RU2555975C1 - Method to treat bottomhole area of production well - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: method includes the detection of dependence between an adsorption layer structure and the concentration of non-ionogenic surfactant. The concentration of the surfactant in an aqueous solution of the non-ionogenic surfactant is accepted on the condition of formation of an "island" adsorption layer on the surface of the rock - alternating hydrophilic sections of an oil reservoir surface and hydrophobic sections of absorbed molecules of the surfactant providing for structuring of oil drops in the flow. A well is selected for the operation. Control measurements of yield, well head and bottom hole pressures are carried out. The wells are investigated at stabilised and transient conditions. An acid-containing solution is pumped to the well bottom hole. Then the acid-containing solution is removed from the well by well flushing with oil. Then a packer device is installed into the well. Further pumping of a water-removing composition is carried out, as well as the aqueous solution of non-ionogenic surfactant, displacing fluid into the production well. The well is soaked, and then oil is uptaken via production wells.EFFECT: increased efficiency of treatment due to the development of a structured adsorption layer of surfactants in a bed.1 ex, 5 tbl, 6 dwg

Description

The invention relates to the oil industry, in particular to methods for processing bottom-hole zone of wells.

Closest to the proposed invention in technical essence is a method of increasing oil recovery, including the injection of an aqueous solution of a surfactant, displacement fluid and subsequent fluid withdrawal through production wells [RU 94025398 A1, IPC 6 ЕВВ 43/27, published on 10.06.1996].

The disadvantage of this method is the lack of consideration of the structure of the formed adsorption layer of surfactants, which reduces the potential effectiveness of the method.

The technical result of the invention is to increase the efficiency of the method of developing oil fields by water flooding, while the amount of oil increases and the amount of water in the production of the producing well decreases.

The technical result is achieved by the fact that the method of processing the bottom-hole zone of a producing well includes determining the dependence of the structure of the adsorption layer on the concentration of a nonionic surfactant, while the concentration of a surfactant in an aqueous solution of a nonionic surfactant is taken from the formation condition of an “island” adsorption layer on the surface of the rock - alternating hydrophilic sections of the surface of the oil reservoir and hydrophobic sections of adsors sourced surfactant molecules, ensuring the structuring of oil droplets in the stream, selecting a well for the operation, conducting control measurements of flow rate, wellhead and bottomhole pressures, studying the well at steady and unsteady conditions, pumping an acid-containing solution to the bottom of the well, removing an acid-containing solution from the well washing the well with oil, installing a packing device in the well, then sequentially injecting a water-removing composition, water a solution of a nonionic surfactant, a squeezing fluid into a production well, holding the solution and subsequent oil selection through the production wells.

Most of the oil reservoirs by the nature of wetting refers to hydrophilic. Water in such reservoirs as the wetting phase moves through the shallow pores, displacing oil into larger pores and pushing it to the bottom of production wells. The use of surfactants without taking into account the effect of the concentration of surfactant in solution on the structure of the adsorption layer leads to their significant adsorption. The resulting continuous adsorption layer in the oil reservoir leads to a change in wettability from hydrophilic to hydrophobic. Water in reservoirs such as a non-wetting phase moves through the largest pores and does not displace oil.

In oil formations with mixed wettability, in which there are both hydrophilic sections of the rock and hydrophobic. Comparison of oil permeability values in hydrophilic and mixed wettability formations under the conditions of water saturation limits showed that the phase permeability value for oil in mixed wettability formations is much higher.

Thus, the creation of an “island” structure of an adsorption layer of hydrophobic particles in the reservoir, leading to the alternation of hydrophilic and hydrophobic sites, will increase the permeability for oil and increase the oil recovery coefficient.

The method is as follows

In FIG. 1 shows the first stage of the treatment of the bottomhole formation zone, where the numbers indicate: 1 - pump; 2 - pressure gauge; 3 - flow meter; 4 - tubing string; 5 production tower; 6 - reservoir; 7 - oil; 8 - valve; 9 - acid-containing solution.

In FIG. 2 shows the second stage of the treatment of the bottomhole formation zone, where the numbers indicate: 1 - pump; 2 - pressure gauge; 3 - flow meter; 4 - tubing string; 5 - production casing; 6 - reservoir; 8 - valve; 10 - packing device; 11 - water-removing composition; 12 - hydrophobic composition; 13 - selling fluid.

In FIG. 3 shows the initial surface of the mica, where the numbers indicate: 14 - nanoparticles of mica; 15 - the correct figure in the center.

In FIG. Figure 4 shows a three-dimensional image of a surface with an adsorption layer deposited at a surfactant concentration of 0.1%, where the numbers indicate: 16 — individual adsorbed molecules of a surfactant.

