RU2614839C1 - Cationic drilling fluid with enhanced both inhibits and studs properties - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to drilling fluids, water-based and can be used for drilling oil and gas wells, mainly in drilling unstable clay and clastic rocks in salt deposits. Cationic drilling fluid contains, in weight %: gel powder 3-5; polydadmac 1.05-2.10; as structurant - cationic polymer Rosflok CF 0.5-2; non-ionic cellulose ether is 0.2-0.5; water the rest.

EFFECT: cationic drilling fluid with improved properties and secures the preservation of stability (integrity) of the borehole wall, while reducing polidadmaha flow.

1 dwg, 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 in terrigenous and salt deposits.

Known drilling mud containing, wt.%: Clay powder 3.3-5.3; VPK-402 - 1.4-2.4; liquid paraffin C ₁₀ -C ₁₆ - 5.3-8.8; antifoam MAS-200 - 0.06-0.2; water - the rest (RF patent for the invention No. 2492207 C1, class C09K 8/18, publ. 09/10/2013). The disadvantages of the known composition include the low fastening properties of the drilling fluid and the high consumption of VPK-402.

The closest technical solution to the proposed is a cationic-inhibiting drilling fluid, which contains, wt.%: Clay powder - 5-8; VPK-402 polyelectrolyte - 7-15; water - the rest (RF patent for the invention No. 2492208 C2, class C09K 8/24, publ. 09/10/2013). Known drilling fluid containing a cationic polymer has high inhibitory properties, which allows to reduce the production time of the solution during the drilling intervals of swelling clays. However, due to the low fixing properties, there is a possibility of loss of integrity of clay rocks on the walls of the well, which is a disadvantage of the known solution.

The technical result to which the invention is directed is to increase the fastening properties of the solution and maintain stability (integrity) of the walls of the wellbore while reducing the consumption of VPK-402. For the present invention, the use of VPK-402 polyelectrolyte is one example of the use of the mentioned polyelectrolyte as a stabilizer - a filter reducing agent, a clay inhibitor. It is possible to use various molecular weights and manufacturers in solutions of polydynamics.

The problem solved by the invention is to create a drilling fluid with specified parameters, in which the consumption of polyelectrolyte is reduced.

The essence of the invention lies in the fact that the cationic drilling fluid, including water, clay powder and polydadm, additionally contains a cationic polymer Rosflock KF and water-soluble non-ionic cellulose ether, in the following ratio, wt.%:

PBMV clay powder 3-5 Polydadmach 1.05-2.10 Rosflock KF 0.5-2 Non-ionic cellulose ether 0.2-0.5 Water rest

Inhibiting drilling fluids are traditionally used to stabilize unstable clay rocks. Inhibitory drilling fluids are effective in swellable clays, however, when drilling intervals of clays containing sand or unstable non-swellable clay rocks - mudstones, the inhibitory properties of the solution are not enough to stabilize the walls of the wellbore. Stabilization of the wellbore is achieved by increasing the fastening properties of the solution by increasing the networks of hydrogen bonds and filling them with hydrophobic components.

As non-ionic water-soluble cellulose ether, hydroxyethyl cellulose (HEC), or hydraethyl cellulose (HEC), or natrosol of various grades are used. Non-ionic water-soluble cellulose ether is a powder from white to cream odorless, completely soluble in cold water.

Polydadmach is a cationic polymer with a linear cyclic structure, obtained by radical polymerization of a dimethyl diallylammonium chloride monomer, which, in turn, is made from allyl chloride and dimethylamine by heating in an alkaline medium. The structural formula of VPK-402 is presented from repeating monomer units.

Polydadmahs are available in the form of a liquid with a uniform consistency, without impurities, from colorless to yellow, of various concentrations or in dry powder form. The molecular weight of the polyaddahs varies over a wide range and averages about 3 × 10 ⁵ . In a marketable product, the molecular weight of VPK-402 may vary from 10 ⁴ to 10 ⁶ or more. Polydadahms in terms of toxicity belong to hazard class 4 - low-hazardous chemicals according to GOST 12.1.007-76. The shelf life of polydadmas for drilling fluids is practically unlimited.

Rosflock KF is a high molecular weight polyacrylamide with a degree of cationicity of 50-95%, an effective emulsion cationic flocculant used for cleaning drilling fluids of any systems and circulating water from mineral-organic components and for dewatering sludge from household wastewater on all types of equipment (centrifuges, filter presses, flotators) . Rosflock KF is an emulsion from white to beige. Rosflock KF in terms of toxicity refers to the 4th hazard class - low-hazard chemicals in accordance with GOST 12.1.007-76. Rosflock KF is produced in accordance with TU 2458-006-22361394-2004 by the Volga plant of NPP KF LLC. The shelf life of Rosflock KF for drilling fluids is practically unlimited.

