EA039360B1 - Method for development of heterogeneous oil reservoir - Google Patents

Abstract

The invention relates to oil producing industry, in particular to methods for oil production from a heterogenous oil reservoir by levelling the profile log of injection wells. The task of this invention is to improve the efficiency of oil displacement by levelling the profile log of injection wells by partial or full blocking of high permeability oil saturated laminations and deviating the injected water to low permeability oil saturated laminations, and to reduce the cost of implementing this method. The set task is solved by the fact that the method for the development of heterogeneous oil reservoir, which includes the injection of colloid-dispersion gel to the reservoir, which contains hydrolyzed polyacrylamide uses sulfurized polyacrylamide, chromium(III) acetate, and nano-powder of titanium(IV) oxide as an additional structure former with the following mixture ratio of the dispersion specified, wt.%: sulfurized polyacrylamide - 15-30; hydrolyzed polyacrylamide - 15-30; chromium(III) acetate - 1-5; nano-powder of titanium(IV) oxide - 0-0.05; water - the rest. At this time, the solution of colloid-dispersion nano-gel is injected to the reservoir as a margin in the amount of 10-20% of the reservoir pore volume, further water is injected for pushing the compound.

Description

The invention relates to the oil industry, in particular to methods for developing oil from a heterogeneous oil reservoir by leveling the injectivity profile of injection wells.

A known method for the development of a heterogeneous oil reservoir, including sequential injection into the reservoir of the gel-dispersed system - HDS and the cross-linked polymer system - ATP. To obtain HDS, polyacrylamide - PAA and chromium-potassium alum were used, to obtain SPS, PAA and chromium acetate were used. GDS injection is carried out in two stages, using at the first stage GDS containing fractions of a larger size than the GDS fraction used in the subsequent stage. At the same time, at the second stage of GDS injection, GDS with gel particles are used, the sizes of which are commensurate with the sizes of pores and small cracks, and fresh water is used as a GDS solvent at the first stage, and at the second stage - water with a salinity of at least 15 g/l[ one].

The disadvantage of this method is that the formation of the gel occurs in the reservoir near the injection well, which leads to a significant increase in injection pressure. The formation of an insulating tampon near the well significantly reduces the amount of additional oil production due to the rapid rounding of the installed tampon by the injected water. In addition, a significant decrease in the efficiency of the method due to the fact that potassium alum has limited solubility and is poorly compatible with wastewater, upon contact with them, aluminum hydroxide precipitates and SO ₄ ^2- ions in the used crosslinker can form a precipitate with divalent metal ions having in formation water, as well as the high cost of implementing the method associated with continuous injection of the composition into the formation.

Also known is a method for developing a heterogeneous oil reservoir, including injection into the reservoir of an aqueous dispersion of colloidal particles of polyacrylamide, or polysaccharide, or cellulose ether containing aluminum polyoxychloride in the following ratio, wt.%: polyacrylamide, or polysaccharide, or cellulose ether 0.005-0.5 ; aluminum polyoxychloride 0.0015-0.1; water - the rest, while the volume of the specified dispersion is calculated by the formula V=nR ² mh, where R is the radius of penetration of the dispersion into the reservoir, m; m - average porosity, fractions of units; h is the total thickness of the receiving intervals, m [2].

The disadvantage of this method is that aqueous dispersions of colloidal particles based on polyacrylamide, polysaccharide, or cellulose ether have low thermal stability and salt resistance in oil reservoir conditions and will be ineffective in wells with temperatures above 90°C. In addition, the method is not effective enough due to the fact that the gelation reaction with aluminum polyoxychloride in the injected solution occurs instantly, and this leads to an increase in injection pressure, thereby complicating the process, as well as the high cost of the method due to the continuous injection of the composition into the formation.

Closest to the proposed invention is a method for the development of a heterogeneous oil reservoir, including the injection of a colloidal-dispersed gel based on hydrolyzed polyacrylamide and aluminum (III) citrate into the reservoir in the following ratio, wt.%: A1 ³⁺ /HPAM-1/2O [3 ].

The disadvantage of this method is that the colloidal-dispersed gel based on hydrolyzed polyacrylamide has a lower thermal stability (at temperatures above 90 ° C, the proposed composition is unstable and decomposes), salt resistance and insulating ability, which is expressed in a low coefficient of residual resistance, as well as high the cost of implementing the method due to the continuous injection of the composition into the reservoir.

