A method for controlling bottom water coning in oil reservoirs based on establishing microbial mineralization partitions

Abstract

The present invention discloses a method for controlling the coning of bottom water in an oil reservoir based on the establishment of a microbial mineralization partition, specifically: injecting nitrogen into the formation through an injection well to depress the bottom water cone, then injecting a microorganism-nutrient agent-gelling material mixed solution, which is mixed with nitrogen in a porous medium to form a gel foam containing a microbial bacterial liquid, and then repeatedly injecting the bacterial liquid and the cementing liquid to strengthen the strength of the partition, and establishing a microbial mineralization partition, wherein the bacterial liquid contains urease-producing Bacillus subtilis. The present invention uses special microorganisms to construct the partition, which has the advantages of low economic cost, long control time, no pollution to the reservoir, and can consume the content of calcium and magnesium ions in the bottom water of the oil reservoir, reduce wellbore scaling, etc., enriches the artificial partition construction method, and is of great significance for controlling the coning of bottom water in oil and gas reservoir exploitation.

Description

Technical Field

[0001] The invention belongs to the technical field of bottom water oil reservoir exploitation, and in particular relates to a method for controlling the coning of bottom water in an oil reservoir based on establishing a microbial mineralization partition. Background Art

[0002] For bottom water reservoirs, as the oil and gas production rates increase, the bottom water interface continues to rise, and finally breaks through into the bottom of the well, resulting in the simultaneous production of oil and water or gas and water. This phenomenon is called bottom water coning. Bottom water coning is not conducive to the exploitation of oil and gas reservoirs. It will lead to reduced oil and gas production efficiency, and in severe cases, it will cause oil and gas wells to stop production. In order to maintain the effective exploitation of bottom water reservoirs, artificial baffles are often injected on the oil-water interface to "suppress water and eliminate cones", reduce the impact of bottom water coning, and improve oil and gas production in the reservoir.

[0003] Among the existing technologies for controlling bottom water coning, there are mainly physical technology and chemical technology. The main physical technologies at present are: drainage oil production technology, water cone technology, gas injection water suppression technology, and water production cone elimination technology, but they all have high technical costs and expensive equipment. Although horizontal well technology has a good effect in suppressing water cones, after the bottom water cone breaks through the oil-water interface, subsequent water control operations are difficult, so physical technologies are rarely implemented on site. In terms of chemical technology, the main ones are: ① polyacrylamide gel bottom water plugging technology, which has the problems of difficult injection and extremely unstable high-temperature gel; ② inorganic weighting fluid control oil well bottom water cone advancement technology, which is very complex, has many links, has very high construction requirements, and is difficult to apply on site; ③ inorganic solid phase chemical plugging technology, although this technology has a good plugging effect, it is difficult to construct, easily pollutes the formation, and is not easy to unblock after plugging; ④ artificial baffle technology, including cross-linked hydrolyzed polyacrylamide baffle technology, particle baffle water plugging technology, nitrogen + gel binary inhibition bottom water baffle technology, etc., but because most bottom water reservoirs have a high water content and serious bottom water cone advancement, these artificial baffle technologies have a high degree of hydrolysis, the ready-made baffles have poor toughness, a short effective period, and poor effects.

[0004] Therefore, for oil reservoir exploitation, low-cost and efficient bottom water coning control technology is still a realistic and urgent need. Summary of the invention

[0005] In view of the problems in the prior art, the present invention constructs a technology for controlling bottom water coning in oil reservoir exploitation based on microbial mineralization, which is not only efficient but also economical and environmentally friendly, and is of great significance for controlling bottom water coning in oil reservoir exploitation.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for controlling the coning of bottom water in an oil reservoir based on establishing a microbial mineralization partition comprises the following steps:

[0008] S1. Inject nitrogen into the formation through the injection well to depress the water cone at the bottom of the well;

[0009] S2, injecting a mixed solution again, which is mixed with nitrogen in the reservoir to form a gel foam, wherein the mixed solution comprises a microbial nutrient, a microbial bacterial solution, a microbial cementing solution and a gelling material, wherein the bacterial solution contains urease-producing Bacillus subtilis;

[0010] S3. Repeatedly inject bacterial solution and cementing solution to establish a microbial mineralization partition.

[0011] Furthermore, in the above technical solution, the gel-forming material includes a polyacrylamide solution, a crosslinking agent and a foaming agent, wherein the crosslinking time between the crosslinking agent and the polyacrylamide is less than the half-life of the foam formed by the foaming agent and the gas.

[0012] Furthermore, in the above technical solution, the microbial nutrient is a substance that can promote the growth of urease-producing Bacillus subtilis, and can be added according to actual needs.