In FIG. 5 shows a three-dimensional image of a surface with an adsorption layer deposited at a surfactant concentration of 1%, where the numbers indicate: 17 - individual aggregates of molecules.

In FIG. 6 shows a three-dimensional image of a surface with an adsorption layer deposited at a surfactant concentration of 5%, where the numbers indicate: 18 - large aggregates of molecules.

At the initial stage, with the help of laboratory experiments, a study is made of the dependence of the structure of the adsorption layer of surfactants on the surface of a solid. These studies are carried out in order to determine the concentration of surfactant at which the formation of the "island" structure of the adsorption layer occurs. To solve this problem, the best way is to use atomic force microscopes.

The following is a selection of wells for the operation. The selection of production wells for impact is based on an analysis of the current stock of production wells. The main criteria for bottomhole treatment are an abnormally high value of water cut in the well compared to other wells, as well as a significant decrease in oil production due to breakthrough of injected water.

Before carrying out work on the producing well, a control measurement of flow rate, wellhead and bottomhole pressures is carried out. The well is examined in steady-state modes to clarify the productivity coefficient (removal of the indicator diagram) and transient modes for assessing the state of the bottom-hole formation zone. Based on the results of the interpretation of the obtained data, a further technological stage of actions is selected: in the absence of deterioration of the bottom-hole zone, they transfer to the injection of a water removal agent.

If a fact of the presence of a zone of impaired filtration properties is detected, the well is pretreated with an acid-containing composition. Hydrochloric acid or clay acid may act as an acid-containing composition. The injection into the well is carried out along the tubing string. The acid-containing composition is forced into the face through tubing with a buffer fluid (anhydrous oil in a volume of 1 m ³ ). Next, hold the well for 2-4 hours for the reaction of the acid-containing composition with the rock. This technological stage is necessary to remove asphalt-resin-paraffin deposits from the bottomhole zone of the well, to clean the filter channels from mechanical impurities and rock particles that limit fluid filtration. The amount of acid-containing composition is determined at the rate of 1 m ³ per 1 m of effective perforated formation thickness. The acid-containing composition is removed from the well by flushing the well with anhydrous oil. The well is flushed by pumping anhydrous oil into the annulus and leaving it through the tubing string (Fig. 1)

Next, the installation of the packing device in the well at a depth exceeding the interval of the productive formation by 100-200 m. Before installing the packing device, it is recommended that the walls of the production casing be pre-cleaned at the installation site of the packing device for its tight fit.

The following is the process of removing moisture from the treated area using water-removing compositions. The water-removing composition is pumped through tubing. Removing excess moisture from the bottomhole zone will prevent the formation of viscous emulsions, and will also increase the efficiency of the proposed invention. The amount of water-removing composition is determined on the basis of 1 m ³ per 1 m of effective perforated formation thickness. Alcohols, acetone, a mixture of acetone with hydrochloric acid can act as a water-removing composition.

Immediately after injection of the water-removing composition, a hydrophobizing composition is introduced, which is a mixture of water and a nonionic surfactant. The concentration of the surfactant is determined by the results of laboratory studies described above, and should ensure the formation of an “island” adsorption layer on the rock surface (alternating hydrophilic sections of the surface of the oil reservoir and hydrophobic sections of the adsorbed surfactant molecules). Such a surface structure will facilitate the structuring of oil droplets in the stream. In hydrophobic areas, oil droplets will increase their speed, while the rate of water filtration in these areas will decrease, which will be reflected in an increase in oil permeability and a decrease in water permeability (Fig. 2).

The next step is the injection of a squeezing fluid into the production well. This stage is necessary for more complete penetration of the hydrophobizing composition into the formation. As such a liquid, anhydrous oil may be used in a volume of 10-15 m ³ .

After completion of the injection of all process fluids, the technological exposure of the well is carried out for 1 hour.

After the operation, the downhole pumping equipment is lowered into the well, the well is connected to all technological systems for collecting, preparing and accounting for the produced products. The inflow from the formation into the well is called up by creating reduced pressure at the bottom of the producing well.

An example of the method

The first stage of work is to study the distribution of molecules of a nonionic surfactant (for example, “Neonol BS-1”) on the surface of a solid (mica) using an Ntegra Aura scanning atomic force microscope. The work is carried out as follows: scanning the surface without applying an adsorption layer, then - in registering changes in the surface structure after interaction with a solution of a nonionic surfactant of various concentrations. Scanning a clean surface is carried out in order to determine the presence of initial deformations, in order not to take them into account as possible surfactant molecules in the future. Clean surface scan results are shown in FIG. 3. The image is a color coded height map. Dark areas are the lowest, light areas are the highest. Translation color - height is given in the scale on the right.

