RU2187533C2 - Foaming composition - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: invention relates to foaming compositions of triple-phase foams for use as drilling muds under anomalously low formation pressures during primary exposition of productive oil and gas deposits or during major repairs of wells. Soft waterbased composition contains, wt %: foaming agent 0.8-1.8, modified starch 5.0- 7.0, sulfacell 0.18-0.3, industrial-grade chalk (seeding agent) 3.0-4.0, and additionally aluminum chloride 1.1-1.4 and soda ash 0.6-0.8. EFFECT: increased foam stability due to reduced filtration and improved structural characteristics of composition to form condensed acid-soluble colloids as solid phase of triple-phase foam. 1 tbl, 2 ex

Description

 The invention relates to the oil and gas industry, in particular to foaming compositions of three-phase foams, for use as drilling and flushing solutions in conditions of abnormally low reservoir pressure (ANPD) during the initial opening of productive deposits of oil, gas and overhaul of wells.

 Known foaming composition containing a foaming agent (sulfonol) 1.5 wt.%, Stabilizer (CMC) 1.0 wt.%, Bentonite 20.0 wt.% And water / 1 /.

 The known composition does not provide the necessary stability ("life" period) of three-phase foams and leads to damage to productive formations due to the difficultly eliminated clogging of pore channels with clay particles.

Closest to the declared purpose and combination of essential features is a foaming composition for killing wells, containing fresh water, a foaming agent, bentonite, polyacrylamide as a foam stabilizer and condensed sulphite-alcohol vinasse (KSSB-4) in the following ratio of ingredients, wt.%: / 2 /
Frother - 1.0-3.0
Bentonite - 1.0-3.0
Polyacrylamide - 0.5-0.7
Condensed sulphite-alcohol stillage (KSSB-4) - 5.0-8.0
Fresh Water - Else
However, the known foaming composition does not provide long-term stability of the foam due to poor structural performance and high filtration. In addition, the presence of bentonite in the composition leads to clogging of the pores of the formation with clay particles.

 The objective of the proposed technical solution is to increase the stability of the foam by reducing filtration and improving the structural parameters of the composition with the formation of condensed acid-soluble colloids as a solid phase three-phase foam.

Отличием предлагаемого пенообразующего состава является использование в качестве стабилизатора - модифицированного крахмала и сульфацелла, в качестве затравки - технического мела и дополнительное введение в состав алюмохлорида и кальцинированной соды в заявляемых соотношениях ингридиентов.To solve this problem, the inventive foaming composition containing fresh water, a foaming agent, a foam stabilizer and a seed contains modified starch and sulfacell as a foam stabilizer, and technical chalk as a seed, while the composition additionally contains aluminum chloride and soda ash in the following ratio of components , wt.%:
Frother - 0.8-1.8
Modified starch - 5.0-7.0
Sulfacell - 0.18-0.3
Chalk technical - 3.0-4.0
Alumochloride - 1.1-1.4
Soda ash - 0.6-0.8
Fresh Water - Else
The foaming composition is a colloidal polymer solution with condensed acid-soluble colloids of aluminum hydrosol. Condensed colloids are formed during the course of the reaction.

The difference between the proposed foaming composition is the use as a stabilizer of modified starch and sulfacell, as a seed, technical chalk and additional introduction of aluminum chloride and soda ash in the claimed ratios of the ingredients.

Technical chalk is a powder of white or white-gray color with a density of 2.74 g / cm ³ , it is easily soluble in hydrochloric acid. When interacting with water forms a suspension. It is produced by construction industry enterprises and is widely used in everyday life, industry, and drilling / 3 /.

 Alumochloride is a clear liquid containing 20-25 wt. % of the main substance or powder is light yellow or greenish with a slight smell of hydrochloric acid, environmentally friendly. Alumochloride is produced by Salavatnefteorgsintez JSC, Caustic JSC Sterlitamak, is a by-product of petrochemical synthesis processes. It is known for its use in water treatment technology and in the composition of drilling fluids, cement cement / 4, 5 /.

