RU2614837C1 - Cationic drilling mud - Google Patents

Abstract

FIELD: soil or rock drilling.

SUBSTANCE: invention relates to water-based drilling fluids and can be used when drilling oil and gas wells, mainly for drilling of unstable clay rocks. Cationic drilling mud contains, wt%: clay powder 3–5; polydadmac 1.75–2.10; structure-forming agent – cationic polymer Rosfloc KF 0.5–2; water – balance.

EFFECT: improved inhibiting properties and improved structural properties of drilling mud.

1 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 closest technical solution to the proposed is a cationic-inhibiting drilling fluid, which contains, wt.%: Clay powder 5-8; VPK-402 7-15 polyelectrolyte; the rest of the water (RF Patent for the invention No. 2492208 C2, class C09K 8/24, publ. 09/10/2013).

A disadvantage of the known composition is the low inhibitory and structural properties of the solution, namely, static shear stress (SSS) and dynamic shear stress (CSN), while VPK-402 is overspended.

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

The technical result to which this invention is directed is to increase the inhibitory properties and improve the structural parameters of the drilling fluid.

It should be noted that the use of VPK-402 as a polyelectrolyte is a special case, in the general case, polydadmas of various molecular weights from various manufacturers are used as a stabilizer - a filter reducing agent, a clay inhibitor.

This technical result is achieved due to the fact that the composition of the drilling fluid, including water, clay powder and polydadm, as an additional structural agent contains a cationic polymer Rosflock KF in the following ratio of components, wt.%:

Clay powder 3-5 Polydadmach 1.75-2.10 Rosflock KF 0.5-2 Water Rest

If necessary, the density of the drilling fluid is increased with carbonate weighting agents (chalk, marble chips, dolomite, siderite), barite concentrate.

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 foreign inclusions, which has shades from colorless to yellow in various concentrations, and can also be produced 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. 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 a low-viscosity emulsion from white to beige, in terms of acute toxicity it belongs to hazard class 4 - 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.

The invention is illustrated in Tables 1-2. In tables 1-2, the following notation and abbreviations are accepted: GP - PBMV grade clay powder; CF - Rosflock CF; P-x - polydadmax, PF - filtration rate for 30 minutes; η _PL - plastic viscosity; τ ₀ - dynamic shear stress; SNA 1/10 - static shear stress for 1 and 10 minutes, respectively. SSS and BPS characterize the following in drilling fluids: the static shear stress when the circulation is stopped prevents the cuttings (sludge) from falling out of the mud; dynamic shear stress - a parameter responsible for the quality of the removal of cuttings.

From Table 1 it is seen that the optimal amount of reagents in the solution is, mass. %: polyadmax from 1.75 to 2.10, Rosflock CF from 0.5 to 2 (Table 1, paragraphs 4-9). Moreover, the polydadmach content (for example, VPK-402) is below 1.75%, and Rosflok KF below 0.5% leads to a deterioration in structural and rheological parameters and an increase in the mud filtration rate (Table 1, p. 3). When the content of Rosflock CF in the solution is above 2%, a significant increase in structural and rheological parameters occurs, in this regard, a further increase in the concentration of the reagent is impractical (Table 1, paragraph 10).

For studies of the inhibitory properties of drilling fluids, clay samples moistened to 30% (plastic) were prepared in the form of cylindrical tablets 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, PBMV grade clay powder was used, which is produced in accordance with TU 2164-004-0013836-2006 “Clay powder”.

The inhibitory properties of the drilling fluid were evaluated by the amount of impregnated fluid in the plastic clay sample tablets, i.e. by the relative increase in the mass of the tablet sample during aging in the drilling fluid for 7 days (table. 2).

The relative increase in sample mass Δm (in%) is determined by the formula:

Δm = (m ₂ -m ₁ ) ⋅100% / m ₁ ,

where m ₁ is the mass of the original sample; m ₂ is the mass of the sample aged 7 days in the test medium.

To increase the inhibitory properties, known electrolytes, for example KCl, NaCl, CaCl ₂ , acetate or sodium formate, are introduced into the solutions.

Claims (2)

Cationic drilling fluid, including water, clay powder, polydadm, characterized in that the solution additionally contains Rosflock KF in the following ratio of components, wt.%: Clay powder 3-5 Polydadmach 1.75-2.10 Rosflock KF 0.5-2 Water rest