[0013] Furthermore, in the above technical solution, the foaming agent is sodium sulfate of fatty alcohol ether, and the cross-linking agent is a composite cross-linking agent of organic chromium and phenolic resin.

[0014] Furthermore, in the above-mentioned composite cross-linking agent, the mass ratio of organic chromium to phenolic resin is 3:5.

[0015] Furthermore, the gel-forming material also includes a foam stabilizer, specifically hydrophobically modified nano-SiO2 particles, such as nano-SiO2 particles modified with N,N-dimethylferrocenylhexadecylmethylammonium bromide.

[0016] Furthermore, in the above technical scheme, the urease-producing Bacillus subtilis is deposited in the China Center for Type Culture Collection, and the preservation number is CCTCC M 2022336, and the preservation date is March 29, 2022.

[0017] The best culture medium formula for the above-mentioned urease-producing Bacillus subtilis is: 6 g / L peptone, 5 g / L sodium chloride, 1 g / L potassium dihydrogen phosphate, and 20 g / L urea. Its best growth temperature and growth pH are 30-50°C and 7-11, respectively.

[0018] Furthermore, in the above technical solution, the binder includes calcium chloride and urea; preferably, the specific formula of the binder may be: the molar concentration ratio of calcium chloride to urea is 1:1, both of which are 2 mol / L.

[0019] Furthermore, in the above technical solution, step S3 is specifically as follows: first inject the bacterial solution, and then inject the binder solution after 2 to 4 hours, once a day, and repeat 7 to 10 times.

[0020] Furthermore, in the above technical solution, the injection volume of the mixed solution is: V(πr 2 h)φ / 3, where V is the total amount of the mixed solution (m 3 ), r is the plugging radius (m), h is the baffle thickness (m), and φ is the reservoir porosity at the plugging point.

[0021] Furthermore, in the above technical solution, the total amount of nitrogen, microbial liquid and microbial cementing liquid injected is: Vπr φ h, where V is the total amount of nitrogen or bacterial solution or cementing solution (m 3 ), r is the plugging radius (m), h is the baffle thickness (m), and φ is the reservoir porosity at the plugging point.

[0022] The present invention injects nitrogen into the well at high speed and high pressure, and the water cone is pressed down by the nitrogen, so that other reagents can enter the hypertonic layer later; the nitrogen used for pressing the cone can also be used as the gas source of the foam temporary plugging agent (i.e., gel foam) injected later, and the foam generated after the injection of the bubbling agent can enhance the cone pressing effect; the density of the foam formed by the injection of the bubbling agent is higher than that of nitrogen, and after entering the water-producing layer, the cone pressing effect can be further enhanced, and the oil layer can be temporarily blocked and protected, ensuring that the subsequent water plugging agent accurately enters the hypertonic layer. The gel foam generated by the bubbling agent, polymer solution, foam stabilizer and cross-linking agent effectively increases the stability and strength of the foam, and at the same time increases its oil resistance.

[0023] The present invention further utilizes the microbial mineralization mechanism to construct a partition for plugging, thereby effectively inhibiting the coning of bottom water. The urease-producing Bacillus subtilis used in the present invention is screened from the produced water of the formation, and it is found that it has a high resistance to mineralization and is more adaptable to reservoir conditions; and it can produce urease, and when urea is used as a nitrogen source, urea can be decomposed to produce a large amount of carbonate ions. When the environment contains a large amount of calcium ions, calcium carbonate precipitation will be produced, and then the cementation plugging of the porous medium at the seepage can be achieved on the basis of gel foam.

[0024] The biological material deposit information in the present invention is as follows:

[0025] The urease-producing Bacillus subtilis (Bacillus sp. YZ-1) was registered and deposited at the China Center for Type Culture Collection (address: Wuhan University, Wuhan) on March 29, 2022, with the deposit number CCTCC M2022336.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: the baffles are constructed using special microorganisms, which have the advantages of low economic cost, short processing time cycle, long control time, no pollution to the reservoir, and can consume the content of calcium and magnesium ions in the bottom water of the oil reservoir, reduce wellbore scaling, etc., enriching the artificial baffle construction method, which is of great significance for controlling the coning of bottom water in oil reservoir exploitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of reservoir conditions under initial flooding conditions;

[0028] Figure 2 This is a schematic diagram of the reservoir condition after the nitrogen cone is injected;

[0029] Figure 3 This is a schematic diagram of the reservoir condition after the mixed solution consisting of a foaming agent, a polymer solution, a foam stabilizer and a cross-linking agent is injected;

[0030] Figure 4 Schematic diagram of reservoir conditions after the partition is formed;

[0031] In the figure, 1-oil-producing layer, 2-water cone, 3-gel foam, 4-partition. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0033] Example 1

[0034] The method for controlling the coning of bottom water in an oil reservoir provided in this embodiment is specifically as follows:

[0035] Urease-producing Bacillus subtilis (with the deposit number of CCTCC M 2022336) was activated and then expanded on a culture medium; the formula of the culture medium used was specifically: 6 g / L peptone, 5 g / L sodium chloride, 1 g / L potassium dihydrogen phosphate, and 20 g / L urea; the culture environment was: temperature 40°C, shaking speed 140 rpm / min, time 48 hours, and a microbial bacterial liquid was obtained.