The objective of the invention is to increase the efficiency of oil displacement from the reservoir by leveling the injectivity profile of injection wells by partially or completely blocking high-permeability flooded interlayers and diverting injected water into low-permeability oil-saturated interlayers, as well as reducing the cost of the method.

The problem is solved by the fact that in the method of developing a heterogeneous oil reservoir, including injection of a colloidal-dispersed gel containing hydrolyzed polyacrylamide into the reservoir, sulfonated polyacrylamide, chromium (III) acetate and titanium (IV) oxide nanopowder are used as an additional structurant in the following ratio of components specified dispersion, wt. %:

sulfonated polyacrylamide 15-30 hydrolyzed polyacrylamide 15-30 chromium (III) acetate 1-5 titanium (IV) oxide nanopowder 0-0.05 water rest

At the same time, a colloidal-dispersed nanogel solution containing sulfonated and hydrolyzed polyacrylamide, chromium (III) acetate, and titanium (IV) oxide nanopowder is pumped into the reservoir in the form of a slug in the amount of 10-20% of the reservoir pore volume, then water is injected to pushing a solution of a colloidal-dispersed gel.

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Sulfonated polyacrylamide (15214-89-8M808); hydrolyzed polyacrylamide (CAS No 9003-05-8); chromium (III) acetate (CAS No 39430-51-8); titanium (IV) oxide nanopowder (CAS No 13463-67-7) and fresh water. To prepare a colloidal-dispersed gel, first of all, a 0.05% water-soluble titanium (IV) oxide nanopowder was dispersed with an anionic surfactant using an ultrasonic bath. Then a monomeric solution of sulfonated and hydrolyzed polyacrylamide was prepared. At the next stage, a dispersed suspension of titanium (IV) oxide nanopowder, an aqueous solution of chromium triacetate, are added to the polymer solution, the pH of the solution is adjusted to 7. Then the resulting solution is stirred at the gelation temperature using a magnetic stirrer and left for 24 hours at room temperature to ensure adequate crosslinking .

The essence of the invention lies in the fact that the effectiveness of the proposed method for the development of a heterogeneous oil reservoir by leveling the injectivity profile of injection wells is increased by injecting a colloidal-dispersed gel slug into the reservoir, which has an increased thermal and insulating ability.

The method has been tested in laboratory conditions. To illustrate the proposed method, samples of a colloidally dispersed gel containing sulfonated and hydrolyzed polyacrylamide, chromium (III) acetate, titanium (IV) oxide nanopowder (CDG1, CDG2, CDG3, CDG4, CDG5, CDG6, prototype) were prepared and injected into a bulk reservoir model (Table 1).

Sample 1. Preparing a colloidal-dispersed gel of the prototype of the following composition, wt.%: hydrolyzed polyacrylamide 20

Aluminum citrate 1 water rest

Colloidal dispersed gels were prepared by adding aluminum citrate crosslinker to a 600 ppm polymer solution prepared in either 1% sodium chloride (NaCl) or synthetic seawater at a polymer to crosslinker ratio of 20:1. The solutions were then stirred at high speed using a magnetic stirrer for 1 hour. The solutions were then stirred at very low speed at 40°C. Before injection of the colloidal-dispersed gel, the solutions were filtered through 40 μm filters.

Sample 2. Prepare a colloidal dispersed gel (CDG1) of the following composition, wt.%:

sulfonated polyacrylamide15 hydrolyzed polyacrylamide15 chromium(III)acetate1 titanium (IV) oxide nanopowder 0.05 water rest

To prepare a colloidal-dispersed gel, first of all, 0.05% of a water-soluble nanopowder of titanium (IV) oxide was dispersed with an anionic surfactant using an ultrasonic bath. Then a monomeric solution of sulfonated (15%) and hydrolysed (15%) polyacrylamide was prepared. At the next stage, a dispersed suspension of titanium (IV) oxide nanopowder, an aqueous solution of chromium triacetate (1%) are added to the polymer solution, and the pH of the solution is adjusted to 7. Then the resulting solution is stirred at the gelation temperature using a magnetic stirrer and left for 24 h at room temperature to ensure adequate crosslinking.

Other samples of the colloidal-dispersed gel CDG3, CDG4, CDG5, CDG6 are made in a similar way.