Improving the fastening properties of the solution provides non-ionic cellulose ether by increasing the hydrogen networks between particles of unstable rock. An additional increase in the fastening properties of the solution is made by introducing hydrocarbon components that ensure filling the cells of the hydrogen networks.

Maintaining and / or increasing the inhibitory properties of the solution is carried out by introducing known electrolytes: KCl, NaCl, CaCl ₂ , sodium acetate, sodium formate.

Translation into a salt-saturated (highly mineralized) cationic solution is carried out by adding technical salt to saturation.

If necessary, the density of the drilling fluid is increased with carbonate weighting agents, such as chalk, marble chips, dolomite or siderite, barite concentrate and galena.

To conduct studies of the fastening properties of drilling fluids, tablet samples were prepared (see Fig. A-d) of cylindrical form from hydration-active clays with a content of 50% sand with a cross-section diameter of 22 mm and a height of 12 mm with a given pressure on a hydraulic press. As an object imitating swelling clay, unmodified PBMV grade bentonite clay powder was used, which is produced in accordance with TU 2164-004-0013836-2006 “Clay powder”, and fractions up to 1 mm in size are used as sand. Samples of hydration-active clays in the solution medium were kept for 3 days.

The invention is illustrated using tables 1-2 and FIG. a-g. Table 1 shows the results of studies on the effect of non-ionic cellulose ether on the fastening properties of the solution; in fact, table 1 provides information on the stability of a hydration-active montmorillonite clay sample with a content of 50% sand in the drilling fluid, i.e. maintaining the integrity of the clay sample with a content of 50% sand. The technological parameters of drilling fluids are shown in Table 2, taking into account the additional inclusion of inorganic inhibitors 3% KCl, 3% NaCl and 1% CaCl ₂ into the solutions (Table 2, paragraphs 1-8).

The research results showed that when the concentration of non-ionic cellulose ether is less than 0.2%, the integrity of the samples is destroyed.

From table 1 it is seen that when the content of Polydadmach, Rosflock KF and non-ionic cellulose ether below 1.05%, 0.5% and 0.2%, respectively, the destruction of the sample occurs (table. 1, p. 3). The research results, FIG. a-d, allow us to conclude that the proposed cationic drilling fluid provides preservation of the integrity of the samples.

An increase in the content of polydadmach, Rosflock CF and non-ionic cellulose ether of more than 2.1%, 2.0% and 0.5%, respectively, is ineffective (Table 2, p. 8), since it leads to an overrun of reagents without a decrease in the filtration rate with a simultaneous deterioration structural and rheological indicators.

In tables 1-2, the following notation and abbreviations are used: 3% GR - 3% clay solution from PBMV clay powder; Px — polydadmach; in the experiments, VPK-402 polyelectrolyte — a cationic polymer — was used; PF - filtration rate for 30 minutes; η _square - plastic viscosity; τ ₀ - dynamic shear stress (CSN); СНС1 / 10 - static shear stress for 1 and 10 minutes, respectively. SSS characterizes in drilling fluids a static shear stress when the circulation is stopped, which prevents the cuttings (sludge) from falling out of the solution; CSN - dynamic shear stress - a parameter responsible for the quality of the removal of cuttings.

From Table 2 it follows that the use of non-ionic cellulose ether in combination with polydadm and Rosflok KF can significantly reduce the consumption of polydmax, provides control of the filtration rate, rheological properties and preserves the stability of clay rocks.

Thus, the optimal ratio of components in the proposed solution is the following, wt.%:

Clay powder 3-5 Polydadmach 1.05-2.10 Rosflock KF 0.5-2 Non-ionic cellulose ether 0.2-0.5 Water rest

This drilling fluid is prepared as follows. First, the water is mixed with clay powder before it is dissolved, then polydadm, Rosflock KF and non-ionic cellulose ether, and, if necessary, inorganic inhibitors, hydrocarbons and weighting agent are added to the clay suspension. The heat resistance of the solution is determined by the heat resistance of non-ionic cellulose ether and is 120-140 ° C. The low heat resistance of the drilling fluid limits its use in conditions of exposure to high temperatures.

Claims (2)

Cationic drilling fluid, including water, clay powder and polydadm, characterized in that the solution additionally contains a cationic polymer Rosflock KF and non-ionic cellulose ether, in the following ratio, wt.%: PBMV clay powder 3-5 Polydadmach 1.05-2.10 Rosflock KF 0.5-2 Non-ionic cellulose ether 0.2-0.5 Water rest

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