CN110591685B

CN110591685B - In-situ self-generated microfoam steering acidizing fluid, acidizing steering method and application

Info

Publication number: CN110591685B
Application number: CN201910872298.8A
Authority: CN
Inventors: 燕永利; 奚琪
Original assignee: Xian Shiyou University
Current assignee: Lanzhou Kaihong Zhongyuan Petroleum Technology Co ltd
Priority date: 2019-09-16
Filing date: 2019-09-16
Publication date: 2022-05-10
Anticipated expiration: 2039-09-16
Also published as: CN110591685A

Abstract

The invention provides a turning acidizing fluid of in-situ self-generated microfoam, an acidification turning method and application, wherein the turning acidizing fluid comprises the following components: 15 to 20 percent of hydrochloric acid, 0.2 to 1.0 percent of corrosion inhibitor, 0.5 to 1.0 percent of anti-swelling agent, 0.5 to 1.0 percent of surfactant and the balance of water, and no gas is introduced; the surfactant is fatty alcohol polyoxyethylene polyoxypropylene ether, nonylphenol polyoxyethylene ether or polyethylene glycol perfluorobutyrate. Spontaneous formation of CO in situ in the formation₂The micro-foam does not need gas injection equipment, a foam generator and the like, greatly simplifies the construction procedure of foam acidification and reduces the construction cost.

Description

In-situ self-generated microfoam steering acidizing fluid, acidizing steering method and application

Technical Field

The invention belongs to the field of oil and gas exploitation, and particularly relates to a diversion acidizing fluid for in-situ self-generated microfoam, an acidification diversion method and application.

Background

The acid fracturing modification process technology is one of the important measures of exploration and development of carbonate oil and gas reservoirs, and yield increase and stable production. For carbonate reservoirs, during the acidification process, as acid reacts with reservoir rock to generate a large number of acid wormholes, the permeability difference between reservoirs is further increased, and the diversion of the carbonate reservoir is more difficult compared with a sandstone reservoir. In the conventional acidification diversion technology, a conventional acidification diversion liquid system usually preferentially penetrates through a high-permeability part or large channels of a reservoir, when a carbonate rock stratum is acidified by common hydrochloric acid, main channels are easily formed in a matrix, acid liquid can further flow along the channels for acidification, and acidification to other rock stratums is difficult, so that the acid liquid is usually difficult to act on low-permeability areas or small channels, and the low-permeability areas and the small channels are areas needing to act. Therefore, a diverter needs to be added into the acid liquor to temporarily block the large pore passage and the high permeability passage, and change the flow profile of the acid liquor so that the acid liquor enters the low permeability area and the small pore passage to achieve the purpose of homogenizing the acidification layer. For deep and ultra-deep carbonate reservoirs, the reservoirs are characterized by deep reservoir burial, high formation temperature, large reservoir thickness, severe reservoir heterogeneity, high carbonate purity in the matrix, and low natural input rate. In the acid fracturing modification operation process, the effective and uniform distribution of the acid liquor in the stratum is the key of the matrix acidification treatment effect. The heterogeneity of the stratum causes the acid liquid to be often directed to a high permeability layer, and a low permeability layer can be effectively treated by means of technologies such as diverting acid and the like.

Currently, the main technologies for acid splitting are: mechanical shunt technology, MAPDR shunt technology, chemical particle shunt technology, thickening acid shunt technology, viscoelastic surfactant shunt technology, foam acidification shunt technology, and the like. The foam acidification technology has the characteristics of low density, small filtration loss, obvious retarding effect and the like, and has good application prospect in oil wells with outstanding contradictions in interlayer layers of reservoir layers.

The construction of the foam acidification process site needs more additional equipment, such as a special nitrogen making vehicle, a foam generator and the like, so that the construction cost of a single well is higher, and the large popularization and application of the foam acidification process site are greatly limited.

Disclosure of Invention

Aiming at the problems in the prior art of carbonate reservoirs, the invention provides a diversion acidizing fluid of in-situ self-generated micro-foam, an acidification diversion method and application, wherein CO is spontaneously formed in situ in a stratum₂The micro-foam does not need gas injection equipment, a foam generator and the like, greatly simplifies the construction procedure of foam acidification and reduces the construction cost.

