CN110819336A - Nitrogen foam fracturing fluid for fracturing coal bed methane reservoir and preparation method thereof - Google Patents
Nitrogen foam fracturing fluid for fracturing coal bed methane reservoir and preparation method thereof Download PDFInfo
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- CN110819336A CN110819336A CN201910923379.6A CN201910923379A CN110819336A CN 110819336 A CN110819336 A CN 110819336A CN 201910923379 A CN201910923379 A CN 201910923379A CN 110819336 A CN110819336 A CN 110819336A
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/70—Compositions for forming crevices or fractures characterised by their form or by the form of their components, e.g. foams
- C09K8/703—Foams
Abstract
The invention belongs to the field of oil and gas resource development, and particularly relates to a nitrogen foam fracturing fluid for coal bed methane reservoir fracturing and a preparation method thereof. The nitrogen foam fracturing fluid for fracturing the coal bed gas reservoir comprises the following volume components under the bottom working condition of the coal bed gas well: nitrogen gas: 60% -90%; foaming agent aqueous solution: 40% -10%; wherein, the foaming agent aqueous solution is a mixed liquid, and the weight components are as follows: water: 94.9% -90.9%; foaming agent: 1 percent; foam stabilizer: 2 percent; and (3) bactericide: 0.1 percent; a cleanup additive: 1% -2%; an anti-swelling agent: 1% -2%. The nitrogen foam fracturing fluid for fracturing the coal bed gas reservoir is suitable for hydraulic fracturing of the coal bed gas reservoir, the oil reservoir and the gas reservoir, has no solid phase residue, small reservoir damage, small filtration loss, long crack formation, strong sand carrying capacity, less liquid consumption, reduction of more than 50 percent and quick gas observation; the preparation steps are simple and the operability is strong.
Description
Technical Field
The invention belongs to the field of oil and gas resource development, and particularly relates to a nitrogen foam fracturing fluid for coal bed methane reservoir fracturing and a preparation method thereof.
Background
Coal bed gas, commonly known as "gas", is an associated resource in coal, and the main component of the coal bed gas is methane. The coal bed gas exists in two states of dissociation and adsorption in the coal rock mineral deposit, wherein the coal bed gas existing in the adsorption state is mainly used, so that the problems of low single well yield, low recovery ratio and the like of the coal bed gas well are prominent. Meanwhile, because coal bed gas cannot be effectively extracted, gas explosion accidents occur frequently in the coal mining process, and the gas explosion accidents become main factors threatening the safe and efficient utilization of coal resources in China. The method for improving the coal bed gas reservoir by hydraulic fracturing is one of the main ways for increasing the yield and the recovery ratio of the coal bed gas well, and is widely popularized and applied in the world at present. Common fracturing fluids for hydraulic fracturing of coal bed gas are: active water, jelly and linear gel fracturing fluid. The following technical problems exist when the fracturing fluid is used for fracturing the coal bed gas reservoir:
1. the reservoir damage is large. Due to the fact that the active water, the jelly glue and the linear gel fracturing fluid contain various chemical substances and complex components, the fracturing fluid and fluid in the coal bed gas reservoir are incompatible, and emulsion is generated. The emulsions can generate Jamin reaction when passing through the capillary and the pore throat, so that the capillary and the pore throat are blocked, the permeability of the coal bed gas reservoir is reduced, and the reservoir damage is caused. Meanwhile, solid phase components in the active water, the jelly and the linear gel fracturing fluid can be separated out and precipitated in the migration process of the fracturing fluid, so that a seepage channel is blocked, and the damage to a reservoir stratum is aggravated.
2. The size of the seam is small, and the yield increasing effect is not obvious. The compressibility of active water, gel and linear gel fracturing fluid is poor, the thickness of a coal bed gas reservoir is small, the strength is low, the release speed of energy carried in the fracturing fluid is high in the hydraulic fracturing process, so that formed cracks quickly penetrate through the whole coal bed gas reservoir to cause the leakage of the fracturing fluid, the size of finally formed cracks is small, a network cannot be formed, and the yield increasing effect is not obvious.
