NL2035020B1 - Oil displacement method and use thereof - Google Patents

Abstract

The present application discloses an oil displacement method and a use thereof, which is a technique for improving an oil displacement recovery rate in the field of oil exploitation. The application has the characteristics of environmental protection, high-efficiency in oil washing and the like, and can improve a fluid sweep range and oil displacement effect, reduce water interface tension, further improve thermal stability, dispersity, and the oil displacement efficiency by 5%-15% to improve an oilfield recovery rate.

Description

OIL DISPLACEMENT METHOD AND USE THEREOF

TECHNICAL FIELD

[01] The present invention relates to, but is not limited to, the field of oil exploitation, in particular to, but not limited to, a technique for improving an oil displacement recovery rate.

BACKGROUND ART

[02] At present, the newly-increased offshore oil resources are mainly low permeability-tight reservoirs. About 34% reservoirs can't be injected with water through water displacement, so it is difficult to establish an effective displacement relationship by conventional water injection in low permeability reservoirs. Due to small pores and complex structures of medium-low permeability reservoirs, there is a problem of "no injection and no production" when fluids flow through therein. Conventional techniques for improving a recovery rate, such as a polymer oil displacement technique and a multi-component compound oil displacement technique, are aimed at solving the problems of water displacement channeling and oil washing efficiency in a water displacement swept area, but the techniques are basically ineffective for low permeability reservoirs with "no injection and no production”. In view of the present situation of water injection, it is urgent to study and establish a novel environmental protection nano oil displacement technique system suitable for medium-low permeability reservoirs.

SUMMARY

[03] The oil displacement system provided by the present application can achieve re-displacement after regulation, improve a fluid sweep range, give full play to the oil displacement effect of fluid, and realize the fixed-point and quantitative release of the oil displacement agent. The application has the characteristics of safety, environmental protection, high-efficiency in oil washing and the like, and can improve a fluid sweep 1 range and oil displacement effect, reduce water interface tension, further improve thermal stability, dispersity, and the oil displacement efficiency by 5%-15% to improve an oilfield recovery rate.

[04] The present application provides an oil displacement method, including: alternately injecting fluid diverting agent slugs and oil displacement agent slugs into a target formation in a water injection well; and then injecting water into the water injection well to displace oil.

[05] The oil displacement agent slug includes amphiphilic nano-silica, nano-Ti02/PAM, and water.

[06] The fluid diverting agent slug includes an anionic-nonionic surfactant and a cationic surfactant. Preferably, the anionic-nonionic surfactant has a molecular general formula of the following Formula (1) and the cationic surfactant has a molecular general formula of the following Formula (2): 7

[07] Formula (1) > R1O~CH(CH,) CHO CH 2e 20% Ry

Ry . — ¥- R | Yr

[08] Formula (2) > Rs A

[09] where: Ry is a C:2-C24 alkyl group or a phenyl group substituted by a Cs-C12 alkyl group, m is an additive number of a propoxy group PO, n=1-15, n ís an additive number of an ethoxy group EO, n=1-30; R: is a C;-Cs hydroxy-substituted alkylene group, X is -COOM or -S03M, and M is selected from an alkali metal or an ammonium group; Rais a C4-C24 alkyl group; R4, Rs and Rs independently select C1-Cs alkyl group or substituted alkyl group; and Y"is an anion with a negative charge number r.

[10] Preferably, a ratio of the slug number of the fluid diverting agent slug to the oil displacement agent slug is (1-4): 1.

[11] Preferably, the fluid diverting agent slug and the oil displacement agent are 2 injected for 1-5 rounds.

[12] Preferably, a sum of injection amounts of the fluid diverting agent slug and the oil displacement agent slug is 100 m*-500 m®.

[13] Preferably, a concentration of the fluid diverting agent slug and the oil displacement slug is 2000 ppm-10000 ppm.

[14] Preferably, an injection rate of the fluid diverting agent slug and the oil displacement slug is 0.1 m*/min - 0.5 m*/min.

[15] Preferably, the amphiphilic nano-silica is prepared from a silicon source compound by sol-gel method, the silicon source compound being selected from one or more of ethyl orthosilicate, dichlorodimethylsilane, y-aminopropyl trimethoxysilane, hexamethyldisilazane, N, N-dimethyl-3-aminopropyl trimethoxysilane, 3-aminopropyltriethoxysilane, and n-dodecyltrimethoxysilane.

[16] Preferably, a method for preparing the amphiphilic nano-silica is sol-gel method, including the following steps:

[7] mixing deionized water with ammonia water or sodium hydroxide, adjusting a pH to 8-11, and then heating in a water bath at 60°C-80°C to obtain a mixed solution; and mixing a silicon source compound with the mixed solution to perform a hydrolysis reaction to obtain the amphiphilic nano-silica.

