RU2567065C1 - Cationic drilling mud - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: drilling mud includes the following components, wt %: gel powder 2-5.46; polymer of PolyDADMAC diallyldimethylammonium chloride 3-5; aluminium sulphate Al₂(SO₄)₃·18H₂O 0.5-6; caustic soda 0.18-2.16; water - the remaining share.

EFFECT: improved structure rheological performance of the mud: increased yield point and shear strength, reduced plastic viscosity.

2 cl, 2 tbl

Description

The invention relates to water-based drilling fluids and can find application in the drilling of oil and gas wells, mainly in the drilling of unstable clay rocks.

The prior art emulsion drilling fluid (patent RU 2213761 C2, C09K 7/06, 10/10/2003) containing the hydrocarbon phase, calcium carbonate, mineral salt, stabilizer and mineralized water. The solution contains FITO-RK starch as a stabilizer, and magnesium dichloride MgCl ₂ and potassium chloride KCl as a mineral salt, and additionally PKD-515 complex-acting surfactant in the following ratio of ingredients, wt.%: Hydrocarbon phase 10- 20, complex surfactant PKD-515 5-7, starch FITO-RK 3-4, MgCl ₂ 5-10, KCl 3-5, calcium carbonate 5-30, mineralized water the rest. Known solution has low values of electrical resistivity, which negatively affects the quality of geophysical surveys.

Closest to the proposed is a drilling fluid, including wt.%: Clay powder 5-8, a clay inhibitor and a filter reducing agent VPK-402 7-15 and water (patent RU 2492208 C2, C09K 8/24, 09/10/2013). The disadvantages of the known composition include unsatisfactory structural and rheological parameters of the known solution.

The technical result, the achievement of which this invention is directed, is to eliminate this drawback, namely the improvement of structural and rheological indicators.

The technical result of the proposed composition is achieved due to the fact that the drilling fluid includes water, clay powder and a polymer of diallyldimethylammonium chloride (Polydadmach), as an auxiliary reagent, a structure-forming agent based on aluminum sulfate and caustic soda is used in the composition in the following ratio of components, wt.%:

Clay powder 2-5.46 Polydadmach 3-5 Aluminum sulfate (Al ₂ (SO4) ₃ · 18H ₂ O) 0.5-6 Caustic soda 0.18-2.16 Water Rest

If necessary, drilling fluid may be weighted with barite concentrate.

For the preparation of the proposed solution, it is possible to use clay powder of various grades. The optimum concentration of clay powder depends on its brand. In the proposed drilling fluid can be used bentonite clay powder of any of the grades PBMA, PBMB, PBMV, PBMG, which is produced in accordance with TU 2164-004-0013836-2006 "Clay powder", except modified with anionic polymers. With a deterioration in the grade of clay powder, its concentration increases, and with an increase in quality, the concentration decreases. Brand, i.e. the grade of clay powder, in the proposed composition does not significantly affect the technological parameters of the solution, but characterizes its consumption.

Diallyldimethylammonium chloride polymer - Polydadmax is synthesized from dimethylamine and allyl chloride. The product is an organic substance with a high cationic charge density that neutralizes positively charged colloidal particles. The reagent can be made in the form of solutions (FLOQUATTM FL or VPK-402 35% concentration) or powders (FLOQUATTM TS from 1.05 to 2, 10% on a dry matter basis).

Powdered Polydadmahs have a bulk density of 0.4 to 0.6. The approximate viscosity of the substance is 15, 50 or 250 cP, depending on the series of products. The maximum working concentration of the substance is 50 g / l. The storage temperature range of the powdered Polydahmas FLOQUATTM TS is 0-35 ° C. The time of complete dissolution in water at 25 ° C is 30 days.

Clay powder of any brand can be used in the invention. The optimum concentration of clay powder is determined by its specific brand. So, for example, a concentration of 2-3% is sufficient for bentonite PMBA clay powder, which is accepted as the base, and for PBMV grade clay powder, the concentration is from 3.74% to 5.46%. With the deterioration of the brand of clay powder, its concentration in the solution increases, and with an increase in quality, the concentration decreases. Brand, i.e. the grade of clay powder, in the proposed composition, does not significantly affect the technological parameters of the solution, but characterizes its consumption.