3. The liquid drainage time is long. Because active water, gel and linear gel fracturing fluid are adopted to carry out fracturing on the coal bed gas reservoir, a large amount of fracturing fluid needs to be injected into a stratum, and meanwhile, the near-well stratum is polluted by the fracturing fluid, so that the drainage time after fracturing is finished is longer, generally needs 7-8 months, and the construction period and the cost are obviously increased.
Therefore, the invention provides a preparation method of a nitrogen foam fracturing fluid for coal bed gas reservoir fracturing, solves the technical problems of active water, gel and linear gel fracturing fluid in the current coal bed gas reservoir fracturing process, and provides technical guarantee for improving the single well yield and recovery ratio of a coal bed gas well.
Disclosure of Invention
Aiming at the defects of large reservoir damage, small seam size, insignificant yield increasing effect and long liquid discharge time of active water, gel fracturing and linear gel fracturing fluid for hydraulic fracturing of a coal bed gas reservoir in the fracturing process, the invention provides a preparation method of nitrogen foam fracturing fluid for fracturing of the coal bed gas reservoir, which is used for overcoming the defects of the active water, the gel and the linear gel fracturing fluid and increasing the single well yield and the accumulated recovery ratio after fracturing of the coal bed gas reservoir.
In order to achieve the purpose, the invention adopts the following technical scheme:
the nitrogen foam fracturing fluid for fracturing the coal bed gas reservoir comprises the following volume components under the bottom working condition of the coal bed gas well:
nitrogen gas: 60% -90%;
foaming agent aqueous solution: 40% -10%.
Wherein, the foaming agent aqueous solution is a mixed liquid, and the weight components are as follows:
water: 94.9% -90.9%;
foaming agent: 1 percent;
foam stabilizer: 2 percent;
and (3) bactericide: 0.1 percent;
a cleanup additive: 1% -2%;
an anti-swelling agent: 1% -2%.
Compared with the prior art, the invention has the following beneficial effects: the invention is suitable for the hydraulic fracturing of coal bed gas reservoirs, oil reservoirs and gas reservoirs; no solid phase residue, small reservoir damage, small filtration loss, long seam making, strong sand carrying capacity, less liquid consumption (reduced by more than 50 percent), and quick gas generation; the preparation steps are simple and the operability is strong.
Detailed Description
The nitrogen foam fracturing fluid for fracturing the coal bed gas reservoir has the volume components as follows under the bottom hole working conditions (pressure and temperature) of the coal bed gas well, wherein the bottom hole pressure is 8MPa and the temperature is 52 ℃ for the embodiment:
nitrogen gas: 60% -90% of the foam used for filling the foam in the nitrogen foam fracturing fluid;
foaming agent aqueous solution: 40% -10% for generating the foam outer wall.
Wherein, the foaming agent aqueous solution is a mixed liquid, and the weight components are as follows:
water: 94.9-90.9 percent of the total weight of the mixture, and is used for dissolving the foaming agent, the foam stabilizer, the bactericide, the cleanup additive and the anti-swelling agent to form a uniform aqueous solution;
foaming agent: 1% for generating foam;
foam stabilizer: 2 percent of the total amount of the additive is used for stabilizing foam and prolonging the retention time of the foam;
and (3) bactericide: 0.1 percent of the total ammonia content, is used for killing bacteria in water and coal bed gas reservoirs and preventing harmful gas from being generated and corroding operation and production strings;
a cleanup additive: 1% -2% of the pressure-cracking operation, and the nitrogen foam pressure-cracking liquid is used for accelerating the discharge of the pressure-cracking operation from the coal bed gas reservoir;
an anti-swelling agent: 1% -2% of the permeability, and is used for preventing the coal bed gas reservoir from swelling and reducing the permeability of the coal bed gas reservoir.