[18] The nano-T102/PAM is prepared by a hydrothermal synthesis method or an ultrasonic synthesis method.

[19] Preferably, a method for preparing the nano-TiO2/PAM includes:

[20] mixing tetrabutyl titanate with anhydrous ethanol, and sonicating the same to obtain a tetrabutyl titanate solution;

[21] mixing polyacrylamide with an HNO: solution to obtain a polyacrylamide solution; and

[22] mixing a first solution and a second solution for an ice bath reaction, and then heating to 80°C for 4 h to obtain a sol; and

[23] performing hydrothermal reaction on the sol with water to precipitate a precipitate, and sequentially washing, centrifuging, and drying the precipitate to obtain 3 the nano-TiO2/PAM.

[24] Preferably, the method for preparing the nano-TiO2/PAM further includes:

[25] mixing nano titanium dioxide particles with deionized water to obtain a suspension liquid,

[26] mixing polyacrylamide with an HNO: solution to obtain a polyacrylamide solution; and

[27] dropping the suspension liquid into the polyacrylamide solution, sequentially sonicating, stirring, and drying the same to obtain the nano-TiO2/PAM.

[28] In the present application, the fluid diverting agent slugs and the oil displacement section slugs are alternately used to improve the sweep range of the oil displacement substance and give full play to the oil displacement effect of the oil displacement substance, thus improving the oil recovery rate of oil fields.

[29] In another aspect, the present application provides a use of the above oil displacement method for oil displacement in permeable reservoirs and permeable reservoirs.

[30] Compared with the prior art, the present application has the following beneficial effects.

[31] The main components used in the oil displacement method provided by the application have a nano spherical structure, which is in the same geometric order as the components of crude oil colloid/asphaltene lamellae, can penetrate into the crude oil colloid/asphaltene lamellar components, break a continuous state, and emulsify the crude oil to form a micro/nano-scale O/W emulsion (viscosity reduction), therefore, a viscosity reduction rate can reach above 93%, and at the same time, the interface tension can be reduced to 0.1-0.5 mN/m. The nano-TiO2/PAM is covalently bonded to the polymer, which can reduce the interface tension of water, further improve the thermal stability, dispersibility, and the oil displacement efficiency by 5%-15%.

[32] The oil displacement method provided by the present application can make oil droplets not easily adsorbed by a rock, greatly reduce the oil-water interface tension, generate a stripping force through a micro-osmotic pressure, strip the remaining oil 4 from a rock surface, thus realizing the controllability of deep profile control. Moreover, the present application can basically realize the sweep of the whole oil reservoir by improving the sweep range and efficiency of the oil displacement substance through re-displacement after regulation. 5

BRIEF DESCRIPTION OF THE DRAWINGS

[33] FIG. 1 is a schematic diagram of the morphology of a polymer formed by a fluid diverting agent of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[34] Example 1

[35] Preparation of a fluid diverting agent:

[36] 2088 g (0.2 mol) of sodium octadecyl polyoxypropylene (m=3) polyoxyethylene (n=10) ether hydroxypropyl sulfonate, 10.5 g (0.04 mol) of dodecyl trimethyl ammonium chloride, and 450 g of an ethanol saline aqueous solution with an ethanol content of 40wt% (the saline water: a 5wt% sodium chloride aqueous solution) were sequentially added into a reaction flask, heated to 70°C and stirred for 2.5 hours, and the ethanol was removed by decompression and distillation to obtain a fluid diverting agent.

[37] Preparation of amphiphilic nano-silica:

[38] deionized water and sodium hydroxide were mixed with a pH of 11, and heated to 60°C in a water bath to obtain a mixed solution; and a silicon source compound (TEOS) was mixed with the mixed solution, and a hydrolysis reaction was performed under a condition of stirring for 6 h to obtain the amphiphilic nano-silica.

[39] Preparation of nano-TiO»/PAM:

[40] tetrabutyl titanate and anhydrous ethanol were mixed, and sonicated to obtain a first solution;

[41] polyacrylamide and an HNO: solution were mixed to obtain a second solution;

[42] the first solution and the second solution were mixed for an ice bath reaction, 5 and then heated to 80°C for 4 h to obtain a sol; and

[43] a hydrothermal reaction was performed on the sol to precipitate a precipitate, and sequentially washed, centrifuged, and dried the precipitate to obtain the nano-TiO72/PAM.