As a result of the combined use of aluminum chloride and chalk, when a pH of 4.35 is reached, the formation of condensed colloids of aluminum hydrosol with a particle size of 4 • 10 ^-6 m, capable of creating a gel structure. Condensed colloids of aluminum hydrosol exist in the form of a solid phase in the range of pH 4.35-10.5, which contributes to their dissolution in the filter cake on the wall of the wellbore and allows the permeability of the reservoir rocks to be restored.

 Modified starch is a white or yellowish powder, which dissolves well in water and saturated salt solutions, has a higher heat resistance than conventional starch. It is known to use modified starch as a reagent to reduce filtration and increase the structural properties of drilling fluids / 6, 7 /.

 Sulfacell - a water-soluble hydroxyethyl cellulose, is a yellowish-white product, readily soluble in water. Sulfacell is available in the form of granules or powder of Polycell JSC.

 It is known to use sulfacell to lower the filtration of drilling and cement slurries / 8, 9 /.

 The use of modified starch strengthens the structural adsorption layers by crosslinking molecules, increasing the stability of the foam.

 The combined use of modified starch and sulfacell as a stabilizer of the foaming composition was not found by the authors.

 The combined use of the modified starch and sulfacell in the inventive composition allows to provide low filtration values and increase the structural parameters of the foaming composition due to the fact that, introduced between the colloidal particles of the gel, the stabilizers take water from the system, strengthening the bonds of the structural lattice. This ensures long-term retention of particles of the condensed solid phase (gel) in suspension, which helps to increase the stability of the foam. The use of one modified starch as a stabilizer can improve the structural parameters of the composition, but at high filtration values. Increasing starch consumption to achieve low filtration values is impractical. When using a single sulfacell as a stabilizer, only low filtration values are achieved, and structural indicators do not improve.

Soda ash - a white crystalline powder with a density of 2.5 g / cm ³ . Aqueous solutions have an alkaline reaction.

 It is known the use of soda ash in the chemical, glass, soap, pulp and paper, textile industries, in drilling / 10, 11 /.

 The use in the inventive composition of soda ash provides a decrease in the ionic strength of the medium of the obtained colloidal solution due to the binding of calcium ions in the composition, which leads to the formation of an additional finely divided solid phase, low filtration values and long-term stability of the foam.

 The authors experimentally found that giving the foaming composition of low filtration and high structural indicators to obtain long-lasting foams became possible due to the integrated use of ingredients in the inventive composition with their new ratio. Initially, the interaction of an aqueous solution of aluminum chloride with chalk forms a condensed solid phase (gel) with a low-strength structural network.

 The addition of soda ash neutralizes the calcium ions in the composition, helping to improve the action of stabilizers. Foaming agent molecules create a mechanically strong adsorption layer with low surface tension in the liquid films between the gas bubbles, providing long-term stability of the foam.

 Achievable during the implementation of the invention, the technical result is to achieve high stability of the foam and to obtain the possibility of its use as a washing liquid in the conditions of the ANPD. Due to the low filtration and acid solubility of the solid phase, the possibility of raskolmatization of the pore channels during development is ensured, as a result of which the permeability of the productive formation increases after exposure to the claimed composition.

In the claimed technical solution, the complex use of distinctive features allows us to solve a new technical problem: increasing the stability of the foam by reducing filtration and improving the structural parameters of the composition, which allows us to conclude that the claimed technical solution meets the criterion of "inventive step"
The composition of the prototype is prepared as follows.

 Example 1

Take 853 g of fresh water. 7 g of polyacrylamide are introduced into 353 g of water, and 30 g of bentonite is introduced into the remaining water. Stirred for 5 minutes and left for a day to swell. To the prepared bentonite solution add 30 g of OP-10 foaming agent, then 80 g of KSSB-4 and the solution is thoroughly mixed. Then, the prepared PAA solution is introduced into this solution and mixed until a homogeneous composition. Parameters obtained foamable composition as follows: density - 758 kg / ^m3, filtering - 24 • 10 ^-6 m ^3/30 min, SNS - 0.8 Pa, SNA ₁ - 0.9 Pa, SNS ₂₄ - 0.9 fold - 2, stability - 0.15 days / cm ³ (experiment 3).