The preparation method of the nitrogen foam fracturing fluid for fracturing the coal bed methane reservoir comprises the following steps:
s1, preparing the materials according to the mixture ratio
Preparing a storage tank with the volume of 40-50 m for carrying out the dry distillation, cleaning the interior of the storage tank, and injecting clear water with the volume of 95% of that of the storage tank into the storage tank; preparing a foaming agent, a foam stabilizer, a bactericide, a discharge aiding agent and an anti-swelling agent according to the weight of clear water, wherein the mass contents of the foaming agent, the foam stabilizer, the bactericide, the discharge aiding agent and the anti-swelling agent are respectively 1%, 2%, 0.1%, 1-2% and 1-2%; the foaming agent, the foam stabilizer, the bactericide, the cleanup additive and the anti-swelling agent are subjected to quality detection, and can be used after being qualified;
the detection quality requirements are as follows:
water: clean water having a pH equal to 7;
foaming agent: the ingredient is sodium dodecyl sulfate, the effective content of the liquid foaming agent is not less than 45 percent, and the foaming volume of the foaming agent (the volume of foam generated by 100ml of foaming agent aqueous solution) is not less than 500 ml;
foam stabilizer: the components are a sulfur agent and a high molecular polymer, the effective content of the liquid foam stabilizer is not less than 50%, and the effective content of the solid foam stabilizer is not less than 98%; the foam stabilizer can prolong the half life of foam liquid separation to be not less than 30 minutes and keep the foam stabilization time to be not less than 500 minutes under the conditions of 25 ℃ and 10MPa pressure; the generated foam has the temperature resistance of not less than 45 ℃, the salinity resistance of not less than 20 PPM, the tolerable pH range of 6-8, the damping factor of not less than 20 and the surface tension of not more than 26 mn/s.
And (3) bactericide: the component is quaternary ammonium salt cation, and the effective content in the liquid bactericide is not lower than 85 percent; the sterilizing rate of the bactericide is not less than 99.9 percent, and the bacteriostasis time is not less than 12 hours.
A cleanup additive: the liquid cleanup additive contains betaine, and the effective content of the liquid cleanup additive is not lower than 15%; the cleanup additive reduces the surface interfacial tension of the nitrogen foam fracturing fluid to be not more than 1mn/m and the surface tension to be not more than 28 mn/m;
an anti-swelling agent: the components are small cationic polymer and choline chloride, and the effective content of the liquid anti-swelling agent is not less than 28 percent; the expansion-preventing agent can reduce the expansion rate of clay in the stratum by not less than 85 percent;
s2, adding bactericide, anti-swelling agent, discharge assistant and foam stabilizer
The quality of the bactericide, the anti-swelling agent, the discharge aiding agent and the foam stabilizer is detected, and the bactericide, the anti-swelling agent, the discharge aiding agent and the foam stabilizer can be used after being qualified; and (3) sequentially adding the bactericide, the anti-swelling agent, the discharge aiding agent and the foam stabilizer into the clear water of the storage tank, and uniformly mixing until no solid substance is deposited at the bottom of the tank.
S3, adding foaming agent
Adding a foaming agent into a storage tank at one time according to the proportion of 1%, standing for more than 12 hours, and preparing a foaming agent aqueous solution; and sampling the foaming agent aqueous solution for detection, and using the foaming agent aqueous solution after the foaming agent aqueous solution is qualified.
S4, adding nitrogen to form nitrogen foam fracturing fluid
Respectively injecting a foaming agent water solution and nitrogen into a foam generator according to a designed proportion to generate nitrogen foam fracturing fluid; the purity of the nitrogen is not less than 99.5 percent (the effective content of the nitrogen); under the bottom working condition of the coal bed gas well (pressure and temperature, in the embodiment, the bottom pressure is 8MPa, and the temperature is 52 ℃), the ratio of the gas volume in the nitrogen foam fracturing fluid to the foam fluid volume is 60-90%; the foam particles are uniform in size, and the ratio of spheres with the diameter of 30-50 microns is more than 80%; the viscosity of the nitrogen foam fracturing fluid is not lower than 500mPas, the half-life of the fluid is not less than 30 minutes, and the foam stabilizing time is not less than 500 minutes.
