RU2651652C1 - Cation drilling mud for unstable clay rocks drilling - Google Patents

Abstract

FIELD: drilling soil or rock.

SUBSTANCE: invention relates to water-based drilling muds and can be used when drilling oil and gas wells, mainly in drilling unstable swelling of clays and mudstone. Drilling mud comprises, wt%: clay powder 2–4; water soluble cationic copolymer Sylphoc-2540 7–15; xanthan gum 0.1–0.2; polysaccharide PolyKR-K 1–2; water – the rest.

EFFECT: increase drilling efficiency, improve the filtration properties of drilling mud, effective control of the filtration index, increasing the stability of clay rocks, increasing drilling speed and reducing equipment wear.

1 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 swelling plastic clays and mudstones.

The prior art inhibiting drilling fluid for drilling in unstable clay rocks (patent RU No. 2237725 C2, class C09K 8/20, 06/27/2008) containing salt-resistant clay, potassium chloride, barium hydroxide, starch, condensed sulfite-alcohol bard KSSB or oxyl and water, in which the polymer contains hydroxyethyl cellulose of the OEC in the ratio of components, wt. %:

Salt resistant clay 5-10 Potassium chloride 5-30 Barium hydroxide 5-10 Starch 2-3. KSSB or Oksil 5-6 OEC 0.75-1.5 Water Rest

Known solution has increased strength and water resistance of clay rocks, however, it has a drawback, which is the multicomponent and high filtration properties of the solution.

Known drilling fluid, including water, clay powder and a filter reducing agent polyelectrolyte VPK-402 (patent RU No. 2492208 C2, C09K 8/24, publ. 09/10/2013), in the following ratio of components, wt. %:

Clay powder 5-8 VPK-402 7-15 Water Rest

A disadvantage of the known composition is the high filtration properties of the solution. The use of such a solution does not provide effective drilling due to the high content of clay powder in the composition.

Closest to the proposed solution is a cationic-inhibiting drilling fluid (patent RU No. 2534546 C1, C09K 8/24, publ. 11/27/2014), including water, clay powder and a polymer of diallyldimethylammonium chloride (Polydadmax). As an additional inhibitor of clay and a decrease in filtration, a cationic acrylamide copolymer is used in the following ratio of components, wt. %:

Clay powder 6-8 Polydadmach 3-6

Cationic Acrylamide Copolymer 0.2-0.4

Water Rest

Known solution has a high inhibitory ability to clay. However, the solution has high filtration rates and does not provide effective drilling due to the high content of clay powder in the composition of the solution.

The problem to which the invention is directed, is to create a drilling fluid devoid of this drawback, which can be used for drilling oil and gas wells in unstable swelling plastic clays and mudstones.

The technical result of the invention is improving drilling efficiency with improved filtration properties of the solution.

Ceteris paribus, maintaining the stability of clay rocks is largely determined by the filtration rate: the lower it is, the higher the stability of the well walls.

The technical result of the invention is achieved due to the fact that xanthan gum is additionally added to the composition of the drilling fluid, including water, clay powder and a cationic copolymer, and Silfok-2540 is used as a cationic copolymer in the solution. As an auxiliary reagent, the composition contains PolysKR-K polysaccharide in the following ratio of components, wt. %:

Clay powder 2-4 Silfok-2540 7-15 Xanthan gum 0.1-0.2 Polysaccharide PoliKR-K 1,5-2 Water Rest

For the preparation of the proposed solution, it is possible to use clay powder of various grades. Any type of bentonite clay powder can be used in the drilling fluid: PBMA, PBMB, PBMV, PBMG, which are produced in accordance with TU 2164-004-0013836-2006 “Clay powder”, with the exception of those 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.

The optimum concentration of clay powder depends on its brand. So, for a PMBA clay powder, a concentration of 2-3% is sufficient, accepted as the base, and for a PBMV clay powder, the concentration is from 3% to 4%.

For the preparation of the proposed solution, it is possible to use xanthan gum, which is produced in accordance with GOST 33333-2015 “Food additives. Xanthan gum E415 ".

To prepare the proposed solution, it is possible to use the PoliKR-K polysaccharide, which has an increased thickening ability, which is produced in accordance with TU 2262-035-97457491-2010.

Silfok-2540 polyelectrolyte is produced in accordance with TU 2227-001-92802291-2013 and is a colorless to yellow color that is homogeneous in consistency (gel-like) liquid without impurities. Silfok-2540 is a water-soluble polymer with a linear cyclic structure, medium molecular weight with a high cationic charge, obtained by radical polymerization of diallyldimethylammonium chloride monomer. It is a coagulant and flocculant and is used to intensify water treatment processes during the deposition of suspended particles, activated sludge, and to ensure effective treatment of turbid waters.

If necessary, the drilling fluid is weighted with barite concentrate.

To prepare the solution, first mix water with clay powder until it dissolves, then add a water-soluble cationic copolymer, for example, Silfok-2540, to the clay suspension, after which xanthan gum, PolysKR-K polysaccharide and, if necessary, barite weighting agent are added.

The invention is illustrated in the table, which shows the results of studies on the effect of the polysaccharide on the parameters of the filtration of drilling fluids stabilized by cationic copolymer Silfok-2540.

The following abbreviations and symbols are used in the table:

GP - clay powder;

Silfok - cationic copolymer Silfok-2540;

Gum - xanthan gum;

PolyKR-K - polysaccharide PolyKR-K;

PF - the rate of filtration (cm ³ for 30 min) at room temperature.

The table shows that when the content of Silfok-2540, xanthan gum and PolyKR-K is below 7%, 0.1% and 1%, respectively, the filtration rate increases (table, p. 3). With an increase in PolyKR-K content from 1% to 2%, gums - from 0.1% to 0, 2% and Silfok-2540 - from 7% to 15%, the filtration properties of the drilling fluid improve (table, paragraphs 4-12) . A further increase in the content of Silfok-2540, xanthan gum, and PolyKR-K more than 15%, 0.2%, and 2%, respectively, is ineffective (table, p. 13) and leads to an overspending of the filter reducing agent and structure former without a significant decrease in the filtration rate.

Thus, it follows from the table that the use of PolyKR-K in combination with Silfok-2540 and xanthan gum can provide effective control of the filtration rate, thereby increasing the stability of clay rocks.

Compared with the known solution, the amount of clay powder in the proposed solution is reduced, which makes it possible to reduce the density of the drilling fluid, thereby increasing the drilling speed and reducing equipment wear, and, therefore, increasing the drilling efficiency.

You can increase the density of the drilling fluid by adding barite in an amount of from 5 to 100 wt. hours per 100 wt. including solution.

Claims (2)

A drilling fluid comprising water, clay powder and a cationic copolymer, characterized in that the solution additionally contains xanthan gum and PolysKR-K polysaccharide, and Silfok-2540 is used as a cationic copolymer in the following ratio, wt.%: clay powder 2-4 Silfok-2540 7-15 xanthan gum 0.1-0.2 PolyKR-K 1,5-2 water rest