A method for improving recovery of fault block reservoirs using microbial man-made gas

Abstract

The application discloses a method for improving the recovery ratio of fault block reservoirs by using artificial microbial gas cap, which comprises the following steps: (1) selection of target reservoirs; (2) selection and optimization of CH4-producing bacteria activators in the reservoirs; (3) selection of polymer-producing bacteria nutrient solution; (4) injection process optimization; (5) adjustment scheme and implementation effect evaluation. The application is suitable for the field of microbial oil recovery technology, has a wide application range, and the injected activator is non-toxic and harmless to human bodies, has normal temperature and pressure and is non-toxic and harmless, is safe and convenient to inject, and is safe and cheap to generate CH4 in the ground. Meanwhile, polymer-producing microorganisms are used to form biofilms to block large pores, to optimize the oil well shut-in and water well injection period, and to accelerate the formation of gas cap by taking multiple measures to ensure the effect. The application has the characteristics of simple process, good injection and good field test effect, and the success rate of field test is 100%, the input-output ratio is greater than 1:10, and the effective period is greater than 5 years.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microbial oil recovery, and particularly relates to a method for improving the recovery efficiency of fault block reservoirs by using microbial artificial gas cap. BACKGROUND

[0002] With the prolongation of water drive development of oil reservoirs and edge low water reservoirs, the oil-water interface rises obviously, and the water content of the oil well at the low position rises rapidly. It is difficult to produce the "attic oil" remaining in the high position and the edge and corner of the reservoir by using the original development method. In addition, the remaining oil is dispersed and complex after the water drive development, and it is difficult to further tap the potential by drilling new wells. The gravity drainage and oil discharge by forming a secondary gas cap through top gas injection is a better method. At present, nitrogen gas is used to form an artificial gas cap to drive oil in sandstone reservoirs, but the effects are quite different. Research shows that the formation of an artificial gas cap needs to meet certain conditions, and is affected by interfacial tension, permeability, fluid, density difference, reservoir pressure, formation dip angle and pore position. The interfacial tension is the most sensitive, and the permeability is the second.

[0003] At present, the commonly used and relatively effective gas for oil displacement is mainly N2, CO2 and CH4.

[0004] Chinese patent CN101555785B discloses a method for carbon dioxide flooding oil recovery. CO2 can greatly expand the volume of crude oil and has good viscosity reduction effect. However, CO2 has high solubility in water, and forms an acidic liquid after dissolution, which is not suitable for high water cut reservoirs in the late stage of water drive. At present, CO2 is mainly used for early development of low permeability reservoirs, and the current CO2 injection is in the form of liquid, which has certain cold damage to the reservoir at low temperature, and the effect is also poor for reservoirs with high crude oil viscosity and low temperature. The injection cost from the ground is high, and a new process for ground preparation is needed, which requires large investment.

[0005] Chinese patent CN105064962B discloses a method for inhibiting heavy oil thermal recovery edge water by nitrogen gas foam. The main mechanism of N2 is energy and pressure increase, and the solubility of N2 in crude oil and water is relatively low, and the effect is relatively single. In addition, gas channeling is easy to occur, so nitrogen gas foam flooding is needed in the present application, and the injection process is relatively complex. The foaming condition of the foam flooding in the ground directly affects the effect of nitrogen gas flooding. Research shows that the interfacial tension of the N2 system with crude oil is larger than that of CO2 and CH4, and the interfacial tension of the latter two with crude oil is significantly reduced under high temperature and high pressure conditions, while the nitrogen gas has little effect, which also leads to the effect of forming an artificial gas cap by using N2 in actual reservoirs to be worse than expected.

[0006] Chinese invention patent CN101555786B discloses an improved natural gas-driven oil recovery method. This method enhances the linkage between injection wells and production wells based on conventional natural gas injection technology. Through pressure monitoring and intermittent switching of surrounding oil wells, gas channeling is prevented, thereby improving recovery rates. The main oil displacement mechanism of CH4 is volume expansion and viscosity reduction, with the main advantages being that it does not damage the formation and does not corrode the tubing. The disadvantages of this invention are high natural gas injection costs, limited gas sources, and due to the characteristics of natural gas, high requirements for the sealing of each node in the tubing, high injection risk, and large investment. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving the recovery rate of fault-block oil reservoirs by utilizing microbial artificial gas caps.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for enhancing oil recovery in fault-block reservoirs using microbial artificial gas caps includes the following steps:

[0010] (1) Screening of target reservoirs;

[0011] (2) Screening and optimization of CH4-producing bacteria activators in oil reservoirs;

[0012] (3) Screening of nutrient solution for polymer-producing microbial agents;

[0013] (4) Optimization of the injection process;

[0014] (5) Evaluation of the adjustment plan and its implementation effect.

[0015] Preferably, in step (1), the screening of the target reservoir includes screening using static and dynamic parameters of the reservoir.

[0016] Preferably, in step (1), the screening criteria for the target reservoir include: meeting the requirements for microbial injection and growth, and the reservoir being conducive to gas rise and the formation of a gas cap.

[0017] Preferably, in step (1), the screening criteria for the target reservoir include: the reservoir type is a water-driven or edge-bottom water-driven reservoir, the reservoir temperature is <90℃, and the permeability is >50×10⁻⁶. -3 μm 2 Oil reservoirs with a dip angle greater than 5° and closed high sections, oil layer thickness greater than 3m, reservoir pressure maintained at a level greater than 80%, and overall water cut greater than 80%.

[0018] Preferably, in step (2), the screening of CH4-producing bacteria activators in the reservoir includes: screening activator formulations that can activate CH4-producing bacteria in the reservoir.

[0019] Preferably, in the step (2), the method for screening the CH4-producing bacteria activator in the oil reservoir is static culture method, and the screening basis is the CH4 production amount.