The invention is realized by the following technical scheme:

a diverting acidizing fluid of in-situ self-generated microfoam comprises the following components in percentage by mass: 15 to 20 percent of hydrochloric acid, 0.2 to 1.0 percent of corrosion inhibitor, 0.5 to 1.0 percent of anti-swelling agent, 0.5 to 1.0 percent of surfactant and the balance of water, and no gas is introduced; the surfactant is fatty alcohol polyoxyethylene polyoxypropylene ether, nonylphenol polyoxyethylene ether or polyethylene glycol perfluorobutyrate.

Preferably, the corrosion inhibitor is urotropin, tolidine or tannic acid.

Preferably, the anti-swelling agent is ammonium chloride, guanidine salt, quaternary ammonium salt or zirconium oxychloride.

A multi-stage injection mode is adopted, the slug of the steering acidizing fluid is injected into the stratum, and then the slug of the main acid fluid is injected, wherein the main acid fluid comprises hydrochloric acid.

Preferably, the main acid liquid further comprises one or more of the following auxiliary agents: corrosion inhibitor, iron ion stabilizer, residual acid-proof emulsifier, clay anti-swelling agent, cleanup additive and organic blocking remover.

The acidizing and diverting method of the diverting acidizing fluid is characterized in that the diverting acidizing fluid is used as a main acidizing fluid to be injected into a stratum.

The diverting acidizing fluid is applied to carbonate formations.

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

the diverting acidizing fluid of the invention is injected into the stratum and then chemically reacts with the carbonate rock core to generate supercritical CO₂Gas, under the action of surfactant, forms CO spontaneously in situ in the formation₂A microfoam. The main reason is that in a certain temperature and pressure range, the acid solution expands, the kinetic energy of the surfactant molecules is increased, the distance between the molecules is increased, the surfactant molecules are easy to be dehydrated and reach the liquid level, the surfactant molecules adsorbed on the liquid level are increased, the surface tension of the liquid film is further reduced, and the foaming is facilitated. In addition, the nonpolar tail of the surfactant extends beyond the supercritical CO₂In phase, the polar heads aggregate into polar nuclei, and water molecules dissolve in the nuclei to form thermodynamically stable states. And supercritical CO₂Has weak van der Waals force and low dielectric constant, so most of hydrophilic or hydrophobic surfactants are insoluble in CO₂In particular ionic surfactants, so that the use of nonionic surfactants has good gas solubility in the supercritical state and enables CO to be present₂The foamed acid system is more stable. CO 2₂The material belongs to nonpolar molecules, and has the advantages of small intermolecular acting force, low melting point, large bond energy, strong interatomic acting force and high thermal stability. The solubility in oil and water is high, the density is high, the critical temperature is high, the influence of conditions such as well depth temperature, pressure, formation water mineralization and the like is avoided, and the application range is wide. Under specific temperature and pressure conditions, i.e., supercritical conditions, exhibit different properties than under conventional pressure and temperature conditions. When CO is present₂In the supercritical state, the properties of the oil change, the density of the oil is close to that of liquid, the viscosity of the oil is close to that of gas, and the diffusion coefficient of the oil is 100 times that of the liquid, so that the oil has a strong dissolving capacity network, and crude oil can be well displaced from a stratum. On the other hand, the gas state can enter a space where many solvents cannot enter, thereby enlarging the oil sweeping area. The self-generating foam system has the function of blocking large and small, and can improve the recovery ratio of medium and low permeable layers. Moreover, the flow resistance of the foam fluid is high, and the gas generated by the system can also be generatedThe air blocking effect blocks the original flow channel, so that the injected fluid is redirected into the medium-low permeability pore channel, the volume sweep coefficient of the system is increased, and the unused crude oil is forced to be displaced. In addition, carbon dioxide, when dissolved in crude oil, causes the crude oil to swell, reduce viscosity, change density, and reduce interfacial tension. When the solution gas in the crude oil is saturated, the viscosity of the crude oil can be greatly reduced, and the oil washing efficiency is improved. The surfactant added into the self-generated foam system can reduce the oil-water interfacial tension, reduce the capillary force to change the wettability of the rock surface from oil wetting to water wetting, and drive away an oil film adhered to the rock surface, thereby improving the oil washing efficiency.

