Carbonate reservoir filtration-loss self-reducing acid

Abstract

The present invention relates to a carbonate reservoir filtration-loss self-reducing acid fracturing method. The carbonate reservoir filtration-loss self-reducing acid fracturing method comprises the steps: (1) calculating a fracture pressure and a fracture extension pressure of a reconstructed reservoir; (2) injecting an agent A into a stratum under a pressure higher than the stratum fracture pressure, so that fractures are generated on the stratum; (3) injecting an agent B into the stratum under a pressure higher than the stratum fracture pressure, such that the agent B extends the fractures and communicates with a natural fracture net; (4) pumping an acid liquor system agent C with a high etching power into the stratum under a pressure higher than the extension pressure but lower than the fracture pressure to improve the conductivity of the fractures; (5) injecting a displacing liquid agent D under a pressure lower than the stratum fracture pressure to jack acid liquor in a well casing into the stratum; and (6) shutting down a well and performing flow-back. The agent A is a gel acid or VES acid, the agent B is a filtration-loss self-reducing gel acid or filtration-loss self-reducing VES acid, the agent C is closed acid, and the agent D is a displacing liquid. According to the method of the present invention, precipitation type solid filter cakes are formed on wall surfaces of the fractures by utilizing a filtration-loss self-reducing system, so as to perform temporary blocking to reduce the filtration loss. The technology is simple with easy injection, and the filtration-reducing agent is easy to disperse and flow back, and the method is safe and environment-friendly.

Claims

1. A carbonate reservoir filtration-loss self-reducing acid fracturing method, sequentially comprising: (1) determining a reservoir level that needs acid fracturing reconstruction according to needs of reservoir reconstruction and geological data of a reservoir, and calculating a fracture pressure P.sub.α of a reconstructed reservoir and a fracture extension pressure P.sub.F of the reconstructed reservoir; (2) injecting an agent A into a stratum by using a hydraulic pump under a pressure higher than a stratum fracture pressure, so that fractures are generated on the stratum, and stopping the hydraulic pump after the fractures reach geometrical dimensions that meet design requirements; (3) injecting an agent B into the stratum under a pressure higher than the stratum fracture pressure, wherein the agent B extends the fractures and communicates with a natural fracture net; (4) pumping an acid liquor system agent C into the stratum under a pressure higher than an extension pressure but lower than the stratum fracture pressure to improve a conductivity of the fractures; (5) injecting a displacing liquid agent D under a pressure lower than the stratum fracture pressure to inject an acid liquor in a well casing into the stratum; (6) shutting down the well for 30-60 min; (7) opening the well and performing flow-back, wherein, in the step (2), the agent A is a gel acid or visco-elastic surfactant (VES) acid, wherein the gel acid is selected from the group consisting in percentage by weight of: 5%-15% of HCl, 0.3-0.5% of gel agent, 0.5-2% of corrosion inhibitor, 0.5-2% of iron ion stabilizer, 0.5-2% of drainage aid, and a balance of water; and the VES acid is selected from the group consisting in percentage by weight of: 5-15% of HCl, 3-10% of VES, 0.5-2% of corrosion inhibitor, 0.5-2% of iron ion stabilizer, 0.5-2% of drainage aid, and a balance of water, wherein the drainage aid is polyoxyethylene ether, nonylphenol polyoxyethylene ether, fluorocarbon surfactant, or mixtures thereof.

2. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein, in the step (1), a process of calculating the fracture pressure P.sub.α of the reconstructed reservoir and the fracture extension pressure P.sub.F of the reconstructed reservoir is as follows: checking a fracture pressure gradient α.sub.F of an oil and gas reservoir where an operating well is located, wherein a well depth H×α.sub.F is the fracture pressure P.sub.α of the reconstructed reservoir α.sub.F; and checking parameters of other operated wells during a fracturing construction at a level of the operating well to obtain a pump stop pressure P.sub.S on a ground, wherein a hydrostatic column pressure during the fracturing construction of the operating well is P.sub.H, and a sum of P.sub.S and P.sub.H is the fracture extension pressure P.sub.F of the reconstructed reservoir.

3. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein, in the step (4), the agent C is a closed acid selected from the group consisting of components in percentage by weight: 15%-20% of HCl, 0-0.2% of gel agent, 0.5% of VES, 0.5-2% of corrosion inhibitor, 0.5-2% of iron ion stabilizer, and 0.5-2% of drainage aid.

4. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein the gel agent is one or more of polyacrylamide and derivatives thereof, or cellulose and derivatives thereof; the polyacrylamide and derivatives thereof are anionic polyacrylamide, cationic polyacrylamide, nonionic polyacrylamide, sulfomethylated polyacrylamide, aminomethylated polyacrylamide, partially hydrolyzed polyacrylamide or methylene polyacrylamide; and the cellulose and derivatives thereof are carboxymethyl cellulose sodium salt, hydroxyethyl cellulose, hydroxypropyl cellulose or carboxymethyl hydroxyethyl cellulose.

5. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein the VES is erucamidopropyl hydroxysultaine, erucamide betaine, cocamidopropyl betaine, octadecyl trimethyl ammonium chloride, octadecyl dimethyl betaine, or mixtures thereof.

6. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein the corrosion inhibitor is methylalkynol, methylpentynol, diethylenetriamine, butynylethanol, hexamethylenetetramine, oleic acid, oleic imidazoline, or mixtures thereof.

7. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein the iron ion stabilizer is ethylenediaminetetraacetic acid, citric acid, nitrilotriacetic acid, L-glutamic acid, isoascorbic acid, or mixtures thereof.

8. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein, in the step (3), the agent B is a filtration-loss self-reducing gel acid or filtration-loss self-reducing VES acid, wherein the filtration-loss self-reducing gel acid is selected from the group consisting of in percentage by weight: 15%-20% of HCl, 5-20% of filtration-loss self-reducing agent, 0.3-1% of gel agent, 0.1-1% of dispersant, 0.5-2% of corrosion inhibitor, 0.5-2% of iron ion stabilizer, 0.5-2% of drainage aid, and a balance of water; the filtration-loss self-reducing VES acid is selected from the group consisting of in percentage by weight: 15%-20% of HCl, 5-20% of filtration-loss self-reducing agent, 5-10% of VES+0.1-1% of dispersant, 0.5-2% of corrosion inhibitor, 0.5-2% of iron ion stabilizer, 0.5-2% of drainage aid, and a balance of water.

9. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 8, wherein the filtration-loss self-reducing agent is hydrofluoric acid, fluoboric acid, ammonium sulfate, ammonium fluoride, or mixtures thereof.

10. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 8, wherein the dispersant is maleic acid-acrylic acid copolymer, polymaleic acid, 1-hydroxy ethylidene-1,1-diphosphonic acid, aminotrimethylene phosphonic acid, diethylene triamine pentamethylene phosphonic acid, sodium tripolyphosphate, or mixtures thereof.

11. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 1, wherein, in the step (5), the agent D is a displacing liquid which is a 1-3 wt % NH.sub.4Cl aqueous solution or 0.1-1 wt % clay stabilizer aqueous solution.

12. The carbonate reservoir filtration-loss self-reducing acid fracturing method according to claim 11, wherein the clay stabilizer is 2,3 epoxy propyl-trimethyl ammonium chloride, γ-aminopropyl triethoxysilane, polydimethyl diallyl ammonium chloride, or mixtures thereof.

Description

DETAILED DESCRIPTION

(1) The present invention is further described below with reference to the accompanying drawings and examples, for those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. To those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, they are all protected.

Embodiment 1

(2) Taking an H well engineering reconstruction of an oilfield B as an implementation object by using a filtration-loss self-reducing acid fracturing process. Before the reservoir reconstruction, working fluids required for constructions are prepared, a gel acid agent A.sub.1, a filtration-loss self-reducing gel acid agent B.sub.1, a closing acid agent C.sub.1, and a displacing fluid agent D.sub.1.

(3) The agent A.sub.1: 15% of HCl+0.3% of sulfomethylated polyacrylamide+0.8% of imidazoline oleate+0.2% of butyne alcohol+0.5% ethylene diaminetetraacetic acid+0.5% of citric acid+1% of fluorocarbon surfactant+0.5% of polyoxyethylene ether, and the balance of water.

