阅读说明：本技术 用于弱非均质性储层酸化的复合式酸液体系及其制备方法 (Composite acid liquid system for weak heterogeneity reservoir acidification and preparation method thereof ) 是由 张博 万传治 李登金 荣元帅 马成 瞿建华 袁浩 郝成舜 徐兵 任本兵 符奇 于 2019-11-19 设计创作，主要内容包括：本发明公开了用于弱非均质性储层酸化的复合式酸液体系及其制备方法,包括以下质量百分比的组分：胶凝剂0.8％～1.2％,稠化剂0.3～0.5％,缓蚀剂4％～6％,助排剂1％～2％,铁离子稳定剂0.5～2％,发泡剂3％～5％,稳泡剂0.2％～0.3％,碳酸钙1％～1.5％,盐酸10％～25％,余量为水。本发明的目的在于提供用于弱非均质性储层酸化的复合式酸液体系及其制备方法,以解决现有技术中胶凝酸体系用于非均质性较弱的储层酸化时,容易对地层造成较为明显伤害的问题,实现提高非均质性较弱的储层使用胶凝体系时对地层伤害的目的。(The invention discloses a composite acid system for weak heterogeneity reservoir acidification and a preparation method thereof, wherein the composite acid system comprises the following components in percentage by mass: 0.8-1.2% of gelling agent, 0.3-0.5% of thickening agent, 4-6% of corrosion inhibitor, 1-2% of cleanup additive, 0.5-2% of iron ion stabilizer, 3-5% of foaming agent, 0.2-0.3% of foam stabilizer, 1-1.5% of calcium carbonate, 10-25% of hydrochloric acid and the balance of water. The invention aims to provide a composite acid system for weak-heterogeneity reservoir acidification and a preparation method thereof, so as to solve the problem that a gelled acid system in the prior art is easy to cause obvious damage to a stratum when used for weak-heterogeneity reservoir acidification, and achieve the purpose of improving the damage to the stratum when used for a weak-heterogeneity reservoir.)

1. The composite acid liquid system for weak heterogeneous reservoir acidification is characterized by comprising the following components in percentage by mass: 0.8-1.2% of gelling agent, 0.3-0.5% of thickening agent, 4-6% of corrosion inhibitor, 1-2% of cleanup additive, 0.5-2% of iron ion stabilizer, 3-5% of foaming agent, 0.2-0.3% of foam stabilizer, 1-1.5% of calcium carbonate, 10-25% of hydrochloric acid and the balance of water.

2. The composite acid system for weak heterogeneous reservoir acidizing according to the claim 1, characterized by comprising the following components in percentage by mass: 1% of gelling agent, 0.4% of thickening agent, 5% of corrosion inhibitor, 1.5% of cleanup additive, 1% of iron ion stabilizer, 4% of foaming agent, 0.3% of foam stabilizer, 1% of calcium carbonate, 15% of hydrochloric acid and the balance of water.

3. The composite acid system for weak heterogeneous reservoir acidizing according to claim 1, wherein said gelling agent is a copolymer of methacryloyloxyethyl trimethyl ammonium chloride and acrylamide.

4. The composite acid system for weak heterogeneous reservoir acidizing according to the claim 1, wherein said viscosifying agent is a copolymer of anionic monomers 2-acrylamido-2-methylpropanesulfonic acid and acrylamide.

5. The composite acid system for weak heterogeneous reservoir acidizing according to claim 1, wherein said corrosion inhibitor is a mannich base quaternary ammonium salt.

6. The composite acid system for weak heterogeneous reservoir acidizing according to claim 1, wherein the concentration of said hydrochloric acid is between 25% and 28%.

7. The method for preparing the composite acid system for weak heterogeneity reservoir acidizing according to any of claims 1 to 6 wherein the components are mixed according to mass percent and stirred at high speed until a milky white evenly dispersed micro-foam liquid phase is formed.

8. The method for preparing the composite acid system for acidizing the weak heterogeneous reservoir according to the claim 8, wherein the high-speed stirring adopts a high-speed stirrer, and the rotating speed is 1800-2000 rpm.

Technical Field

The invention relates to the field of acidification and yield increase, in particular to a composite acid system for weak heterogeneity reservoir acidification and a preparation method thereof.

Background

In the acidizing construction, because the reaction speed of acid rocks is high and the penetration distance of acid is short, the damage to the stratum in the near wellbore zone can be eliminated. Therefore, the penetration distance of the acid liquid can be properly increased by increasing the concentration of the acid. The effective period of the increase in production by acidification is short, and after the sandstone is acidified, the clay particles or other particles are easy to migrate to cause the blockage of oil flow channels, so that the initial yield of the acidification is increased quickly, and the later yield is reduced quickly. In carbonate reservoirs, the acid system needs to be considered comprehensively when acidizing the reservoir because the acid reacts with the carbonate too quickly, so that fractures far from the bottom of the well are not easily acidized.

