RU2266312C1 - Polymeric drilling fluid for exposing production formations - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: polymeric drilling fluid comprises, wt %: xanthane-type biopolymer 0.3-0.5, polyanion cellulose (Drispac) 0.4-0.7, inhibiting additive 3.0-7.0, carbonate whitening agent 5.0-12.0, modifier 0.5-1.5, bactericide 0.1-0.2, complex organic additive (additional component) 0.5-1.0, foam suppressor 0.02-0.05, and water - the rest, wherein modifier is potassium salt of anionic acryl amide copolymer (Thermopass ^TM 34) or polyvinyl alcohol. Drilling fluid is applicable when boring horizontal holes or offshoots under various hydrogeological conditions.

EFFECT: increased removing and retention capacities of drilling fluid and reduced into-formation filterability at the same principal working parameters under salt attack and elevated temperature conditions.

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Description

The invention relates to the field of well drilling, in particular to compositions of drilling fluids for opening productive formations, including when drilling horizontal and sidetracks in various hydrogeological conditions.

Recently, polymer drilling fluids have been widely used to open productive formations. Their advantage is that such solutions do not form a thick crust, which occurs in clay drilling fluids, which leads to sticking to the drilling equipment, complicating the drilling process. Due to the low content of colloidal solid particles in the solution, a high drilling speed is provided, which, ultimately, can significantly reduce the cost of drilling.

Drilling fluids based on biopolymers have pronounced pseudoplasticity, which contributes to the good removal of cuttings, especially from a horizontal trunk. In addition, biopolymers are capable of degrading both independently and as a result of chemical treatment, which contributes to the easy development of wells after drilling.

The use of acrylamide polymers in drilling fluids is also justified. The effectiveness of the application is associated with the features of their composition and structure. Acrylamide polymers with specific molecular characteristics can successfully control the rheological and filtration characteristics of drilling fluids. The choice of reagents for polymer drilling fluids for the opening of productive formations has a great influence on the quality of the opening of the formation. Their synergy of action should be such as to ensure the stability of the characteristics of the drilling fluid during drilling and to preserve the reservoir properties of the exposed reservoir as much as possible.

Drilling fluid for opening productive formations should have the following properties:

- high rheology and structural and mechanical properties to provide the necessary remote and retaining ability of the drilling fluid;

- low rate of filtration of the drilling fluid into the formation in order to avoid damage to the reservoir properties of the formation;

- low coefficient of surface tension at the boundary of the drilling fluid-hydrocarbon fluid to facilitate the flow of oil;

- high inhibitory properties to maintain the stability of clay rocks.

Polymer drilling fluids possess all of these properties, including various regulatory additives in certain proportions, with which polymer components are well combined, which makes it possible to obtain drilling fluids with optimal characteristics, leading to an improvement in the quality of the formation opening.

A number of drilling fluids are known for opening productive formations designed to preserve reservoir properties. For example, in patent RU No. 2200180, class. From 09 To 7/02, 2003, “Solution for the opening of productive formations” containing a solid phase - clay powder and chalk. The solution has a low filterability due to the formation of a dense clay-crust, which clogs the formation. Its disadvantage is the difficulty in well development due to the difficult decolmation of clay particles.

Known patent RU No. 2179568, class. From 09 To 7/02, 2002 "Clay-free drilling mud for opening productive formations." The well-known drilling fluid containing starch, biopolymer, carbonate weighting agent, polyglycol, hydrophobic surfactant - PKD-515, a lubricating additive - DSB-4TT reagent and water, has several advantages: the drilling fluid has low filtration rates, has low interfacial coefficients surface tension and has a hydrophobic ability, which allows to improve the phase permeability to oil. The disadvantage of this known drilling fluid is that the drilling fluid does not have sufficient stability due to the lack of a reliable bactericide, which leads to rapid biodegradation of the polymers contained in the drilling fluid, and the violation of its technological characteristics. The noted positive quality of polyglycol as a bactericide is not entirely justified, because polyglycol can only slow down the biodegradation process for a short period of time.

Known clay-free drilling fluid containing polyacrylamide, xanthan gum, aluminum sulfate, calcium carbonate, potassium chloride and water (patent RU No. 2226540, CL 09 K 7/02, 2004).

Known drilling fluid has improved structural, mechanical and rheological characteristics, which allows for a high sludge-holding and sludge-bearing ability of the drilling fluid due to the formation of crosslinked aluminum salt polymer structure. Unfortunately, the authors do not indicate which acrylamide polymer can be used in the specified drilling fluid, what are its molecular characteristics. As you know, the quality of the obtained crosslinked structures, their stability depends on the type, number of ion-active groups of a high molecular weight compound and its molecular weight. The main disadvantage of the well-known clay-free drilling fluid containing polyacrylamide, xanthan gum, aluminum sulfate, calcium carbonate, potassium chloride and water is its low stability at elevated temperatures and, as a consequence, increased filterability in the formation.