The invention directly utilizes the conventional acidification process without gas injection equipment, greatly simplifies the construction procedure of foam acidification, reduces the construction cost, enhances the applicability of foam acidification and can popularize the foam acidification technology. In-situ CO formation during acid fracturing by acidification₂The steering and slow acidification functions of the foam are utilized to achieve the purposes of uniform acid distribution, effective length of the acid-etched crack and flow conductivity of the acid-etched crack after acid fracturing. On the other hand, the gas-liquid separation device also has a drainage assisting effect, the generated gas increases the elastic driving energy of formation fluid, the crude oil can flow in the formation, the productivity is improved, and the purpose of quickly returning acid liquor is achieved.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

The invention relates to a diverting acidizing fluid of in-situ self-generated microfoam, which comprises the following components in percentage by mass: 15 to 20 percent of hydrochloric acid, 0.2 to 1.0 percent of corrosion inhibitor, 0.5 to 1.0 percent of anti-swelling agent, 0.5 to 1.0 percent of surfactant and the balance of water. The surfactant is fatty alcohol polyoxyethylene polyoxypropylene ether, nonylphenol polyoxyethylene ether or polyethylene glycol perfluorobutyrate.

The corrosion inhibitor is urotropin, rhodine or tannic acid; the anti-swelling agent is ammonium chloride, guanidine salt, quaternary ammonium salt or zirconium oxychloride.

According to the stratum conditions, the steering acidizing fluid can be used independently or can be matched with a main body acid fluid for use. The main acid liquid comprises 15-20% of hydrochloric acid by mass percent, and the main acid liquid also contains one or more of the following auxiliary agents: 0.2 to 1 percent of corrosion inhibitor, 0.5 to 1 percent of iron ion stabilizer, 0.5 to 1 percent of residual acid-proof emulsifier, 0.5 to 1 percent of clay anti-swelling agent, 0.2 to 0.5 percent of cleanup additive, 1 to 2 percent of organic blocking remover and the balance of water.

Depending on the formation conditions, two injection processes may be employed:

A. and (3) flow diversion and acidification of the foam slug: and multi-stage injection is adopted, a diverting acidizing fluid slug is injected into each stage firstly to play a temporary plugging role on a high-permeability layer, and then a main body acidizing fluid slug is injected to perform unblocking and acidizing on a low-permeability layer. The acid liquor can enter rock strata with different permeabilities, the solid particles and the residual liquid after acidification are returned by utilizing the higher apparent viscosity and the higher carrying capacity of the foam acid, the secondary damage is reduced, and the problems that other shunting modes damage the rock strata and the residual liquid cannot be completely returned are solved.

B. And (3) flow splitting and acidification of the foam acid: the diverting acidizing fluid is used as a main acid fluid to be pumped, namely, only the diverting acidizing fluid is injected. The surfactant is added into the conventional acidizing fluid to form a homogeneous phase system, the foam acid with the acidizing fluid as a continuous phase and bubbles as a dispersed phase is formed in the process of continuously injecting the foam acid into the stratum, the flow splitting of the acidizing fluid is realized by utilizing the flow splitting characteristic of the foam acid, and the process has the advantage of good flow splitting effect. The method can effectively solve the problem of the arrangement of acidizing fluid of the heterogeneous reservoir and the problem of the conventional acidizing of the heterogeneous reservoir. The foam diversion acidification is generally high in permeability of a high-water-content layer, if the water plugging effect in the previous stage is not ideal, and part of water outlet channels are not plugged effectively, so that excessive acidification of the water outlet channels can be prevented according to the principle that the foam is large in plugging and small in plugging. The foam system has large gas proportion, high self expansion, easy energy increasing and back discharging and almost no secondary damage. The foam can form a compound membrane surface in the throat, prevent the wall surface from contacting with liquid, reduce the water-sensitive pollution of the stratum and simultaneously reduce the filtration of acidizing fluid to the stratum.

The residual acid liquid flowback process comprises the following steps:

and closing the well, reacting for 3 hours and open-blowing. And (4) washing the well with active water to drain residual acid until all the acid liquor entering the well is drained.

