CN107090287B

CN107090287B - Low-viscosity mixed fracturing fluid, application thereof and oil-gas reservoir transformation method

Info

Publication number: CN107090287B
Application number: CN201710352667.1A
Authority: CN
Inventors: 周国君
Original assignee: BEIJING CSI ENERGY TECHNIQUES Co Ltd
Current assignee: BEIJING CSI ENERGY TECHNIQUES Co Ltd
Priority date: 2017-05-18
Filing date: 2017-05-18
Publication date: 2020-01-24
Anticipated expiration: 2037-05-18
Also published as: CN107090287A

Abstract

The invention relates to a low-viscosity mixed fracturing fluid, application thereof and an oil and gas reservoir transformation method. The mixed fracturing fluid is prepared by adding acid and an active agent into the fracturing fluid without adding a cross-linking agent, has low viscosity, low friction resistance and strong sand carrying capacity, can be used as the fracturing fluid and an acid solution when being applied to the process of oil and gas reservoir transformation, enables the two reservoir transformation methods of fracturing (or sand fracturing) and acidizing to be carried out simultaneously, and can be used for carrying out acid etching on the wall surface (filtration zone) of a fractured reservoir while fracturing the reservoir, the wide part of the fracture is filled and supported by sand carried by the mixed fracturing fluid, sand in the narrow part of the fracture or small branch fractures cannot go into the narrow part of the fracture, but the acid in the mixed fracturing fluid can enter the narrow part of the fracture for carrying out acid etching and cleaning, so that the fracture part without sand support also has certain flow conductivity, and the oil displacement function of the active agent is added, and the reservoir transformation effect is greatly improved.

Description

Low-viscosity mixed fracturing fluid, application thereof and oil-gas reservoir transformation method

Technical Field

The invention relates to an acid-adding mixed fracturing fluid and application thereof, in particular to a low-viscosity uncrosslinked fracturing fluid which is mixed with acid (or acid and an active agent) and has three functions of sand-adding fracturing, acidification and oil displacement. The invention also relates to a method for modifying a reservoir of an oil and gas field, in particular to a novel reservoir modification method which combines three modes of acidification, sand adding fracturing and oil displacement and can be simultaneously carried out in the process of modifying a clastic rock reservoir.

Background

At present, the transformation process of clastic rock reservoirs is sand fracturing, which plays an important role in the transformation of reservoirs developed in oil and gas fields, and the main action principle is as follows: by utilizing the principle of liquid pressure transmission, a high-pressure and large-displacement pump is adopted to inject the fracturing fluid into an oil layer at high pressure, so that the pressure in a shaft is gradually increased, the high pressure is suppressed at the bottom of the shaft, and when the pressure is greater than the ground stress near the wall of the shaft and the tensile strength of stratum rocks, a crack is generated in the stratum near the bottom of the shaft: and continuously injecting fracturing fluid, wherein the fracture extends forwards and is filled with proppant such as sand and the like, so that a sand filling fracture with certain geometric dimension and high flow conductivity is formed in the stratum near the bottom of the well, and the aims of increasing production and injection of oil exploitation are fulfilled.

Although the existing method can open a seam in the clastic rock reservoir through hydraulic power and then support the seam by sand, the drainage area can be increased, and the oil and gas yield can be improved. However, the high viscosity cross-linking fracturing fluid (gel) commonly used in the fracturing process at present has damage to the fractured fracture wall surface (residual gel blocking), and oil gas flows out of the reservoir from the fracture wall surface into the fracture and then flows into a shaft, so that the improvement of the seepage capability of the fracture wall surface is important. In addition, the fractures fractured by the existing sand fracturing method are wedge-shaped, the far ends of the fractures are too narrow, sand can not enter, small branches at the edges of the main fractures can also cause sand not to enter due to the narrow fractures, and the problem of sand carrying performance of the fracturing fluid at high temperature of the stratum (sand blocking can occur) is solved, so that the supporting effect of the propping agent (sand) on the fractures cannot be expected, the flow conductivity of the fractures can be influenced, and the final reconstruction of the reservoir cannot achieve the expected effect.

The existing sand fracturing technology requires high viscosity and low fluid loss (such as adding a fluid loss additive) of the fracturing fluid so as to ensure good fracturing performance.

Disclosure of Invention

Technical problem to be solved

In order to solve the problems in the prior art, the invention provides a low-viscosity mixed fracturing fluid and application thereof, wherein acid (or acid and an active agent) is added into the mixed fracturing fluid, sand fracturing and acidification technologies are combined, a fracture is formed by fracturing a reservoir stratum, and the pores of a reservoir stratum matrix on the wall surface of the fracture are corroded by acid, so that the seepage capability of the reservoir stratum on the wall surface of the fracture is improved; when the mixed fracturing fluid carries sand, the mixed fracturing fluid plays a supporting role in a wide place of a crack, and carried acid is used for carrying out acid etching and cleaning on a narrow crack which cannot be reached by the sand, so that the narrow place of the crack also has certain flow conductivity, and the reservoir transformation effect is greatly improved.

The invention also provides an oil gas reservoir transformation method combining sand fracturing and acidification, which adopts the technology combining acid addition and sand addition in the fracturing fluid matrix, and can carry out fracturing and acidification simultaneously, so that not only can the sand carried by the fracturing fluid matrix be used for supporting the wide part of the fracture, but also the acid carried by the fracturing fluid matrix can be used for carrying out acid etching and cleaning on the narrow fracture which can not be reached by the sand, so that the narrow part of the fracture also has certain flow conductivity, and the acid carried by the fracturing fluid matrix can be used for acidifying the reservoir on the wall surface of the fracture, thereby leading the seepage capability of the filtration zone around the fracture to be improved, and greatly improving the transformation effect of the reservoir.

(II) technical scheme

In order to achieve the purpose, the invention adopts the main technical scheme that:

a low viscosity hybrid fracturing fluid, comprising:

the fracturing fluid matrix comprises a thickening agent with the mass percent of 0.1-0.8%;

acid, wherein the concentration of the acid is 1-12% of the mass of the fracturing fluid matrix;

the concentration of the active agent is 0-10% of the mass of the fracturing fluid matrix;

and the sand accounts for 0-50% of the volume of the fracturing fluid matrix.

The mixed fracturing fluid provided by the invention is added with acid (or acid and active agent) in a matrix of the fracturing fluid, so that the mixed fracturing fluid contains the acid and sand at the same time or only contains the acid (or the acid and the active agent) and does not contain the sand.

Preferably, the fracturing fluid matrix is a non-crosslinked fracturing fluid in which no crosslinking agent is added and the apparent viscosity is less than 80 mPa sec (as measured by a six-speed rotational viscometer at 100 rpm).

The acid-containing mixed fracturing fluid is low in viscosity, so that the fluid loss is facilitated to enter the wall surface of a fracture for acidizing, and the traditional fracturing fluid is required to be high in viscosity and resistant to fluid loss.

The mixed fracturing fluid of one embodiment of the invention, wherein the acid is hydrochloric acid or a mixture of hydrochloric acid and hydrofluoric acid.