[0020] Preferably, in the step (2), the method for screening the CH4-producing bacteria activator in the oil reservoir is as follows: a container with a volume of 100-200 ml is taken, 50-60 mL of the produced liquid of the test oil reservoir is added, and the activator is added; then the container is placed at the temperature of the test oil reservoir for 45-90 days; the CH4 production amount in the culture bottle is determined to determine the formula of the CH4-producing bacteria activator.

[0021] Preferably, in the step (2), the CH4-producing bacteria activator is composed of a carbon source, a nitrogen source and a phosphorus source, the carbon source is at least one of glucose, sucrose, maltose, glycerol and corn powder, the nitrogen source is at least one of ammonium nitrate, urea, beef extract and peptone, and the phosphorus source is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phospholipid, calcium hydrogen phosphate, aluminum phosphate and calcium superphosphate.

[0022] Preferably, in the step (2), the mass concentrations of the carbon source, the nitrogen source and the phosphorus source of the CH4-producing bacteria activator are 1.0-4.0%, 0.2-0.8% and 0.05-0.2%, respectively.

[0023] Preferably, in the step (2), the mass concentrations of the carbon source, the nitrogen source and the phosphorus source of the CH4-producing bacteria activator are 2.0-3.0%, 0.3-0.6% and 0.05-0.1%, respectively.

[0024] Preferably, in the step (2), the method further comprises: according to the CH4 production amount, the injection concentration of the CH4-producing bacteria activator is determined for the screened activator formula.

[0025] Preferably, in the step (2), the method for determining the injection concentration of the CH4-producing bacteria activator is as follows:

[0026] A reaction container with a volume of 100-200 ml is taken, 50-60 mL of the produced liquid of the test oil reservoir is added, and the screened activator formula with a concentration of 1-5% is added;

[0027] Then the container is placed at the temperature of the test oil reservoir for 45-90 days;

[0028] The CH4 production amount in the culture bottle is determined to determine the injection concentration of the CH4-producing bacteria activator.

[0029] Preferably, in the step (2), the optimization of the CH4-producing bacteria activator in the oil reservoir comprises: injection concentration optimization.

[0030] Preferably, in the step (2), the polymer production activator is composed of carbon source, nitrogen source and phosphorus source, the carbon source is at least one of glucose, sucrose, maltose, glycerol and corn flour, the nitrogen source is at least one of ammonium nitrate, urea, beef extract and peptone, and the phosphorus source is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phospholipid, calcium hydrogen phosphate, aluminum phosphate and calcium superphosphate.

[0031] Preferably, in the step (2), the mass concentrations of the carbon source, the nitrogen source and the phosphorus source of the activator are 1.0-5.0%, 0.3-1.0% and 0.03-0.1% respectively.

[0032] Preferably, in the step (2), the mass concentrations of the carbon source, the nitrogen source and the phosphorus source of the activator are 2.0-4.0%, 0.5-0.8% and 0.05-0.08% respectively.

[0033] Preferably, in the step (3), the screening of the polymer production nutrient solution of the bacteria includes: screening the polymer production bacteria suitable for the selected oil reservoir and screening the corresponding activator.

[0034] Preferably, in the step (3), the method for screening the polymer production bacteria suitable for the selected oil reservoir includes:

[0035] In the reaction container, 50-60 mL of the production liquid of the test oil reservoir is added, 1-6 mL of the mixed solution of the polymer production bacteria and the activator suitable for the temperature of the oil reservoir is added, wherein the bacteria solution accounts for 5-20%, and then the mixed solution is cultured at the temperature of the test oil reservoir for 10-30 days; the viscosity of the mixed solution is tested, and the polymer production bacteria with the highest viscosity at 50°C is screened out.

[0036] Preferably, in the step (3), the polymer production microorganism is one or more of Pseudomonas, Alcaligenes, Aureobasidium pullulans, citric acid fermentation waste mycelium, Aspergillus niger and Acetobacter xylinum, and preferably one of Pseudomonas, Alcaligenes and Acetobacter xylinum.

[0037] Preferably, in the step (3), the method for screening the corresponding activator includes:

[0038] Multiple 50-60 mL of the production liquid of the test oil reservoir is taken, 1-3 mL of the polymer production microorganism screened out before is added to each of the production liquid, different activators with the same concentration are added respectively, and then the production liquid is cultured at the temperature of the test wellbore for 5-15 days; the concentration of the polymer production bacteria in the different culture solutions is determined, and the activator formula is screened out according to the concentration.

[0039] Preferably, in the step (4), the injection process optimization includes: optimizing and designing the process parameters such as injection amount, injection concentration and injection cycle.

[0040] Preferably, in the step (4), the injection process optimization method is indoor static culture method, and the well shut-in period optimization basis is the CH4 producing bacteria gas production period.

[0041] Preferably, in the step (4), it further includes: designing a pressure observation well in the oil reservoir in advance, and reading the oil reservoir static pressure periodically and continuously.

[0042] Preferably, in the step (4), the injection mode is slug injection, and the gas producing bacteria liquid and the activator are injected first, and then the polymer producing bacteria liquid and the activator are injected.

[0043] Preferably, in the step (4), the injection period of the CH4 producing bacteria activator is according to the CH4 gas production period, and the injection is performed once every 2-3 months.

[0044] Preferably, in the step (4), after a period of injection of the CH4 producing bacteria activator in each round, the oil well needs to be shut down, and the shut-down time and duration are determined according to the CH4 gas production period optimization in the step (2).

[0045] Preferably, in the step (4), the CH4 producing bacteria and the activator are injected first, and when the oil reservoir static pressure increases by 0.2-0.3 MPa, the polymer producing formula is injected, and then the gas producing formula is injected after adjustment, and the above process is repeated for several times until there is no economic benefit.

[0046] Preferably, in the step (4), the determination formula of the CH4 producing bacteria activator amount injected in each round is: Q1=q*L*c1.