According to the energy of the reservoir, two process technologies of well mouth open flow and foam lifting flowback are respectively adopted. After the measure well with higher reservoir pressure, good permeability and larger production potential is subjected to foam acidizing modification, the accumulated liquid in the shaft is subjected to flow-back by adopting a well mouth open flow-back process technology; and for wells with poor permeability and low reservoir productivity, acid is discharged by adopting a foam lifting flowback mode. The foam lifting flowback has very obvious protection effect on reservoirs with poor permeability, low formation pressure and reservoir sensitivity.

The method aims at the difference of heterogeneity and pollution degree of a carbonate reservoir in the longitudinal direction, adopts a diversion acidizing fluid system, and generates CO through the chemical reaction of the diversion acidizing fluid system and a carbonate rock core in the acidizing acid fracturing process₂Gas (existing in a supercritical state) under the action of a surfactant, and CO is spontaneously formed in situ in the stratum₂The micro-foam fluid utilizes the turning and slow acidification functions of foam to achieve the purposes of uniformly distributing acid, the effective length of acid-etched cracks and the flow guide capacity of the acid-etched cracks after acid fracturing, and simultaneously utilizes the characteristic of low surface tension of the turning acidification liquid to quickly and efficiently discharge residual liquid back to a stratum, thereby improving the discharge back efficiency of the acidification residual liquid in low-permeability low-pressure reservoirs and the like, reducing the damage of the residual liquid to the low-permeability reservoirs and recovering the oil well productivity to the maximum extent.

Construction step

1. Moving the well, taking out the original well water injection pipe column for inspection, checking data and cleaning.

2. Construction injection parameters

(1) The injection mode is as follows: graded injection/direct injection.

(2) Injection pressure: the pressure is lower than the oil layer fracture pressure, the grading injection is less than or equal to 15Mpa, and the direct injection is less than or equal to 30 Mpa.

(3) Injection speed: the water injection well is determined according to the water absorption capacity of the water injection well, and the pressure is required to be stably injected in the construction process. The injection is carried out with the displacement as large as possible, and the penetration distance of the blockage removing liquid is increased.

3. Acidifying, pressure reducing and injection increasing construction:

(1) and (6) putting an acidizing drilling tool.

(2) And (3) connecting the ground pipeline, testing the pressure of the wellhead and the ground pipeline at 30MPa, and detecting to obtain a qualified product without puncture and leakage.

(3) Preparing an acidizing fluid.

(4) Active water is circulated to the annular space for returning water.

(5) Injecting preposed acid solution (the invention is turned to acidizing fluid) with the dosage of 0.5m per meter of oil layer³+0.6m³Activated water, the pressure is less than or equal to 20MPa, and the well closing reaction is carried out for 60 min.

(6) Injecting main acid liquor with the dosage of 1-2 m per meter of oil layer³。

(7) Post acid liquor is injected for 6m³The pressure is less than 20MPa, the discharge capacity is as large as possible, and the well closing reaction is carried out for 12 hours.

(8) Closing the sleeve gate, forward extruding active water to 3.9m³And the pressure is less than or equal to 20MPa, and the well is washed in a large-discharge reverse circulation mode until the reaction residual acid is completely returned.

Or:

(5) injecting the steering acidizing fluid into the oil reservoir with the dosage of 5-8 m per meter³。

(6) Closing the sleeve gate, and forward extruding active water to 3.9m³And the pressure is less than or equal to 20MPa, and the well is washed by large-discharge reverse circulation until the reaction residual acid is completely returned.

4. After the acidification is finished, the water absorption index is calculated under four different pressures (the pressure grade is 2MPa) above the starting pressure, and 5m of water is squeezed respectively³. And (4) judging that the starting pressure is less than 15MPa and the water absorption capacity is more than 50L/min to be qualified, and if the water absorption capacity is unqualified, reporting to the technical management department in time, and determining the next step scheme. After water absorption is finished, 20m of active water is squeezed into the stratum³。

5. And pressing the seat seal. And opening the casing gate, and pressurizing by using a cement truck under the conditions of 14MPa, 16MPa and 18MPa respectively from the oil pipe, stabilizing the pressure for 5min, and determining that the pressure drop is not more than 2 MPa.