The method for exploiting the coal bed gas by adopting the nitrogen foam fracturing fluid for fracturing the coal bed gas reservoir comprises the following steps of:
s1, determining the total volume and the total sand adding amount of the required nitrogen foam fracturing fluid according to the design scheme, and preparing sufficient nitrogen foam fracturing fluid and sand; injecting the nitrogen foam fracturing fluid into a coal bed gas fracturing construction operation shaft by using a fracturing pump truck;
s2, adding sand to the nitrogen foam fracturing fluid in stages by a sand adding vehicle according to the requirements of a design scheme, wherein the mass percent of the sand added in the first stage is 10%, the mass percent of the sand added in each stage is increased by 5-10%, and the mass percent of the sand added at the maximum is not more than 40%; the sand adding amount of each stage is determined according to the requirements on the design scheme;
s3, determining the injection displacement, the total injection volume, the sand adding mass percentage and the sand adding amount of the nitrogen foam fracturing fluid at each stage according to the design scheme requirement, and completing the injection of the nitrogen foam fracturing fluid;
s4, stopping adding sand, adding a defoaming agent into the nitrogen foam fracturing fluid, wherein the mass of the defoaming agent is 4% of that of the displacement fluid, generating the displacement fluid, and continuously injecting the displacement fluid into the shaft to the designed amount; the defoaming agent component is polydimethylsiloxane, the defoaming time is not more than 15 seconds, and the foaming inhibition time is not less than 17 minutes.
And S5, pulling out the fracturing operation pipe column to finish the fracturing operation.
The invention provides a preparation method of nitrogen foam fracturing fluid for coal bed methane reservoir fracturing, and the method has the advantages of clear operation steps and clear parameter value range; the prepared nitrogen foam fracturing fluid has good fracturing effect, and can obviously improve the single well yield and the cumulative recovery ratio of the coal bed gas well.
Claims (4)
1. A nitrogen foam fracturing fluid for fracturing a coal bed gas reservoir comprises the following volume components under the bottom working condition of a coal bed gas well: nitrogen gas: 60% -90%; foaming agent aqueous solution: 40% -10%; the method is characterized in that:
the foaming agent aqueous solution is a mixed liquid and comprises the following components in parts by weight:
water: 94.9% -90.9%;
foaming agent: 1 percent;
foam stabilizer: 2 percent;
and (3) bactericide: 0.1 percent;
a cleanup additive: 1% -2%;
an anti-swelling agent: 1% -2%.
2. The nitrogen foam fracturing fluid for fracturing the coal bed methane reservoir as claimed in claim 1, wherein the bottom working condition of the coal bed methane well is that the bottom pressure is 8MPa and the temperature is 52 ℃.
3. The method for preparing the nitrogen foam fracturing fluid for fracturing the coalbed methane reservoir, which is characterized by comprising the following steps of:
s1, preparing the materials according to the mixture ratio
Preparing a storage tank with the volume of 40-50 m for carrying out the dry distillation, cleaning the interior of the storage tank, and injecting clear water with the volume of 95% of that of the storage tank into the storage tank; preparing a foaming agent, a foam stabilizer, a bactericide, a discharge assistant and an anti-swelling agent according to the weight of clear water, and performing quality detection on the foaming agent, the foam stabilizer, the bactericide, the discharge assistant and the anti-swelling agent, wherein the detection quality requirements are as follows:
water: clean water having a pH equal to 7;
foaming agent: the component is lauryl sodium sulfate, the effective content of the liquid foaming agent is not less than 45 percent, and the foaming volume of the foaming agent is not less than 500 ml;
foam stabilizer: the components are a sulfur agent and a high molecular polymer, the effective content of the liquid foam stabilizer is not less than 50%, and the effective content of the solid foam stabilizer is not less than 98%; the foam stabilizer can prolong the half life of foam liquid separation to be not less than 30 minutes and keep the foam stabilization time to be not less than 500 minutes under the conditions of 25 ℃ and 10MPa pressure; the generated foam has the temperature resistance of not less than 45 ℃, the salinity resistance of not less than 20 PPM, the tolerable pH range of 6-8, the damping factor of not less than 20 and the surface tension of not more than 26 mn/s;