(4) Each 100 g of agent A.sub.1 is prepared:

(5) adding 42.9 g of 35% HCl, 0.3% of sulfomethylated polyacrylamide, 0.8 g of imidazoline oleate, 0.2 g of butyne alcohol, 0.5 g of ethylene diaminetetraacetic acid, 0.5 g of citric acid, 1 g of fluorocarbon surfactant, 0.5 g of polyoxyethylene ether, and 53.3 g of water.

(6) The agent B.sub.1: 20% of HCl+5% of HF+5% of ammonium sulfate+0.3% of sulfomethylated polyacrylamide+0.3% of sodium tripolyphosphate+0.1% of polymaleic acid+1.2% of imidazoline oleate+0.3% of butyne alcohol+1% of ethylene diaminetetraacetic acid+0.5% of citric acid+1% of fluorocarbon surfactant+0.5% of polyoxyethylene ether, and the balance of water.

(7) Each 100 g of agent B.sub.1 is prepared:

(8) adding 57.2 g of 35% HCl, 12.5 g of 40% HF, 5 g of ammonium sulfate, 0.3 g of sulfomethylated polyacrylamide, 0.3 g of sodium tripolyphosphate, 0.1 g of polymaleic acid, 1.2 g of imidazoline oleate, 0.3 g of butyne alcohol, 1 g of ethylene diaminetetraacetic acid, 0.5 g of citric acid, 1 g of fluorocarbon surfactant, 0.5 g of polyoxyethylene ether, and 20.1 g of water.

(9) The agent C.sub.1: 20% of HCl+1.5% of imidazoline oleate+0.5% of butyne alcohol+1.5% ethylene diaminetetraacetic acid+0.5% of citric acid+0.8% of fluorocarbon surfactant+0.2% of polyoxyethylene ether, and the balance of water.

(10) Each 100 g of agent C.sub.1 is prepared:

(11) adding 57.2 g of 35% HCl, 1.5 g of imidazoline oleate, 0.5 g of butyne alcohol, 1.5 g of ethylene diaminetetraacetic acid, 0.5 g of citric acid, 0.8 g of fluorocarbon surfactant, 0.2 g of polyoxyethylene ether, and 37.8 g of water.

(12) The agent D.sub.1: 1% of NH.sub.4Cl, and the balance of water.

(13) Each 100 g of agent D.sub.1 is prepared:

(14) adding 1 g of NH.sub.4Cl and 99 g of water.

(15) In the step 1, Well H is a gas production well, the lithology is carbonate rock, and the well depth of the reconstructed section is 3250-3390 m. The fracture pressure gradient α.sub.F (MPa/m) of the reservoir in this well is 0.02 MPa/m, and the fracture pressure P.sub.α, of this well is (3250+3390)/2×0.02=66.4 MPa. The hydrostatic column pressure P.sub.H of this well is 35.1 MPa, the instantaneous pump stop pressure P.sub.S on the ground is 21 MPa, and the extension pressure P.sub.F is 56.1 MPa.

(16) In step 2, 35000 Kg of gel acid agent A.sub.1 is injected at 68-73 MPa and a pump is stopped.

(17) In step 3, 120000 Kg of filtration-loss self-reducing gel acid B.sub.1 is injected at 68-80 MPa and the pump is stopped.

(18) In step 4, 50000 Kg of closing acid agent C.sub.1 is injected at 58-63 MPa and the pump is stopped.

(19) In step 5, 15000 Kg of displacing fluid agent D.sub.1 is injected at 50-60 MPa and the pump is stopped.

(20) In step 6, the well is closed for 45 min.

(21) In step 7, the well is closed for flowback.