6. And (3) installing a wellhead according to the standard, testing the pressure under 20MPa without leakage, and connecting a ground water injection pipeline. And the operation team is removed from the well site after the well site is picked up.

The detailed description is as follows

Example 1

The indoor simulation experiment of a certain oil field core is taken as an example for explanation.

Carbonate cores with different permeabilities are adopted to carry out a flow experiment to simulate the permeability of fluid in a reservoir due to the heterogeneity of the reservoir under the formation condition. The core is from Sichuan Amei Longwang Temple group core, and is numbered 1 #. 1# core: diameter of 2.36cm, porosity of 30.5%, and permeability of 698 × 10^-3μm²The simulated temperature is 60 ℃ and the pressure is 1 MPa.

Preparing acid liquor: (1) the diverting acidizing fluid (pre-acidizing fluid) for in-situ self-generation of micro-foam comprises: 15 percent of hydrochloric acid, 0.5 percent of fatty alcohol polyoxyethylene polyoxypropylene ether, 0.2 percent of corrosion inhibitor urotropine, 0.5 percent of anti-swelling agent ammonium chloride and the balance of active water. (2) The main acid liquid comprises: 20% of hydrochloric acid, 0.5% of corrosion inhibitor urotropine, 0.5% of clay anti-swelling agent, 0.5% of residual acid-proof emulsifier, 0.5% of cleanup additive, 0.5% of iron ion stabilizer, 1% of organic blocking remover and the balance of active water. (3) The post acid solution comprises: 8 percent of hydrochloric acid, 0.5 percent of corrosion inhibitor, 0.3 percent of cleanup additive and the balance of active water. The acid compositions are shown in table 1.

Injecting acid liquor in stages, namely injecting the preposed acid liquor, then injecting the main acid liquor and finally injecting the postposed acid liquor. And measuring the permeability change condition before and after core acidification. The experimental result shows that the permeability of the rock core reaches 3420 multiplied by 10^-3μm^2，The permeability is 4.9 times of the initial permeability, and a good effect is achieved.

TABLE 1 acid solution compositions

Example 2

Carbonate cores with different permeabilities are adopted to carry out a flow experiment to simulate the permeability of fluid in a reservoir due to the heterogeneity of the reservoir under the formation condition. The core is from Sichuan Anyue Longwanggao group core, and is numbered 2 #. Core # 2: diameter of 2.68cm, porosity of 28.7%, and permeability of 590X 10^-3μm²The simulated temperature is 60 ℃ and the pressure is 2 MPa.

Preparing acid liquor (the diverting acidizing fluid of the in-situ self-generated microfoam of the invention) comprises the following steps: 18 percent of hydrochloric acid, 0.8 percent of polyethylene glycol perfluorobutyrate, 0.3 percent of corrosion inhibitor tannic acid, 0.7 percent of anti-swelling agent zirconium oxychloride and the balance of active water. The composition of the diverted acidizing fluid for the in situ autogenous microfoam is shown in table 2.

The diverting acidizing fluid of the in-situ self-generated microfoam is directly injected as a main body acid fluid, and the permeability change condition before and after core acidizing is measured. The experimental result shows that the permeability of the rock core reaches 4423 multiplied by 10^-3μm²And the permeability is 7.5 times of the initial permeability, so that a good effect is achieved.

TABLE 2 composition of diverting acidizing fluid for in situ autogenous microfoam

Components	Content (wt.)
		Hydrochloric acid (wt%)	18
Surfactant (wt%)	0.8
		Corrosion inhibitor (wt%)	0.3
Anti-swelling agent (wt%)	0.7
		Active Water (wt%)	80.2％

Example 3

Carbonate cores with different permeabilities are adopted to carry out a flow experiment to simulate the permeability of fluid in a reservoir due to the heterogeneity of the reservoir under the formation condition. The core is from Sichuan Anyue Longwanggao group core, and is numbered 3 #. Core # 3: diameter of 2.46cm, porosity of 31.4%, permeability of 627X 10^-3μm²The simulated temperature is 60 ℃ and the pressure is 2 MPa.