Brightened spots 14 are nanoparticles of mica. Surface scanning is carried out in two modes - in contact (direct contact of the scanning element with the surface) and semi-contact modes (the sensitive element moves at an angle to the surface, the pressure force of the element on the surface is much lower, which allows you to determine the height of the adsorbed elements by the amplitude of oscillation of the scanning "needle" )

The figure in the center 15 is formed by multiple scans of a smaller area in the tapping and contact modes, in which there was a displacement of particles 14 to the boundaries of the scanning area with a needle.

After obtaining the digital structure of the initial surface, an adsorption layer is applied. To apply the adsorption layer on the surface of the mica, solutions of nonionic surfactants were used in the concentration range from 0.1 to 5 wt%. The treatment is carried out as follows: the test sample is placed in a solution of a nonionic surfactant for 30 minutes. Then the mica plates are dried at room temperature for 3 hours and then in an oven for 5 hours at a temperature of 30 ° C. Next, re-scan the surface in contact and tapping modes. The results are presented in FIG. 4-6.

The studies of the structure of the adsorption layer provide information on the distribution of the adsorbed nonionic surfactant on the surface of the mica at various concentrations.

When the concentration in the surfactant solution is 5% (Fig. 6), adsorption occurs in the form of large aggregates of molecules 16 (d = 100 nm). The adsorbed substance completely covers the surface of the solid and forms a continuous layer with a thickness of about 5-7 nm.

The formation of a continuous layer occurs at a concentration of non-ionic surfactant in a solution of 1% (Fig. 5). According to the results of surface scanning in the tapping mode, the thickness of such a layer is about 1.4 nm. The surface images show that, in addition to the complete coverage of the mica surface with surfactant molecules, the adsorption of individual aggregates 17 also occurs (d = 1–4 nm).

Thus, at a concentration of 0.1% of a nonionic surfactant, the structure of the adsorption layer will have an “island” structure, such an arrangement of hydrophobic particles will accelerate the filtration of oil in the liquid stream, expressed as an increase in phase permeability for the hydrocarbon phase.

The second stage is to study the effect of adsorption of nonionic surfactants (using the example of Neonol BS-1 at a concentration of 0.1%) on the filtration of oil and water in a porous medium. To solve this problem, core material was used (table 1).

Table 1 The main filtration and capacitive parameters of core samples Sample No. Brief lithological characteristic By the _by,% K _ol , * 10 ^-3 μm ² 64-11 Sandstone m / z, silty, n / n, with clay. cement 21.91 307.70 75p-11 Sandstone m / z, silty, n / n, with clay. cement 22.31 294.60 95-11 Sandstone m / z, silty, n / n, with clay. cement 19.76 305.50 110-11 Sandstone m / z, silty, with clay. cement 21.29 29.70 113-11 Sandstone m / z, silty, with clay. cement 21.42 28.70 115p-11 Sandstone m / z, silt, with clay. cement 22.21 28.80

where K _on - coefficient of open porosity; To _pr - absolute permeability.

The essence of the work is to evaluate the initial values of the phase permeabilities for oil and water on an unmodified core, treat the core with a solution of a nonionic surfactant, followed by water displacement and remeasure the values of the phase permeabilities on the core with an adsorption layer. A brief description of the stages of conducting streaming experiments is presented in table 2. The results are shown in table 3.

table 2 Stages of Streaming Experiments Stage Number Description Type of filtration one Water filtration at 100% water saturation 2 Creation of residual water saturation by water displacement by kerosene drainage 3 Oil substitution for kerosene drainage four Oil displacement by water impregnation 5 Surfactant solution injection 6 Substitution of oil by water impregnation 7 Creation of residual water saturation by water displacement by kerosene drainage 8 Oil substitution for kerosene drainage

Table 3 Streaming Experiment Results Filtration Mode No. Fluid injection rate Pressure drop Fluid Injection Volume AF on water Oil FP Water saturation Oil saturation cm ³ / h at cm ³ 10 ^-3 μm ² 10 ^-3 μm ² d. d. Core column with permeability ≈30 × 10 ^-3 μm ² one 10.5 0.08 14.51 one 0 2 10.5 0.42 2 10.5 1.82 155 0.553 0.447 3 10.5 0.63 78 8.03 0.542 0.458 four 10.5 1.79 155 0.66 0.750 0.250 5 10.5 7.75 0.750 0.250 6 10.5 1.71 155 0.69 0.824 0.176 7 10.5 0.21 7 73.5 1.02 155 8 10.5 0.46 78 10.99 Salt core with permeability ≈300 × 10 ^-3 μm ² one 110 0.09 141.55 one 0 2 110 0.69 76.96 0.265 0.735 2 1100 6.01 161 0.192 0.808 3 110 1.80 161 6.84 0.679 0.321 four 110 8.05 0.679 0.321 5 110 1.70 161 7.24 0.750 0.250 6 110 0.65 81.69

Studies have been conducted to evaluate the effect of adsorption of surfactants on the filtration of hydrocarbons under conditions that simulate the initial opening of the reservoir and the inflow. To solve this problem, the change in the reservoir properties of rocks is evaluated under the influence of a drilling fluid containing surfactants.

