RU2541666C1 - Mud fluid for stabilisation of mud shale - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: proposed mud fluid comprises the following components in wt %: clay powder - 4-8; shale stabilisers to make well walls stable, a tall oil - 5-15, filtration attenuator - 0.2-1, water making the rest.

EFFECT: better stabilising properties.

2 cl, 1 tbl, 1 dwg

Description

The invention relates to water-based drilling fluids and may find application in drilling oil and gas wells in unstable deposits, especially when drilling intervals of unstable clay rocks.

A well-known water-based drilling fluid (see RF patent No. 2492207 C1, C09K 8/18, 09/10/2013), which can be used in the construction of oil and gas wells, mainly when drilling unstable clay rocks and salt deposits under high bottomhole conditions temperatures up to 220 ° C. Known drilling fluid has an increased clay inhibitory ability, a reduced filtration rate, and increased salt and thermal stability. The drilling fluid contains, wt.%: Clay powder 3.3-5.3; filtering agent 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. Despite the increased inhibitory ability of the solution to clays, this solution has a low stabilizing ability to unstable fractured shales, mudstones and siltstones.

The closest in composition to the technical solution of the proposed solution is aerated clay solution (see RF patent No. 2172760 C1, C09K 7/02, 08/27/2001), designed to drill "depleted" formations with abnormally low reservoir pressure. Aerated clay solution contains water, bentonite clay powder, stabilizer - carboxymethyl cellulose - CMC and a foaming agent, as a foaming agent it contains saponified tall pitch - OTP or emulsion in the following ratio of components, wt.%: Clay powder 5-6, CMC 0.2-0.4 , OTP or emultal 0.4-0.6, the rest is water. Known drilling fluid has a low stabilizing ability to shale, which does not allow for the stability of the walls of the wells.

The problem solved by the proposed composition of the drilling fluid is to create a solution with a high stabilizing ability in the shales and preserving the stability of the wellbore, while the composition must meet safety requirements and should not include toxic components.

The technical result of the proposed composition is to increase the stabilizing properties of the solution.

The technical result of the invention is achieved by imparting colmatating properties to the solution with hydrophobic materials, which ensures shale stability.

The essence of the invention lies in the fact that the drilling fluid, including water, clay powder, a decrease in filtration and a stabilizer, as a stabilizer for shale, ensuring the stability of the walls of the wells, the solution contains tall oil, in the following ratio, wt.%:

Clay powder 4-8; Tall Oil (TM) 5-15; Filtration Reducer 0.2-1; Water rest.

In the proposed drilling fluid, either polyanionic cellulose - PAC, or starch, or carboxymethyl cellulose - CMC, or Polydadmach, or hypane are used as a filtration reducing agent.

Tall oil is a mixture of organic compounds, primarily fatty (C ₈ -C ₂₄ ) and resin acids. It is a product of the treatment of sulfuric acid with sulfate soap, obtained as a by-product in the pulping of the sulfate method. Tall oil is produced in raw and refined form under the brands of CTM, HTM, LTM. TU 13-0281078-119-18.

PAC-H, PAC-B polyanionic cellulose is used to control viscosity and filter drilling fluids. Effective as stabilizing agents (protective colloids) in all types of water-based drilling fluids.

Due to the encapsulating properties, the use of PAC in the composition of the proposed solution ensures stabilization of the borehole walls during drilling in shales and helps to reduce the solid phase in the drilling fluid. PAC is produced according to TU 2231-015-32957739-00.

Hypan - hydrolyzed polyacrylonitrile is obtained in the process of hydrolysis of polyacrylonitrite with caustic soda. Gipan is a viscous dark yellowish liquid of 8-10% concentration with a density of 1.05-1.07 g / cm ³ , pH = 12 or more, or a powder of yellowish, cream or pink color with a moisture content of 10%, which can be used in marketable or in the form of a solution of 10% concentration with ρ = 1.05 g / cm ³ . Hypane, like other acrylic polymers, forms strong polymer clay structures with clay particles due to chelate bonds.

