RU2327853C1 - Gas releasing foaming composition for initial exposing of productive formation and well development - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the mining industry and to the compositions of the drilling solutions for initial exposing of the productive formations with the abnormal low bed pressure and to the compositions of liquids for evoking influx in development of the oil and gas wells. The composition contains the foaming agent, foam stabiliser, gas-forming components and water; biopolymer and carboxymethyl cellulose are used as stabiliser, sodium carbonate or hydrocarbonate and sulfamic acid are used as the gas-forming components at the following ratio, in mass percent: 0.2-0.5 of foaming agent; 0.3-0.5 of biopolymer; 0.7-0.9 of carboxymethyl cellulose; 0.38-1.60 of sodium carbonate or hydrocarbonate; 0.68-3.00 of sulfamic acid; remaining - water.

EFFECT: increased stability of foam for initial exposing of the productive formations at low density, filtration, high rheologic characteristics of the structure and lack of solid.

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Description

The invention relates to the oil industry, and in particular to gas-generating foam-forming systems used for the initial opening of reservoirs with abnormally low reservoir pressures (ANPD), to cause the inflow, restoration and conservation of reservoir properties of reservoirs during development and overhaul of wells, and also to increase injectivity of wells.

Known foaming composition containing, wt.%: Ammonium chloride - 19.4, sodium nitrite - 23.6, sulfonol NP-3 - 2.1, organic acid - 0.029 and water [1].

A disadvantage of the known solution is the difficulty of carrying out the gasification reaction. Even if a gassing reaction is initiated, the organic acid may not fully react in solution, creating an acidic environment that is favorable for equipment corrosion.

Also known foaming composition for well development, containing, wt.%: Urea - 0-12.8, nitrite of an alkali or alkaline earth metal - 12.1-58.7, clay acid - 0.2-24.3, ammonium chloride - 0 -41.0, CMC or PAA - 0.1-1.5, surfactants - 0.1-1.5 and water [2].

The disadvantages of the known composition are the low values of the rheological parameters and the fact that low density solutions are achieved only at very high values of the multiplicity of the foam.

The closest to the claimed technical essence, composition and the achieved effect is a foaming composition, including fresh water, a foaming agent, a foam stabilizer - modified starch and sulfacell, seed - technical chalk and additionally - aluminum chloride and soda ash in the following ratio, wt.%: foaming agent - 0.8-1.8, modified starch - 5.0-7.0, sulfacell - 0.18-0.3, technical chalk - 3.0-4.0, aluminum chloride - 1.1-1, 4, soda ash - 0.6-0.8, fresh water - the rest [3].

A decrease in the density of this composition is achieved mainly due to air entrainment and aeration and partly due to a chemical reaction between chalk and aluminum chloride with the release of carbon dioxide.

The disadvantages of this composition are the low values of the rheological parameters, the complexity of preparing a composition of a certain density and regulation of this indicator, since the amount of entrained air during aeration is difficult to control. In addition, this foam-air mixture is difficult to pump into the well by a pumping unit. These shortcomings reduce the technological capabilities of the use of this composition when opening productive formations by drilling and well development.

The aim of the invention is the creation of a gas-generating foam-forming composition of low density with high structural and mechanical properties.

To achieve this goal, the inventive gas-generating foaming composition containing water, a foaming agent, a foam stabilizer and gas-forming components, contains carboxymethyl cellulose and xanthan gum as a foam stabilizer, and sodium carbonate or hydrogen carbonate and sulfamic acid as gas-forming components in the following ratio of components, wt.%% :

Frother - 0.2-0.5

Xanthan gum - 0.3-0.5

Carboxymethyl cellulose - 0.7-0.9

Carbonate or

sodium bicarbonate - 0.38-1.60

Sulfamic acid - 0.68-3.00

Fresh Water - Else

A comparative analysis with the prototype allows us to conclude that the inventive gas-emitting foaming composition differs from the known one in that it contains carboxymethyl cellulose and xanthan gum as a foam stabilizer, and sodium carbonate or hydrogen carbonate and sulfamic acid as gas-forming components. Therefore, the claimed technical solution meets the criterion of "novelty."