At the initial stage of work, the core is saturated with a reservoir water model. By pumping kerosene (at least 10 pore volumes), mobile water was removed from the samples and residual water saturation was formed. Permeability is measured by kerosene (K _etc.) before treatment, followed by injection of the test fluid with tangential washing of the input end face of the core. This technique of fluid injection allows you to simulate the movement of the drilling fluid along the wellbore. At least 5 pore volumes of the test fluid are pumped, after which exposure is carried out for 8 hours in order for the fluid to react with the rock. Next, the inflow call was simulated by pumping kerosene in the opposite direction (at least 10 pore volumes). After stabilization of the process, kerosene permeability is measured.

At the end of the experiment, the coefficient of permeability recovery (K _vpr ) is _estimated , which is the ratio of permeability after treatment to permeability before core treatment.

The permeability coefficient is calculated by the formula

$${\mathrm{TO}}_{\mathrm{at}PR}=\frac{{\mathrm{TO}}_{PR\left(\mathrm{to}\right)\mathrm{one}}}{{\mathrm{TO}}_{PR\left(\mathrm{to}\right)2}}\left(\mathrm{one}\right)$$

where K _vpr - the recovery coefficient of permeability; To _{pr (k) 1} - kerosene permeability after processing; To _{pr (k) 2} - initial kerosene permeability.

The composition of the solution is presented in table 4. The results of the experiments are presented in table 5.

Table 4 Solution composition Inbound components The ratio,% Sodium - carboxymethyl cellulose (КМЦ-700) 1.5 Starch Reagent (PolyKR) 1.5 Sodium Chloride (NaCl) 5.0 Sodium Hydroxide (NaOH) 0.05 Water-repellent grease FC-2000 Plus 1.5 Sludge 6.0 Water rest

Table 5 Experiment Results Type of solution Conditional sample 10 ^-3 μm ² Kerosene permeability, 10 ^-3 μm ² _Forwards , d. before after Polymeric one 4.33 0.588 0.733 1.245 2 4.33 1.554 2.551 1.641 slightly mineralized 3 4.13 2.544 2.671 1.050 four 4.01 1.793 2.289 1.276 Average value 1.726 2.168 1.257

The work performed showed that penetration into the pore space of the test solution does not cause permeability deterioration. An increase in the value of phase permeability for kerosene is observed on average 20%. This effect is probably due to the effect of accelerating the filtration due to the frequency of adsorption of the hydrophobizing additive, which in this case is FC-2000.

The studies using an atomic force microscope confirmed the "island" structure of the adsorption layer of a surfactant. At a surfactant concentration of 1% and 5%, the formation of a continuous adsorption layer on the mica surface is noted. An analysis of the data showed that in the region of low concentrations of hydrophobizing substances, a partial coating of the treated surface with adsorbate occurs.

In the course of stream studies after processing core material with a surfactant solution, an acceleration of the movement of oil particles was noted, expressed in an increase in the value of phase permeability to oil. The value of phase permeability after treatment increases compared to the initial value by 36% (for medium permeable samples) and 4% (for high permeability); for experiments on modeling the initial opening of the formation, the increase was about 20%.

Thus, the obtained data confirm the achievement of the claimed technical result in the conditions of formation of the "island" structure of the adsorption layer, expressed in increasing the value of phase permeability for oil.

Claims (1)

A method for treating the bottom-hole zone of a producing well, including determining the dependence of the structure of the adsorption layer on the concentration of a nonionic surfactant, wherein the concentration of a surfactant in an aqueous solution of a nonionic surfactant is taken from the formation condition of an “island” adsorption layer on the rock surface — alternating hydrophilic sections of the surface of the oil reservoir and hydrophobic sections of adsorbed molecules are surface-active about substances that provide for the structuring of oil droplets in the stream, choosing a well for the operation, conducting control measurements of flow rate, wellhead and bottomhole pressures, studying the well at steady and unsteady conditions, injecting an acid-containing solution into the bottom of a well, removing an acid-containing solution from the well by flushing the well with oil, installation of a packing device in the well, further sequential injection of a water-removing composition, an aqueous solution of a nonionic surfactant th substance, squeezing fluid into the production well, the wells exposure and subsequent selection of oil through the production wells.

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