The proposed composition of the solution has higher stabilizing properties to unstable clay rocks, and the use of tall oil meets environmental standards.

The concentration of tall oil to ensure the stabilization of shale is determined experimentally, during drilling, depending on the geological and technical conditions and ranges from 5 to 15%.

For example, in well No. 2062 of the Astrakhan gas condensate field in the interval 1557-1565 m, the percentage of HM before opening this interval was 5.5%. In fissured clayey-argillite rocks, this content for hydrophobic mudding was not enough. By increasing the TM content to 10–11% during 2–3 washing cycles, the shedding of clay – mudstone rocks was completely stopped. In general, the result of the use of drilling fluid in this well showed that, while observing the component composition of the fluid, it has fairly good collimating properties and is able to stabilize the wellbore with occurrence of fractured clay-argillite rocks in the drilling interval 1557-3600 m in the trough zone.

The results of the experiments are confirmed by photographs explaining the effect of different compositions of drilling fluids on the stability of shales (see Fig. A-e), and the information given in the Table, which shows the dependence of changes in the technological parameters of the drilling fluid on the concentration of tall oil when using various filtration reducers.

When checking the effect of various compositions of drilling fluids on the stability of shales, the samples were kept for 10 days. It has been noted that mudstone, a sedimentary rock formed in the water as a result of compaction, dehydration and cementation of clays, quickly loses stability without swelling (see photo a) cracking into small plates of various geometric shapes. Adding 0.5% PAC (photo b) increases the viscosity of water, which leads to a slowdown in the destruction of the sample. The hydrophobic colmatant (photo c) turned out to be less effective in a clayey solution (3% clay solution + 0.5% PAC + 10% TM) than when it was introduced into a sludge viscous solution (10% clay solution + 0.5 % PAC + 10% sludge, photo g). The stability of mudstone samples increases significantly in a viscous solution with a sufficient amount of colmatants (10% clay solution + 0.5% PAC + 10% sludge + 10 TM) (photo e) and in an anhydrous hydrocarbon solution (photo e).

In the proposed drilling fluid can be used bentonite clay powder of any of the grades PBMA, PBMB, PBMV, PBMG and PKGN, which is produced in accordance with TU 2164-004-0013836-2006 "Clay powder".

Instead of PAC, it is possible to use CMC (line 5), starch (line 4), acrylate (hypane, line 7), cationic reagents of the Polydadmach series (VPK-402, line 6) (see Table).

Table No. The composition of the solution, wt.% Solution indicators F, cm3 η _pl, MPa · s τ _{0 Pa} Suggested Solution one 6% GP + 5% TM + 0.5% PAC + 88.5% water 5 25 10,2 2 6% GP + 10% TM + 0.5% PAC + 83.5% water four 29th 12.8 3 6% GP + 15% TM + 0.5% PAC + 78.5% water 3 34 14.6 four 6% GP + 10% TM + 1.5% starch + 82.5% water 3,5 33 16,2 5 6% GP + 10% TM + 0.5% CMC + 83.5% water four 26 9.6 6 6% GP + 10% TM + 7% VPK-402 + 77% water 2 36 6.6 7 6% GP + 10% TM + 0.5% hypane + 83.5% water 3 32 8.8 Note: GP - clay grade PMBV; F is an indicator of filtration; η _PL - plastic viscosity; τ ₀ - dynamic shear stress.

Claims (2)

1. A drilling fluid, including water, clay powder, a filtration reducer and a stabilizer, characterized in that tall oil is introduced as a shale stabilizer to ensure stability of the walls of the wells, in the following ratio, wt.%:
Clay powder 4-8 Tall oil 5-15 Filtration Reducer 0.2-1 Water rest 2. The drilling fluid according to claim 1, characterized in that either polyanionic cellulose — PAC, or starch, or carboxymethyl cellulose — CMC, or Polydadmach, or hypane is used as a filtration reducing agent.

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