[0047] Q1: the CH4 producing bacteria activator amount injected in each round, kg;

[0048] q: the daily water injection amount of the injection water well, m 3 / d;

[0049] L: injection period, days;

[0050] c1: activator injection concentration, %

[0051] Preferably, in the step (4), the injection amount of the polymer producing formula is determined by the following formula:

[0052] Q2=3.14*R 2 *h*φ*β;

[0053] R=T*V / 2;

[0054] Q2: the polymer producing formula injection amount in each round, m 3 ;

[0055] R: flow radius, m;

[0056] T: injection time, the injection time of the water well before the shut-in of the oil well in the early stage of optimization;

[0057] V: average water line propulsion speed;

[0058] h: thickness of the polymer, 0.1m;

[0059] φ: reservoir porosity, %;

[0060] β: gas channeling coefficient, 0.5-3.0;

[0061] The bacterial liquid accounts for 5-20% in the mixed formula, and the activator accounts for 80-95%.

[0062] The value of β is gradually increased appropriately with the round if the gas-oil ratio of the oil well does not change much.

[0063] If the gas-oil ratio of the oil well rises obviously, the rising amplitude and the proportion of the rising well are determined.

[0064] Preferably, in the step (5), the adjustment scheme includes: carrying out field test according to the process parameters determined in the step (4), and formulating the adjustment scheme.

[0065] Preferably, in the step (5), the effect evaluation includes: evaluating the effect of the field test after the experiment, and the evaluation indexes include: oil increment, input-output ratio and effective period.

[0066] Preferably, in the step (5), the formulation of the adjustment scheme includes:

[0067] If the rise of the reservoir static pressure is still lower than 0.3MPa within half a year, the activation effect of the activator is poor due to the adsorption and dilution of the reservoir, and the injection concentration of the gas production activator needs to be increased.

[0068] If the rising amplitude of the gas-oil ratio of part of the oil wells is greater than 10 times, it indicates that the gas channeling is serious, so it is necessary to block the gas channeling channel by means of profile control, and then inject according to the method after blocking.

[0069] In summary, due to the adoption of the above technical scheme, the beneficial effects of the present application are:

[0070] (1) The present application has a wide range of reservoir applications, especially for reservoirs with edge and bottom water and high angle;

[0071] (2) The injected activator of the present application is non-toxic and harmless to the human body, and is safe and convenient to inject at normal temperature and pressure without harm and pollution to the formation and environment;

[0072] (3) The present application utilizes microorganisms to produce CH4 gas cap to drive oil in the oil reservoir, screens suitable oil reservoirs, avoids the risk of surface injection, and realizes safe and inexpensive CH4 generated by underground reaction due to high natural gas price;

[0073] (4) The present application simultaneously utilizes polymer-producing microorganisms to form biofilm and block large pores, optimizes oil well shut-in and water well injection period, and takes multiple measures to accelerate the formation of gas cap and ensure the effect;

[0074] (5) The present application has the characteristics of simple process, good injection, and good field test effect, and the success rate of field test is 100%, the input-output ratio is greater than 1:10, and the effective period is greater than 5 years. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 is a flow chart of a method for improving the recovery rate of a fault block oil reservoir by using a microbial artificial gas cap according to the present application;

[0076] Figure 2 is a schematic diagram of the value of gas channeling coefficient β in the method for improving the recovery rate of a fault block oil reservoir by using a microbial artificial gas cap according to the present application;

[0077] Figure 3 is a schematic diagram of the optimization of CH4-producing activator screening concentration in the method for improving the recovery rate of a fault block oil reservoir by using a microbial artificial gas cap according to the present application Figure 1 ;

[0078] Figure 4 is a schematic diagram of the optimization of CH4-producing activator screening concentration in the method for improving the recovery rate of a fault block oil reservoir by using a microbial artificial gas cap according to the present application Figure 2 . DETAILED DESCRIPTION

[0079] The specific implementation of the method for improving the recovery rate of a fault block oil reservoir by using a microbial artificial gas cap according to the present application will be further described below in combination with the accompanying Figures 1-4 drawings, which is not limited to the following examples.

[0080] Example 1:

[0081] This embodiment gives a specific implementation of a method for improving the recovery rate of a fault block oil reservoir by using a microbial artificial gas cap, as shown in Figure 1 , which includes the following steps:

[0082] (1) Screening of target oil reservoirs;

[0083] (2) Screening and optimization of CH4-producing bacteria activators in the oil reservoir;

[0084] (3) Screening of polymer-producing bacteria nutrient solution;

[0085] (4) injection process optimization;

[0086] (5) adjustment scheme and implementation effect evaluation.

[0087] Further, in step (1), the screening of the target reservoir includes: screening by using static and dynamic parameters of the reservoir.

[0088] Further, in step (1), the screening criteria of the target reservoir include: meeting the injection and growth of microorganisms, and the reservoir is conducive to the gas rising and forming a gas cap.

[0089] Further, in step (1), the screening criteria of the target reservoir include: the reservoir type is water drive or edge and bottom water drive reservoir, the reservoir temperature is < 90℃, the permeability is > 50x10 -3 μm 2 , the formation dip angle is greater than 5° and the high part is closed, the oil layer thickness is greater than 3m, the reservoir pressure retention level is greater than 80%, and the comprehensive water content is greater than 80%.

[0090] Further, in step (2), the screening of the CH4 producing bacteria activator in the reservoir includes: screening the activator formula capable of activating the CH4 producing bacteria in the reservoir.

[0091] Further, in step (2), the screening method of the CH4 producing bacteria activator in the reservoir is static culture method, and the screening basis is the CH4 production amount.

[0092] Further, in step (2), the screening method of the CH4 producing bacteria activator in the reservoir is: taking a container with a volume of 100-200ml, adding 50-60ml of the produced liquid of the test reservoir, and adding the activator; then placing it in the test reservoir temperature for 45-90d; measuring the CH4 production amount in the culture bottle to determine the formula of the CH4 producing bacteria activator.