 Similarly prepare the inventive foaming composition.

 The technological parameters of the compositions are determined by standard devices according to known methods / 12 /.

 The multiplicity of the foam is determined by the ratio of the volume of the foamed foaming composition to the volume of the non-foaming foaming composition. Stability is the ability of a foamed compound to maintain its original volume. The criterion for evaluating the foam stability index is the lifetime of a liquid film between gas bubbles.

When conducting laboratory tests were used:
- as a foaming agent - OP-10 according to GOST 8433-81 (surfactant of nonionic type), sulfanol according to TU 6-01-862-73 (surfactant of anionic type);
- as a stabilizer - modified starch according to GOST 7698-93 and sulfacell according to TU 6-55-221-1210-91;
- as a seed - technical chalk according to GOST 17498-72;
- aluminum chloride according to TU 6-01-00203312-160-95, Sterlitamak and according to TU 38.3021-63-89 of JSC Salavatnefteorgsintez;
- soda ash in accordance with GOST 5100-85;
- process water with a hardness of 12 mg.eq / l.

 Example 2

To prepare a foaming composition in 867.5 g of fresh water, 40 g of technical chalk is introduced, mixed in a hazardous mixer for 10 minutes, 11 g (in terms of dry matter) of aluminum chloride (concentration of 25 wt.%) Are added, mixed to obtain a colloidal solution. 6 g of soda ash are added to the prepared solution with stirring, stirred for 10 minutes, then 60 g of modified starch, 2.5 g of sulfacell are added and mixed until the stabilizers are completely dissolved, after which 13 g of OP-10 (neonol or other nonionic surfactant) are added . Foaming is carried out in a paddle mixer for 30 minutes until a constant volume of foam is formed and composition indicators are determined. The technological parameters of the composition are as follows:
P = 580 kg / m ³ , SNS = 9.2 Pa, SNS ₁ = 10.8 Pa, SNS ₂₄ = 10.9 Pa, Ф = 0.5 • 10 ^-6 m ³ / 30min, K = 5, stability 12 days / cm ³ (experiment 9).

 Compositions were prepared in a similar manner at various concentrations of ingredients, and the research results are presented in the table.

Analysis of the table data showed that the foaming composition of the prototype has a multiplicity of 2-5, a high density of P = 756-924 kg / m ³ , low values of static shear stress in time SNA = 0.4-0.8 Pa, SNA ₁ = 0.4-0.9 Pa, SNS ₂₄ = 0.4-0.9 Pa and high filtration indices Ф = 24 • 10 ^-6 -36 • 10 ^-6 kg / m ³ , which leads to the formation of unstable foam (experiments 1-4).

Proposed foamable composition with a content of components in the claimed range at a multiplicity of from 4 to 10 and density 430 to 632 kg / m ³ has lower values filtratootdachi 0.5 to 2,5 • 10 ^-6 m ^3/30 min and high performance static shear stress SNS = 7.8-15.4 Pa, SNS ₁ = 8.0-16.4 Pa, SNS ₂₄ = 8-16.6 Pa (experiments 5-15), which contributes to the long-term stability of fine foam from 3 to 20 days / cm ³ . The content in the foaming composition of chalk in the range of 3-4 wt.% And aluminum chloride in the range of 1.1-1.4 wt.% Is optimal (experiments 5-15).

 The content in the composition of chalk more than 4 wt.% And aluminochloride more than 1.4 wt.% Is not economically feasible (experiments 16, 17), since there is no greater improvement in performance.

 The content of chalk in the composition is less than 3 wt.% And alumina chloride less than 1.1 wt.% Does not allow to achieve the task in view of obtaining unstable foam due to the low structural parameters of the foaming composition (experiments 18, 19).