A well-known drilling fluid based on a water-oil emulsion, including bentonite powder, mineral oil, multifunctional surfactants, caustic soda, cellulose wood, including carboxymethyl cellulose, as well as a polymer from the group: polysaccharides, alginates, polyvinyl alcohol, antifoam, aluminum stearate hydrophobized silica and water (US patent No. 5858928, class C 09 K 7/02, 1999).

Known clay-free drilling fluid, including biopolymer, polysaccharide, alkali metal hydroxide, lubricant, water-soluble salt of silicic acid and water (patent RU No. 2186819, CL 09 K 7/02, 2002). The known composition has a high rheology and structural-mechanical properties, which ensures good retention of the dispersed phase in the solution and the outflow ability of the drilled rock to the surface. In addition, the presence of a surfactant in the solution can reduce the surface tension at the oil-water interface, which facilitates the flow of oil. The disadvantage of this drilling fluid is that it is not resistant to the effects of mineralized waters containing alkaline earth metal ions. The presence of a water-soluble salt of silicic acid in the drilling fluid will lead to precipitation in the form of alkaline earth metal silicates and an imbalance in the balance of ions, which will ultimately lead to instability of the drilling fluid characteristics.

The closest in composition and technical essence is a clay-free drilling fluid for opening productive formations, including a xanthan biopolymer, a polyalkylene glycol component and water, as well as an additional filter reducing agent, clay swelling inhibitor, biocide, colmatant and a weighting additive (RU patent No. 2168531, C. From 09 To 7/02, 2001). Known drilling fluid has low values of filtration characteristics due to improved surface-active and hydrophobic properties. However, this known drilling fluid does not have sufficient stability in conditions of salt aggression and elevated temperatures.

The aim of this invention is to develop a drilling fluid for opening productive formations with optimal characteristics, allowing to provide high remote and holding ability of the drilling fluid, with low filterability in the reservoir and preserving the main technological parameters in conditions of salt aggression and elevated temperatures.

This goal is achieved in that the polymer drilling fluid for opening productive formations, including xanthan biopolymer, polyanionic cellulose, an inhibitory additive, carbonate weighting agent, modifier, bactericide and water, is characterized in that it contains a potassium salt of the Termopas acrylamide anion copolymer as a modifier ™ -34 "or polyvinyl alcohol and optionally the complex organic additive FC 2000 plus and antifoam, in the following ratio, wt.%:

xanthan biopolymer  0.3-0.5 polyanionic cellulose  0.4-0.7 inhibitory additive  3.0-7.0 carbonate weighting agent  5.0-12.0 specified modifier  0.2-1.5 bactericide  0.1-0.2 specified additive  0.5-1.0 antifoam  0.02-0.05 water  rest

The potassium salt of the anionic copolymer of acrylamide "Termopas ™ -34" TU 2216-185-07507800-2002 is produced by the production of "Acrylate" FSUE Perm Plant named after Kirov ". The recommended concentration range in the inventive polymer drilling mud is, wt.% 0.5-1.5.

Polyvinyl alcohol (PVA) is produced in accordance with GOST 10779-78. The recommended concentration range in the inventive polymer drilling fluid is, wt.% 0.2-0.5.

Due to the introduction of the anionic copolymer of acrylamide or polyvinyl alcohol into the polymer drilling fluid of the potassium salt, the performance of the polymer drilling fluid for opening the reservoir is improved.

These polymers in combination with a xanthan biopolymer and polyanionic cellulose create a stable structure due to the formation of additional bonds between macromolecules with a high charge density and containing several ionic groups in each macromolecule, and therefore the electrostatic interactions between the chains increase sharply.

Such synergism allows you to get a drilling fluid with a high remote and retaining ability. In addition, the potassium salt of the anionic acrylamide copolymer or polyvinyl alcohol imparts thermal stability and salt resistance to the drilling fluid, and reduces water loss. These polymers are well combined with all the functional additives included in the drilling fluid.

To increase the inhibitory properties and density, the composition of the drilling fluid contains potassium chloride.

Chalk is added to the drilling fluid to create additional density.

To increase the biological stability of the polymer base of the drilling fluid, a bactericide is introduced into it.

To ensure lubricity and reduce interfacial tension at the boundary "drilling mud filtrate - hydrocarbon" a complex organic additive is introduced into it, which includes vegetable oils and surfactants.