[0093] Further, in step (2), the CH4 producing bacteria activator is composed of carbon source, nitrogen source and phosphorus source, the carbon source is at least one of glucose, sucrose, maltose, glycerol and corn powder, the nitrogen source is at least one of ammonium nitrate, urea, beef extract and peptone, and the phosphorus source is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phospholipid, calcium hydrogen phosphate, aluminum phosphate and calcium phosphate superphosphate.

[0094] Further, in step (2), the mass concentrations of the carbon source, nitrogen source and phosphorus source of the CH4 producing bacteria activator are 1.0-4.0%, 0.2-0.8% and 0.05-0.2% respectively.

[0095] Further, in step (2), the mass concentrations of the carbon source, nitrogen source and phosphorus source of the CH4 producing bacteria activator are 2.0-3.0%, 0.3-0.6% and 0.05-0.1% respectively.

[0096] Further, in step (2), the injection concentration of the CH4-producing bacteria activator is determined according to the CH4 production of the screened activator formula.

[0097] Further, in step (2), the method for determining the injection concentration of the CH4-producing bacteria activator is:

[0098] A reaction container with a volume of 100-200 ml is used, 50-60 ml of the produced liquid of the test oil reservoir is added, and the screened activator formula with a concentration of 1-5% is added.

[0099] Then, it is placed in the test oil reservoir temperature for 45-90 days of cultivation.

[0100] The CH4 production of the cultivation bottle is determined to determine the injection concentration of the CH4-producing bacteria activator.

[0101] Further, in step (2), the optimization of the CH4-producing bacteria activator in the oil reservoir includes injection concentration optimization.

[0102] Further, in step (2), the polymer-producing activator is composed of a carbon source, a nitrogen source, and a phosphorus source, the carbon source is at least one of glucose, sucrose, maltose, glycerol, and corn powder, the nitrogen source is at least one of ammonium nitrate, urea, beef extract, and peptone, and the phosphorus source is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phospholipid, calcium hydrogen phosphate, aluminum phosphate, and calcium phosphate superphosphate.

[0103] Further, in step (2), the mass concentrations of the carbon source, the nitrogen source, and the phosphorus source of the activator are 1.0-5.0%, 0.3-1.0%, and 0.03-0.1%, respectively.

[0104] Further, in step (2), the mass concentrations of the carbon source, the nitrogen source, and the phosphorus source of the activator are 2.0-4.0%, 0.5-0.8%, and 0.05-0.08%, respectively.

[0105] Further, in step (3), the screening of the polymer-producing bacteria nutrient solution includes screening the polymer-producing bacteria suitable for the selected oil reservoir and screening the corresponding activator.

[0106] Further, in step (3), the method for screening the polymer-producing bacteria suitable for the selected oil reservoir includes:

[0107] In the reaction container, 50-60 ml of the produced liquid of the test oil reservoir is added, and 1-6 ml of the polymer-producing bacteria and activator mixed solution suitable for the oil reservoir temperature is added, wherein the bacteria solution accounts for 5-20%; then, it is placed in the test oil reservoir temperature for 10-30 days of cultivation; the viscosity of the mixed solution is tested, and the polymer-producing bacteria strain with the highest viscosity at 50°C is screened out.

[0108] Further, in step (3), the polymer-producing microorganism is one or more of Pseudomonas, Alcaligenes, Aureobasidium pullulans, citric acid fermentation waste mycelium, Aspergillus niger, and Acetobacter xylinum, preferably one of Pseudomonas, Alcaligenes, and Acetobacter xylinum.

[0109] Further, in step (3), the method for screening the corresponding activator includes:

[0110] Multiple 50-60 mL samples of the test oil reservoir production fluid are taken, 1-3 mL of the previously screened polymer-producing microorganism is added to each sample, different activators of the same concentration are then added to the samples, respectively, and the samples are then incubated at the temperature of the test wellbore for 5-15 days. The concentration of the polymer-producing bacteria in the different incubation liquids is determined, and the activator formulation is screened according to the concentration.

[0111] Further, in step (4), the injection process optimization includes: optimizing and designing the process parameters such as injection volume, injection concentration, and injection cycle.

[0112] Further, in step (4), the injection process optimization method is an indoor static culture method, and the well shut-in cycle optimization basis is the CH4-producing bacteria gas production cycle.

[0113] Further, in step (4), it also includes: designing a pressure observation well in the oil reservoir in advance, and regularly and continuously reading the static pressure of the oil reservoir.

[0114] Further, in step (4), the injection method is a slug injection method, in which the CH4-producing bacteria liquid and the activator are injected first, and then the polymer-producing bacteria liquid and the activator are injected.

[0115] Further, in step (4), the injection cycle of the CH4-producing bacteria activator is according to the CH4 gas production cycle, and the CH4-producing bacteria activator is injected once every 2-3 months.

[0116] Further, in step (4), after a period of injection of the CH4-producing bacteria activator in each round, the oil well needs to be shut in, and the shut-in time and duration are determined according to the CH4 gas production cycle optimization in step (2).

[0117] Further, in step (4), the CH4-producing bacteria and the activator are injected first, and when the static pressure of the oil reservoir increases by 0.2-0.3 MPa, the polymer-producing formulation is injected instead, and then the gas-producing formulation is injected after adjustment, and this is repeated multiple times until there is no economic benefit.

[0118] Further, in step (4), the determination formula for the amount of the CH4-producing bacteria activator injected in each round is: Q1=q*L*c1;

[0119] Q1: the amount of the CH4-producing bacteria activator injected in each round, KG;

[0120] q: daily injection volume of water injection well, m 3 / d;

[0121] L: injection cycle, day;

[0122] c1: activator injection concentration, %;

[0123] Further, in step (4), the injection amount when injecting the polymer production formula is determined by the following formula:

[0124] Q2 = 3.14 * R 2 *h*φ*β;

[0125] R = T * V / 2;

[0126] Q2: injection amount of polymer production formula per round, m 3 ;

[0127] R: flow radius, m;

[0128] T: injection time, the injection time of the water well before the oil well shut-in in the early stage is optimized;

[0129] V: average water line advancing speed;

[0130] h: thickness of polymer, taking 0.1m;

[0131] φ: reservoir porosity, %;

[0132] β: gas channeling coefficient, taking 0.5-3.0;

[0133] The bacterial solution accounts for 5-20% in the mixed formula, and the activator accounts for 80-95%;

[0134] The value of β, if the gas-oil ratio of the oil well does not change much, the value can be gradually increased appropriately with the round;

[0135] If the gas-oil ratio of the oil well rises significantly, it is determined according to the rising amplitude and the proportion of the rising well.