The mixed fracturing fluid provided by the embodiment of the invention has the advantages that when the mixed fracturing fluid is specifically applied and the acid is mixed between hydrochloric acid and hydrofluoric acid, the concentration of the hydrochloric acid is positively correlated with the content of calcium in reservoir rock, and the concentration of the hydrofluoric acid is negatively correlated with the concentration of the calcium in the reservoir rock.

The mixed fracturing fluid provided by the embodiment of the invention is characterized in that the acid is added with a corrosion inhibitor accounting for 0.1-2.5% of the matrix mass of the fracturing fluid.

Preferably, the concentration of the corrosion inhibitor is directly correlated to the concentration of the acid.

The corrosion inhibitor is added to avoid corrosion of the wellbore, and can be imidazoline or acetylene oxygen methylamine. Imidazoline and alkynyloxymethyl amine can effectively inhibit the corrosion of acid on the shaft and protect the shaft.

The mixed fracturing fluid provided by the embodiment of the invention is characterized in that the sand is quartz sand or ceramsite sand, and the size of the sand is 20-100 meshes.

Preferably, the sand content is 5-50% of the volume of the fracturing fluid matrix.

More preferably, the sand is present in an amount of 17% to 23% by volume of the fracturing fluid matrix. The mixed fracturing fluid has good enough fracturing effect, and also has good fluid loss and resistance reducing performance.

The mixed fracturing fluid of one embodiment of the invention, wherein the activator is sodium dodecyl benzene sulfonate or the like (such as sodium tetrapropylene benzene sulfonate and sodium diisooctyl succinate sulfonate).

Preferably, the concentration of the active agent is 2-9% of the mass of the fracturing fluid matrix;

more preferably, the concentration of the active agent is 3-6% of the mass of the fracturing fluid matrix. The function of the active agent increases the reaction rate of acid rock and the fluidity of crude oil, has the capacity of displacing oil and can further improve the yield.

The mixed fracturing fluid of one embodiment of the invention is characterized in that the fracturing fluid matrix is an aqueous solution containing 0.1-0.8 mass% of a thickening agent, and the thickening agent is biogum (biopolymer or polysaccharide obtained by microbial fermentation), such as xanthan gum (extracellular acidic heteropolysaccharide produced by Xanthomonas campestris fermentation) or a derivative thereof. The mixed fracturing fluid provided by the embodiment of the invention is characterized in that the thickening agent in the fracturing fluid matrix is fenugreek gum or a derivative thereof without a cross-linking agent.

Wherein the concentration of the thickening agent (xanthan gum or fenugreek gum or derivatives thereof) in the fracturing fluid is positively correlated with the formation temperature and/or the acid concentration.

Preferably, the concentration of the xanthan gum in the xanthan gum non-crosslinked fracturing fluid matrix is 0.1-0.8%. More preferably 0.4 to 0.6%.

Preferably, the concentration of the fenugreek gum in the fenugreek gum non-crosslinked fracturing fluid matrix is 0.1-0.8%. More preferably 0.4 to 0.6%.

The mixed fracturing fluid of one embodiment of the present invention, wherein the thickening agent comprises xanthan gum and fenugreek gum, preferably in a weight ratio of 3:2, for example, the fracturing fluid comprises 0.45% of xanthan gum and 0.3% of fenugreek gum. These all can improve the sand-carrying performance and resistance-reducing performance of the mixed fracturing fluid.

The invention also provides application of any one of the mixed fracturing fluids in oil and gas reservoir transformation.

The mixed fracturing fluid provided by the embodiment of the invention further comprises 0.001-0.003% of sodium borohydride, 0.002-0.005% of amino resin, 0.001-0.006% of methacrylic acid and 0.03-0.1% of hydroxyethyl cellulose in percentage by mass.

The viscosity of the xanthan gum non-crosslinked fracturing fluid matrix can be further increased by the amino resin and the hydroxyethyl cellulose, and the sodium borohydride can further increase the thermal stability of the fracturing fluid as an auxiliary thickening agent; methacrylic acid can be used to increase the viscosity and stability of the fracturing fluid matrix.

The mixed fracturing fluid provided by the embodiment of the invention further comprises 0.02-0.1% of potassium chloride and 0.005-0.01% of salicylate.

Wherein, potassium chloride and salicylate can be used as fluid stabilizer to further increase the stability of the fracturing fluid matrix.

For example, the fracturing fluid can be used as slickwater fracturing fluid or pre-fracturing fluid in oil and gas reservoir transformation, can also be used as sand carrying fluid, can also be used as acid solution for reservoir acidification, and can also be used as flooding fluid.

Where the hydrocarbon reservoir is referred to as a clastic rock reservoir.

The invention also provides an oil and gas reservoir transformation method combining sand fracturing and acidification, which combines two modes of sand fracturing and acidification, namely fracturing fluid simultaneously contains acid and sand, and the two modes simultaneously carry out reservoir transformation; the fracturing fluid is the mixed fracturing fluid which is acid and alkali resistant.

According to the method for improving the oil and gas reservoir, the mixed fracturing fluid is obtained by adding acid into a fracturing fluid matrix and then adding sand, so that the fracturing fluid contains the acid and the sand at the same time. Whereby acid (or acid and active agent) and sand enter the reservoir fracture simultaneously for sand fracturing and acidizing (and possibly simultaneous flooding).

The method for modifying the oil and gas reservoir disclosed by the embodiment of the invention is characterized in that the acid and the sand are simultaneously added into the mixed fracturing fluid, so that the matrix of the fracturing fluid simultaneously contains the acid and the sand. Whereby acid (or acid and active agent) and sand enter the reservoir fracture simultaneously for sand fracturing and acidizing (and possibly simultaneous flooding).

The method for modifying the oil and gas reservoir disclosed by the embodiment of the invention is characterized in that the mixed fracturing fluid is used as slickwater fracturing fluid, or as pre-fracturing fluid, or as acid liquor for acidification, or can be used as flooding fluid only by adding acid (or acid and an active agent) into a fracturing fluid matrix without adding sand.

A hydrocarbon reservoir reformation method of one embodiment of the present invention, wherein when there is more sand added (i.e., when the sand ratio is high), the acid concentration is low (no or little acid added).

The method of hydrocarbon reservoir reconstruction of any of the embodiments above, wherein the hydrocarbon reservoir may be a clastic rock reservoir.

(III) advantageous effects

The invention has the beneficial effects that:

the mixed fracturing fluid is prepared by adding sand and acid (or acid and an active agent) into the fracturing fluid, so that sand fracturing and acidification (and an oil displacement technology) can be combined, when the mixed fracturing fluid is applied to oil and gas reservoir transformation, not only can the sand carried by the fracturing fluid be used for supporting a wide place of a crack, but also the acid carried by the fracturing fluid can be used for carrying out acid etching and cleaning on a narrow crack which cannot be reached by the sand, so that the narrow place of the crack has a certain flow conductivity, and the oil displacement effect of the active agent is added, so that the reservoir transformation effect is improved.