During the preparation and circulation of the drilling fluid, its foaming is possible, which can lead to a violation of technological characteristics. Therefore, antifoam is introduced into the drilling fluid.

The achieved effect is ensured by the integrated effect of all the components that make up the inventive polymer drilling mud for opening productive formations.

From the current level of technology, we do not know that the components that make up the inventive drilling fluid in this combination provide the above properties, which allows us to conclude that the proposed technical solution meets the criterion of "inventive step".

In the preparation of the inventive polymer drilling fluid for the opening of reservoirs in laboratory conditions, the following substances were used:

- Biopolymer of xanthan gum with the trade name "ALKNOL-1602", manufactured by DAYREN (Japan).

- Polyanionic cellulose of the Policell-PAC-v brand, manufactured by CJSC Cellulose Ethers Corporation (TU 2231-015-32957739-00).

- Potassium salt of the anionic acrylamide copolymer "Termopas ™ -34" manufactured by "Acrylate" FSUE Perm Plant named after Kirov "(TU 2216-185-07507802-2002).

- Polyvinyl alcohol brand PVS-16/1, GOST 10779-78.

- Potassium chloride, technical, GOST 4868-95.

- Complex organic additive FC-2000 Plus manufactured by NITPO LLC, Krasnodar (TU 2458-001-49472578-98).

- Sulfacid - 10A, as a bactericide, manufactured by Beraton OJSC, Bereznyaki (TU 2458-285-00204197-2003).

- Antifoam - “Penta-465” manufactured by NPK “Penta” (TU 2257-001-40245042-98).

- Chalk technical production of JSC "Building Materials", Belgorod (TU 21-020350-06-92).

- The water is fresh.

An example of a laboratory preparation of the inventive polymer drilling fluid for opening productive formations:

To prepare a 1000 ml solution in 675 ml of water, 60 g of potassium chloride are dissolved, then 3.5 g of biopolymer, 4 g of polyanionic cellulose are added with vigorous stirring. Mixing is carried out until the viscosity of the solution stabilizes. 35 g of a 30% solution (commercial product) of the potassium salt of the anionic acrylamide copolymer, 2 g of bactericide, 10 g of the complex organic additive FC-2000 Plus are introduced into the finished solution. In another container, 150 g of water are mixed with 60 g of chalk, then a suspension of chalk is introduced into the polymer solution. After mixing, the solution is considered ready. The procedure for preparing a solution with polyvinyl alcohol is similar, but a 10% PVA solution is preliminarily prepared, and 50 g of a 10% PVA solution is introduced instead of the potassium salt of the anionic acrylamide copolymer.

Thus, a solution is obtained with the following content of components, wt.%: Biopolymer - 0.376, polyanionic cellulose - 0.43, potassium salt of the anionic acrylamide copolymer - 1.075 (or PVA - 0.5), bactericide - 0.215, potassium chloride - 6, 45, complex organic additives FC-2000 Plus - 1.0, chalk - 6.45, water - the rest. The density of the prepared solutions is 1078 kg / m ³ .

Drilling mud according to the prototype is prepared as follows:

To prepare 1000 g of the solution, 10 g of potassium chloride are introduced into 700 ml of water, and then 10 g of biopolymer (Rhodopol brand) are dissolved with vigorous stirring, a PAC solution is prepared separately, for which 3 g of PAC is dissolved in 156.3 ml of water. The prepared solutions are mixed and 10 g of PP-2504 and 10 g of Laprol-5003 are successively added to the resulting viscous liquid with vigorous stirring for 20 minutes. 100 g of chalk, 0.2 g of bactericide and 0.5 g of KOH are added to the resulting drilling fluid. Thus, the composition of the solution according to the prototype contains, wt.%: Biopolymer - 1.0, polyanionic cellulose - 0.3, PP-2504 - 1.0, Laprol-5003 - 1.0, chalk - 10.0, potassium chloride - 1.0, bactericide - 0.02, KOH - 0.05, water - the rest.

Evaluation of the main technological parameters of drilling fluids was carried out using standard instruments and methods in accordance with RD 39-2-645-81 “Methodology for monitoring the parameters of drilling fluids”.