Attempts to increase the structural and rheological parameters of the solution by adding clay powder in dry form and in the form of hydrated paste are ineffective and practically lead to an increase in plastic viscosity, which is fraught with cost overruns (Table 1, p. 2, 3).

In the proposed solution, it is advisable to use aluminum hydroxide as a builder, which is formed by the interaction of aluminum sulfate with caustic soda. Aluminum hydroxide structures this system, increases dynamic shear stress and static shear stress (SSS), and also reduces plastic viscosity. This crosslinking is temperature resistant.

The invention is illustrated in tables 1 and 2.

Table 1 shows the results of studies on the influence of structure-forming agents: aluminum sulfate and caustic soda, on the technological parameters of the drilling fluid formed by the interaction of these structure-forming agents with a clay powder and polymer of diallyldimethylammonium chloride (VPK-402). Thermostating was carried out for 36-40 hours at 1200C. In tables 1 and 2, the following abbreviations and symbols are used:

PF - an indicator of a filtration;

HC - conditional viscosity;

η _PL - plastic viscosity;

τ ₀ - dynamic shear stress;

CHC ₁ - statistical shear stress per 1 minute;

SNA ₁₀ - statistical shear stress in 10 minutes;

CA - aluminum sulfate (Al ₂ (SO4) ₃ * 18H ₂ O)

GB - PBMA clay powder;

3% GR - 3% clay solution;

* - there is a loss of clay phase;

HC - conditional viscosity;

** - 1% aluminum sulfate and 0.36% NaOH were added to the solution.

The results of the experiments are shown in table 1, from which it follows that when the content of aluminum sulfate and caustic soda is less than 0.5% and 0.18%, respectively, the structural and rheological parameters before and after thermostating do not improve (table. 1, p. 4) , and the PF filtering rate decreases.

During drilling in clay deposits, the mud enriches the clay phase and rheological parameters of the plastic viscosity η _PL and dynamic shear stress τ ₀ increase.

An increase in the content of aluminum sulfate and caustic soda by more than 6% and 2.16%, respectively, is also ineffective (Table 1, p. 10), since it leads to an overuse of these reagents without a significant improvement in the structural and rheological parameters of the solution.

As a result of the experiments, it was also established that in some cases, after thermostating (Table 1, items 2, 3, 7, 10), a clay phase precipitates.

Field tests of this builder with the proposed cationic solution were carried out while drilling well No. 939 of the Astrakhan gas condensate field. Due to the high inhibitory and self-cleaning properties of the cationic solution, no solution was observed in the process of deepening the production of the solution. For comparison, the average volume of utilized drilling fluid according to the "Regulation on the use of drilling fluids in the construction of production wells at the Astrakhan gas condensate field. Gazprom OJSC: Gazprom dobycha Astrakhan LLC:

In practice, the accumulated and utilized volumes of drilling fluids exceed the regulated ones. At well No. 939 of the Astrakhan gas condensate field, the volume of the utilized solution was 300 m ³ .

The average technological parameters of the drilling fluid with VPK-402 before and after the introduction of aluminum sulfate and caustic soda (working solution of well No. 939 of the Astrakhan gas condensate field) are shown in Table 2.

If necessary, an increase in the density of the drilling fluid is made by the addition of barite in an amount of from 5 to 150 parts by weight. per 100 parts by weight solution.

The proposed drilling fluid is prepared as follows. First, water and clay powder are mixed until it dissolves, then VPK-402 is added to the clay suspension, and then, with vigorous stirring, aluminum sulfate and caustic soda are added sequentially, and if necessary, barite weighting agent is added.

Claims (2)

1. Drilling fluid, including water, clay powder and Polydadmach, characterized in that it additionally contains aluminum sulfate and caustic soda in the following ratio, wt.%:
Clay powder 2-5.46 Polydadmach 3-5 Aluminum sulfate (Al ₂ (SO ₄ ) ₃ · 18H ₂ O) 0.5-6 Caustic soda 0.18-2.16 Water Rest 2. A solution according to claim 1, characterized in that barite concentrate is used as a weighting agent in an amount of from 5 to 150 parts by weight. per 100 parts by weight solution.