(22) During the construction process, the change in the oil pressure of the injected fluid during the filtration-loss self-reducing acid fracturing process in Well H of Oilfield B is recorded. Under the same discharge displacement of 4.9 m.sup.3/min, the oil pressure is increased by 3.6 MPa during the injection process of the filtration-loss self-reducing gel acid B, which indicates that the filtration-loss self-reducing system achieves a better filtration loss reducing effect in the process of acid fracturing without adding any filtration loss reducing agent, reduces the filtration loss of acid liquor, improves the effectiveness of the acid liquor, and effectively improves the turning effect of the acid liquor. The filtration-loss self-reducing products generated after the construction can be quickly discharged with residual acid. The discharged filtration-loss self-reducing products are dispersed particles, rather than solid-state agglomerates, which facilitates the removal of the filtration-loss self-reducing system, without any serious damages on the stratum. The field construction verification in Embodiment 1 shows that the method of the present invention can effectively reduce the filtration loss of the acid liquor during the acid fracturing of carbonate reservoirs, increase the effective rate of the acid liquor, and reduce the capital consumption of acid fracturing construction. In addition, the liquid can be injected in an easier manner than acid fracturing in which the filtration loss reducing agent is added directly, and has less damages to equipment.

Embodiment 2

(23) Taking an M well engineering reconstruction of an oilfield B as an implementation object by using a filtration-loss self-reducing acid fracturing process. Before the reservoir reconstruction, working fluids required for constructions are prepared, a VES acid agent A.sub.2, a filtration-loss self-reducing VES acid agent B.sub.2, a closing acid agent C.sub.2, and a displacing fluid agent D.sub.2.

(24) The agent A.sub.2: 5% of HCl+5% of erucamidopropyl hydroxysultaine+0.3% of imidazoline oleate+0.1% of diethylene triamine+0.1% of methylalkynol+0.2% of citric acid+0.3% of L-glutamic acid+1% of fluorocarbon surfactant, and the balance of water.

(25) Each 100 g of agent A.sub.2 is prepared:

(26) adding 14.3 g of 35% HCl, 5 g of erucamidopropyl hydroxysultaine, 0.3 g of imidazoline oleate, 0.1 g of diethylene triamine, 0.1 g of methylalkynol, 0.2 g of citric acid, 0.3 g of L-glutamic acid, 1 g of fluorocarbon surfactant, and 78.7 of water.

(27) The agent B.sub.2: 18% of HCl+5% of HF+5% of NH.sub.4F+5% of ammonium sulfate+8% of erucamidopropyl hydroxysultaine+0.5% of HEDP+0.1% of polymaleic acid-acrylic acid copolymer+1% of imidazoline oleate+0.3% of diethylenetriamine+0.2% of methylalkynol+0.5% of citric acid+1% of L-glutamic acid+1% of fluorocarbon surfactant, and the balance of water.

(28) Each 100 g of agent B.sub.2 is prepared:

(29) adding 51.5 g of 35% HCl, 12.5 g of 40% HF, 5 g of NH.sub.4F, 5 g of ammonium sulfate, 8 g of erucamidopropyl hydroxysultaine, 0.5 g of HEDP, 0.1 g of polymaleic acid-acrylic acid copolymer, 1 g of imidazoline oleate, 0.3 g of diethylene triamine, 0.2 g of methylalkynol, 0.5 g of citric acid, 1 g of L-glutamic acid, 1 g of fluorocarbon surfactant, and 13.4 g of water.

(30) The agent C.sub.2: 20% of HCl+3% of erucamidopropyl hydroxysultaine+1.2% of imidazoline oleate+0.4% of diethylene triamine+0.4% of methylalkynol+0.5% of citric acid+1.5% of L-glutamic acid+1% of fluorocarbon surfactant, and the balance of water.

(31) Each 100 g of agent C.sub.2 is prepared:

(32) adding 57.2 g of 35% HCl, 3 g of erucamidopropyl hydroxysultaine, 1.2 g of imidazoline oleate, 0.4 g of diethylene triamine, 0.4 g of methylalkynol, 0.5 g of citric acid, 1.5 g of L-glutamic acid, 1 g of fluorocarbon surfactant, and 34.8 of water.

(33) The agent D.sub.2: 0.5% of polydimethyl diallyl ammonium chloride, and the balance of water.

(34) Each 100 g of agent D.sub.2 is prepared:

(35) adding 0.5 g of polydimethyl diallyl ammonium chloride, and 99.5 g of water.