For a reservoir with weak heterogeneity, a gelled acid liquid system is generally used for acidification in the prior art, and the characteristics of small frictional resistance of gelled acid are utilized to achieve the effects of improving the acidification discharge capacity and reducing the performance requirements on ground equipment. The existing gelled acid system has good fluid loss reducing effect, can delay the reaction speed of acid rocks and increase the penetration distance of active acid, and has been widely applied at home and abroad; but the problem of damage to the formation by gelled acid formulations is gradually being valued by the industry: the damage of the high molecular polymer in the gelled acid formula to the stratum often greatly affects the construction effect of acidification, and the construction effect is directly affected. Particularly in reservoirs with weak heterogeneity, the damage has strong continuity, so that the influence on the yield is more easily reflected on the macro scale.

Disclosure of Invention

The invention aims to provide a composite acid system for weak heterogeneity reservoir acidification and a preparation method thereof, so as to solve the problem that a gelled acid system in the prior art is easy to cause obvious damage to a stratum when used for weak heterogeneity reservoir acidification, and realize the purpose of reducing the damage to the stratum when used for a weak heterogeneity reservoir.

The invention is realized by the following technical scheme:

the composite acid liquid system for weak heterogeneous reservoir acidification comprises the following components in percentage by mass: 0.8-1.2% of gelling agent, 0.3-0.5% of thickening agent, 4-6% of corrosion inhibitor, 1-2% of cleanup additive, 0.5-2% of iron ion stabilizer, 3-5% of foaming agent, 0.2-0.3% of foam stabilizer, 1-1.5% of calcium carbonate, 10-25% of hydrochloric acid and the balance of water.

Aiming at the problem that when a gelled acid system is used for acidizing a reservoir with weak heterogeneity in the prior art, the stratum is easily and obviously damaged, the invention provides a composite acid system for acidizing the reservoir with weak heterogeneity, wherein the components in the system comprise a gelling agent, a thickening agent, a corrosion inhibitor and the like used in the conventional gelled acid, and in addition, the scheme also comprises foamingThe foaming agent is used for foaming in a gelled acid system, and the foam stabilizer is used for keeping the stability of bubbles. The essence of the scheme is the compounding of two acidification systems of gelled acid and foamed acid, the scheme utilizes the reaction of calcium carbonate and acid liquor after the uniform mixing and stirring to generate carbon dioxide, and the carbon dioxide gas is mixed with the foam generated by the foaming agent, so that the foam generation can be promoted through the carbon dioxide, and the foam generated by the foaming agent is more stable. The acid liquor in the scheme enters the reservoir during the acidification process, and has the following advantages in the reservoir with strong heterogeneity: (1) the foam has selectivity on permeability, has stronger plugging effect on a high-permeability layer and weaker plugging effect on a low-permeability layer, and more acid liquor systems with the gelling agents enter low-permeability pores by plugging high-permeability pores through the foam; after the gelling agent enters the low-permeability pore gaps, because the filtration loss of the gelling agent is low, the water locking phenomenon cannot occur in the low-permeability pore gaps, the slow reaction speed of the acid liquid in the low-permeability pore gaps can be ensured, and the penetration distance of the acid liquid can be increased. Therefore, compared with the technology that the traditional gelled acid cleans the hypertonic reservoir layer in a large scale and causes acid liquor to flow into the hypertonic reservoir layer so that the hypotonic reservoir layer is difficult to improve, the yield increasing effect on the hypotonic region of the reservoir layer is obviously improved. For oil and gas wells, a reservoir hypertonic region of the oil and gas wells has not much production increase value, a hypotonic region needs to be increased in yield, and the scheme perfectly realizes the basic idea of acidification production increase. (2) The foam is selective to the oil-water layer, and because the interfacial tension of the oil is low, the foam entering the water is relatively stable compared with the foam entering the oil, and the foam preferentially enters the oil layer; foam gets into the oil reservoir along with gelling acid liquid in this application, realizes the preferential acidizing to the oil reservoir, avoids the acidizing fluid extravagant in the higher region of moisture content, not only can improve the utilization ratio to whole acidizing fluid system, can also slow down the water content of water-cut time, reduction later stage output even. (3) Utilize the interpolation of calcium carbonate in this scheme for foam and carbon dioxide intensive mixing, unstable foam receives carbon dioxide gas invasion and accompany high-speed stirring in the ground mixing process of earlier stage, can be quick broken, make remaining foam performance, resistance to compression all comparatively stable, can receive overlying rock after avoiding traditional foam acid system to get into the stratumThe problems of high pressure and confining pressure are solved. (4) After foam is added into the gel system, the foam is attached to the surface, and the foam is positioned close to the rock stratum after acid liquid is injected into the stratum, so that H in the foam⁺The acid liquor of the gelling system is basically higher in apparent viscosity only by being spread to the surface of the rock through the external phase, and after foams generated by the foaming agent and bubbles generated by carbon dioxide are added, the apparent viscosity is higher, the interface diffusion speed can be obviously reduced, so that the corrosion reaction rate of the scheme is lower than that of the traditional gelling acid liquor phase acid liquor system, the purpose of slowing acidification is achieved, and a deeper corrosion channel is formed. (5) The viscosity of residual acid of a traditional gelled acid system is low, generally ranges from 10 to 15mPa · s, and solid-phase particles in a stratum fracture after reaction can be carried easily, but due to limited energy, the flowback effect is obvious, and the residual acid is one of the reasons for secondary damage of gelled acid pressure to the stratum. In this scheme, the carbon dioxide that calcium carbonate produced when ground stirring mixes, must mix in acidizing fluid in a large number, back in the injection well, can appear gradually under the high temperature effect of stratum, and gas expansion can be for the residual acid flowback provides the energy, makes the residual acid flowback more thoroughly, consequently this application utilizes the expansion of carbon dioxide in the pit can mutually support with the raffinate that carries the solid phase particle, is showing to improve the flowback effect, has very obvious advantage in the aspect of preventing the secondary and deposiing.