[44] Preparation of an oil displacement substance:

[45] the above fluid diverting agent and water were mixed (stirring condition: 120 rmp, 30 min) to form a fluid diverting agent slug, and the amphiphilic nano-silica, nano-TiO2/PAM, and water were mixed (stirring condition: 120 rmp, 30 min) to form an oil displacement agent slug, the water being seawater.

[46] Application Example 1

[47] The oil displacement substance prepared in Example 1 was added into injection water (a total salinity TDS of 500 mg/L, and Mg*+Ca** of 25 mg/L) in a low permeability reservoir (an average air measured permeability of 45»10~ um?) of Shag 7 oilfield in Jiangsu Province, stirred at 30°C for 2 hours to obtain a 0.6wt% oil displacement substance solution, and diluted with water of a same salinity to different concentrations. The oil-water interface tension between the oil displacement substance solution and dehydrated crude oil in the block was measured at 83°C. In a range of 0.005-0.6wt%, the dynamic interface tension value between the oil displacement substance solution and the crude oil could reach a low interface tension value of 102-10" mN/m, and the results were shown in Table 3. The interface tension was measured by a TX500 spinning drop interface tensiometer manufactured by University of Texas, USA.

[48] Table 3 Dynamic interface tension between an oil displacement substance solution and crude oil ee nen 0.005 0.01 0.05 0.1 0.3 0.6 wt% 6

Interface 9.45x10

[49] Application Example 2

[50] A Well W2 was a group of water injection wells in a 3™ well area of Shahejie formation in a deep layer of a W oilfield.

[51] A production horizon included two oil groups: E2s3U IV+V and E2s3M [up +1 down +11. A vertical thickness of a perforated water injection layer was 24 m, which was divided into four sand control sections. A vertical depth of a middle reservoir was 2617.65 m, and a formation temperature was 70°C.

[52] A Well W2 had a completion depth of 2894 m, a vertical depth of 2844.63 m after drilling, a distance between tubing and bushing of 19.55 m, and a maximum deviation of 15.72° at a deviation depth of 2569.58 m, and a vertical depth of 2504.01 m.

The completion mode was casing perforation + non-sand control completion.

[53] The production of the well group had the following problems: non-water absorption of some horizons due to poor physical properties of some small horizons, prominent inter-layer contradictions, high starting pressure, and difficultly of injected water to seep into porous media. The moisture contents of six oil wells changed from 24.07% to 87.48%, as shown in Table 4. Table 4 showed that the horizontal water injection and oil displacement was uneven, the remaining oil was distributed in the middle and bottom of a structure with poor physical properties, and a water injection plane had low sweep efficiency and a small sweep coefficient. A cumulative oil production changed from 3.07x10* m* to 15.62x10* m3, and a recovery degree changed from 13.55% to 25.66%, as shown in Table 5. Table 5 showed that the plane contradiction of the well group was not prominent, the moisture contents around well group were different, and the remaining oil reserves in the plane were more, which had a good mining potential for the remaining oil. The average permeability of the reservoir was 25.5 mD. 5

[54] Table 4 Moisture content in oil well oro pg [rte snes [oe

Oil well

W2

[55] Table 5 Oil production of oil well “me met "2 pr

Moisture | Control radius Recovery degree

Well name production reserves pa Jo eee

[56] According to the oil-water characteristics of the oilfield and the development problems of a W2 well group, the oil displacement method provided in Example 1 was selected to improve the plane oil displacement effect of the W2 well group.

[57] Process parameters were as follows. A ratio of the numbers of the fluid diverting agent slugs to the oil displacement agent slugs was 2: 1, and a volume dosage of each slug was equal. The fluid diverting agent slug and the oil displacement slug were injected for 3 rounds, with an injection concentration of 4500 ppmw (water being seawater), a total injection volume of 400 m° (calculated according to a formation porosity), and an injection rate of 0.4 m*/min. 8

[58] The effect started after 35 days of drug injection, and the oil was accumulated by 1.3x10* m* during a validity period.

[59] Application Example 3.

[60] Al oilfield was located in the Bohai Sea. There were 10 polymer injection wells and 28 effective wells in the oilfield, which were concentrated on a W platform. The polymer injection layers were I, II, III, and V oil groups, which had the following problems.

[61] An injection pressure of water injection wells was high, up to 14.5MPa, with an average injection pressure of 13.9 MPa, accounting for 72%. An overall injection pressure was high. There were 9 wells with the injection pressure higher than an average pressure and 2 under injection wells.

[62] An average moisture content was 90.42% after entering a high moisture content development stage. Of the 28 oil wells, 24 were opened, with the moisture content below 80% in two, below 90% in two, 90%-95% in eleven, and above 95% in nine. The average permeability of the reservoir was 38.7 mD.

