阅读说明：本技术 一种用于低压气井中的低伤害压井液及配置方法 (Low-damage well killing fluid for low-pressure gas well and preparation method ) 是由 蒋文学 万向辉 李勇 吴增智 郑维师 陈平 金娜 王坤 谭欢 黄永章 武月荣 于 2019-12-04 设计创作，主要内容包括：本发明涉及低压气井增产改造和储层保护技术领域,具体涉及一种用于低压气井中的低伤害压井液及配置方法,通过以重量百分比计,其组分为：可降解暂堵颗粒：10-20％；携带液：4-6％；解除剂：3-5％；其余为水。采用本发明可实现低压气井低伤害压井作业,压井液中的液相通过粘性增加携带固相颗粒,降低液体滤失,同时清洗近井筒有机和无机堵塞物,压井液中的固相颗粒通过组合桥架、自粘合形成高强度,强封堵段塞体,完成压井作业后自降解。低伤害压井液可提高修井作业效率,降低压井液滤失量,提高储层近井筒渗透性,达到低压气井低伤害压井作业的增产目的。(The invention relates to the technical field of low-pressure gas well production-increasing transformation and reservoir protection, in particular to a low-damage well killing fluid for a low-pressure gas well and a preparation method thereof, wherein the low-damage well killing fluid comprises the following components in percentage by weight: degradable temporary plugging particles: 10 to 20 percent; carrying fluid: 4 to 6 percent; a releasing agent: 3 to 5 percent; the balance of water. The invention can realize low-damage well killing operation of a low-pressure gas well, liquid phase in well killing fluid carries solid-phase particles through viscosity increase, the fluid filtration loss is reduced, organic and inorganic plugs close to a shaft are cleaned, the solid-phase particles in the well killing fluid form a high-strength and strong-plugging section plug body through a combined bridge frame and self-adhesion, and the self-degradation is realized after the well killing operation is completed. The low-damage well killing fluid can improve the efficiency of workover operation, reduce the filtration loss of the well killing fluid, improve the permeability of a reservoir near a shaft and achieve the purpose of increasing the yield of low-damage well killing operation of a low-pressure gas well.)

1. A low damage well killing fluid for a low pressure gas well is characterized in that: the composite material comprises the following components in percentage by weight: degradable temporary plugging particles: 10 to 20 percent; carrying fluid: 4 to 6 percent; a releasing agent: 3 to 5 percent; the balance of water.

2. A low damage kill fluid for use in low pressure gas wells as defined in claim 1 wherein: the degradable temporary plugging particles comprise the following components in percentage by weight of the particles:

a main agent: 45 to 65 percent;

auxiliary agents: 15 to 25 percent;

a crosslinking agent: 5 to 10 percent;

degradation promoting agent: 5 to 10 percent;

antioxidant: 4 to 6 percent;

curing agent: 4 to 6 percent;

initiator: 2 to 4 percent.

3. A low damage kill fluid for use in low pressure gas wells as claimed in claim 2 wherein: the main agent comprises the following components in percentage by weight:

40-50% of polyethylmethacrylate;

10-15% of acrylonitrile-methyl acrylate copolymer;

the content of polyethylene glycol diacrylate is 40-45%.

4. A low damage kill fluid for use in low pressure gas wells as claimed in claim 2 wherein: the molecular weight of the polyethylene glycol diacrylate is 6000-8000.

5. A low damage kill fluid for use in low pressure gas wells as claimed in claim 3 wherein: the monomer molar ratio of acrylonitrile monomer to methyl acrylate in the acrylonitrile-methyl acrylate copolymer is 2: 5.

6. A low damage kill fluid for use in low pressure gas wells as claimed in claim 2 wherein: the auxiliary agent is as follows: 2-hydroxy-1, 4-naphthoquinone;

the cross-linking agent is: one or a mixture of methoxyethyl acrylate or 2-propylheptyl acrylate;

the degradation promoting agent is: one or a mixture of diisobutyl ketone or 4-methyl-2-pentanone;

the antioxidant is: one or a mixture of dibutyltin maleate or lead salicylate;

the curing agent is: one or a mixture of cobalt naphthenate or cobalt octoate;

the initiator is as follows: one or a mixture of dimethylaniline or methylaniline.

7. A low damage kill fluid for use in low pressure gas wells as defined in claim 1 wherein: the carrying fluid is as follows: 4-6% of tallow amine polyoxyethylene ether and 1-2% of tallow dihydroxyethyl betaine by weight percentage.