The invention relates to an oil gas reservoir transformation method combining acid adding and sand adding fracturing, which adopts a fracturing technology combining acid adding and sand adding, namely in the hydraulic fracturing process, the fracturing fluid contains acid and sand, so that the sand can enter a wide place of a fracture to play a supporting role, the sand carried by the fracturing fluid cannot enter a narrow place of the fracture, but the acid carried by the fracturing fluid can enter the fracture, the acid can acid-etch the fracture and clean the fracture, including a filtration zone around the fracture, and the narrow place of the fracture is ensured to have certain flow conductivity, thus the chemical and physical methods are combined, so that the far ends of all the fractures and the fractures can be ensured to have better flow conductivity, the seepage capacity of the filtration zone around the fracture can be improved, and the reservoir transformation effect is greatly improved.

Detailed Description

The design idea of the invention is mainly as follows: the traditional fracturing fluid cannot contain acid, needs crosslinking, has high viscosity and only has a sand fracturing function, but the mixed fracturing fluid developed by the invention has no crosslinking and low viscosity, has several functions of sand fracturing and acidizing (and oil displacement) after acid (or acid and an active agent) is added, can simultaneously perform sand fracturing and acidizing, improves the traditional fracturing process, and particularly enables the acid in the mixed fracturing fluid to enter narrow cracks which cannot be removed by adopting the sand carried by the traditional fracturing fluid originally, changes ineffective cracks into effective cracks, and greatly increases the modification range and the modification effect of a reservoir stratum.

Meanwhile, the traditional fracturing fluid is required to have high viscosity, and the fluid loss resistance is required in the fracturing process, but the mixed fracturing fluid disclosed by the invention is low in viscosity due to acid, so that the fluid loss can be required to deeply acidify the pores of a reservoir matrix on the wall surface of a fracture in the fracturing and slotting process, thereby changing the concept (fluid loss property) of the fracturing fluid and overcoming the technical bias.

The mixed fracturing fluid of the invention adds acid into the uncrosslinked low-viscosity fracturing fluid, and utilizes the higher filtration property of the low-viscosity fracturing fluid in the fracturing and slotting process, so that the acid is deeply inserted into the pores of the matrix of the reservoir on the wall surface of an acidized fracture, the stratum reconstruction effect of the fracturing fluid is obviously improved, and the technical prejudice that the fracturing fluid cannot have filtration property and cannot contain acid in the prior art is overcome.

The active agent can further increase the acid corrosion reaction efficiency of acid, and simultaneously, the mixed fracturing fluid has oil displacement capacity in the injection and flowback processes. The cross-linked high-viscosity fracturing fluid in the prior art cannot contain acid at the same time, and has no acidification function, because the acid can seriously damage the sand suspending capacity of the high-viscosity fracturing fluid and influence the fracturing performance of the high-viscosity fracturing fluid.

By adding the sand, the fracturing performance of the mixed fracturing fluid is improved, the low-viscosity uncrosslinked fracturing fluid can be used for obtaining a good enough fracturing effect, and the sand has good filtration and resistance reduction performance.

For a better understanding of the present invention, reference will now be made in detail to the present invention by way of specific embodiments thereof.

The method for modifying clastic rock reservoir by combining acidification and sand fracturing is described in detail below by taking modification of clastic rock reservoir by xanthan gum non-crosslinked fracturing fluid (Zhongxing energy technology Co., Ltd. in Beijing century) as an example.

The steps of the first embodiment are as follows:

s1: preparing (e.g., preparing at a well site) a 0.45 mass% aqueous solution of xanthan gum, i.e., a non-crosslinked fracturing fluid, at 300 f (or continuously compounding);

s2: the method is characterized in that a fracturing truck is used for pumping fracturing fluid into an underground reservoir through a shaft, and in the pumping process, a tank (or a buffer tank) for containing the fracturing fluid and a sand mixer truck (with a hopper) are respectively connected with a wellhead through the fracturing truck, and specifically:

s2.1: in the process of pumping the first half (150 square) of the fracturing fluid, acid is added into a hopper of a sand mixing truck, 9 wt% of hydrochloric acid (namely the fracturing fluid contains 9 wt% of HCl, the same below), 2 wt% of hydrofluoric acid (namely the fracturing fluid contains 2 wt% of HF, the same below) and 2 wt% of corrosion inhibitor (any existing corrosion inhibitor can be used, imidazoline is adopted in the embodiment) are mixed uniformly with the fracturing fluid and pumped into an underground reservoir through the fracturing truck,

s2.2: in the latter half (150 square) process of pumping the fracturing fluid, 30-50 meshes of ceramsite sand which accounts for 20% of the volume of the fracturing fluid is added through a hopper of a sand mixer, uniformly mixed with the fracturing fluid and pumped into underground reservoir fractures through a shaft;

s3: and replacing the fracturing fluid mixture with ammonium chloride or clear water or fracturing fluid with about 10 square meters.

The steps of the second embodiment are as follows:

s1: preparing (e.g., formulating at a well site) a 0.45% mass concentration xanthan gum non-crosslinked fracturing fluid 300 square (or continuous compounding);

s2.1: in the process of pumping 100 times of fracturing fluid, acid and sodium dodecyl benzene sulfonate are added into a bucket of a sand mixing truck until the acid and the sodium dodecyl benzene sulfonate contain 9 wt% of hydrochloric acid, 2 wt% of active agent, 2 wt% of hydrofluoric acid and 2.1 wt% of alkynyloxymethyl amine, the materials and the fracturing fluid are uniformly mixed and then pumped into an underground reservoir through the fracturing truck,

s2.2: in the process of pumping 100 square of the fracturing fluid, 30-50 meshes of ceramsite sand which accounts for 10% of the volume of the fracturing fluid in the part is added through a bucket of a sand mixing truck, acid is added until the fracturing fluid contains 7 wt% of hydrochloric acid and 0.5 wt% of corrosion inhibitor, the mixture is uniformly mixed with the fracturing fluid, and the mixture is pumped into underground reservoir fractures through a shaft.

S2.3: in the process of pumping 100 times of the fracturing fluid, 30-50 meshes of ceramsite sand which accounts for 20% of the volume of the fracturing fluid is added through a hopper of a sand mixing truck, is uniformly mixed with the fracturing fluid and is pumped into underground reservoir fractures through a shaft;

s3: and replacing the fracturing fluid with 7-10 square ammonium chloride replacing fluid.