(36) In the step 1, Well H is a gas production well, the lithology is carbonate rock, and the well depth of the reconstructed section is 3218-3355 m. The fracture pressure gradient α.sub.F (MPa/m) of the reservoir in this well is 0.02 MPa/m, and the fracture pressure P.sub.α of this well is (3218+3355)/2×0.02=65.73 MPa. The hydrostatic column pressure P.sub.H of this well is 34.5 MPa, the instantaneous pump stop pressure P.sub.S on the ground is 21 MPa, and the extension pressure P.sub.F is 55.5 MPa.

(37) In step 2, 30000 Kg of gel acid agent A.sub.2 is injected at 66-70 MPa and a pump is stopped.

(38) In step 3, 150000 Kg of filtration-loss self-reducing gel acid B.sub.2 is injected at 66-75 MPa and the pump is stopped.

(39) In step 4, 60000 Kg of closing acid agent C.sub.2 is injected at 56-60 MPa and the pump is stopped.

(40) In step 5, 12000 Kg of displacing fluid agent D.sub.2 is injected at 40-50 MPa and the pump is stopped.

(41) In step 6, the well is closed for 60 min.

(42) In step 7, the well is closed for flowback.

(43) During the construction process, the change in the oil pressure of the injected fluid during the filtration-loss self-reducing acid fracturing process in Well M of Oilfield B is recorded. Under the same discharge displacement of 4.8 m.sup.3/min, the oil pressure is increased by 4.5 MPa during the injection process of the filtration-loss self-reducing gel acid B, which indicates that the filtration-loss self-reducing system achieves a better filtration loss reducing effect in the process of acid fracturing without adding any filtration loss reducing agent, reduces the filtration loss of acid liquor, improves the effectiveness of the acid liquor, and effectively improves the turning effect of the acid liquor. The filtration-loss self-reducing products generated after the construction can be quickly discharged with residual acid. The discharged filtration-loss self-reducing products are dispersed particles, rather than solid-state agglomerates, which facilitates the removal of the filtration-loss self-reducing system, without any serious damages on the stratum. The field construction verification in Embodiment 2 shows that the method of the present invention can effectively reduce the filtration loss of the acid liquor during the acid fracturing of carbonate reservoirs, increase the effective rate of the acid liquor, and reduce the capital consumption of acid fracturing construction. In addition, the liquid can be injected in an easier manner than acid fracturing in which the filtration loss reducing agent is added directly, and has less damages to equipment.

Embodiment 3

(44) Taking a Q well engineering reconstruction of an oilfield B as an implementation object by using a filtration-loss self-reducing acid fracturing process. Before the reservoir reconstruction, working fluids required for constructions prepared, i.e., a VES acid agent A.sub.3, a filtration-loss self-reducing VES acid agent B.sub.3, a closing acid agent C.sub.3, and a displacing fluid agent D.sub.3.

(45) The agent A.sub.3: 10% of HCl+0.5% of carboxymethyl hydroxyethyl cellulose+0.6% of imidazoline oleate+0.2% of oleic acid+0.2% of hexamethylene methyl tetramine+0.3% of nitrilotriacetic acid+0.7% of L-glutamic acid+1% of fluorocarbon surfactant, and the balance of water.

(46) Each 100 g of agent A.sub.3 is prepared:

(47) adding 28.6 g of 35% HCl+0.5 g of carboxymethyl hydroxyethyl cellulose+0.6 g of imidazoline oleate+0.2 g of oleic acid+0.2 g of hexamethylene methyl tetramine+0.3 g of nitrilotriacetic acid+0.7 g of L-glutamic acid+1 g of fluorocarbon surfactant, and 67.9 g of water.

(48) The agent B.sub.3: 15% of HCl+3% of HF+5% of ammonium sulfate+3% of octadecyl dimethyl betaine+3% of erucamidopropyl hydroxysultaine+0.3% of HEDP+0.1% of polymaleic acid+0.2% of diethylenetriamine penta methylene phosphonic acid+0.8% of imidazoline oleate+0.2% of oleic acid+0.2% of hexamethylenetetramine+0.5% of ethylene diaminetetraacetic acid+0.3% of citric acid+0.4% of L-glutamic acid+1.2% of fluorocarbon surfactant, and the balance of water.