8. A low damage kill fluid for use in low pressure gas wells as defined in claim 1 wherein: the remover is as follows: 3-5% of sulfamic acid and glycolic acid, wherein the weight percentage of sulfamic acid is 1-2%, and the weight percentage of glycolic acid is 2-3%.

9. A method of deploying a low damage kill fluid for use in a low pressure gas well comprising the use of a low damage kill fluid for use in a low pressure gas well as claimed in any one of claims 1 to 8, wherein: comprises the following steps

The method comprises the following steps: adding all water into a stirring tank of a ground sand mixing truck, firstly adding a release agent with a formula amount, and stirring for 5min at a stirring speed of 100 r/min;

step two: on the basis of the first step, adding the carrying fluid with the formula amount, controlling the stirring speed of 60r/min, and stirring for 2 min;

step three: on the basis of the second step, after stirring for 2min, slowly adding the degradable temporary plugging particles in the formula amount, keeping the stirring speed of 100r/min, and stirring for 3 min;

step four: and on the basis of the third step, directly supplying the mixture to a cement pump truck after stirring for 3min, pumping the low-damage well killing fluid into the stratum at the speed of 400L/min by the cement pump truck, keeping the pressure rising all the time in the pumping process, stopping when the pressure rises to the safety pressure limit of the cement pump truck, keeping the pressure stabilization for 30min, and finishing the well killing construction.

Technical Field

The invention relates to the technical field of low-pressure gas well production increasing transformation and reservoir protection, in particular to low-damage well killing fluid for a low-pressure gas well and a preparation method thereof.

Background

In the production and development process of the gas well, along with the extraction of natural gas, the energy of a near-wellbore region is slowly reduced, the bound water in the stratum is converted into flowing state due to the reduction of pressure, the stratum water is extracted along with the natural gas, and the stratum energy is reduced, so that the well is changed into a low-pressure gas well. The reasonable development of the low-pressure gas well still has higher industrial value, and the low-pressure gas well is mainly subjected to secondary well repair measures at present to improve the single-well productivity. The main problem faced during workover is how to control damage to the workover.

In the process of workover operation of a low-pressure gas well, due to the reasons of low formation pressure, water production, scaling of a near wellbore of a reservoir and the like, a great deal of filtration loss of a well killing fluid is often caused, so that the well killing fluid is seeped into the reservoir to cause secondary damage of the reservoir, meanwhile, the filtration loss of the reservoir by the well killing fluid causes unbalance of the liquid level of the wellbore of the gas well, and a great well control risk exists.

Chinese patent No. CN104946221A, 2015, 9, 30 discloses a low-density and low-damage well killing fluid, which comprises, by weight, 5-35% of a density regulator, 0.2-5% of a fluid loss agent, 0.1-0.5% of a colloid protective agent and the balance of water with the mineralization degree of 0-20 ppm, wherein the density regulator comprises 0.02-0.2 part of a foaming agent, 0.01-0.05 part of a foam stabilizer, 1.0-5.0 parts of a shielding temporary plugging agent, 0.1-0.5 part of sodium silicate glass, 0-5.0 parts of silicon aluminum oxide and 0-10.0 parts of bentonite. The invention has the characteristics of good temporary plugging performance, low filtration loss, moderate viscosity, quick and thorough flowback, small friction resistance, easy pumping and the like, and solves the problems of difficult liquid drainage, serious stratum damage, difficult recovery of productivity and the like caused by the conventional working fluid to the stratum with low productivity and large leakage; the present invention can be widely used for the production increasing measures of drilling, well completion, well repair and oil and gas wells of low-pressure, easy-to-leak, water-sensitive and acid-sensitive stratums. Chinese patent No. CN103131402A, 6 months and 5 days 2013, discloses a high-temperature-resistant solid-free low-damage well killing fluid and a preparation method thereof, and belongs to the field of petroleum and natural gas exploration and development. The high-temperature-resistant solid-free low-damage well killing fluid disclosed by the invention comprises the following components: the multifunctional polymer comprises modified lignite, water-soluble cellulose ether derivatives, a high-temperature corrosion inhibition stabilizer, an organic salt weighting agent and water, and the mass percentage of each component is as follows: 0.3-2% of multifunctional polymer, 0.5-5% of modified lignite, 0.3-2% of water-soluble cellulose ether derivative, 0.01-0.3% of high-temperature corrosion inhibition stabilizer, and the dosage of the organic salt weighting agent is controlled to ensure that the density of the well killing fluid reaches 1.0g/cm 3-2.3 g/cm3, and the balance is water. The well killing fluid has low filtration loss and thin filter cake, protects the stratum environment from being polluted and damaged, ensures that the viscosity of the well killing fluid is kept more than half under the condition of high-temperature stratum shearing for a long time, and has the functions of expansion prevention and corrosion inhibition.