[0136] Further, in step (5), the adjustment scheme includes: carrying out field test according to the process parameters determined in step (4), and formulating the adjustment scheme.

[0137] Further, in step (5), the effect evaluation includes: evaluating the effect of field test after the experiment, and the evaluation indexes include: oil increment, input-output ratio, and effective period.

[0138] Further, in step (5), the formulation of the adjustment scheme includes:

[0139] If the oil reservoir static pressure rises within six months is still less than 0.3 MPa, considering the adsorption and dilution of the oil reservoir, the activating effect of the activator is poor, and the injection concentration of the gas activating agent needs to be increased;

[0140] If the gas-oil ratio of part of the oil wells increases by more than 10 times, it indicates that the gas channeling is serious, so it is necessary to use profile control means to plug the gas channeling channel, and then inject according to the method after plugging.

[0141] Example 2

[0142] Test well profile: ST1 of a block in Shengli Oilfield, water drive development, reservoir temperature 65℃, porosity 27%, permeability 390x10 -3 μm 2 , high part of the formation dip angle 5-8°, lithology sealing, oil layer thickness 8m, reservoir pressure retention level 92%, block comprehensive water cut 92%; the current gas-oil ratio is 32m 3 / m 3 .

[0143] A method for improving the recovery of fault block reservoir by using microbial artificial gas cap, as shown in Figures 1-4 , comprising the following steps:

[0144] (1) Selection of target reservoir, the selection criteria include reservoir type is water drive or edge-bottom water drive reservoir, reservoir temperature <90℃, formation dip angle is greater than 5° and high part of the reservoir is sealed, oil layer thickness is greater than 3m, reservoir pressure retention level is greater than 80%, and comprehensive water cut is greater than 80%; meet the selection criteria of the present application, the present application can be implemented.

[0145] (2) Selection and optimization of CH4 producing bacteria activator in the reservoir: take 100mL anaerobic bottle, add 50mL of test reservoir produced liquid, add activator; then place in the test reservoir temperature for 60d; determine the amount of CH4 produced in the culture bottle, and determine the formula of CH4 producing bacteria activator.

[0146] Table 1 CH4 activator screening

[0147]

[0148] Among them, No. 2 formula: sucrose 3.0%, ammonium nitrate 0.6%, dipotassium hydrogen phosphate 0.1% has the highest gas production, so the formula of CH4 producing bacteria activator is determined.

[0149] For formula 2, according to the yield of CH4 gas, the injection concentration of CH4 bacteria activator is determined. The specific method is as follows: take 100 mL anaerobic bottle, add 60 mL of the output fluid of the test reservoir, add 0.1%, 0.3%, 0.5% of the activator formula screened in the last step; then place it at the temperature of the test reservoir for 60 days; measure the yield of CH4 gas in the culture bottle, according to the results, when the concentration is higher than 0.3%, the gas production increases slowly, considering the economy, the injection concentration of CH4 bacteria activator is selected as 0.3%.

[0150] In this step, the gas pressure change in the bottle is recorded every day, from the pressure change, the gas production is very low in the first 32 days, and the gas production becomes large after the 33rd day, and the gas production reaches the peak value on the 51st day. Take the 10 days with the fastest gas production increase as the oil well shut-in time. The 41-50 days are taken in this area. Therefore, after injecting the activator into the water well, the oil well is shut in for 10 days at the 41st day, and then it is opened for production.

[0151] Table 2: Optimization of CH4 activator screening concentration

[0152]

[0153] (3) Screening of polymer-producing bacteria nutrient solution, screening of polymer-producing bacteria suitable for selected reservoirs, and screening of corresponding activators.

[0154] The screening method of polymer-producing bacteria is static culture method, and the screening basis is the yield of polymer. The specific method is as follows: take 100 mL anaerobic bottle, add 60 mL of the output fluid of the test reservoir, add 3 mL of polymer-producing bacteria and activator mixed solution suitable for the temperature of the reservoir, wherein the bacteria solution accounts for 10%; then place it at the temperature of the test reservoir for 20 days; test the viscosity of the mixed solution, and screen out the polymer-producing bacteria with the highest viscosity of the mixed solution. According to the results, we select the SL-3 bacteria with the highest yield.

[0155] Table 3: Screening of polymer-producing microorganisms

[0156]

[0157] Then determine the activator corresponding to the polymer-producing microorganism: take multiple 50 mL of the output fluid of the test reservoir, add 1 ml of SL-3 bacteria to each; then add different activators with the same concentration respectively; then place them at the temperature of the test well for 15 days respectively; according to the bacteria concentration, optimize and determine formula 3.

[0158] Table 4: Screening of polymer-producing microorganism activator

[0159]

[0160]

[0161] (4) Injection process optimization.

[0162] A, determination of the amount of CH4 bacteria activator injected per round: Q1 = q * L * c1

[0163] q: daily water injection volume of injection well, 50 m 3 / d.

[0164] L: injection period, 60 days.

[0165] c1: activator injection concentration, 3%.

[0166] The calculated amount of CH4 bacteria activator injected per round is: 90 m 3 .

[0167] Monitor the pressure of the oil well, when the pressure rises by 0.3 MPa, inject the polymer production formula.

[0168] Table 5 Pressure Change and Polymer Production Bacteria Injection Table

[0169]

[0170]

[0171] By December 2020, a total of 6 rounds of polymer production formula injection were made in this block.