Further, the paint comprises the following components in percentage by mass: 1% of gelling agent, 0.4% of thickening agent, 5% of corrosion inhibitor, 1.5% of cleanup additive, 1% of iron ion stabilizer, 4% of foaming agent, 0.3% of foam stabilizer, 1% of calcium carbonate, 15% of hydrochloric acid and the balance of water.

Further, the gelling agent is a copolymer formed by methacryloyloxyethyl trimethyl ammonium chloride and acrylamide. Namely a copolymer formed by a methacryloyloxyethyl trimethyl ammonium chloride monomer and an acrylamide monomer.

Further, the thickening agent is a copolymer formed by anionic monomers, namely 2-acrylamide-2-methylpropanesulfonic acid and acrylamide.

Further, the corrosion inhibitor is a Mannich base quaternary ammonium salt.

Further, the concentration of the hydrochloric acid is 25-28%.

The preparation method of the composite acid liquid system for weak heterogeneous reservoir acidification is characterized in that the components are mixed according to mass percentage and stirred at high speed until a milky uniformly dispersed micro-foam liquid phase is formed.

Further, a high-speed stirrer is adopted for high-speed stirring, and the rotating speed is 1800-2000 rpm. Traditional acidizing fluid mixes, and the rotational speed is generally more than 3000rpm, can lead to the carbon dioxide too much to appear scattering and overflowing for in this application, consequently the stirring rotational speed of this scheme is lower relatively, can ensure to mix sufficient carbon dioxide gas in the acidizing fluid, is convenient for the later stage to provide the energy for the residual acid flowback. Of course, if the site engineer determines that the carbon dioxide gas production is insufficient, the nitrogen gas may be artificially added for replenishment.

Compared with the prior art, the invention has the following advantages and beneficial effects:

1. the composite acid system for weak heterogeneity reservoir acidification and the preparation method thereof perfectly realize the basic idea of acidification yield increase, and compared with the technology that the hypotonic reservoir is difficult to improve due to the fact that the traditional gelled acid washes the hypertonic reservoir on a large scale and causes the acid to flow into the hypertonic reservoir, the yield increase effect on the hypotonic region of the reservoir is remarkably improved.

2. According to the composite acid liquid system for weak heterogeneity reservoir acidification and the preparation method thereof, foam enters the oil layer along with gelled acid liquid, preferential acidification of the oil layer is realized, acid liquid waste in a region with higher water content is avoided, the utilization rate of the whole acid liquid system can be improved, the water breakthrough time can be reduced, and even the water content produced in the later period is reduced.

3. According to the composite acid liquid system for weak heterogeneity reservoir acidification and the preparation method thereof, calcium carbonate is added, so that foam and carbon dioxide are fully mixed, unstable foam is invaded by carbon dioxide gas in the early ground mixing process and can be quickly crushed along with high-speed stirring, the performance and the compression resistance of the remaining foam are stable, and the problem that the traditional foam acid system is greatly destroyed by overburden pressure and confining pressure after entering a stratum is solved.

4. The composite acid liquid system for weak heterogeneity reservoir acidification and the preparation method thereof have the advantages of larger apparent viscosity, obviously reduced interface diffusion speed, lower corrosion reaction rate than that of the traditional gelled acid liquid phase acid liquid system, and slow acidification, thereby being beneficial to forming deeper corrosion channels.

5. The invention relates to a composite acid liquid system for weak heterogeneous reservoir acidification and a preparation method thereof, wherein carbon dioxide generated by calcium carbonate is inevitably mixed in acid liquid in a large amount when being stirred and mixed on the ground, and can be gradually separated out under the action of high temperature of a stratum after being injected into a well, and gas expansion can provide energy for residual acid flowback, so that the residual acid flowback is more thorough.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not used as limitations of the present invention.