The low-damage well killing fluid represented by the patent is mainly used for reducing the filtration loss and density adjustment of the polymer, reducing the filtration loss of the well killing fluid and reducing the damage of the well killing fluid to a reservoir layer by quickly discharging the well killing fluid back into the reservoir layer. But the method is not suitable for low-pressure gas wells, because the low-pressure gas well of a low-permeability reservoir is subjected to fracturing modification in the early stage, the pressure coefficient of part of the gas well is as low as about 0.2-0.4, the amount of a reservoir fracture space is huge, a large amount of filtration loss of the well killing fluid cannot be prevented by means of density adjustment and shielding temporary plugging agents, and a foaming agent in the simple well killing fluid cannot meet the requirement of flowback of the well killing fluid due to the extremely low formation pressure coefficient. The well killing fluid can not remove the scaling blockage of the front near wellbore zone, and the additional introduction of working fluid with other mineralization degrees can aggravate the scaling blockage of the near wellbore zone. When the filter cake generated by the high molecular polymer or starch filtrate reducer on the wall surface of the crack reaches the plugging pressure balance, the gas channeling well control risk is high, great damage and decrement are brought to the later-stage reservoir protection and productivity of the low-pressure gas well, and even the risk of no yield after the well killing of the low-pressure gas well is brought. The method aims to improve the working efficiency of the killing fluid of the low-pressure gas well, reduce the filtration loss of the killing fluid in a reservoir and the well control risk in the working process, reduce the damage of the killing fluid to the reservoir, improve the reservoir protection of the killing fluid and the permeability of a near wellbore of the reservoir and improve the integral recovery ratio of the gas reservoir. There is a need to develop a low-damage well killing fluid which can better solve the above problems, and meet the requirements of low-damage well repairing technology development of low-pressure gas wells.

Disclosure of Invention

The invention overcomes the defects of the prior art, provides the low-damage well killing fluid for the low-pressure gas well and the preparation method thereof, and particularly has the characteristics of improving the working efficiency of the well killing fluid of the low-pressure gas well, reducing the filtration loss of the well killing fluid in a reservoir and the well control risk in the working process, reducing the damage of the well killing fluid to the reservoir, improving the reservoir protection of the well killing fluid and the permeability of a near wellbore of the reservoir, and improving the overall recovery ratio of the gas reservoir.

The technical problem solved by the invention can be realized by adopting the following technical scheme:

a low damage well killing fluid for a low pressure gas well comprises the following components in percentage by weight: degradable temporary plugging particles: 10 to 20 percent; carrying fluid: 4 to 6 percent; a releasing agent: 3 to 5 percent; the balance of water.

The degradable temporary plugging particles comprise the following components in percentage by weight of the particles:

a main agent: 45 to 65 percent;

auxiliary agents: 15 to 25 percent;

a crosslinking agent: 5 to 10 percent;

degradation promoting agent: 5 to 10 percent;

antioxidant: 4 to 6 percent;

curing agent: 4 to 6 percent;

initiator: 2 to 4 percent.

The main agent comprises the following components in percentage by weight:

40-50% of polyethylmethacrylate;

10-15% of acrylonitrile-methyl acrylate copolymer;

the content of polyethylene glycol diacrylate is 40-45%.

The molecular weight of the polyethylene glycol diacrylate is 6000-8000.

The monomer molar ratio of acrylonitrile monomer to methyl acrylate in the acrylonitrile-methyl acrylate copolymer is 2: 5.

The auxiliary agent is as follows: 2-hydroxy-1, 4-naphthoquinone;

the cross-linking agent is: one or a mixture of methoxyethyl acrylate or 2-propylheptyl acrylate;

the degradation promoting agent is: one or a mixture of diisobutyl ketone or 4-methyl-2-pentanone;

the antioxidant is: one or a mixture of dibutyltin maleate or lead salicylate;

the curing agent is: one or a mixture of cobalt naphthenate or cobalt octoate;

the initiator is as follows: one or a mixture of dimethylaniline or methylaniline.

The carrying fluid is as follows: 4-6% of tallow amine polyoxyethylene ether and 1-2% of tallow dihydroxyethyl betaine by weight percentage.