The steps of the third embodiment are as follows:

s2: the method is characterized in that a fracturing truck is used for pumping fracturing fluid into an underground reservoir through a shaft, and in the pumping process, a tank (or a buffer tank) for containing the fracturing fluid and a sand mixer truck (with a hopper) are connected with a wellhead through the fracturing truck, and specifically:

s2.1: in the process of pumping 50 parts before the fracturing fluid, acid is added into a hopper of a sand mixing truck until the acid contains 10 wt% of hydrochloric acid, 1 wt% of hydrofluoric acid and 1 wt% of alkynyloxymethyl amine, the acid and the fracturing fluid are uniformly mixed and then pumped into an underground reservoir through the fracturing truck,

s2.2: in the second 50-square process of pumping the fracturing fluid, 50-80 mesh ceramsite sand and acid which account for 15% of the volume of the fracturing fluid are added through a hopper of a sand mixing truck until the fracturing fluid contains 8 wt% of hydrochloric acid and 0.5 wt% of imidazoline, the mixture is uniformly mixed with the fracturing fluid and is pumped into underground reservoir fractures through a shaft,

s2.3: in the third 50-way process of pumping the fracturing fluid, acid is added through a hopper of a sand mixing truck until the acid contains 9 wt% of hydrochloric acid, 2 wt% of hydrofluoric acid and 1 wt% of imidazoline, the acid and the fracturing fluid are uniformly mixed, the mixture is pumped into underground reservoir fractures through a shaft,

s2.4: in the fourth 50-square process of pumping the fracturing fluid, 30-50 meshes of ceramsite sand and acid accounting for 25% of the volume of the fracturing fluid are added through a hopper of a sand mixing truck, until the fracturing fluid contains 7 wt% of hydrochloric acid and 0.5 wt% of imidazoline, the mixture is uniformly mixed with the fracturing fluid and is pumped into underground reservoir fractures through a shaft,

s2.5: in the process of pumping 100 times of the fracturing fluid, 30-50 meshes of ceramsite sand which accounts for 30% of the volume of the fracturing fluid is added through a hopper of a sand mixing truck, is uniformly mixed with the fracturing fluid and is pumped into underground reservoir fractures through a shaft;

s3: and replacing the fracturing fluid mixture with 10-12 square ammonium chloride or clear water.

The steps of the fourth embodiment are as follows:

s1: preparing 100 parts of 0.35 mass% xanthan gum non-crosslinked fracturing fluid, 100 parts of 0.6 mass% xanthan gum non-crosslinked fracturing fluid and 100 parts of 0.45 mass% xanthan gum non-crosslinked fracturing fluid;

s2: injecting the fracturing fluid prepared in the step S1 into the well, specifically:

s2.1: adding acid into xanthan gum non-crosslinked fracturing fluid with mass concentration of 0.35% until the xanthan gum non-crosslinked fracturing fluid contains 1 wt% of hydrochloric acid, mixing uniformly, injecting,

s2.2: adding acid and 12-square sand into xanthan gum non-crosslinked fracturing fluid with the mass concentration of 0.6%, uniformly mixing, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 8 wt% of hydrochloric acid and 0.5 wt% of imidazoline, the sand is 30-50 meshes of ceramsite sand,

s2.3: adding acid and 5.2 square sand into 0.45 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 8 wt% of hydrochloric acid, 1 wt% of hydrofluoric acid and 0.5 wt% of imidazoline, the sand is 50-80 mesh quartz sand,

The steps of the fifth embodiment are as follows:

s1: preparing 100 parts of 0.55 mass% xanthan gum non-crosslinked fracturing fluid, 100 parts of 0.4 mass% xanthan gum non-crosslinked fracturing fluid and 100 parts of 0.45 mass% xanthan gum non-crosslinked fracturing fluid;

s2.1: adding acid into xanthan gum non-crosslinked fracturing fluid with mass concentration of 0.55% until the xanthan gum non-crosslinked fracturing fluid contains 3 wt% of hydrochloric acid, 2 wt% of hydrofluoric acid and 0.5 wt% of imidazoline, mixing uniformly, injecting,

s2.2: adding acid and 2.9 square sand into 0.4 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 8.5 wt% of hydrochloric acid and 0.5 wt% of imidazoline, the sand is 50-80 mesh ceramsite,

s2.3: adding acid and 12-square sand into xanthan gum non-crosslinked fracturing fluid with the mass concentration of 0.45%, uniformly mixing, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 10 wt% of hydrochloric acid, 1 wt% of hydrofluoric acid and 1 wt% of imidazoline, the sand is 80-100 meshes of quartz sand,

s3: and replacing the fracturing fluid with 10-square ammonium chloride replacing fluid.

The steps of the sixth embodiment are as follows:

s1: preparing 100 parts of 0.45 mass% xanthan gum non-crosslinked fracturing fluid, 100 parts of 0.35 mass% xanthan gum non-crosslinked fracturing fluid and 100 parts of 0.5 mass% xanthan gum non-crosslinked fracturing fluid;

s2.1: adding acid into xanthan gum non-crosslinked fracturing fluid with mass concentration of 0.45% until the xanthan gum non-crosslinked fracturing fluid contains 9 wt% of hydrochloric acid and 0.5 wt% of imidazoline, mixing uniformly, injecting,

s2.2: adding acid and 9.2 square sand into 0.35 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 12wt percent hydrochloric acid and the sand is 30-50 meshes of ceramsite sand,

s2.3: adding acid and 22-square sand into 0.5 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 5 wt% of hydrochloric acid and 0.5 wt% of imidazoline, the sand is 50-80 mesh ceramsite sand,

s3: and replacing the fracturing fluid with 10-12 square ammonium chloride replacing fluid.

The steps of the seventh embodiment are as follows:

s1: preparing 100 parts of 0.45 mass% xanthan gum non-crosslinked fracturing fluid, 50 parts of 0.35 mass% xanthan gum non-crosslinked fracturing fluid, 50 parts of 0.6 mass% xanthan gum non-crosslinked fracturing fluid, 50 parts of 0.55 mass% xanthan gum non-crosslinked fracturing fluid and 50 parts of 0.4 mass% xanthan gum non-crosslinked fracturing fluid;

s2.1: adding acid and active agent into 0.45% xanthan gum non-crosslinked fracturing fluid, mixing, injecting, wherein the solution contains 8 wt% hydrochloric acid, 0.5 wt% imidazoline and 3 wt% active agent (tetrapropylene sodium benzenesulfonate),

s2.2: adding acid and 1.2 square sand into 0.35 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 4 wt% of hydrofluoric acid, the sand is 30-50 meshes of quartz sand,

s2.3: adding acid into xanthan gum non-crosslinked fracturing fluid with mass concentration of 0.6% until the xanthan gum non-crosslinked fracturing fluid contains 11 wt% of hydrochloric acid and 1 wt% of imidazoline, mixing uniformly, injecting,

s2.4: adding acid and 7.2 square sand into 0.55 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 9.8 wt% of hydrochloric acid and 0.5 wt% of imidazoline, the sand is 50-80 mesh quartz sand,

s2.5: adding 18-square sand into 0.4 mass percent xanthan gum water-containing solution, mixing uniformly and injecting, wherein the sand is 30-50 meshes of quartz sand,

The steps of the eighth embodiment are as follows:

s1: preparing 100 parts of non-crosslinked fracturing fluid containing 0.25% of xanthan gum, 0.002% of sodium borohydride, 0.003% of amino resin, 0.003% of methacrylic acid and 0.2% of hydroxyethyl cellulose aqueous solution in mass concentration;

s2: adding acid and 12-square sand into the xanthan gum non-crosslinked fracturing fluid prepared in the step S1, uniformly mixing, and injecting into a well, wherein the xanthan gum non-crosslinked fracturing fluid contains 9.5 wt% of hydrochloric acid, 1.5 wt% of hydrofluoric acid and 1 wt% of alkynyloxymethyl amine, and the sand is 30-50 meshes of ceramsite sand;

s3: and replacing the fracturing fluid with 8-10 square ammonium chloride replacing fluid.

