RU2661172C2 - Drilling mud - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the field of drilling oil and gas wells, in particular to non-clay drilling fluids used for washing wells during drilling and opening of a productive formation with a vertical, oblique-directed or horizontal section of the shaft. Drilling mud comprises, wt%: Xanthan Petro biopolymer 0.3-0.45; modified starch 1.5-2.5; magnesium oxide 0.2-0.5; liquid water repellant - Petro Safe reagent 0.03-0.06; potassium alum 0.03-1.0; water - the balance. If necessary, the drilling mud may further contain at least one component from the group comprising a bactericide 0.01-0.05 wt%, marble chips 5-30 wt% or barite 5-40 wt%, sodium hydroxide 0.01-0.1 wt%, polyglycol 1-3 wt%, a lubricating additive 0.4-3 wt%.

EFFECT: technical result is lower interfacial tension at the boundary between the filtrate of the drilling mud and the formation fluid, reduced filtration of drilling mud into the reservoir with increased thermal stability of the mud.

1 cl, 1 tbl, 12 ex

Description

The invention relates to the field of drilling for oil and gas, in particular to clay-free drilling fluids used for flushing wells during drilling and opening a reservoir with a vertical, directional or horizontal section of the barrel.

Known biopolymer drilling fluid containing, by weight. %: Ket-X xanthan biopolymer - 0.3; modified starch Hibtrol LV - 1.0; water is the rest. (Penkov A.I. et al. Improvement of biopolymer systems with polyanionic stabilizers of drilling fluids. // Proceedings of the Institute of NPO Burenie. - 1998. - S. 293-298).

This small-component biopolymer solution containing a polyanionic filtrate recovery agent is characterized by pseudoplastic rheology and low filtration properties, along with their ease of regulation.

The disadvantage of this drilling fluid is its relatively low inhibitory and flocculating ability, which can lead to significant thickening of the fluids during drilling, accompanied by an increase in plastic viscosity and dynamic shear stress, and hence hydraulic resistance in the circulation system. In addition, this drilling fluid has low resistance to temperature effects.

The closest is a drilling fluid containing, by weight. %: xanthan biopolymer Rodopol 0.5-2, modified starch 0.2-2.5, lignosulfonate reagent 0.2-1.5, sodium carbonate 0-0.4, calcium oxide 0-0.2, magnesium oxide 0 -0.2, potassium chloride 0-5, protein hydrolyzate 0.1-1, biocide 0-1, the rest of the water (RU 2301822, publ. 06.27.2007).

The disadvantage of this drilling fluid is also its low inhibitory and flocculating ability, which leads to a thickening of the drilling fluid, accompanied by an increase in plastic viscosity and dynamic shear stress and, accordingly, hydraulic resistances in the circulation system.

The technical result of the invention is to reduce interfacial tension at the boundary of the drilling fluid filtrate with the formation fluid, reducing the filtration of the drilling fluid into the reservoir with increased heat resistance of the solution.

The specified technical result is achieved in that the drilling fluid, including water, xanthan biopolymer, modified starch and magnesium oxide, contains Xanthan Petro xanthan biopolymer as an xanthan biopolymer and, in addition, Petro Safe reagent and alum-potassium alum in the following ratio of components, wt. %:

Xanthan Petro Biopolymer 0.3-0.45 modified starch 1.5-2.5 magnesium oxide 0.2-0.5 reagent Petro Safe 0.03-0.06 potassium alum 0.03-1.0 water rest

If necessary, the drilling fluid additionally contains at least one component from the group comprising a bactericide of 0.01-0.05 wt. %, marble chips 5-30 wt. % or barite 5-40 wt. %, sodium hydroxide 0.01-0.1 wt. % polyglycol 1-3 wt. %, lubricating additive of 0.4-3 wt. %

The following materials are used to prepare the claimed drilling fluid.

