RU2612040C2 - Polymer-emulsion drilling mud - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil and gas industry. The polymer-emulsion drilling mud comprises an integrated reagent Unidrill, consisting of organic acids, being plasticizers, water-repellents and inhibitors, where plasticizers are oxalic acid salts together with oxides of amphoteric metals, and water-repellents are oxalic acid salts together with oxides of amphoteric metals and salts of hydrobromic acid, and inhibitors are microgels, with the following ratio of mud ingredients: wt % rheology-Xhantan Gum 0.2-0.5;. filtering-Fitter Check 2-2.5; filtering-PAC-LV 0.5-1; inhibitor-MgO 0.5-2; calcium carbonate, 5-50; integrated reagent Unidrill 25-30; dispersion medium-water, the rest; lubricant SBU-DR-5-10 from the whole volume.

EFFECT: invention provides for reduction in drilling time, maintaining the stability of the drilling mud, environmental protection while reducing the cost of the drilling mud.

1 tbl, 1 dwg

Description

The invention relates to the oil and gas industry, in particular to drilling fluids used when opening productive formations in difficult conditions, when drilling softened, active, unstable clay rocks, inclined and horizontal wells at high temperatures and high reservoir pressures.

Background to the invention. Analysis of the current level of technology in this field showed the following.

Devonian sediments are one of the main objects of oil exploitation on the territory of the Romashkinskoye field. During drilling during the passage of the rocks of the Devonian age tires, represented by clay and carbonate-clay rocks, complications are observed, accompanied by collapse, water manifestations and absorption. It is necessary to reduce the influence of negative factors affecting the stability of the wellbore. For this, various types of drilling fluids are used that can minimize or eliminate this type of complications.

To solve the problems during the opening of fault tectonics, complicated by erosion cuts (Kynov clays), it is necessary to use new complex drilling fluids that are responsible for many factors. So, at the opening of the Kyn mudstones (especially at zenith angles of more than 50 °), it is necessary to select an impact complex:

1) plasticization (in which all Coulomb forces that bind clay particles become ionic), while at a reservoir pressure of more than 10 atm, an initial compaction of softened rock is observed;

2) after the transition of the rock to the stage of ion exchange (active phase), inhibition must be carried out, and this stage must take place in two stages:

- encapsulation with water-repellent inhibitors, in which the microcracks remaining after compaction are filling, the channels of which can potentially increase in size;

- hardening by gel inhibitors, in which there is a crosslinking of the rock structure with the main calcium and sodium binders.

A known solution comprising water and clay powder containing VPK-402 polyelectrolyte as a clay inhibitor, filter reducing agent and viscosity regulator and additionally containing liquid hydrocarbons (RF Patent No. 2492208, class C09K 8/24, “Cationic inhibiting drilling fluid”).

The disadvantage of this solution is that it is not effective enough for opening depleted rocks, and the presence of liquid hydrocarbons prevents the observance of environmental conditions.

There is a drilling fluid containing water, a polyhydric alcohol, a biopolymer, an anionic emulsion ROSFLOK PV, sodium acetate and a bactericide, and further comprising tall oil, potassium chloride and PBMV clay powder (Patent of the Russian Federation No. 2501828, class C09K 8/20, “Alcohol drilling fluid” )

The disadvantage of the existing drilling fluid is the multicomponent composition, entailing the complexity of preparation and use.

Closest to the claimed polymer-emulsion drilling fluid is adopted by us as the closest analogue, that is, the prototype, PremiumGel drilling fluid, which is a solution based on hydrogels of salts with a solid phase content and having the following composition, wt. %:

CaCl ₂ 23 complex mineralizer Bau DF MK 7 NaOH 0.2 complex reagent Bau DF Riomix 2.0-3.0 calcium carbonate (calculated) 5-75 Bau DF Lube + drilling fluid lubricant 5.0-10.0 dispersed medium (water) rest

This drilling fluid is used in drilling processes when opening softened, depleted rocks (Collection of reports of the II open scientific-practical conference “Actual problems of construction and repair of oil and gas wells”, Gelendzhik, 2013, pp. 30-33, a copy is attached) .

The disadvantages of this drilling fluid are the presence of a solid phase, a short time to maintain stable parameters of the solution, which creates repression on the formation and the likelihood of hydraulic fracturing and does not preserve the filter cake, thereby preventing the stability of the walls of the wellbore, and also a long drilling time.

The obvious disadvantages of the well-known drilling fluid include compliance with increased safety measures used when working with flammable liquids, preventing reagents from entering open areas of the body, equipping the rooms with forced-air and exhaust ventilation, and discharging the spent fluid into barns with reliable waterproofing and deboning , as a result, this set of measures leads to a rise in the cost of drilling fluid.

The objective of the present invention is to remedy these disadvantages, namely reducing the drilling time, maintaining the stability of the drilling fluid and environmental protection conditions, as well as reducing its cost.

The problem is solved by the use of polymer-emulsion drilling fluid containing the following components, wt.%:

Rheology - Xhantan Gum 0.2-0.5 Filtration - Fitter Check 2-2.5 filtration - PAC-LV 0.5-1 lubricating additive - SBU-DR 5-10 of the volume inhibitor - MgO 0.5-2 calcium carbonate 5-50 complex compound - Unidrill 25-30 dispersed medium - water rest

Unidrill - a comprehensive compound of various reagents:

- salts of oxalic acid;

- oxides of amphoteric metals;

- salts of hydrobromic acid;

- microgels.