The steps of the ninth embodiment are as follows:

s1: preparing (e.g., preparing at a well site) 150 parts of xanthan gum non-crosslinked fracturing fluid with a mass concentration of 0.27%, 150 parts of xanthan gum non-crosslinked fracturing fluid with a mass concentration of 0.4% (or continuously blending);

s2.1: adding acid into 0.27% xanthan gum non-crosslinked fracturing fluid until the xanthan gum non-crosslinked fracturing fluid contains 8.5 wt% hydrochloric acid, 2.5 wt% hydrofluoric acid and 1.1 wt% alkynyloxymethyl amine, mixing uniformly, injecting,

s2.2: adding 41.4-square quartz sand of 40-70 meshes into xanthan gum non-crosslinked fracturing fluid with the mass concentration of 0.4%, and injecting the mixture into a well after uniformly mixing;

s3: and replacing the fracturing fluid mixture with 7-9 square ammonium chloride or clear water or fracturing fluid.

The steps of the tenth embodiment are as follows:

s1: preparing (e.g., preparing at a well site) 200 parts of xanthan gum non-crosslinked fracturing fluid with a mass concentration of 0.45% and 100 parts of xanthan gum non-crosslinked fracturing fluid with a mass concentration of 0.48% (or continuously blending);

s2.1: in the process of pumping xanthan gum non-crosslinked fracturing fluid with the mass concentration of 0.45 percent at the front 100 sides, acid is added into a hopper of a sand mixing truck until the acid contains 7 weight percent of hydrochloric acid, 3 weight percent of hydrofluoric acid and 0.9 weight percent of alkynyloxymethyl amine, the mixture is evenly mixed with the fracturing fluid and then injected,

s2.2: in the process of pumping 0.45 mass percent of xanthan gum non-crosslinked fracturing fluid at the rear 100 sides, acid and 8.9 sides of 60-80 meshes of quartz sand containing 4wt percent of hydrochloric acid are added, and the mixture is uniformly mixed with the fracturing fluid and then injected.

S2.3: in the process of pumping 0.48 mass percent of xanthan gum non-crosslinked fracturing fluid, adding acid and 36.5 square 20-40 mesh ceramsite sand, wherein the ceramsite sand contains 4 wt% of hydrochloric acid and 0.1 wt% of corrosion inhibitor alkynyloxymethyl amine, uniformly mixing with the fracturing fluid, and pumping the mixture into underground reservoir fractures through a wellbore;

s3: and (3) replacing the fracturing fluid with 9-11 square ammonium chloride replacing fluid.

The steps of the eleventh embodiment are as follows:

s1: preparing (e.g., formulating at a well site) a 0.7% mass concentration xanthan gum non-crosslinked fracturing fluid 300 square (or continuous compounding);

s2.1: adding acid in the process of pumping the front 50-square fracturing fluid until the acid contains 6.5 wt% of hydrochloric acid and 0.2 wt% of hydrofluoric acid, mixing the acid with the fracturing fluid uniformly, injecting the mixture,

s2.2: adding 6.7 parts of 30-50 mesh quartz sand and acid in the process of pumping the second 50 parts of fracturing fluid until the mixture contains 7.5 wt% of hydrochloric acid and 0.3 wt% of imidazoline, mixing the mixture with the fracturing fluid uniformly and injecting the mixture,

s2.3: in the process of pumping the third 50-square fracturing fluid, acid is added through a hopper of a sand mixing truck until the acid contains 11 wt% of hydrochloric acid and 0.7 wt% of imidazoline, the acid and the fracturing fluid are uniformly mixed and then injected,

s2.4: adding 7.2 parts of 60-80 mesh ceramsite sand and acid in the process of pumping the fourth 50 parts of fracturing fluid, wherein the acid concentration is 6 percent of hydrochloric acid and 0.2 percent of imidazoline, mixing the hydrochloric acid and the imidazoline with the fracturing fluid uniformly, injecting the mixture,

s2.5: adding 46.4 square of 20-40 mesh quartz sand into 100 square of fracturing fluid (the concentration of hydrochloric acid is 2%) after pumping, uniformly mixing with the fracturing fluid, and injecting;

s3: and replacing the fracturing fluid mixture with 12-15 square ammonium chloride or clear water.

The steps of the twelfth embodiment are as follows:

s1: preparing 100 parts of 0.35 mass% xanthan gum non-crosslinked fracturing fluid, 100 parts of 0.8 mass% xanthan gum non-crosslinked fracturing fluid and 100 parts of 0.45 mass% xanthan gum non-crosslinked fracturing fluid;

s2.1: adding acid and sodium dodecyl benzene sulfonate into xanthan gum non-crosslinked fracturing fluid with the mass concentration of 0.35%, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 7 wt% of hydrochloric acid and 2 wt% of active agent,

s2.2: adding acid and 22.3-square sand into 0.8 mass percent xanthan gum non-crosslinked fracturing fluid at the front 50 sides, uniformly mixing, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 9 wt% of hydrochloric acid, 3.5 wt% of hydrofluoric acid and 0.1 wt% of imidazoline, the sand is 20-40 mesh ceramsite sand,

s2.3: adding acid, diisooctyl succinate sodium sulfonate and 25-square 20-40 mesh quartz sand into 0.8 mass percent xanthan gum non-crosslinked fracturing fluid at the rear 50 sides, wherein the sulfuric acid contains 1wt percent of hydrochloric acid and 10wt percent of active agent, and injecting the mixture after uniformly mixing with the fracturing fluid;

s2.4: adding acid and 18.2 square sand into 0.45 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 7.5 wt% of hydrochloric acid and 0.45 wt% of imidazoline, the sand is quartz sand of 60-80 meshes,

s3: and replacing the fracturing fluid with 8-9 square ammonium chloride replacing fluid.

The steps of the thirteenth embodiment are as follows:

s1: preparing 100 parts of 0.1% by mass xanthan gum non-crosslinked fracturing fluid, 100 parts of 0.27% by mass xanthan gum non-crosslinked fracturing fluid, and 100 parts of non-crosslinked fracturing fluid containing 0.27% by mass xanthan gum, 0.001% of sodium borohydride, 0.002% of amino resin, 0.001% of methacrylic acid, 0.05% of hydroxyethyl cellulose and 0.08% of potassium chloride and 0.005% of sodium salicylate aqueous solution;

s2.1: adding acid into xanthan gum non-crosslinked fracturing fluid with mass concentration of 0.1%, mixing uniformly, injecting, wherein the acid contains 5 wt% of hydrochloric acid and 0.4% of imidazoline,

s2.2: adding acid and 8.9 square sand into 0.27 mass percent xanthan gum non-crosslinked fracturing fluid, mixing uniformly, injecting, wherein the xanthan gum non-crosslinked fracturing fluid contains 9.5 wt% of hydrochloric acid and 0.4 wt% of corrosion inhibitor, the sand is 60-80 mesh ceramsite,

s2.3: adding acid and 33.8 square sand into non-crosslinked fracturing fluid of 0.27% of xanthan gum, 0.001% of sodium borohydride, 0.002% of amino resin, 0.001% of methacrylic acid, 0.05% of hydroxyethyl cellulose and 0.08% of potassium chloride, 0.005% of sodium salicylate water solution, mixing uniformly, injecting, wherein the mixture contains 3 wt% of hydrochloric acid and the sand is 20-40 mesh quartz sand,

The properties of the fracturing fluids in the above examples were analyzed in combination with experimental data.