 The content of modified starch is 5-7 wt.% And sulfacell 0.18-0.3 wt. % is optimal. The content of modified starch is less than 5 wt.% And sulfacell less than 0.18 wt.% Leads to high filtration values (experiments 20, 21), which does not provide long-term stability of the foam. A content of more than 7 wt.% Starch and more than 0.3 wt.% Sulfacell is impractical (experiments 22, 23), since low filtration values to obtain stable foams have already been achieved.

 The content of soda ash is 0.6-0.8 wt. % in the claimed composition is optimal for the complete binding of calcium ions in the composition, which interfere with obtaining low filtration values. The content of less than 0.6 wt.% Soda ash in the composition does not allow to obtain a stable foam due to the high values of the filtration of the foaming composition, since calcium ions in the solution are not completely connected (experiments 18, 19). A soda ash content of more than 0.8 wt.% Is impractical, since all calcium ions are already bound, filtration values are achieved that provide stable foams (experiments 16, 17).

 The content of the foaming agent in the range of 0.8-1.8 wt.% Is optimal (experiments 5-15). At a lower surfactant content, high foaming of the composition is not ensured (experiments 20, 21). When the content of the foaming agent is more than 1.8 wt. % of a further increase in air entrainment into the foaming composition is not observed, and only an unjustified overspending of the reagents occurs (experiments 16, 17). Along with OP-10 and sulfonol, other nonionic or anionic surfactants or mixtures thereof can be used as surfactants. Thus, the inventive composition has significantly better filtration and structural characteristics, providing long-term stability of the foam.

The proposed technical solution allows to obtain long-term stable three-phase foams based on a polymer-colloidal foaming composition, in which the solid clay phase is replaced by an acid-soluble condensed solid phase (gel) and the reservoir productivity is restored by standard methods of well stimulation during well development. The use of long-term stable foams during well drilling is more effective than flushing fluids and provides:
- safety of drilling operations through the creation of regulatory repression on the reservoir;
- conditions for maintaining the permeability of the rocks due to the creation of a durable mud screen by a foam gel composition;
- the best performance of bit development by increasing the efficiency of the removal of sludge, cleaning the face;
- solving urgent problems of maintaining well-drained rocks when killing wells and reducing the volume of injected killing fluid during overhaul, etc.

SOURCES OF INFORMATION TAKEN INTO ACCOUNT WHEN FORMING THE APPLICATION FOR THE INVENTION
1. Amiyan V. A. and others. "Opening and development of oil and gas layers", M., "Nedra", 1980, p. 114-119, 310-316.

 2. A.S. USSR N1208192.4 MKI E 21В 33/138, B.I. N 4, 1986 (prototype).

 3. Chalk technical GOST 17498-72.

 4. Aluminum chloride TU 38.302163-89.

 5. RF patent N2135542 6 IPC C 09 K 7/02, B.I. N 24 1999.

 6. Ryazanov Ya. A. "Guide to drilling fluids", Moscow., "Nedra", 1979, p 82.

 7. GOST 7698-93.

 8. . Penkov A.I. and others. "Stabilization of drilling fluids with sulfacell when testing wells under conditions of polymineral aggression", PH, series "Drilling", M., VNIIOENG, N12, 1981.

 9. RF patent N2136843, 6 IPC E 21B 33/138, B.I. N 25, 1999.

 10. GOST 5100-85.

 11. A.I. Busev, I.P. Efimov. "Dictionary of chemical terms", publishing house "Enlightenment", Moscow, 1971, p. 154.

 12. RD 39-2-645-81.

Claims (1)

A foaming composition containing fresh water, a foaming agent, a stabilizer and a seed, characterized in that it contains modified starch and sulfacell as a foam stabilizer, and technical chalk as a seed, while the composition additionally contains aluminum chloride and soda ash in the following ratio of components, wt.%:
Frother - 0.8-1.8
Modified starch - 5.0-7.0
Sulfacell - 0.18-0.3
Chalk technical - 3.0-4.0
Alumochloride - 1.1-1.4
Soda ash - 0.6-0.8
Freshwater - Rest

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