[63] The horizontal production capacity of oil wells was uneven, and the horizontal contradiction was prominent. An average fluid production volume of 28 oil wells was 263 m’/d, and an average oil production volume was 172 md. There were 13 wells with lower than the average fluid production and 16 wells with lower than the average oil production volume.

[64] The longitudinal water absorption/fluid production capacity was uneven, and the inter-layer contradiction was prominent. The relative fluid production ratios obtained by a fluid production profile test of oil group I, oil group II, oil group III, and oil group V were 43.68%, 53.74%, 5.91%, and 2.63%, respectively.

[65] Long-term injection of polymer caused a blockage problem. One day, when replacing a pipe column due to serious leakage, it was found that plugs suspected of polymers were attached on outer walls of oil pipes in wells W5-6.

[66] The problem of polymer blockage was found in a well COS during pump inspection in a year. 9

[67] Wells E4-5 absorbed a large amount of mixture of polymer and sand at a pump suction port during pump inspection in a month.

[68] According to the oil-water characteristics of the oilfield and the development problems of a J oilfield, the oil displacement substance and method provided in

Example 1 were selected to improve the plane oil displacement effect of the J oilfield.

[69] Process parameters were as follows. A ratio of the numbers of the fluid diverting agent slugs to the oil displacement agent slugs was 2: 1, and a volume dosage of each slug was equal. The fluid diverting agent slug and the oil displacement slug were injected for 3 rounds, with an injection concentration of 6500 ppmw (water being seawater), a total injection volume of 500 m’, and an injection rate of0.5 m*/min.

[70] The effect started after 40 days of drug injection, and the oil accumulated by 2.5+10* m? during a validity period.

[71] Although the examples disclosed in the present application are as above, the contents described are only for the convenience of understanding the present application, and are not used to limit the present application. Any person skilled in the field to which the present application belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present application, but the scope of patent protection of the present application shall still be subject to the scope defined in the appended claims. 10

Claims (4)

S11 - Conclusions 1. 1. A method of oil displacement, comprising: alternately injecting fluid bypass agent slugs and oil-displacing agent slugs into a target formation in a water injection well; and then injecting water into the water injection well to displace oil, the oil-displacing agent slug comprising amphiphilic nano-silica, nano-T102/PAM and water, the fluid bypass agent slug being composed of an anionic-nonionic surfactant and a cationic surfactant in a molar ratio of 1:(0.01-0.99); the anionic-nonionic surfactant having a general molecular formula as the following Formula (1), and the cationic surfactant having a general molecular formula as the following Formula (2): R, 0—~CH(CH;) CHO) CH,CH,0%-R,, Formula (1) — OR - NR | Yr Formula (2) > ° Rs ï where R 1 is a C 12 -C 24 alkyl group or a phenyl group substituted by a C s -C:2 alkyl group, m is an additive number of a propoxy group PO, n=1-15, n is an additive number of an ethoxy group EO, n=1-30; R z is a C ; -C 8 hydroxy-substituted alkylene group, X is -COOM or -SO sM and M is selected from an alkali metal or an ammonium group, R 3 is a C 4 -C:2 alkyl group; R 4 , R s and R s are independently selected as a C 1 -C ; alkyl group or substituted alkyl group; and Y* is an anion with a negative charge number r; a ratio of the slug number of the liquid bypass agent slug to the oil displacing agent slug (1-4): 1; the amphiphilic nanosilica from a silicon source compound is prepared by the sol-gel method; the nano-TiO2/PAM is prepared by a hydrothermal synthesis method or an ultrasonic synthesis method. 2. The oil displacement method according to claim 1, wherein the preparation of nano-TiO2/PAM by the hydrothermal synthesis method comprises: mixing tetrabutyl titanate with anhydrous ethanol and sonicating to obtain a tetrabutyl titanate solution; mixing polyacrylamide with an HNO2 solution to obtain a polyacrylamide solution; mixing a first solution and a second solution for an ice bath reaction and then heating to 80°C for 4 hours to obtain a sol; and conducting a hydrothermal reaction on the sol with water to precipitate and successively washing, centrifuging and drying the precipitate to obtain the nano-TiO2/PAM. 3. The oil displacement method according to claim 1, wherein the preparation of nano-TiO2/PAM by the ultrasonic synthesis method comprises: mixing nano-titanium dioxide particles with deionized water to obtain a suspension liquid; mixing polyacrylamide with a HNO2 solution to obtain a polyacrylamide solution; and lowering the suspension liquid into the polyacrylamide solution, successively sonicating, stirring and drying it to obtain the nano-TiO2/PAM. 4. Use of an oil displacement method according to any of claims 1-3 for oil displacement in medium-low permeability reservoirs and extra-low permeability reservoirs.