Salts of oxalic acid together with amphoteric metal oxides contribute to the plasticization of the rock (turning it into a kind of plasticine), while the oxides temporarily prevent the mudstones from collapsing at the cationic anion level. This combination in the composition with salts of hydrobromic acid promotes high hydrophobization of the rock itself, which prevents the penetration of water into the microchannels, and also maintains a clean opening of the reservoir of the reservoir.

Microgels are inhibitors that allow to cure the softened structure of mudstones. In addition, in conjunction with salts of hydrobromic acid, a synergistic effect is formed: a decrease in the stickiness of the crust and the friction force, which allows multi-meter intervals of horizontal sections to pass with a minimum content of lubricants.

Drilling Fluid Components:

1. Xhantan Gum (Xanthan Bipolymer), TU 2458-010-82330939-2009, as amended. No. 1-5, rheology.

2. Fitter Check (rye-based starch-containing extrusion reagent), STO 0190450908-001-2013, filtration.

3. PAC-LV (low viscosity polyanionic cellulose, PAC-NV, Osnopak brand НТ), TU 2231-011-63121839-2010, as amended. No. 1, 2, filtration.

4. SBU-DR (lubricant for drilling fluids), TU 2458-001-6824973-2011.

5. Unidrill (modification of the reagent by Silin VN-M, TU 2145-014-13002578-2008 and Sodium Formiate, TU 2432-008-50685486-2004 Grade B), a comprehensive compound.

The effects described above together allow you to build wells in almost all intervals of softened mudstones of any profiles and lengths, since the strengthening effect lasts throughout the entire extended section, allowing you to keep the borehole diameter nominal for wide ranges of properties of the polymer-emulsion drilling mud itself.

The invention is illustrated in graphic materials.

Table 1 shows a comparison of the inventive polymer-emulsion drilling fluid with the prototype.

The figure shows an analysis of the dynamics of development of the reservoir.

The proposed polymer-emulsion drilling fluid was introduced at the facilities of OAO TATNEFT in 2013.

During the period of successful pilot work, 13 wells were drilled: 6479 g, 4605 g, 21337 g, 24689 g, 24757 g, 29364 g, 29365 g, 4996 g, 3005 g, 8621 g, 10933, 6044 and 4063.

Wells were drilled without complications and in a short time. It is also noted that the use of a minimum density of polymer-emulsion drilling fluid of 1350 kg / m ² per well. 6479 g, 24689 g and 8621 g allows you to increase the drilling speed in difficult intervals, as well as to prevent hydraulic fracturing, which affects the quality of cementing and optimize the cost of construction of the entire well as a whole.

So, the cost of building wells using the inventive polymer-emulsion drilling fluid is (table 1) compared with the prototype Premium Gel.

All evaluated wells had the same method of entry into the Kyn horizon and drilling conditions. Analysis of the use of polymer-emulsion drilling fluid shows that the proposed polymer-emulsion drilling fluid is suitable for opening at any zenith angle in softened rocks, prone to erosion and collapse.

An analysis of the dynamics of reservoir development shows (see the figure) that the polymer-emulsion drilling fluid is also recommended for the initial opening of the reservoir.

The polymer-emulsion drilling fluid is characterized by the following advantages: it does not contain a solid phase, reduces drilling time (from 5 to 14 days compared to using Premium Gel from 8 to 144 days).

In the process of drilling, the stability of the parameters of the polymer-emulsion drilling fluid is maintained at a density of ≈ 1350 kg / m ³ , compared with Premium Gel, in which the stability of the barrel is achieved at a density of ≈ 1500 kg / m ³ , i.e. less repression is created on the formation, the likelihood of hydraulic fracturing is reduced, and a phased weighting of polymer-emulsion drilling fluid is not required during the passage of the Kyn horizons.

The volume of prepared polymer-emulsion drilling fluid for well construction is significantly less than that of the prototype (see column 3 of table 1).

The cost of the proposed polymer-emulsion drilling mud is significantly lower ≈ 17500 rubles (compared with Premium Gel ≈ 26000 rubles) as a result of the minimum amount of lubricating agents.

The positive results of the use of polymer-emulsion drilling fluid, including:

- prevention of hydration and swelling of clays;

- high sedimentation stability;

- preservation of reservoir properties of the productive horizon;

- increase in the mechanical drilling speed;

- this solution does not contain hydrocarbons, since salts of organic origin are used, which are biodegradable and environmentally friendly;

- high quality of technological processes allowing to build wells of any profiles and lengths.

Claims (2)

A polymer-emulsion drilling fluid comprising water, a complex reagent, an inhibitor and a lubricating additive, characterized in that the solution contains a Unidrill complex compound consisting of organic acids, which are plasticizers, water repellents and inhibitors, the plasticizers being oxalic acid salts together with amphoteric oxides metals, and water repellents - oxalic acid salts together with amphoteric metal oxides and hydrobromic acid salts, while the microgels are inhibitors in the following ratio of ingredients, wt.%: Rheology - Xhantan Gum 0.2-0.5 Filtration - Fitter Check 2-2.5 filtration - PAC-LV 0.5-1 lubricating additive - SBU-DR 5-10 of the volume inhibitor - MgO 0.5-2 calcium carbonate 5-50 complex compound - Unidrill 25-30 dispersed medium - water rest

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