The density of the solutions was determined by the gravimetric method. Reference viscosity was measured with a VBR-1 viscometer. Water loss was controlled on a VM-6 device. Structural and rheological characteristics on the devices SNS-2 and VSN-3. In addition, using filtration experiments, we determined the influence of the filtrate of drilling fluids on the phase permeability of oil. Filtration experiments were carried out at a temperature of 60 ° C. The studies were carried out on linear bulk models with a length of 20 cm and an area of 5.31 cm ² . The porous medium was quartz sand. Permeability was controlled by sand particle size. The cores were evacuated and saturated with oil. The porosity of the model was determined. Two pore volumes of oil with a viscosity of 5 MPa · s were pumped in the forward direction at a constant flow rate. At this stage, core permeability and oil mobility were determined. Then, in the opposite direction, two pore volumes of drilling mud filtrate were pumped into the core. The core was kept for 5 hours in isothermal conditions, after which the oil was pumped in the forward direction to the established filtration mode. The mobility of oil and its change compared to the initial mobility were calculated. The influence of the mud filtrate on the permeability of the oil reservoir was evaluated by the change in the phase permeability of the core in oil and the value of the recovery coefficient of permeability equal to the ratio of mobility.

Table 1 shows data on the component composition of the investigated solutions and their technological characteristics.

Table 2 shows the results of filtration experiments on the degree of influence of the inventive drilling fluid and prototype on the phase permeability of the porous medium in oil.

The effectiveness of the stabilizing effect that the potassium salt of the anionic acrylamide or PVA copolymer exerts was evaluated by changing the structural and rheological parameters and the amount of water loss when a drilling fluid was exposed to water-soluble salts of calcium and magnesium and keeping the solutions at a temperature of 90 ° C for 5 hours. The results are shown in table 3.

As follows from the analysis of the data in Table 1, the parameters of the inventive polymer drilling mud satisfy the main technological parameters presented to drilling fluids for opening productive formations. The water loss of the composition of the prototype is higher than that of the inventive solution. From table 2 it is seen that the filtrate of the inventive polymer drilling fluid when penetrating into the reservoir slightly reduces the phase permeability of the porous medium in oil. In addition, the phase permeability of oil can be significantly increased further by treating the bottom-hole zone with reagents, with the help of which the polymer components of the drilling fluid are easily destroyed.

The experimental results (Table 3) on the effectiveness of the stabilizing effect that occurs with the introduction of an anionic copolymer of acrylamide or PVA into the polymer solution of potassium salt show that when the inventive polymer drilling fluid is kept under elevated temperatures and salt aggression, the structural and rheological characteristics do not change, and the amount of water loss varies slightly, while in the solution, which is taken as a prototype, water loss increased to a greater extent (from 5.8 to 15.0).

Thus, the inventive polymer drilling fluid for opening productive formations has an optimal structure, which allows to achieve high-quality drilling while maintaining permeability of the bottomhole zone and at the same time ensure the stability of the structural-rheological and filtration properties of the drilling fluid in the conditions of polysalt mineralization and in a wide temperature range (up to 90 ° C), which will reduce the cost of regulating the properties of the drilling fluid during drilling by reducing the total flow rate of the reaction entov due to increased stability of technological parameters of the drilling fluid.

table 2 The phase permeability of the core in oil, μm ² The recovery coefficient of core permeability,% Source Ultimate, after pumping 5 pore volumes of oil Prototype The inventive solution Prototype The inventive solution 0.01 0.0078 0.0081 77.9 80.7 0.05 0,039 0,041 78.1 81.1 0.10 0,079 0.0835 78.9 83.5 0.50 0,040 0.4215 80.3 84.3 1.00 0.815 0.857 81.5 85.7 Table 3 Drilling fluid composition The salt content,% (CaCl ₂ + MgCl ₂ ) Technological indicators * Plast viscosity, MPa · s PDNS, dPa SNA, dPa (1/10) Water loss, cm ^3/30 min According to the prototype 0,0

According to the prototype 1,5

The inventive No. 2 0,0

The inventive No. 2 1,5

The inventive No. 5 0,0

The inventive No. 5 1,5

* In the numerator - after cooking;
in the denominator - after exposure for 5 hours at a temperature of 90 ° C

Claims (1)

Polymer drilling fluid for opening productive formations, including a xanthan biopolymer, polyanionic cellulose, an inhibitory additive, a carbonate weighting agent, a modifier, a bactericide and water, characterized in that it contains as a modifier the potassium salt of the Thermopas ^TM 34 acrylamide copolymer or polyvinyl alcohol and additionally a complex organic additive FC 2000 plus and antifoam, in the following ratio of components, wt.%: Xanthan Biopolymer 0.3-0.5 Polyanionic cellulose 0.4-0.7 Inhibitory supplement 3.0-7.0 Carbonate weighting compound 5.0-12.0 The specified modifier 0.5-1.5 Bactericide 0.1-0.2 Specified Additive 0.5-1.0 Antifoam agent 0.02-0.05 Water Rest