The remover is as follows: 3-5% of sulfamic acid and glycolic acid, wherein the weight percentage of sulfamic acid is 1-2%, and the weight percentage of glycolic acid is 2-3%.

A method for preparing low-damage well killing fluid for a low-pressure gas well comprises any one of the steps of

The method comprises the following steps: adding all water into a stirring tank of a ground sand mixing truck, firstly adding a release agent with a formula amount, and stirring for 5min at a stirring speed of 100 r/min;

step two: on the basis of the first step, adding the carrying fluid with the formula amount, controlling the stirring speed of 60r/min, and stirring for 2 min;

step three: on the basis of the second step, after stirring for 2min, slowly adding the degradable temporary plugging particles in the formula amount, keeping the stirring speed of 100r/min, and stirring for 3 min;

step four: and on the basis of the third step, directly supplying the mixture to a cement pump truck after stirring for 3min, pumping the low-damage well killing fluid into the stratum at the speed of 400L/min by the cement pump truck, keeping the pressure rising all the time in the pumping process, stopping when the pressure rises to the safety pressure limit of the cement pump truck, keeping the pressure stabilization for 30min, and finishing the well killing construction.

The invention has the beneficial effects that:

compared with the prior art, the invention comprises the following steps:

1. the liquid phase of the low-damage well killing fluid for the low-pressure gas well has the characteristic of automatic viscosity change. The synergistic effect of two surfactants, i.e. tallow amine polyoxyethylene ether and tallow dihydroxy ethyl betaine, in the carrying fluid is mainly used for thickening and viscosity changing, and the tallow amine polyoxyethylene ether has good emulsifying and thickening performances and is dispersed in water; the tallow dihydroxyethyl betaine is a zwitterionic surfactant, has excellent stability under acidic and alkaline conditions, is combined in an aqueous solution through intermolecular hydrogen bonds and van der Waals force, is thickened by molecular winding in water, and is subjected to temperature change and viscosity increase. The viscosity of the well killing fluid in a shaft is increased, the gas invasion phenomenon in the well killing process is reduced, solid-phase particles can be well carried, the turbulent flow state of the solid-phase particles which are low in harm to the well killing fluid in the pumping process can be reduced, and the plugging of the solid-phase particles to cracks and blastholes is facilitated. Meanwhile, after the low-damage well killing fluid is tackified in a liquid phase, a large amount of filtration loss of the well killing fluid in a plugging process can be reduced, and the damage of the well killing fluid to a water lock of a low-pressure gas well is reduced.

2. The liquid phase viscosity of the low-damage well killing fluid for the low-pressure gas well can be automatically reduced when encountering hydrocarbon substances in natural gas. After the two surfactants, i.e. the tallow amine polyoxyethylene ether and the tallow dihydroxy ethyl betaine, in the carrying fluid complete well killing operation, hydrocarbon substances can destroy intermolecular van der Waals force to enable the molecular chains of the surfactants to curl, so that the viscosity of the well killing fluid is reduced, meanwhile, the two surfaces can foam and stabilize, the density of the flowback fluid is reduced, the pressure of a clean fluid column is reduced, and the flowback of the well killing fluid is facilitated.

3. The liquid phase of the low-damage well killing fluid for the low-pressure gas well can remove the scaling blockage in the zone close to the well barrel. The gas well is scaled due to the gradual reduction of the formation pressure, the divalent metal ions and the bicarbonate radical in the formation water are scaled due to the change of temperature and pressure, and the difference of the temperature and the pressure of a near wellbore zone is the largest, so that the scaling amount is the largest, and the scaling amount is mainly calcium carbonate. The sulfamic acid and the glycolic acid in the remover are both acid solutions, and can slowly remove inorganic blockages in the near wellbore zone. The two types of the organic acid are both organic acids, and the organic plugging (gas wells mainly adopt colloid) liquid in the stratum can be slowly dissolved and emulsified, so that the stratum is drained back after the operation is finished, the plugging removal and cleaning of a shaft zone are realized, and the purpose of restoring the permeability of the reservoir is achieved.

4. The solid phase particles have lower dosage, greatly enhanced plugging capability and large reduction range of permeability of the kill plug due to the self-bonding function. Meanwhile, the self-degradation can be realized after the operation is finished, and the damage to a reservoir stratum is reduced.

Drawings

The invention is further illustrated with reference to the following figures and examples.

FIG. 1 is a schematic diagram of a viscosity change test curve of the low damage kill fluid at different temperatures according to the present invention.

Detailed Description