZhS flotoreagent, the still residue of higher fatty alcohols, is dissolved in an aqueous solution of calcium chloride in an amount from 1.8 to 2.0% by weight of the carbonic acid salt solution. Ammonium bicarbonate can be used as the carbonic acid salt. 2 tablets

Description

The alleged invention relates to the oil and gas industry, more specifically, to physicochemical methods of blocking absorbing formations during drip repair of wells.

A known method of waterproofing a formation in a well, comprising sequentially injecting aqueous solutions of a gelling agent acryl trimethyl ammonium chloride and hydrolyzed polyacrylamide into the formation in a ratio of 4.0-4.5: 1, when mixed in a porous medium, an insoluble polymer complex is formed, which precipitates and clogs the pores of the reservoir (see the USSR AS N 1177461, class E 21 B 43/32).

The disadvantage of the method as. No. 1177461 is that after carrying out repair and insulating works, if it is necessary to call an inflow, it is very difficult to restore the well production that was before the well stopped for overhaul. Known composition for temporary plugging of the reservoir A. with. USSR No. 599049, class E 21 B 33/138 containing water, a thickener

and a filler, for example, chalk of various fractions, characterized in that, in order to ensure complete subsequent removal of the composition from the formation, it contains, as a thickener, an oxyethylation product of fatty alcohols, for example GO precocel, and the components are taken in the following ratio, wt.% : chalk 56-64; prevocel 5-8: the rest is water.

The lack of composition is the lack of structural and mechanical properties, the great complexity of its preparation, the large waste of chalk of large fractions

The closest to the implementation of the analogue, the prototype of the proposed method is a method of isolating the influx of formation water according to US patent No. 2272672, class. 166-21 for 1942

This method involves the sequential injection into the formation of two reactive reactants, aqueous solutions of MaaCO3 and CaCfe, separated by a buffer liquid, which controls the onset of sediment formation.

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The known method is designed to isolate the influx of formation water, while the proposed method is intended to block the bottom-hole zone of the absorbing formations from the filling fluid.

The disadvantage of this method is the low structural and mechanical properties of the resulting precipitate and, therefore, low insulating properties.

The aim of the invention is to increase the efficiency of formation isolation by increasing the structural, mechanical and adhesive properties of the insulating material.

The goal is achieved by the fact that sequential injection of aqueous solutions of calcium chloride and carbonic acid salt is performed in the well. Preliminarily, the VZhS flotoreagent is introduced into the aqueous solution of the carbonic acid salt — the bottom residue of higher fatty alcohols in an amount of 1.8 to 2.0% by weight of the carbonic acid salt solution.

Ammonium bicarbonate is used as the carbonic acid salt.

The VZhT flotoreagent (distillation residue of higher fatty alcohols - sodium salts of monodicarboxylic acids) is added to the solution of carbonic salts to accelerate the chemical reaction and the deposition of chalk and give the precipitate high structural and mechanical properties.

A comparable analysis of the claimed solution with the prototype shows that the claimed method differs from the known one in that the formation of the chalky viscoelastic composition occurs in the wellbore against the absorbing formations, and not in the pore space of these formations.

In addition, the method is characterized in that, as a result of its implementation, a composition is formed of high structural-mechanical (visco-elastic) properties with low water loss compared to the prototype, as a result of which it cannot be pressed into the pore space of the blocked formations even when overpressure is created on them and does not impair the permeability of the bottomhole zone.

From a comparable analysis of the prototype and the claimed technical solution, it follows that the claimed method meets the criteria of the invention of Novelty.

A known method of isolating the influx of formation water in the well (AS USSR No. 960424, class E 21 B 43 / 32J in which granular magnesium is pumped into the formation together with the carrier fluid, the last contact with formation water forms an insoluble precipitate in pore space, and

granular magnesium remaining in the well as a result of sedimentation processes forms a bridge overlying the flooded formation, as in the claimed method. However, to solidify the precipitate, he needs to be at rest for 60 hours. In our technical solution, a viscoelastic chalk composition with minimal water loss is formed within 6090 minutes after contacting the mixtures. The properties of the obtained composition and the rate of its formation allows us to conclude that the proposed technical solution meets the criterion of Significant differences.

Example 1. The implementation of the method in a laboratory setting,

A calculated amount of an aqueous bicarbonate solution was poured into a graduated cylinder

ammonium with a concentration of May 19.6. %, then the calculated volume of the aqueous solution of calcium chloride with a concentration of CaCl2 in the solution of 36.1 wt.% was poured. The test temperature was 20 ° C. The chemical equation of the reaction is as follows:

2 NH.4C03 + CaCl2 CaCO3 + 2 +

+ CO2 + H20

As a result of the reaction of solutions of ammonium bicarbonate and calcium chloride, chemically precipitated chalk, a solution of ammonium chloride, carbon dioxide and water were obtained. Chalk precipitated to form chalk chalk, carbon dioxide was removed from the solution, and ammonium chloride and water remained in the solution. After the completion of the reaction, the chalk precipitated under the influence of gravitational forces. Process

chalk deposition took place within 2-3 hours. The resulting sediment had a loose structure with high water loss and was unsuitable for blocking formations. A number of reagents have been tested to improve the properties of the precipitate. The best results are shown for the VZhS photoreagent (VAT residue of high fatty alcohols - sodium salts of monodicarboxylic acids). Laboratory experiments established that the input into the solution

The ammonium bicarbonate flotation reagent VZhS accelerates the reaction between solutions of ammonium bicarbonate and calcium chloride and the precipitation of chalk resulting from the reaction. In addition, the VZhS flotation reagent leads to an increase in SSS and a decrease in the water loss (B) of the sediment (see Table 1), i.e., the precipitate acquires viscoelastic properties with minimal water loss.