Test results 1

The test example is used for detecting the apparent viscosity of the non-crosslinked fracturing fluid after adding acid, the sedimentation rate of 0.45-0.9 mm ceramsite sand (20-50 meshes) in the mixed fracturing fluid and the drag reduction rate of the mixed fracturing fluid. The apparatus used to measure the apparent viscosity was a FANN-35 type viscometer. The results are shown in Table 1.

TABLE 1

From experimental data, the mixed fracturing fluid, namely the non-crosslinked xanthan gum fracturing fluid and the acid (or the acid and the active agent) have strong sand suspending capacity after being mixed, and especially have strong sand carrying capacity in a flowing process. The mixed fracturing fluid has good resistance reduction performance, reduces frictional resistance, can more effectively transmit pressure to the bottom of a well, and has strong fracturing and crack-making functions.

Test results 2

The test example was conducted to examine the corrosion of the sandstone sample by the acid in the first to thirteenth embodiments of the present invention. The sandstone sample is a rock debris sample of a test well in a Clamayy oil field land beam area. The test method is in accordance with the industry standard. The results are shown in Table 2.

TABLE 2

From experimental data, the acid carried by the fracturing fluid of the present invention can erode some of the rock components of the reservoir (fluid loss zone) in and on the walls of the sandstone reservoir. In the narrow place of crack, the sand that fracturing fluid carried can not get into, but the acid that fracturing fluid carried can get into, because acid has certain corrosion rate, can let the narrow crack also have certain water conservancy diversion ability, and the seepage flow ability on the crack wall face also can become better. Where the fracture is wide, sand and acid carried by the fracturing fluid can enter. The results of the experiments for the other examples are substantially similar.

The invention is further illustrated below in comparison with comparative examples of the prior art.

In 2013, 13 wells were tested in the land beam oil field and a certain oil field of the cramary oil field by carrying sand and acid with xanthan gum non-crosslinked fracturing fluid according to the first to thirteenth examples, 13 adjacent wells (comparison wells) were carried out with sand with conventional guar gel fracturing fluid, and after three years of production, yield comparison was performed, and the comparison results are shown in table 3.

TABLE 3

Comparison of yield after 3 years of putting into production	Average daily output (ton)	Average daily oil production (ton)
			Test well	16.13	6.39
Contrast well	8.9	2.45

As can be seen from table 3, the reforming effect (especially the yield increase effect) of the reservoir reforming technology of the present invention is much better than that of the conventional technology, the liquid yield is basically doubled, and the oil yield is approximately tripled.

The mixed fracturing fluid can be used as a thickening agent in the fracturing fluid by using biological gums (such as xanthan gum and derivatives thereof) such as biological polymers or polysaccharides obtained by microbial fermentation, and can also be used as a thickening agent in the fracturing fluid by using fenugreek gum and derivatives thereof without a cross-linking agent.

For example, a mixed fracturing fluid of any of the formulations described below may be used.

Modified xanthan gum BX (obtained by etherification of xanthan gum with 1-bromotetradecane as a modifier), fenugreek gum FG, and hydroxypropyl fenugreek gum HPFG will be described below as an example.

Formula 1: in the 100-square mass percent 0.1% modified xanthan gum BX non-crosslinked fracturing fluid, acid and 1-square sodium tetrapropylene benzene sulfonate are added, wherein the acid contains 6 wt% hydrochloric acid.

And (2) formula: adding acid into 100 square mass percent of 0.15 percent of modified xanthan gum BX non-crosslinked fracturing fluid until the modified xanthan gum BX non-crosslinked fracturing fluid contains 5 weight percent of hydrochloric acid and 0.1 weight percent of alkynyloxymethyl amine.

And (3) formula: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.28 percent in 100 prescription is added with acid and 13.5 prescription of sand, wherein the acid comprises 3.7 weight percent of hydrochloric acid and 0.3 weight percent of alkynyloxymethyl amine, and the sand is 50-80 meshes of ceramsite sand.

And (4) formula: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.34 percent in 100 prescription is added with acid and 18.7 prescription of sand, wherein the acid contains 2 weight percent of hydrochloric acid, and the sand is 20-40 mesh quartz sand.

And (5) formula: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.4 percent in 100 square is added with acid and 9.5 square sand, wherein the modified xanthan gum BX non-crosslinked fracturing fluid contains 8.4 weight percent of hydrochloric acid, 2 weight percent of hydrofluoric acid and 0.7 weight percent of corrosion inhibitor, and the sand is quartz sand with the mesh size of 40-70.

And (6) formula: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.44 percent in 100 square is added with acid and 21 square of sand, wherein the sand contains 7.9 weight percent of hydrochloric acid, 1.5 weight percent of hydrofluoric acid and 1 weight percent of imidazoline, and the sand is 30-50 meshes of ceramsite sand.

And (3) formula 7: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.45 percent in 100 prescription is added with acid and 43 prescription of sand, wherein the acid and 43 prescription of sand comprise 10.7 weight percent of hydrochloric acid and 0.4 weight percent of imidazoline, and the sand is 30-50 meshes of ceramsite sand.

And (4) formula 8: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.46 percent in 100 is added with acid and 13.6-square sand, wherein the acid and 13.6-square sand comprise 12 weight percent of hydrochloric acid and 1.5 weight percent of imidazoline, and the sand is quartz sand with 30-50 meshes.

Formula 9: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.53 percent in 100 square is added with acid, sodium dodecyl benzene sulfonate and 15.4 square sand, wherein the modified xanthan gum BX non-crosslinked fracturing fluid contains 12 weight percent of hydrofluoric acid, 0.2 weight percent of imidazoline and 6 percent of active agent, and the sand is 20-40 mesh ceramsite sand.

Formula 10: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.58 percent in 100 square is added with acid and 32.5 square sand, wherein the modified xanthan gum BX non-crosslinked fracturing fluid contains 9 weight percent of hydrochloric acid, 1.8 weight percent of hydrofluoric acid and 0.5 weight percent of imidazoline, and the sand is quartz sand with 30-50 meshes.

Formula 11: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.66 percent in 100 square is added with acid and 47.3 square of sand, wherein the sand contains 11 weight percent of hydrochloric acid, 0.7 weight percent of hydrofluoric acid and 1.2 weight percent of imidazoline, and the sand is 20-40 mesh quartz sand.

Formula 12: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.72 percent in 100 sides is added with acid and 9 sides of sand, wherein the sand contains 6.5 weight percent of hydrochloric acid and 0.5 weight percent of alkynyloxymethyl amine, and the sand is quartz sand with the mesh of 30-50.