Xanthan Petro Biopolymer - (xanthan gum, xanthan gum) - a biopolymer obtained as a result of enzymatic reactions of Xanthamonis Campestris bacteria on plant starch, a powder that is highly soluble in water. Manufactured by industry according to TU 2458-007-89593895-2010, it is a natural polysaccharide obtained by fermenting corn paste with Xanthomonas campestris cultures. After the fermentation is completed, ethanol or isopropyl alcohol is added to the substance, which makes it possible to obtain gum in the form of a precipitate. To obtain a marketable form, the precipitate is filtered and dried. CAS 11138-66-2, EC number 11138-66-2.

Magnesium oxide - magnesite, a crystalline powder of white or gray color, depending on the purity of the product. Magnesium oxide is insoluble in water, while the powder absorbs water well. It is produced by industry in the form of a chemically pure reagent according to GOST 4526-75 and in the form of a technical product with a different degree of purity according to GOST 1216-87.

Petro Safe reagent is a liquid hydrophobizing agent manufactured in accordance with TU 2458-002-89593895-2014 Petroengineering LLC and is a mixture of sodium palmitic acid CAS No. 408-35-5 EC No. 206-988-1 (20% by weight), polyalkyl glucoside C8 -C16CAS No. 141464-42-8 (20% wt.), Rapeseed oil (50% wt.), Polyalkylglucoside C10-C16 (lauryl glucoside), CAS No. 110615-47-9 (10% wt.).

Modified starch for drilling fluids, which is a carboxymethylated starch obtained by chemical treatment of potato starch, CAS 9057-06-1, it is also possible to use any other types of modified starches used for drilling fluids.

Potassium alum is a powder as a crosslinking and inhibitory additive.

Sodium hydroxide is used in an amount of 0.01-0.1% wt. to ensure the pH of the drilling fluid in the range of 10-10.5.

Polyglycols (mixtures of glycols of di-, tri-, tetra-ethylene glycol, monoethyl ethers of these glycols and resins) are produced by industry and are available on the market. For example, Polyglycol according to TU 2422-057-52470175-2005, POLYGLYCOL P-400 E CAS No. 25322-69-4, RICHMOLE Component 100 according to TU 2458-065-18947160-2008, etc. The inhibitory effect of polyglycols consists in adsorption on clay particles and clogging of pores and cracks. Polyglycols are characterized by good lubricity, low toxicity, and have no significant effect on the rheological properties of drilling fluids at low temperatures. Polyglycols have the ability to form gel structures in aqueous solutions at a certain elevated temperature, which increases the inhibitory effect of solutions and reduces the filtration of solutions in a porous medium. For the grades listed above, the gelation temperature is 80-95 ° C. By special order, manufacturers of polyglycols are able to supply a product with a given gelation temperature. The inclusion of polyglycols in the composition of the claimed drilling fluid is determined by: 1) the presence of active clay minerals in the section of the well, 2) the requirements of the Project for the well on the need to use an inhibited drilling fluid. The use of a particular brand of polyglycols is determined by the actual reservoir temperature. So, for example, for deposits in Western Siberia, the average reservoir temperature of productive formations is 90-100 ° C, therefore, standard grades of polyglycols with a gelation temperature of 80-95 ° C can be used at these facilities. The content of polyglycols in the drilling fluid varies from 1-3% wt.

Lubricating additives are used to reduce the coefficient of friction of the drill string against the borehole wall in the drilling fluid. In the specified drilling fluid, any lubricant additives for drilling fluids compatible with other components of the fluid may be used. For example, industrially produced additives "Petro Lube" of the brands "R", "S", "Eco", "Extra" according to TU 2458-009-89593895-2013, "LUB BKE" according to TU 2458-001-89593895-2009 can be used etc. The concentration of a lubricant in a drilling fluid is determined by the manufacturer, customer, design organization, or by measuring the friction coefficient of the prepared drilling fluid in field conditions. The content of the lubricant in the specified drilling fluid varies between 0.4-3% wt.

Collimating and weighting additive - marble chips, barite.