[0172] The injection volume when injecting the polymer production formula is determined by the following formula. Among them, the bacteria liquid accounts for 10% in the mixed formula, and the activator accounts for 90%.

[0173] Q2 = 3.14 * R 2 *h*φ*β

[0174] R = T * V / 2

[0175] Q2: Polymer production formula injection volume per round, m 3 .

[0176] R: flow radius, m.

[0177] T: injection time, optimized injection time of water well before oil well shut-in

[0178] V: average water line advancing speed

[0179] h: thickness of polymer, 0.1 m.

[0180] φ: reservoir porosity, %.

[0181] β: gas channeling coefficient, 0.5-3.0.

[0182] Table 6 Flow radius calculation parameter table

[0183] T 42 V 3 R 63

[0184] Table 7 Polymer production amount calculation

[0185]

[0186] (5) Adjustment scheme and implementation effect evaluation, according to the process parameters determined in step (4), field test is carried out, and an adjustment scheme is made. After the experiment, the effect of the field test is evaluated, and the evaluation indexes include: oil increment, input-output ratio, and effective period.

[0187] During the implementation process, the polymer injection amount was gradually increased according to the oil-gas ratio and gas channeling well. By December 2020, a total of 610,000 yuan was invested, with an incremental oil of 1293 tons, an input-output ratio of 1:4.9, and an effective period of 27 months, which is currently in effect.

[0188] Example 3

[0189] Test well profile: SG2 of a block in Shengli Oilfield, with active edge and bottom water, natural energy development, reservoir temperature 70℃, porosity 24%, permeability 1650x10 -3 μm 2 , high position lithology sealing with 8-13° formation dip, oil layer thickness 6m, reservoir pressure retention level 90%, block comprehensive water cut 95%; the current gas-oil ratio is 26m 3 / m 3 .

[0190] A method for improving the recovery of fault block reservoirs by using microbial artificial gas cap, as shown in Figures 1-4 , comprising the following steps:

[0191] (1) Selection of target reservoirs, the selection criteria include reservoir type being water drive or edge and bottom water drive reservoir, reservoir temperature <90℃, formation dip greater than 5° and high position sealing reservoir, oil layer thickness greater than 3m, reservoir pressure retention level greater than 80%, and comprehensive water cut greater than 80%; the selection criteria of the present application are met, and the present application can be implemented.

[0192] (2) Selection and optimization of CH4-producing bacteria activator in the reservoir: take 100mL anaerobic bottle, add 60mL of output fluid of the test reservoir, and add the activator; then place it in the test reservoir temperature for 90d; determine the amount of CH4 produced in the culture bottle, and determine the formula of the CH4-producing bacteria activator.

[0193] Table 1 CH4-producing activator selection

[0194]

[0195] Among them, the No. 1 formula: sucrose 2.0%, ammonium nitrate 0.4%, dipotassium hydrogen phosphate 0.1% has the highest gas production, so the CH4 activator formula is determined.

[0196] For formula 1, the injection concentration of CH4 activator is determined according to the CH4 gas production. The specific method is as follows: take 100 mL anaerobic bottle, add 50 mL of the produced liquid of the test reservoir, and add 0.1%, 0.3%, 0.5%, 0.8% of formula 1; then place it at the temperature of the test reservoir for 90 days; measure the CH4 gas production; according to the results, when the concentration is higher than 0.5%, the gas production increases slowly, considering the economy, the injection concentration of CH4 activator is selected as 0.5%.

[0197] In this step, the gas pressure change in the bottle is recorded every day, and from the pressure change, the early gas production is very low, and from the 39th day, the gas production becomes large, and the 81st day reaches the peak value. The gas production time is relatively long, and the 15 days with the fastest gas production increase are taken as the oil well shut-in time. The 60-75 days in this area are taken. Therefore, after injecting the activator into the water well, the 61st day corresponds to the oil well shut-in for 15 days, and then the well is opened for production.

[0198] Table 2 Screening concentration optimization of CH4 activator

[0199]

[0200] (3) Screening of polymer-producing bacteria nutrient solution, screening of polymer-producing bacteria suitable for selected reservoirs, and screening of corresponding activators.

[0201] The screening method of polymer-producing bacteria is static culture method, and the screening basis is the yield of polymer. The specific method is as follows: take 100 mL anaerobic bottle, add 50 mL of the produced liquid of the test reservoir, add 6 mL of polymer-producing bacteria and activator mixed liquid suitable for the temperature of the reservoir, and the bacteria liquid accounts for 10%; then place it at the temperature of the test reservoir for 15 days; test the viscosity of the mixed liquid, and screen out the polymer-producing bacteria with the highest viscosity of the mixed liquid. According to the results, we select the highest yield ZP-2 bacteria.

[0202] Table 3 Screening of polymer-producing microorganisms

[0203]

[0204]

[0205] Then determine the corresponding polymer-producing microorganisms activator: take several 50 mL of test reservoir production fluid, add ZP-2 bacteria 2 ml to each; then add different activators of the same concentration respectively; then place them respectively at the test wellbore temperature for 15 days; according to the bacteria concentration, optimize and determine No. 1 formula.

[0206] Table 4 Screening of polymer-producing microorganism activator

[0207]

[0208] (4) Injection process optimization.

[0209] A. Determination of the amount of CH4-producing bacteria activator injected per round: Q1=q*L*c1

[0210] q: daily water injection volume of injection well, 70 m 3 / d.

[0211] L: injection period, 90 days.

[0212] c1: activator injection concentration, 0.5%.

[0213] The calculated CH4 bacteria activator injection amount per round is: 31.5 m 3 .

[0214] Six months after injection, the reservoir pressure rises less than 0.3 MPa, so the injection concentration is adjusted to 1% injection. Continue to monitor the pressure of the oil well, when the pressure rises 0.3 MPa, inject polymer-producing mixed formula. By December 2020, the polymer-producing round is 6 times.