Formula 13: the modified xanthan gum BX non-crosslinked fracturing fluid with the mass percent of 0.8 percent in the 100 formula is added with acid, diisooctyl succinate sodium sulfonate (9 percent) and 50 formula of sand, wherein the sand contains 11.6 percent by weight of hydrochloric acid, 0.4 percent by weight of hydrofluoric acid and 0.5 percent by weight of imidazoline, and the sand is 30-50 meshes of ceramsite sand.

The following description will take fenugreek gum (Anhui Sixian plant Gum factory) as an example.

Formula 14: in the 100-square mass percent 0.1 percent non-crosslinked fenugreek gum fracturing fluid, acid is added, wherein the acid comprises 5 weight percent of hydrochloric acid and 0.1 weight percent of alkynyloxymethyl amine.

Formula 15: in the fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.17 percent of 100, acid, diisooctyl succinate sodium sulfonate (3 percent) and sand with the mass of 13 are added, wherein the hydrochloric acid with the mass percent of 1 percent is contained, and the sand is 50-80 meshes of ceramsite sand.

Formula 16: in the 100-square mass percent of fenugreek gum non-crosslinked fracturing fluid, acid and 9.6-square sand are added, wherein the acid and the 9.6-square sand comprise 10 wt% of hydrochloric acid and 0.6 wt% of alkynyloxymethyl amine, and the sand is 80-100 meshes of quartz sand.

Formula 17: in the 100-square mass percent fenugreek gum non-crosslinked fracturing fluid, acid and 25.7-square sand are added, wherein the acid and the 25.7-square sand comprise 3 wt% of hydrochloric acid and 1 wt% of hydrofluoric acid, and the sand is 30-50 mesh ceramsite sand.

Formula 18: in the fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.42 percent of 100, acid, 8-square sodium dodecyl benzene sulfonate and 50-square sand are added, wherein the acid, the 8-square sodium dodecyl benzene sulfonate and the 50-square sand contain 3 weight percent of hydrochloric acid, and the sand is 80-100 meshes of quartz sand.

Formulation 19: in the 100-square mass percent fenugreek gum non-crosslinked fracturing fluid, acid and 32.1-square sand are added, wherein the acid and the 32.1-square sand comprise 8 wt% of hydrochloric acid, 1.8 wt% of hydrofluoric acid and 0.15 wt% of imidazoline, and the sand is 30-50 meshes of ceramsite sand.

The formula 20 is as follows: in the 100-square mass percent of fenugreek gum non-crosslinked fracturing fluid, acid and 18.2-square sand are added, wherein the acid comprises 10 wt% of hydrochloric acid, 1 wt% of hydrofluoric acid and 1 wt% of alkynyloxymethyl amine, and the sand is 30-50-mesh quartz sand.

Formula 21: in the 100-square mass percent of the fenugreek gum non-crosslinked fracturing fluid, acid and 7.8-square sand are added, wherein the acid and the 7.8-square sand contain 12 wt% of hydrochloric acid and 0.8 wt% of imidazoline, and the sand is quartz sand with 30-50 meshes.

Formula 22: in the 100-square mass percent fenugreek gum non-crosslinked fracturing fluid, acid and 30.3-square sand are added, wherein the acid and the 30.3-square sand contain 7 wt% of hydrofluoric acid, and the sand is 60-80 mesh quartz sand.

Formula 23: in the fenugreek gum non-crosslinked fracturing fluid with the mass percent of 100, acid, 3-square sodium tetrapropylene benzene sulfonate and 36.5-square sand are added, wherein the acid, the 3-square sodium tetrapropylene benzene sulfonate and the 36.5-square sand contain 9 wt% of hydrochloric acid and 2 wt% of hydrofluoric acid, and the sand is 30-50 meshes of ceramsite sand.

Formula 24: in the 100-square mass percent of the fenugreek gum non-crosslinked fracturing fluid, acid and 23.9-square sand are added, wherein the acid comprises 6 wt% of hydrochloric acid, and the sand is 30-50 meshes of quartz sand.

Formulation 25: in the 100-square mass percent fenugreek gum non-crosslinked fracturing fluid, acid and 5-square sand are added, wherein the acid and the 5-square sand comprise 9 wt% of hydrochloric acid and 1.5 wt% of hydrofluoric acid, and the sand is 20-40 mesh ceramsite sand.

Formulation 26: in the 100-square mass percent of fenugreek gum non-crosslinked fracturing fluid, acid and 48-square sand are added, wherein the acid and the 48-square sand comprise 11 wt% of hydrochloric acid and 2.5 wt% of alkynyloxymethyl amine, and the sand is 20-40 mesh ceramsite sand.

The following description will be given by taking hydroxypropyl fenugreek gum (Shanghai Shangqijiu food chemical Co., Ltd.) as an example.

Formulation 27: 0.1 percent of hydroxypropyl fenugreek gum non-crosslinked fracturing fluid in 100 percent by mass is added with acid, wherein the acid contains 7.5 percent by weight of hydrochloric acid.

Formula 28: in 100-square mass percent 0.2 percent hydroxypropyl fenugreek gum non-crosslinked fracturing fluid, acid and 8-square sand are added, wherein the acid and the 8-square sand comprise 4.2 weight percent hydrochloric acid and 0.2 weight percent alkynyloxymethyl amine, and the sand is 50-80 meshes of quartz sand.

Formulation 29: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.3 percent in the 100 formula is added with acid and 8.5 formula of sand, wherein the sand contains 2.3 weight percent of hydrochloric acid and 1 weight percent of hydrofluoric acid, and the sand is 30-50 mesh ceramsite sand.

The formula is 30: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.38 percent in 100 parts is added with acid, 4 parts of sodium dodecyl benzene sulfonate and 10.7 parts of sand, wherein the acid, the 4 parts of sodium dodecyl benzene sulfonate and the 10.7 parts of sand contain 11.5 weight percent of hydrochloric acid and 2 weight percent of alkynyloxymethyl amine, and the sand is quartz sand with the granularity of 30-50 meshes.

Formulation 31: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.41 percent in the 100 formula is added with acid and 35 formula of sand, wherein the sand contains 3.3 weight percent of hydrochloric acid, 1 weight percent of hydrofluoric acid and 0.1 weight percent of imidazoline, and the sand is quartz sand with the mesh of 60-80.

Formulation 32: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.45 percent in 100 formula is added with acid and 42.2 formula of sand, wherein the sand contains 10.8 weight percent of hydrochloric acid and 1.5 weight percent of imidazoline, and the sand is 50-80 meshes of quartz sand.

Formulation 33: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.45 percent in 100 formula is added with acid and sand with the mass percent of 41.6 formula, wherein the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid contains 9.5 weight percent of hydrochloric acid, 1.2 weight percent of hydrofluoric acid and 1 weight percent of imidazoline, and the sand is 30-50 meshes of ceramsite sand.

Formula 34: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.47 percent in the 100 formula is added with 26 formula of sand, wherein the sand contains 5.6 weight percent of hydrochloric acid and is 20-40 mesh quartz sand.

Formula 35: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.56 percent in 100 prescription is added with acid and 45 prescription of sand, wherein the acid and the 45 prescription of sand contain 12 weight percent of hydrochloric acid, and the sand is 40-70 mesh ceramsite sand.