Marble chips (KM) are used in the form of a composition of various grades according to particle size distribution (grades with a maximum particle size of 2, 5, 10, 20, 40, 60, 80, 100, 200 microns and others available on the market). The total content of marble chips in the drilling fluid varies between 5-30% wt. and is determined by [2] on the basis of data on the maximum predicted reservoir pressure, taking into account the requirements of the Safety Rules in the oil and gas industry. The share of each brand of marble chips in the composition is selected from the specified limits according to the calculation of the dense packing of particles [1] based on data on the size of pore channels in the permeable layers of a particular geological section. For example, for a permeable formation with a pore channel size of 60 μm according to [1], it is necessary to use the following composition of marble chips: grade KM-2 - 34% of the total content of marble chips, grade KM-10 - 14% of the total content of marble chips and grade KM -40 - 52% of the total content of marble chips.

Barite is used mainly as a weighting agent. The total content of barite in the drilling fluid varies between 5-40% wt. The specific concentration of barite is also determined by calculation [2] on the basis of data on the maximum predicted reservoir pressure, taking into account the requirements of the Safety Rules in the oil and gas industry. The particle size of barite in powders of widely used grades KB-3 and KB-5 is 2-70 microns.

As a bactericide, any brand available on the market is used to prevent the biological degradation of polysaccharide drilling fluids, for example, Petro Cide according to TU 2458-005-89593895-2010, ATREN Bio grade A according to TU 2458-011-82330939-2009 and others. The content of bactericide in the drilling fluid is determined by the manufacturer's recommendations and, as a rule, is 0.01-0.05% wt.

Examples of the preparation of the proposed drilling fluid

Example 1

For cooking took, wt. %: Xanthan Petro biopolymer - 0.4, modified starch - 2.5, magnesium oxide - 0.5, Petro Safe reagent - 0.06, potassium alum - 0.7, water - 95.84. All ingredients were mixed and received the proposed drilling fluid.

Example 2

For cooking took, wt. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.2, Petro Safe reagent - 0.03, potassium alum - 0.05, water - 97.92. All ingredients were mixed and received the proposed drilling fluid.

Other formulations with additional additives were similarly prepared:

Example 3

Mas. %: Xanthan Petro biopolymer - 0.45, modified starch - 2.0, magnesium oxide - 0.3, reagent Petro Safe - 0.04, biocide - "Petro Cide" - 0.03, potassium alum - 0.03, water - 97.45.

Example 4

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.95, marble chips (composite) - 25, water - 71 , 80.

Example 5

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.95, barite - 25, water - 71.80.

Example 6

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.95, sodium hydroxide - 0.05, water 96.75 .

Example 7

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.95, polyglycol - 2.0, water - 94.8 .

Example 8

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.95, lubricant additive - “PetroLube” brand “R” - 2, water - 94.8.

Example 9

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.7, barite - 5, polyglycol - 2, water - 90 , 05.

Example 10

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.9, marble chips - 5, biocide - “PetroCide” - 0.05, water - 91.8.

Example 11

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.9, barite - 10, biocide - “Petro Cide” - 0.01, sodium hydroxide 0.02, water 86.82.

Example 12

Mas. %: Xanthan Petro biopolymer - 0.3, modified starch - 1.5, magnesium oxide - 0.4, Petro Safe reagent - 0.05, potassium alum - 0.9, marble chips - 10, biocide - “Petro Cide” - 0.02, sodium hydroxide - 0.01, the lubricant additive "Petro Lube" of the brand "R" - 0.5, water - 86.32.

Test results

In laboratory studies suggested the following properties were determined muds: relative viscosity (HC, s), filtratootdacha at a pressure drop of 0.7 MPa (F, ^cm3 / 30 min), the interfacial tension of the mud filtrate at the boundary with kerosene (σ, mJ / m ² ), dynamic shear stress (τ ₀ , dPa), plastic viscosity (η _PL , mPa⋅s), static shear stress for 10 s and 10 min (θ, dPa), pH of the medium. Rheological parameters of drilling fluids were determined by the least squares method using the Shvedov-Bingham rheological model. In addition, the dependences of the interfacial tension of the drilling fluid filtrate at the interface with the reservoir oil model, kerosene, were determined.