[0036] First, nitrogen is injected into the formation at high speed and high pressure through the injection well, where the total amount of nitrogen injected is Vπr 2 h (V is the nitrogen dosage, r is the plugging radius, and h is the thickness of the baffle). The injected nitrogen will depress the water cone at the bottom of the well, causing the reservoir condition to change from Figure 1 Transformed into Figure 2 shown.

[0037] Then, a mixed solution consisting of microbial liquid, microbial nutrients, microbial cementing liquid (the concentration of calcium chloride and urea are both 2 mol / L) and gelling materials is injected into the well, wherein the gelling materials include sodium sulfate of fatty alcohol ether, 0.3-0.4wt% polyacrylamide solution, nano-SiO2 particles modified with N,N-dimethylferrocenylhexadecylmethylammonium bromide salt, and a composite cross-linking agent of organic chromium and phenolic resin in a mass ratio of 3:5. The injection amount of the gelling material is aimed at temporarily suppressing the water cone. The gelling material and the microbial liquid are mixed in the porous medium of the reservoir with the nitrogen injected previously to form a microbial-gel foam, as shown in the following figure. Figure 3 shown.

[0038] On the second day, inject the microbial solution into the well first, and then inject the cementing solution containing calcium chloride and urea after an interval of 4 hours. Inject the bacterial solution and cementing solution once a day, and repeat 7 to 10 times to build a partition with sufficient strength, small porosity and low permeability (such as Figure 4 The total injection volume of bacterial solution and cementing solution is: Vπr 2 h, where V is the total amount of nitrogen or bacterial solution or cementing solution, r is the plugging radius, h is the baffle thickness, and φ is the porosity of the oil and gas reservoir at the plugging point.

[0039] The baffles are constructed through microorganisms and reservoir conditions. Not only is the construction difficult, but it is also long-lasting and stable, and does not pollute the reservoir. It is of great significance for controlling bottom water coning.

[0040] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for controlling the coning of bottom water in an oil reservoir based on establishing a microbial mineralization partition, characterized in that: The following steps are involved: S1. Inject nitrogen into the formation through the injection well to depress the water cone at the bottom of the well; S2, re-injecting a mixed solution, which is mixed with nitrogen in the oil reservoir to form a microorganism-gel foam, wherein the mixed solution includes a microbial nutrient, a microbial bacterial solution, a microbial cementing solution and a gelling material, wherein the microbial bacterial solution contains urease-producing Bacillus subtilis screened from produced water of the formation; S3, repeatedly injecting microbial liquid and microbial cementing liquid to establish a microbial mineralization partition; The gelling material comprises a polyacrylamide solution, a crosslinking agent and a foaming agent, the crosslinking time between the crosslinking agent and the polyacrylamide is less than the half-life of the foam formed by the foaming agent and the gas, the foaming agent is sodium sulfate of fatty alcohol ether, the crosslinking agent is composed of organic chromium and phenolic resin in a mass ratio of 3:5, and the gelling material also comprises hydrophobically modified nano-SiO2 particles; The urease-producing Bacillus subtilis is deposited in the China Center for Type Culture Collection, and its deposit number is CCTCC M 2022336. The microbial cementing liquid includes calcium chloride and urea; Step S3 specifically includes: first injecting microbial liquid, and then injecting microbial cementing liquid after 2 to 4 hours, once a day, and repeating 7 to 10 times.

2. The method for controlling reservoir bottom water coning based on establishing a microbial mineralization partition according to claim 1, characterized in that: The injection volume of the mixed solution is: V = (πr 2 h)φ / 3, where V is the total amount of the mixed solution, r is the plugging radius, h is the thickness of the partition, and φ is the porosity of the reservoir at the plugging point.

3. The method for controlling reservoir bottom water coning based on establishing a microbial mineralization partition according to claim 1, characterized in that: The total amount of nitrogen, microbial liquid and microbial cementing liquid injected is: V = πr 2 hφ, where V is the total amount of nitrogen or microbial solution or microbial cementing solution, r is the plugging radius, h is the partition thickness, and φ is the reservoir porosity at the plugging point.

Images