[0215] Table 5 Pressure change and polymer-producing bacteria liquid injection table

[0216]

[0217]

[0218] The injection amount of polymer-producing formula is determined by the following formula. Among them, the bacteria liquid accounts for 10% in the mixed formula, and the activator accounts for 90%.

[0219] Q2=3.14*R 2 *h*φ*β

[0220] R=T*V / 2

[0221] Q2: polymer-producing formula injection amount per round, m 3 .

[0222] R: flow radius, m.

[0223] T: injection time, injection time of water well before the shut-in of the oil well in the early optimization

[0224] V: average water line propulsion speed

[0225] h: thickness of the polymer, 0.1 m.

[0226] φ: reservoir porosity, %.

[0227] β: gas channeling coefficient, 0.5-3.0.

[0228] Table 6 Flow radius calculation parameter table

[0229]

[0230] Table 7 Polymer production amount calculation

[0231]

[0232] (5) Adjustment scheme and implementation effect evaluation, according to the process parameters determined in step (4) to carry out field test, and make adjustment scheme. After the experiment, the effect of field test is evaluated, and the evaluation index includes: oil increment, input-output ratio, effective period.

[0233] In this implementation process, the polymer injection amount was gradually increased according to the oil-gas ratio and gas channeling well. In August 2020, a well appeared serious gas channeling, and the gas-oil ratio increased by 11 times, so the water well was first profiled. By December 2020, a total of 120.9 million yuan was invested, with a cumulative oil increment of 2100 tons, an input-output ratio of 1:4.2, and an effective period of 27 months, which is currently in continuous effect.

[0234] Principle: This method has the characteristics of strong reservoir adaptability, simple injection process, low cost, green and pollution-free; by injecting nutrient solution into the oil well to activate the methane-producing bacteria in the reservoir, using the characteristics of low interfacial tension of methane and crude oil under high temperature and high pressure and gravity differentiation, it is easy to form an artificial gas cap, and the oil displacement effect is good. Because the microbial gas production is more balanced, and the compounded polymer-producing microorganisms form a biofilm in the reservoir, preventing gas from channeling out along the large pore channel, isolating gas and liquid within a certain pressure range, and replacing time with space, gas migrates to the top of the reservoir due to density difference and structural height difference, accelerating the formation of gas cap. At the same time, the water well uses slug injection, and the oil well is shut in at the peak gas production period of each round, further reducing the channeling of gas and ensuring the effect.

[0235] The above is further detailed description of the present application in combination with specific preferred embodiments, and cannot be deemed as limitation of the specific implementation of the present application to these descriptions. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions or substitutions can be made, and all of them shall be deemed as falling within the protection scope of the present application.

Claims

1. A method for enhancing recovery of oil from a fault block reservoir using microbial man-made gas cap, characterized by, The method comprises the following steps: (1) selection of target oil reservoir; (2) selection and optimization of CH4 producing bacteria activator in the oil reservoir; (3) selection of polymer producing bacteria nutrient solution; (4) injection process optimization; (5) adjustment scheme and implementation effect evaluation; The screening criteria of the target oil reservoir in step (1) include: the oil reservoir type is water drive or edge and bottom water drive oil reservoir, the oil reservoir temperature is < 90℃, the permeability is > 50x10 -3 μm 2 , the formation dip angle is greater than 5° and the oil reservoir with high position closed, the oil layer thickness is greater than 3m, the oil reservoir pressure maintenance level is greater than 80%, and the comprehensive water content is greater than 80%. In the step (1), the selection criteria of the target oil reservoir include: meeting the injection and growth of microorganisms, and the reservoir being conducive to gas rising and forming a gas cap; In the step (4), the injection process optimization includes: optimization and design of injection amount, injection concentration, and injection cycle process parameters; In the step (4), the injection process optimization method is indoor static culture method, and the well shut-in cycle optimization basis is the gas production cycle of the CH4 producing bacteria; In the step (4), it further includes: designing a pressure observation well in the oil reservoir in advance, and regularly and continuously reading the static pressure of the oil reservoir; In the step (4), the injection mode is slug injection, and the CH4 producing bacteria solution and the activator are injected first, and then the polymer producing bacteria solution and the activator are injected; In the step (4), the injection cycle of the CH4 producing bacteria activator is according to the gas production cycle of CH4, and the injection is performed once every 2-3 months; In the step (4), after a period of injection of the CH4 producing bacteria activator in each round, the oil well needs to be shut down, and the shut-down time and duration are determined according to the gas production cycle optimization of CH4 in the step (2); In the step (4), the CH4 producing bacteria and the activator are injected first, and when the static pressure of the oil reservoir increases by 0.2-0.3 MPa, the polymer producing formula is injected, the gas producing formula is injected after adjustment, and the above process is repeated for multiple times until there is no economic benefit; In the step (4), the determination formula of the CH4 producing bacteria activator injection amount in each round is: Q1=q*L*c1; Q1: CH4 producing bacteria activator injection amount in each round; q: daily water injection amount of the injection well; L: injection cycle; c1: activator injection concentration; In the step (4), the injection amount of the polymer producing formula is determined by the following formula: Q2 = 3.14 * R 2 h φ β; R=T*V / 2; Q2: polymer producing formula injection amount in each round; R: flow radius; T: injection time, the injection time of the water well before the well shut-down in the early stage; V: average water line advancing speed; h: thickness of the polymer; φ: reservoir porosity; β: gas channeling coefficient, 0.5-3.0; The bacteria solution accounts for 5-20% in the mixed formula, and the activator accounts for 80-95%; The value of β is gradually increased with the round if the gas-oil ratio of the oil well changes little; If the gas-oil ratio of the oil well rises obviously, the value is determined according to the rising amplitude and the proportion of the rising well.

2. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 1, wherein, In the step (1), the selection of the target oil reservoir includes: selection by using the static and dynamic parameters of the oil reservoir.