Preparing acid liquor (the diverting acidizing fluid of the in-situ self-generated microfoam of the invention) comprises the following steps: 20% of hydrochloric acid, 1.0% of fatty alcohol polyoxyethylene polyoxypropylene ether, 1.0% of corrosion inhibitor, namely butyl, 1.0% of anti-swelling agent guanidine salt and the balance of active water. The composition of the diverted acidizing fluid for the in situ autogenous microfoam is shown in table 3.

The diverting acidizing fluid of the in-situ self-generated microfoam is directly injected as a main body acid fluid, and the permeability change condition before and after core acidizing is measured. The experimental result shows that the permeability of the rock core reaches 4201 multiplied by 10^-3μm²The initial permeability is 6.7 times, and a good effect is achieved.

TABLE 3 composition of diverting acidizing fluid for in situ autogenous microfoam

Example 4

The erosion rate of solubles between the acid and the formation is an important measure of the performance of the acid. And (3) utilizing the reaction of the foamed acid and the carbonate rock debris, calculating the corrosion amount, and evaluating the excellent performance of the acid solution. And (3) screening the carbonate rock debris of the sampling Tahe oil field through a 18-mesh sieve, drying and weighing the rock debris with certain mass. Preparing 50mL of diversion acidification liquid: 17% of hydrochloric acid, 0.5% of nonylphenol polyoxyethylene ether, 0.5% of urotropine, 0.5% of ammonium chloride and the balance of active water, and the composition is shown in table 4. Will be provided withPouring the prepared diverting acidification liquid into a gas flow foaming device, and filling CO at the flow rate of 95ml/min₂Gas is used for enabling the foaming acid liquid to reach a fully foaming state; and adding weighed carbonate rock debris into the airflow foaming device, and simultaneously adjusting the airflow speed to 45ml/min to maintain the foaming state of the foaming acid in the device. After reacting for a period of time, washing the carbonate rock debris, drying and weighing, and calculating the corrosion amount.

The corrosion rate of the acid rock reaction is calculated according to the mass difference of the rock sample before and after the reaction, and the used calculation formula is as follows, wherein eta is (m1-m2)/m1 multiplied by 100 percent, wherein eta is the corrosion rate of the rock sample, m1 is the mass of the rock sample before the reaction, and m2 is the mass of the rock sample after the reaction.

TABLE 4 diverting acidizing fluid composition

Components	Content (wt.)
		Hydrochloric acid (wt%)	17
Surfactant (wt%)	0.5
		Corrosion inhibitor (wt%)	0.5
Anti-swelling agent (wt%)	0.7
		Active Water (wt%)	81.3％

Through experiments, the reaction lasts for 60 minutes at room temperature, the corrosion rate is up to 87%, and the effect is good.

Claims

1. The in-situ self-generated microfoam diverting acidizing fluid is characterized by comprising the following components in percentage by mass: 15 to 20 percent of hydrochloric acid, 0.2 to 1.0 percent of corrosion inhibitor, 0.5 to 1.0 percent of anti-swelling agent, 0.5 to 1.0 percent of surfactant and the balance of water, and no gas is introduced; the surfactant is fatty alcohol polyoxyethylene polyoxypropylene ether, nonylphenol polyoxyethylene ether or polyethylene glycol perfluorobutyrate; the corrosion inhibitor is urotropine, rhodine or tannic acid; the anti-swelling agent is ammonium chloride, guanidine salt, quaternary ammonium salt or zirconium oxychloride.

2. The method for acid diversion of the diverted acidizing fluid based on the claim 1, wherein the method of multi-stage injection is adopted, the slug of the diverted acidizing fluid of the claim 1 is injected into the stratum, and then the slug of the main acidizing fluid is injected, and the main acidizing fluid comprises hydrochloric acid.

3. The acid diversion method of claim 2, wherein the bulk acid further comprises one or more of the following adjuvants: corrosion inhibitor, iron ion stabilizer, residual acid-proof emulsifier, clay anti-swelling agent, cleanup additive and organic blocking remover.

4. The method of acid diversion based on the diverted acidizing fluid of claim 1 wherein the diverted acidizing fluid is injected into the formation as the host acidizing fluid.

5. Use of the diverting acidizing fluid of claim 1 in carbonate formations.