Formulation 36: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.67 percent in the 100 formula is added with acid and 47 formulas of sand, wherein the acid and 47 formulas of sand contain 1 weight percent of hydrochloric acid, and the sand is 30-50 meshes of ceramsite sand.

Formulation 37: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.72 percent in the 100 formula is added with acid and 46.9 formula of sand, wherein the acid comprises 3.8 weight percent of hydrochloric acid, and the sand is 30-50 mesh ceramsite sand.

Formulation 38: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.78 percent in 100 formula is added with acid and 37 formula of sand, wherein the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid contains 10 weight percent of hydrochloric acid, 1.6 weight percent of hydrofluoric acid and 0.4 weight percent of alkynyloxymethyl amine, and the sand is 20-40 mesh ceramsite sand.

Formulation 39: the hydroxypropyl fenugreek gum non-crosslinked fracturing fluid with the mass percent of 0.8 percent in the 100 formula is added with acid, diisooctyl sulfosuccinate with the 3.8 formula and sand with the 34 formula, wherein the hydrochloric acid is contained by 10 weight percent, and the sand is quartz sand with the mesh of 20-40.

The formula 40 is that 0.45 percent of non-crosslinked xanthan gum fracturing fluid in 100 formula by mass also contains 0.3 percent of fenugreek gum in mass, acid and sand are also added, the acid contains 10 percent of hydrochloric acid, 1 percent of hydrofluoric acid and 1 percent of alkynyloxymethyl amine by mass, the sand is 80-100 meshes of quartz sand, and the dosage is 10 formula.

Similar to the xanthan gum non-crosslinked fracturing fluid, the mixed fracturing fluid can be added with acid and then added with sand, or added with sand and added with acid simultaneously, or added with sand and added with acid alternately.

Any of the above-mentioned mixed fracturing fluids can also reduce or even completely avoid the occurrence of "sand-blocking", and further, in order to better avoid or reduce the sedimentation of sand, avoid the occurrence of "sand-blocking" before the addition of acid or before the action of acid corrosion, thereby obtaining the best possible reconstruction effect, preferably, the sand addition is performed after the addition of acid, or simultaneously.

In practical applications, for example, in the process of oil and gas reservoir transformation, one of the above formulations may be used as the fracturing fluid, a plurality of the above formulations may be used as the fracturing fluid to be input into the well at different stages, or one or more of the above formulations may be used in combination with the existing fracturing fluid, for example, the fracturing fluid may be input into the well at different stages.

The mixed fracturing fluid in the formula is detected by the method for detecting the non-crosslinked fracturing fluid of the xanthan gum, and the result is shown in the following table 4 (wherein XG represents the xanthan gum, BX represents modified xanthan gum obtained by etherifying the xanthan gum by using 1-bromotetradecane as a modifier, FG represents fenugreek gum, and HPFG represents hydroxypropyl fenugreek gum).

TABLE 4

Therefore, the mixed fracturing fluid (the modified xanthan gum BX, the fenugreek gum FG and the hydroxypropyl fenugreek gum HPFG) with the formulas 1-39 has performance similar to that of the xanthan gum fracturing fluid, and can achieve similar transformation effect on a reservoir stratum. The mixed fracturing fluid (xanthan gum mixed fenugreek gum FG) of the formula 40 has better viscosity and resistance reduction performance compared with the mixed fracturing fluids, and can achieve better modification effect on a reservoir stratum.

In conclusion, the mixed fracturing fluid of the invention has good resistance reducing performance and suspension performance, so that the mixed fracturing fluid has the fracturing performance and carrying performance of common fracturing fluid, not only can carry sand into wide fractures through the good sand suspension performance of the mixed fracturing fluid, so that good support is formed at the wide fractures, and good flow conductivity is obtained, but also has good acid corrosion performance, and has good carrying performance on acid liquid, so that better flow conductivity can be obtained at wide fractures under the further corrosion action of acid, and even at narrow fractures, sand playing a supporting role cannot be removed, but the mixed fracturing fluid can carry acid, so that the mixed fracturing fluid can utilize the corrosion action of acid, carry out acid corrosion and clean fractures (including filtration zones around the fractures), and enable narrow fractures (such as far ends of the fractures) to have certain flow conductivity, the seepage capability on the fracture wall surface is also improved. And the oil displacement effect of the active agent contained in the mixed fracturing fluid. Therefore, the invention can obviously improve the transformation effect on the oil and gas reservoir and improve the oil extraction efficiency and the yield through the improvement.

Claims

1. A low viscosity hybrid fracturing fluid, comprising:

the fracturing fluid matrix comprises 0.1-0.8% of thickening agent aqueous solution in percentage by mass;

the concentration of the active agent is 2-9% of the mass of the fracturing fluid matrix;

sand, the content of which is 0-50% of the volume of the fracturing fluid matrix;

the thickening agent is biological glue; the biogum is xanthan gum or a derivative thereof, fenugreek gum or a combination of one or more of the derivatives;

the active agent is sodium dodecyl benzene sulfonate, sodium tetrapropylene benzene sulfonate or sodium diisooctyl succinate sulfonate;

the fracturing fluid matrix further comprises 0.001-0.003 mass percent of sodium borohydride, 0.002-0.005 mass percent of amino resin, 0.001-0.006 mass percent of methacrylic acid and 0.03-0.1 mass percent of hydroxyethyl cellulose;

the fracturing fluid matrix also contains 0.02-0.1% of potassium chloride and 0.005-0.01% of salicylate by mass percent respectively.

2. The hybrid fracturing fluid of claim 1, wherein: the acid is hydrochloric acid, or the acid is a mixture of hydrochloric acid and hydrofluoric acid.

3. The hybrid fracturing fluid of claim 2, wherein: the acid is also added with a corrosion inhibitor accounting for 0.1-2.5% of the mass of the fracturing fluid matrix, and the corrosion inhibitor is imidazoline or alkynyloxymethyl amine.

4. The hybrid fracturing fluid of claim 1, wherein: the content of the sand is 5% -50% of the volume of the fracturing fluid matrix, the sand is quartz sand or ceramsite sand, and the size of the sand is 20-100 meshes.

5. Use of the mixed fracturing fluid of any one of claims 1 to 4 in hydrocarbon reservoir modification as slickwater fracturing fluid, or as pre-fracturing fluid, or as sand carrier fluid, as acid fluid for reservoir acidizing, and as flooding fluid in hydrocarbon reservoir modification.

6. A method for transforming oil and gas reservoirs by combining sand fracturing and acid acidification, which combines the sand fracturing and the acid acidification and is characterized in that the mixed fracturing fluid of any one of claims 1 to 4 is adopted for reservoir transformation.

7. The method of combined sand fracturing and acidizing hydrocarbon reservoir modification of claim 6 wherein:

adding acid and an active agent into a fracturing fluid matrix to enable the fracturing fluid to contain the acid and the active agent; or

Firstly, adding acid and an active agent into a fracturing fluid, and then adding sand, so that the fracturing fluid simultaneously contains the acid, the active agent and the sand; or

Adding acid and an active agent simultaneously with the sand, so that the fracturing fluid simultaneously contains the acid, the active agent and the sand;

the oil and gas reservoir is a clastic rock reservoir.