3. A method for enhancing recovery of fractured block reservoirs by using microbial gas cap, as claimed in claim 1 wherein, In the step (2), the selection of the CH4 producing bacteria activator in the oil reservoir includes: selection of the activator formula capable of activating the CH4 producing bacteria in the oil reservoir.

4. A method for enhancing recovery of fractured block reservoirs by using microbial gas cap, according to claim 3, characterized in that, In the step (2), the selection method of the CH4 producing bacteria activator in the oil reservoir is static culture method, and the selection basis is the CH4 gas production amount.

5. A method for enhancing recovery of fractured block reservoirs by using microbial gas cap, as claimed in claim 4 wherein, In the step (2), the method for screening the CH4 producing bacteria activator in the oil reservoir is as follows: a container with a volume of 100-200ml is taken, 50-60ml of the produced liquid of the test oil reservoir is added, and the activator is added; then the container is placed in the test oil reservoir temperature for 45-90d; the CH4 gas production of the culture bottle is measured to determine the formula of the CH4 producing bacteria activator.

6. A method for enhancing recovery of fractured block reservoirs by using microbial gas cap, as claimed in claim 5 wherein, In the step (2), the CH4 producing bacteria activator is composed of carbon source, nitrogen source and phosphorus source, the carbon source is at least one of glucose, sucrose, maltose, glycerol and corn powder, the nitrogen source is at least one of ammonium nitrate, urea, beef extract and peptone, and the phosphorus source is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phospholipid, calcium hydrogen phosphate, aluminum phosphate and superphosphate of calcium phosphate.

7. A method for enhancing recovery of fractured block reservoirs by using microbial gas cap, as claimed in claim 6 wherein, In the step (2), the mass concentration of the carbon source, nitrogen source and phosphorus source of the CH4 producing bacteria activator is 1.0-4.0%, 0.2-0.8% and 0.05-0.2% respectively.

8. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 7, wherein, In the step (2), the mass concentration of the carbon source, nitrogen source and phosphorus source of the CH4 producing bacteria activator is 2.0-3.0%, 0.3-0.6% and 0.05-0.1% respectively.

9. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 8, wherein, In the step (2), the method for determining the injection concentration of the CH4 producing bacteria activator is as follows:

10. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 9, wherein, A reaction container with a volume of 100-200ml is taken, 50-60ml of the produced liquid of the test oil reservoir is added, and the selected activator formula with a concentration of 1-5% is added; then the container is placed in the test oil reservoir temperature for 45-90d; the CH4 gas production of the culture bottle is measured to determine the injection concentration of the CH4 producing bacteria activator. In the step (2), the optimization of the CH4 producing bacteria activator in the oil reservoir includes the optimization of the injection concentration. In the step (3), the polymer producing activator is composed of carbon source, nitrogen source and phosphorus source, the carbon source is at least one of glucose, sucrose, maltose, glycerol and corn powder, the nitrogen source is at least one of ammonium nitrate, urea, beef extract and peptone, and the phosphorus source is at least one of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phospholipid, calcium hydrogen phosphate, aluminum phosphate and superphosphate of calcium phosphate. In the step (3), the mass concentration of the carbon source, nitrogen source and phosphorus source of the activator is 1.0-5.0%, 0.3-1.0% and 0.03-0.1% respectively.

11. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 10, wherein, In the step (3), the mass concentration of the carbon source, nitrogen source and phosphorus source of the activator is 2.0-4.0%, 0.5-0.8% and 0.05-0.08% respectively.

12. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 11, wherein, In the step (3), the method for screening the polymer producing bacteria activator includes screening the polymer producing bacteria suitable for the selected oil reservoir and screening the corresponding activator.

13. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 12, wherein, In the step (3), the method for screening the polymer producing bacteria suitable for the selected oil reservoir includes:

14. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 13, wherein, ​ 15. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 1, wherein, ​ 16. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 15, wherein, ​ In the reaction vessel, 50-60 mL of the test oil reservoir production fluid is added, 1-6 mL of the polymer-producing bacteria and activator mixture at the appropriate reservoir temperature is added, wherein the bacteria solution accounts for 5-20%; then it is placed at the test reservoir temperature for 10-30 days; the viscosity of the mixture is tested, and the polymer-producing bacteria species with the highest viscosity at 50°C is selected.

17. A method for enhanced recovery of oil from a fault block reservoir using microbial gas cap according to claim 16, wherein, In the step (3), the polymer-producing microorganism is one or several of Pseudomonas, Alcaligenes, Aureobasidium pullulans, citric acid fermentation waste mycelium, Aspergillus niger, and Acidoxobacter xylinus.

18. A method for enhanced recovery of oil from a fault block reservoir using microbial gas cap according to claim 17, wherein, In the step (3), the method for screening the corresponding activator includes: Multiple 50-60 mL of the test oil reservoir production fluid is taken, 1-3 mL of the previously selected polymer-producing microorganism is added to each, and then different activators of the same concentration are added; then they are respectively placed at the test wellbore temperature for 5-15 days; the polymer-producing bacteria concentration in the different culture solutions is determined, and the activator formulation is selected according to the bacteria concentration.

19. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 1, wherein, In the step (5), the adjustment scheme includes: performing field test according to the process parameters determined in step (4), and formulating the adjustment scheme.

20. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 1, wherein, In the step (5), the effect evaluation includes: evaluating the field test effect after the experiment, and the evaluation indexes include: oil increment, input-output ratio, and effective period.

21. A method for enhancing recovery of fractured block reservoirs using microbial gas cap, as claimed in claim 1, wherein, In the step (5), the formulation of the adjustment scheme includes: If the oil reservoir static pressure is still lower than 0.3 MPa within six months, the activator activation effect is poor due to the adsorption and dilution of the oil reservoir, and the injection concentration of the gas-producing activator needs to be increased; If the gas-oil ratio of some oil wells increases by more than 10 times, it indicates that the gas channeling is serious, and the profile control means needs to be used to plug the gas channeling channel, and then the method is used for injection after plugging.

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