Experience 1. Studied the rheological properties of samples (CDG1, CDG2, CDG3, CDG4, CDG5, CDG6, prototype) colloidal-dispersed gel. The rheological properties were measured using a PhysicaMCR 501 rheometer (AntonPaar, Austria) with a geometry of concentric cylinders. The rheometer is equipped with a temperature control system to achieve and maintain the set temperature. The intuitive RheoCompass software offers predefined as well as customizable measurement templates. The results of the experiments showed a slight decrease in viscosity within 7 days, which is explained by intramolecular crosslinking of polymer chains. Further, the viscosity of all tested solutions stabilized and remained constant. A small concentration of polymer in the composition of CDG prevents the formation of a structured gel system with a three-dimensional network formed by intermolecular cross-linking bonds. Obviously, the duration of the crosslinking reaction is about 7 days. The observed patterns were identical for all samples (Table 2).

Experience 2. Studied thermal degradation of samples (CDG1, CDG2, CDG3, CDG4, CDG5, CDG6, prototype) colloidal-dispersed gel. Thermal degradation of the resulting gel was carried out by placing CDG samples in aging cells at the following temperatures of 80-170°C for 30 days. After this period, the rheological properties of these samples were evaluated with identical unaged samples of the studied compositions.

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It is well known that reservoir conditions have a devastating effect on polymer systems. The dispersed phase of CDG and the absence of a continuous polymer network significantly reduce the negative impact of reservoir conditions, preventing the destruction of the polymer structures of the composition under consideration. This is ensured by the small contact area of the CDG polymer coils compared to the bulk gel and the formation of a buffer zone with low salinity, formed as a result of mixing the dispersed phase of the CDG solution and formation water.

In the presence of titanium (IV) oxide nanopowder in the composition of CDG, a higher thermal stability was noted, regardless of the mineralization of the dispersed phase.

The results of the experiments (Table 2) showed that the thermal destruction of the colloidal-dispersed gel occurs at 120°C, the thermal destruction of the colloidal-dispersed gel with the addition of titanium (IV) oxide nanopowder occurs at 150°C, and the thermal destruction of the prototype at 90°C.

Experience 3. Studied the insulating ability of samples (CDG1, CDG2, CDG3, CDG4, CDG5, CDG6, (prototype) colloidal-dispersed gel.

All experiments were carried out on a 10-meter bulk model on the Strata-SlimTube installation with an absolute water permeability of 0.5-1D. The general setup diagram is shown in Fig. one.

Sand fractions ranging in size from 45 to 75 microns were used to obtain the required permeability. Sand production from the fill model was prevented by installing a fiberglass screen at the inlet and outlet. A weighting method based on the difference between the dry and saturated mass of the bulk model was used to determine the porosity. After preparing the model, the prepared samples were pumped into the reservoir, and the resistance factor (RF _cαc ), and the residual resistance factor (RRF _osm ) were determined.

During the experiments, the main indicators for evaluating the effectiveness were the resistance factor during injection of the solution (RF _zak ), the initial shear pressure gradient ( _{ΔР init} ) and the residual resistance factor of the colloidal-dispersed gel (RRF _osm ).

The results of the experiments showed that the residual resistance factor for the developed gel (RRF _osm ) increases by 34-46% compared with the prototype (table. 3).

Experience 3. To study the effect of the volume of the slug of injected reagents on the residual oil displacement efficiency from flooded reservoirs, experimental studies were carried out on a layered inhomogeneous bulk reservoir model, where the permeability of the low-permeability layer was 0.5 µm, and the high-permeability layer was 1 µm. The geometric dimensions of the model are as follows: length - 0.8 m, inner diameter - 0.04 m. The model was filled with quartz sand. The general setup diagram is shown in Fig. 2.

Porosity and pore volume were calculated from the difference between the weights of wet and dry reservoir models. After piping the unit, at a constant temperature (30°C) and flow rate, the models were saturated with formation water, then the water was displaced by oil with a viscosity of 9 centipoise (cP). To create a model of a watered reservoir, oil was displaced by formation water until it was absent from the filtrate at the outlet of the model. Next, rims of the prepared CDG2 sample of various volumes were pumped in (in the amount of 2–30% of the pore volume). Then water was pumped until the oil production stopped. The results of experimental work are shown in table. 4.