The inventive composition is a polymer foam system with a strong thixotropic structure and low density with small values of the multiplicity of the foam formed during the following reactions:

Na ₂ CO ₃ +2 (NH ₂ SO ₃ ) Н → 2Na (NH ₂ SO ₃ ) + ↑ CO ₂ + H ₂ O

NaHCO ₃ + (NH ₂ SO ₃ ) H → Na (NH ₂ SO ₃ ) + CO ₂ ↑ + Н ₂ О

For the formation of 1 g mole (22.4 l) of CO ₂ it is necessary to take 106 g of Na ₂ CO ₃ and 194.2 g of sulfamic acid or 84 g of NaHCO ₃ and 97.1 g of sulfamic acid. The reaction proceeds without initiators and seeds, proceeds completely in accordance with the law of stoichiometry, while creating a neutral medium in the drilling fluid. The method of preparing the foaming composition is simple, technologically advanced. To maintain the pH of the solution above neutral, you can take Na ₂ CO ₃ or NaHCO ₃ in excess. Excess of these reagents allows not only to maintain the pH of the solution above 7.0, but also to neutralize the excess of calcium ions in the process of using the foam system, as well as to prevent the hydration of clay particles.

In the proposed solution, the qualitative and quantitative composition of the components makes it possible to obtain a gas-generating foam-forming composition that meets the conditions for the high-quality opening of productive formations with low reservoir pressures, causing inflow, restoration and preservation of the reservoir properties of the productive formations during well development and overhaul.

In the foaming composition, xanthan gum has a long polymer chain and, in combination with CMC and a foaming agent, creates a unique rheological profile for holding gas bubbles formed due to a chemical reaction. In this polymer medium, there is practically no slipping of the bubbles of the formed gas, due to which, at low values of the multiplicity of the foam, the density of the foam system significantly decreases, rheological parameters and stability increase. As a result, the foam system has high stability, a certain rigidity and elasticity.

The advantages of the proposed structure are:

- low density, high rheological parameters, low filtration, neutral or slightly alkaline environment;

- the absence in the composition of the solid phase (chalk or condensed solid phase of an aluminum hydrogel in the composition of the prototype);

- the ability to obtain the composition of the required density by adjusting the composition of the number of gas-forming components;

From the current level of technology we do not know that the ingredients that make up the proposed foaming composition in a given ratio of components provide the above properties, which allows us to conclude that the proposed technical solution meets the criterion of "inventive step".

The technology of practical application of the proposed foaming composition provides for the dissolution of polymers in fresh water, the sequential addition of a foaming agent and sodium carbonate (hydrogen carbonate) to the polymer solution, and after their complete dissolution, the calculated amount of sulfamic acid is added.

An example of the preparation of a foaming composition (composition No. 5).

9.0 g of CMC and 3.0 g of xanthan gum are simultaneously dissolved in 974 ml of fresh water. After the polymers are completely dissolved, 3.8 g of sodium carbonate and 3.0 g of a foaming agent are added to the solution and mixed again. For pricing, 6.8 g of sulfamic acid are gradually added to the solution. The reaction is very intense, forming a stable foam system.

The properties of the fluids are determined by standard instruments designed to control the parameters of the drilling fluid.

Xanthan gum is a microbial exopolysaccharide and is marketed under various trademarks (Bioksan according to TU 2458-001-16636639-2005 is manufactured by Tetra (Yekaterinburg), KhSD - Polymer, Kern - Tron, Idvis, Bio Vis, Biolam and others are issued by foreign firms).

Instead of CMC, polysaccharides with various structures, such as heat-resistant KMC-TS, carboxymethylated starch - KMK, carboxymethyloxyethyl cellulose of the SK-N brand, and hydroxyethyl cellulose can be included in the foam-forming system.

As a foaming agent can be used surfactants brands ML-81B, OP-10, neonol.

The composition and properties of the inventive gas-generating foaming composition and composition of the prototype are shown in the table.

The proposed composition is a two-phase foam, which, according to its technological properties, satisfies the requirements for opening the formations with AIP and development of wells with different reservoir pressures. When using it, normative repression on the formation is ensured, as a result, the safety of drilling operations, high-quality opening of the productive formation due to low filtration and the formation of a stable insulating film on the well wall are increased. The low density of the composition ensures the creation of depression on the formation, causing inflow from the formation and cleaning the bottom-hole zone during well development.

Information sources

1. RF patent No. 1273508, MKI E21B 43/00, BI No. 15, 1986.

2. RF patent No. 2085567, MKI C09K 7/08, EV 43/25, BI No. 27, 1997.

3. RF patent No. 2187533, MKI S09K 7/08, BI No. 20, 2002.

Claims (1)

A gas-generating foam-forming composition for the initial opening of productive formations and development of wells, containing water, a foaming agent, a foam stabilizer and gas-forming components, characterized in that it contains carboxymethyl cellulose and xanthan gum as a foam stabilizer, and sodium carbonate or sulfamines as gas-releasing components acid in the following ratio of components, wt.%: Foaming agent  0.2-0.5 Xanthan gum  0.3-0.5 Carboxymethyl cellulose  0.7-0.9 Carbonate or Sodium bicarbonate  0.38-1.60 Sulfamic acid  0.68-3.00 Fresh water  rest