(49) Each 100 g of agent B.sub.3 is prepared:

(50) adding 42.9 g of 35% HCl, 7.5 g of HF, 5 g of ammonium sulfate, 3 g of octadecyl dimethyl betaine, 3 g of erucamidopropyl hydroxysultaine, 0.3 g of HEDP, 0.1 g of polymaleic acid, 0.2 g of diethylenetriamine penta methylene phosphonic acid, 0.8 g of imidazoline oleate, 0.2 g of oleic acid, 0.2 g of hexamethylenetetramine, 0.5 g of ethylene diaminetetraacetic acid, 0.3 g of citric acid, 0.4 g of L-glutamic acid, 1.2 g of fluorocarbon surfactant, and 34.4 g of water.

(51) The agent C.sub.3: 18% of HCl+0.1% of carboxymethyl hydroxyethyl cellulose+1% of imidazoline oleate+0.2% of oleic acid+0.3% of hexamethylene methyl tetramine+0.5% of ethylene diaminetetraacetic acid+0.5% of citric acid+0.5% of L-glutamic acid+1.5% of fluorocarbon surfactant, and the balance of water.

(52) Each 100 g of agent C.sub.3 is prepared:

(53) adding 51.5 g of 35% HCl, 0.1 g of carboxymethyl hydroxyethyl cellulose, 1 g of imidazoline oleate, 0.2 g of oleic acid, 0.3 g of hexamethylene methyl tetramine, 0.5 g of ethylene diaminetetraacetic acid, 0.5 g of citric acid, 0.5 g of L-glutamic acid, 1.5 g of fluorocarbon surfactant, and 43.9 g of water.

(54) The agent D.sub.3: 2% of NH.sub.4Cl, and the balance of water.

(55) Each 100 g of agent D.sub.3 is composed of:

(56) 2 g of NH.sub.4Cl and 98 g of water.

(57) In the step 1, Well Q is a gas production well, the lithology is carbonate rock, and the well depth of the reconstructed section is 3280-3380 m. The fracture pressure gradient α.sub.F (MPa/m) of the reservoir in this well is 0.02 MPa/m, and the fracture pressure P.sub.α of this well is (3280+3380)/2×0.02=66.6 MPa. The hydrostatic column pressure P.sub.H of this well is 34.9 MPa, the instantaneous pump stop pressure P.sub.S on the ground is 21 MPa, and the extension pressure P.sub.F is 55.9 MPa.

(58) In step 2, 35000 Kg of gel acid agent A.sub.3 is injected at 67-75 MPa and a pump is stopped.

(59) In step 3, 150000 Kg of filtration-loss self-reducing gel acid B.sub.3 is injected at 67-80 MPa and the pump is stopped.

(60) In step 4, 60000 Kg of closing acid agent C.sub.3 is injected at 50-65 MPa and the pump is stopped.

(61) In step 5, 12000 Kg of displacing fluid agent D.sub.3 is injected at 40-50 MPa and the pump is stopped.

(62) In step 6, the well is closed for 45 min.

(63) In step 7, the well is closed for flowback.

(64) During the construction process, the change in the oil pressure of the injected fluid during the filtration-loss self-reducing acid fracturing process in Well Q of Oilfield B is recorded. Under the same discharge displacement of 5.1 m.sup.3/min, the oil pressure is increased by 3.3 MPa during the injection process of the filtration-loss self-reducing gel acid B, which indicates that the filtration-loss self-reducing system achieves a better filtration loss reducing effect in the process of acid fracturing without adding any filtration loss reducing agent, reduces the filtration loss of acid liquor, improves the effectiveness of the acid liquor, and effectively improves the turning effect of the acid liquor. The filtration-loss self-reducing products generated after the construction can be quickly discharged with residual acid. The discharged filtration-loss self-reducing products are dispersed particles, rather than solid-state agglomerates, which facilitates the removal of the filtration-loss self-reducing system, without any serious damages on the stratum. The field construction verification in Embodiment 3 shows that the method of the present invention can effectively reduce the filtration loss of the acid liquor during the acid fracturing of carbonate reservoirs, increase the effective rate of the acid liquor, and reduce the capital consumption of acid fracturing construction. In addition, the liquid can be injected in an easier manner than acid fracturing in which the filtration loss reducing agent is added directly, and has less damages to equipment.