The results of the experiments (Table 4) showed that the maximum increase in the oil displacement efficiency (20.3-21.4%) was obtained by injecting a colloidal-dispersed gel slug in an amount of 10-20% of the formation pore volume. With a further increase in the volume of the slug, the increase in the value of the oil displacement efficiency was insignificant (0.5-1.3%) and is not economically feasible due to a significant increase in the consumption of chemical reagents.

Under field conditions, the method of developing a heterogeneous oil reservoir is carried out in the following sequence: a set of geophysical and hydrodynamic studies is carried out on a selected area of the oil deposit before the event. Based on the data of these studies, the required volume of the rim is calculated. The proposed colloidal-dispersed gel is prepared at the wellhead and pumped through the injection well into the formation in the form of a slug in the amount of 10-20% of the pore volume, then water is injected to push the colloidal-dispersed gel.

Table 1

Composition of the colloidally dispersed gel (wt %) Samples CDG1 CDG2 CDG3 CDG4 CDG 5 CDG6 sulfonated polyacrylamide fifteen fifteen 20 20 thirty thirty hydrolyzed polyacrylamide fifteen fifteen 20 20 thirty thirty chromium(III) acetate one one 5 5 5 5 titanium (IV) oxide nanopowder 0 0.05 0 0.05 0 0.05 water rest rest rest rest rest rest

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table 2

Samples Viscosity (mPas) 22"C 80°C 90°C 100°C Software °C 120 C 130°C 140°C 150°C 160°C 170°C CDG1 3.85 3.76 3.42 3.40 3.39 2.75 2.10 - - - - CDG 2 3.11 3.10 3.09 3.09 3.07 3.06 3.04 3.04 2.62 1.85 - CDG3 3.93 3.84 3.50 3.48 3.47 2.83 2.25 - - - - CDG4 3.28 3.27 3.25 3.23 3.23 3.21 3.19 2.85 2.05 - - CDG 5 4.00 3.83 3.81 3.80 3.77 3.25 2.63 - - - - CDG6 3.35 3.32 3.30 3.29 3.29 3.26 2.83 1.98 - - - prototype 4.03 4.02 3.21 1.25 - - - - - - -

Table 3

Samples RF RRF Thermal degradation °C CDG1 8.2 745 120 CDG2 7.5 820 150 CDG3 8.3 730 120 CDG4 8.0 800 140 CDG 5 8.4 715 120 CDG6 8.1 790 130 Prototype '8.5 560 90

Table 4

model no. Oil recovery factor before sample injection, % Volume of injected SP G2,% of pore volume Oil displacement ratio after sample injection, % Growth of displacement efficiency, % one 53.8 2 58.9 5.1 2 53.4 5 63.8 10.4 3 52.9 7 68.7 15.8 4 53.9 ten 74.2 20.3 5 53.9 20 75.3 21.4 6 53.8 thirty 75.4 21.6 eight 53.8 continuously 75.6 21.8 Prototype 53.7 continuously 62.0 8.3

Literature

1. Patent RU 2469184 Cl, E21B 43/22, publ. 12/10/2012.

2. Patent RU 2298088 Cl, E21B 43/22, C09/K 8/88, publ. 04/27/2007.

3. SPE 129927, Propagation of colloidal Dispersion Gels (CDG) in Laboratory Corefloods, US 2007/0204989, E21B 43/22, 33/138, 33/128, publ. 24-28.04.2010.

CLAIM

Claims (1)

CLAIM A method for developing a heterogeneous oil reservoir, including injection into the reservoir of a colloidal-dispersed gel containing hydrolyzed polyacrylamide, characterized in that sulfonated polyacrylamide, chromium (III) acetate and titanium (IV) oxide nanopowder are used as an additional structurant in the following ratio of the components of the specified dispersion, wt. %: sulfonated polyacrylamide - 15-30; hydrolyzed polyacrylamide - 15-30; chromium (III) acetate - 1-5; nanopowder of titanium oxide (IV) - up to 0.05; water - the rest, while the colloidal-dispersed nanogel solution is pumped into the formation in the form of a slug in the amount of 10-20% of the formation pore volume, then water is injected to push the composition. -4039360 -1 Section 1~| I section; | | Section 3~| {.....Section 4~~| | Section S~] I Sections | OIL BATH Fig. one 1-registrar; 2-source; 3-manometer; 4-column with a porous medium; 5-load cell Sapphire; 6-PVT camera; 7-compensator; 8-ultrathermostat; 9-distribution manifold and pressure regulator; 10 dosing pump; 11-shut-off valves; 12 - resistance box.