Numerous experiments have established

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Shear and minimal loss of water are achieved when the content of VGS in the solution of ammonium bicarbonate in the amount of 1.8-2 May. % by weight of a solution of ammonium bicarbonate see table 2. Table 1 summarizes the preparation of a composition for blocking absorbent formations. ,

It was established by laboratory studies that the optimal structural and mechanical properties of the Cretaceous pulp are achieved when the content of the catalyst for flotation of the VZhG agent is within the range of 1.8–2 wt.% In a solution of ammonium bicarbonate.

Example 2. Implementation of the method in field conditions using the example of well No. 105 of the Solokhovskoye gas condensate field.

Technical characteristics of the well:

Production tower

outer diameter 168 mm

and inner diameter

148 mm lowered on

depth 917m.

Artificial slaughter

wells905 m.

Perforation interval 889-899 m.

Formation Pressure 6.1 MPa

Tubing 89x6.45 mm

lowered to a depth of 889 m.

For the period of repair and insulation work, it is necessary to close the perforation interval in the viscoelastic chalk composition. For this, the composition should be in the range of 905-885 m, i.e. the bridge of viscoelastic composition should be 20 m high.

Define the volume of the bridge

nD2

V

h 0.785-0.148Z 20

 0.343 MJ,

We determine the volumes of the initial components, i.e. volumes of a solution of ammonium bicarbonate, calcium chloride and VGS to obtain a precipitate with a volume of 0.343 m3.

Laboratory studies and calculations, starting from the reaction equation and the conditions for the complete reaction of the initial solutions, showed that when 3 volumes of ammonium bicarbonate solution, with a concentration of 19.6 wt.%, 1 volume of calcium chloride solution with a concentration of 36, 1 wt.% And 0,041 volumes

VZhS receives 1/8 volume of sediment, with a density of 1440 kg / m3 and 7/8 of a filtrate with a density of 1040 kg / m3.

Based on experimental data, the total volume of solutions included in the reaction will be:

VpaciB. Voc. 8 0.343-8 2.744 m3. Of these, 2.058 m1 of ammonium bicarbonate and 0.686 m of calcium chloride, the rest is VZhS (0.041 m3).

Thus, 2.058 m of a solution of ammonium bicarbonate with dissolved VZHS is pumped into a well, then a separate volume of water is 100-150 liters, then 0.686 m3 of a solution of calcium chloride, then a killing liquid and a chalky precipitate is obtained in the well within 60-90 minutes 20 m with viscoelastic properties.

After repair and isolation work, the blocking zone is destroyed by subsequent hydrochloric acid treatment.

The advantages of the proposed method of blocking the bottom-hole zone of the absorbing layers in comparison with the known following:

-improving the quality of blocking the bottom-hole zones of the absorbing formations;

-decrease in the cost of repairs due to the reduction in cost of the initial components used in blocking;

-Reducing the complexity of blocking;

-improving the culture of production. - reducing the time and cost of well repair.

Claims (2)

SUMMARY OF THE INVENTION A method of blocking the bottom-hole zone of an absorbing formation, comprising the sequential injection of aqueous solutions of calcium chloride and a salt of carbonic acid, characterized in that, in order to increase the efficiency of isolation layers by increasing the structural-mechanical and adhesive properties of the insulating material, the VZhS flotation reagent - bottom residue is pre-introduced into the aqueous solution of carbonic acid salt production of higher fatty alcohols, in an amount of from 1.8 to 2.0% by weight of a solution of a salt of carbonic acid. Table 1 f. Ras t yur bicarbonate AMNONMZH Amioca bicarbonate 13.6 4letore gent 8SC "Ode - the rest 2. Calcium chloride solution IJ5Q calcium chlormetm - 36.1 vcgqj rest 1. Ammonium bicarbonate solution) ammonium bicarbonate - 19 (61060 VHS flotoreagent - 1.3 water - Else Z, Calcite Chloride Solution calcium chloride 36 t1350 code rest 1. A solution of atoni bicarbonate ammonium bicarbonate - 13.61060 fpotoreagent VIS - 2.37 water - the rest 2. CALCIUM CHLORIDE SOLUTION i calcium porous 36,11} $ 0 ostapyuo waters Precipitation chalk - 62.3 BHC flotoreagent - 3.2 ammonium chloride - 5 water - the rest Filtrate Iel - absent DXC - absent ymmomium chloride 10.8 water - rest Sediment: mep - 62.2 BCC flotoreagent 3.3 ammonium chloride - 4 "Yes - the rest is leachate small - missing 8ZhS - absent ammonium chloride - 10.8 water - the rest Sediment chalk - 62.0 Flotoreagent BIC - 13.0 Ammonium Hporista Z - 3 ode - rest Filtrate: "Ate - no HCV - no I-.MQMHQ chloride 10.8 soda the rest f - 1590 T - SNS does not flow - 260 8-in r P - 1520 T - on flowing SNA - 360 AT 5 f - p - iuo T - SNS does not flow - 800 V - 1 f - 1HO