Data on the component composition of the drilling fluid, the composition of natural pollutants and performance indicators are given in the table. The second section of the table shows the parameters of the proposed brown mud according to example No. 10, contaminated with a model composition of drilled rock and aged in rotating autoclaves at a temperature of + 49 ° C for 16 hours before the measurement.

The data shown in the table show that the proposed clayless biopolymer drilling fluid has a low viscosity. The solution has a low filtrate recovery, decreased after temperature control from 3.9 to 3.3 cm ³ . Low values of dynamic shear stress and plastic viscosity, as well as conditional viscosity, will help to reduce hydraulic losses in the circulation system, as well as hydraulic losses in the near-well zone of the reservoir when the inflow is caused. Tests of drilling mud contaminated with cuttings show the resistance of the parameters of the proposed drilling fluid to pollution at a process temperature. As can be seen from the table, the pH of the solution remained almost unchanged, the filter cake has the same thickness, the rheological parameters of the contaminated solution did not increase significantly, the ratio of rheological parameters remained almost unchanged (the ratio of τ ₀ to η _PL changed from 6.71 to 6.72). Thus, the thermal stability of the drilling fluid, the resistance of the parameters to contamination with drill cuttings, low filtration values - in comparison with the prototype.

In addition, to confirm the low filtration characteristics of the proposed drilling mud, filtration studies of the mud were carried out on a natural core of sandstone of the YuV-1 formation of the Jurassic Formation of the West Siberian field. As a result of the studies, it was shown that the depth of penetration of the drilling fluid into the core with a permeability of 40 mD at a pressure drop of 6.8 MPa and a complete stop of filtration in 95 min was 2.6 cm, which indicates the almost complete absence of the effect of the drilling fluid on the permeability of the borehole zone of the reservoir . Filtration studies of the inflow call on the same core sample showed that the peel pressure of the proposed drilling fluid from the end surface of the core is quite low (0.32 MPa) - significantly lower than the depressions used in practice when the inflow is called (up to 3-5 MPa), which says low adhesion of the filter cake to the rock. Thus, according to the results of filtration tests, it is shown that the proposed drilling fluid has a low filtration into the reservoir, decaying to zero with time, and also forms an easily removable filter cake.

Information sources

1. Myasnikov Y. V., Gadzhiev S. G., Ionenko A. V., Evdokimov I. N., Losev A. P., Cronin A. M. MarCS Engineer program for calculating the tight packing of particles of drilling fluid weighting agents // Drilling and Oil. 2014. No5. S. 35-37.

2. Ryazanov Y.A. Encyclopedia of drilling fluids. - Orenburg: Chronicle, 2005.S. 203.

3. RD 39-00147001-773-2004. Technique for monitoring the parameters of drilling fluids. - Krasnodar: OAO NPO Burenie, 2004. - 137 p.

4. ST RK ISO 10414-1-2012. Oil and gas industry. Field tests of drilling fluids. Part 1. Water-based solutions. - Astana: Gosstandart of the Republic of Kazakhstan. 2012 .-- 98 s.

Claims (3)

1. A drilling fluid comprising water, xanthan biopolymer, modified starch and magnesium oxide, characterized in that it contains Xanthan Petro xanthan biopolymer and additional Petro Safe reagent and alum-potassium alum in the following ratio, wt.%: Xanthan Petro Biopolymer 0.3-0.45 modified starch 1.5-2.5 magnesium oxide 0.2-0.5 reagent Petro Safe 0.03-0.06 potassium alum 0.03-1.0 water rest 2. The drilling fluid according to claim 1, characterized in that it further comprises at least one component from the group comprising a bactericide 0.01-0.05 wt.%, Marble chips 5-30 wt.% Or barite 5-40 wt. %, sodium hydroxide 0.01-0.1 wt.%, polyglycol 1-3 wt.%, lubricating additive 0.4-3 wt.%.