and (3) bactericide: the component is quaternary ammonium salt cation, and the effective content in the liquid bactericide is not lower than 85 percent; the degerming rate of the bactericide is not less than 99.9 percent, and the bacteriostasis time is not less than 12 hours;
a cleanup additive: the liquid cleanup additive contains betaine, and the effective content of the liquid cleanup additive is not lower than 15%; the cleanup additive reduces the surface interfacial tension of the nitrogen foam fracturing fluid to be not more than 1mn/m and the surface tension to be not more than 28 mn/m;
an anti-swelling agent: the components are small cationic polymer and choline chloride, and the effective content of the liquid anti-swelling agent is not less than 28 percent; the expansion-preventing agent can reduce the expansion rate of clay in the stratum by not less than 85 percent;
s2, adding bactericide, anti-swelling agent, discharge assistant and foam stabilizer
The quality of the bactericide, the anti-swelling agent, the discharge aiding agent and the foam stabilizer is detected, and the bactericide, the anti-swelling agent, the discharge aiding agent and the foam stabilizer can be used after being qualified; sequentially adding a bactericide, an anti-swelling agent, a discharge aiding agent and a foam stabilizer into the clear water of the storage tank, and uniformly mixing until no solid substance is deposited at the bottom of the tank;
s3, adding foaming agent
Adding a foaming agent into a storage tank at one time according to the proportion of 1%, standing for more than 12 hours, and preparing a foaming agent aqueous solution; sampling the foaming agent aqueous solution for detection, and using the foaming agent aqueous solution after the foaming agent aqueous solution is qualified;
s4, adding nitrogen to form nitrogen foam fracturing fluid
Respectively injecting a foaming agent water solution and nitrogen into a foam generator according to a designed proportion to generate nitrogen foam fracturing fluid; the purity of the nitrogen is not less than 99.5 percent; the ratio of the gas volume in the nitrogen foam fracturing fluid to the foam fluid volume is 60-90% under the bottom working condition of the coal bed gas well; the foam particles are uniform in size, and the ratio of spheres with the diameter of 30-50 microns is more than 80%; the viscosity of the nitrogen foam fracturing fluid is not lower than 500mPas, the half-life of the fluid is not less than 30 minutes, and the foam stabilizing time is not less than 500 minutes.
4. A method for exploiting coal bed gas by using the nitrogen foam fracturing fluid for fracturing a coal bed gas reservoir as defined in claims 1-2, which comprises the following steps:
s1, determining the total volume and the total sand adding amount of the required nitrogen foam fracturing fluid according to the design scheme, and preparing sufficient nitrogen foam fracturing fluid and sand; injecting the nitrogen foam fracturing fluid into a coal bed gas fracturing construction operation shaft by using a fracturing pump truck;
s2, adding sand to the nitrogen foam fracturing fluid in stages by a sand adding vehicle according to the requirements of a design scheme, wherein the mass percent of the sand added in the first stage is 10%, the mass percent of the sand added in each stage is increased by 5-10%, and the mass percent of the sand added at the maximum is not more than 40%; the sand adding amount of each stage is determined according to the requirements on the design scheme;
s3, determining the injection displacement, the total injection volume, the sand adding mass percentage and the sand adding amount of the nitrogen foam fracturing fluid at each stage according to the design scheme requirement, and completing the injection of the nitrogen foam fracturing fluid;
s4, stopping adding sand, adding a defoaming agent into the nitrogen foam fracturing fluid, wherein the mass of the defoaming agent is 4% of that of the displacement fluid, generating the displacement fluid, and continuously injecting the displacement fluid into the shaft to the designed amount; the defoaming agent component is polydimethylsiloxane oil, the defoaming time is not more than 15 seconds, and the foaming inhibition time is not less than 17 minutes;
and S5, pulling out the fracturing operation pipe column to finish the fracturing operation.
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| CN201910923379.6A CN110819336A (en) | 2019-09-27 | 2019-09-27 | Nitrogen foam fracturing fluid for fracturing coal bed methane reservoir and preparation method thereof |
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