RU2567066C1 - Cationic drilling mud - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: drilling mud includes the following components, wt %: gel powder 2-5.46; PolyDADMAC 7-15; aluminium sulphate 0.2-0.5; water - the remaining share.

EFFECT: improved structure rheological performance of the mud - plastic viscosity and yield point, control of fluid loss indicator.

2 cl, 1 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 saline 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 a surfactant with complex action PKD-515 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, saline water - the rest. Known solution has low values of electrical resistivity, which negatively affects the quality of geophysical surveys.

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

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 for the proposed composition is achieved due to the fact that in the drilling fluid, including water, clay powder and a polymer of diallyldimethylammonium chloride (Polydadmax), aluminum sulfate is additionally contained as an auxiliary reagent in the following ratio of components,%:

Clay powder 2-5.46 Polydadmach 7-15 Aluminum sulphate 0.2-0.5 Water Rest

As an auxiliary reagent that improves filtration performance in the proposed solution, the well-known in drilling reagent is aluminum sulfate. For the preparation of the proposed solution, it is possible to use clay powder of various grades. 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.

If necessary, weighting of the drilling fluid with barite concentrate is possible.

The invention is illustrated using the table (see the end of the description), which shows the results of studies on the effect of aluminum sulfate on the technological parameters of drilling fluids stabilized by a polymer of diallyldimethylammonium chloride such as cationic polymer VPK-402.

The following abbreviations and symbols are used in the table:

PF - an indicator of a filtration;

η _{PL, room} - plastic viscosity at room temperature;

τ _{0, room} - dynamic shear stress at room temperature;

η _{PL, 50 °} - plastic viscosity at a temperature of 50 °;

τ _{0, 50 °} - dynamic shear stress at a temperature of 50 °;

η _{PL, 82 °} - plastic viscosity at a temperature of 82 °;

τ _{0, 82 °} - dynamic shear stress at a temperature of 82 °;

CA - aluminum sulfate (Al ₂ (SO ₄ ) ₃ * 18H ₂ O)

GR - PBMA clay powder;

3% GR - 3% clay solution;

* in rows 2, 8 of the table - the clay solution is salted with 1% CaCl ₂ - 6% NaCl.

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

The experimental results shown in the table allow us to see that when aluminum sulfate 0.1% is introduced into the drilling mud containing clay and VPK-402, the filtration parameters of the drilling mud increase (table, p. 5). With an increase in the aluminum sulfate content from 0.2% to 0.5%, the technological parameters of the drilling fluid improve (table, paragraphs 6-11). A further increase in the concentration of aluminum sulfate in the solution is inefficient and leads to an overuse of the builder (table, p. 12) and a deterioration of technological indicators (table, p. 13).

Thus, the table shows that the use of aluminum sulfate in combination with VPK-402 provides control of the filtration rate and structural and rheological properties.

The increase in the density of the drilling fluid is made by the addition of barite in an amount of from 5 to 150 mass. hours per 100 mass. including solution.

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

Claims (2)

1. Drilling fluid, including water, clay powder and Polydadmach, characterized in that as an auxiliary filter reducing agent and a regulator of structural and rheological parameters, aluminum sulfate is used in the following ratio of components, wt.%:
Clay powder 2-5.46 Polydadmach 7-15 Aluminum sulphate 0.2-0.5 Water Rest 2. Drilling fluid according to claim 1, characterized in that barite concentrate is used as a weighting agent in an amount of 5 to 150 parts by weight. per 100 parts by weight solution.