Mine water recharging reservoir scaling trend prediction and descaling permeation enhancement method

Abstract

The application discloses a kind of mine water recharge reservoir scaling tendency prediction and scale removal permeability enhancement method, and the tendency prediction method is: according to the hydrogeological information of recharge reservoir, the water quality of mine water and monitoring well is analyzed by conventional physical and chemical indexes, based on the Rizheno index method and relative saturation R.S., respectively quickly determine the scaling condition of carbonate, sulfate and silicate;When scaling occurs, the ion concentration change on the path is revealed by the Transport and Equilibrium_Phases module in the PHREEQC software, and the measured value of monitoring well is verified;Then according to the percentage of mineral dissolution and precipitation reaction and reservoir rock sample composition, the reaction amount and porosity are calculated to develop mine water recharge reservoir permeability enhancement optimization scheme.The application can effectively predict the scaling tendency of mine water recharge reservoir, and monitor the recharge process, which is helpful for the continuous operation of mine water deep well recharge and storage work.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water quality detection, and particularly relates to a mine water recharge reservoir scaling trend prediction and descaling permeability enhancement method. BACKGROUND

[0002] As an important unconventional water resource, mine water has important significance in coal mine safety production and ecological environment protection. According to statistics, the mine water discharge accounts for 1% of the total amount of national groundwater resources. The water quality characteristics of mine water are mainly characterized by high TDS (total dissolved solids), high suspended solids, high sulfate, high Na + With the implementation of relevant policies such as environmental protection by the state and local governments, strict requirements are imposed on mine water discharge, and some regions explicitly require zero discharge of mine water. Recharging and storing mine water produced in mineral exploitation is a solution. However, in the process of long-term recharge of high-salinity mine water into the reservoir aquifer, water-rock interaction occurs after the mine water mixes with the reservoir groundwater, and with the change of reservoir temperature and pressure, the solubility of various minerals in the reservoir groundwater changes, thereby destroying the ion balance state of Ca 2+ , Mg 2+ , HCO3 - , SO4 2- and other easily scaling ions dissolved in the groundwater, and some minerals such as calcite, gypsum, and quartz precipitate and scale, which eventually causes problems such as poor permeability of the recharge layer and increased water injection pressure, greatly affecting the sustainable operation of the mine water recharge system. Therefore, it is necessary to study the scaling trend during the mine water recharge process. SUMMARY

[0003] To solve the above problems, the present application provides a mine water recharge reservoir scaling trend prediction and descaling permeability enhancement method. By collecting recharge reservoir water sample analysis data, combining Ryzner index method and relative saturation R.S. method to quickly judge the water quality scaling trend. According to the water quality characteristics of mine water and monitoring wells, the PHREEQC numerical simulation software is used to reveal the changes of ion concentration on the migration path of mine water, and the mineral precipitation amount and reservoir void ratio are calculated through the percentage of mineral dissolution and precipitation reaction and reservoir rock sample composition, so as to formulate the corresponding mine water recharge reservoir permeability enhancement optimization scheme.

[0004] The technical scheme adopted by the present application is:

[0005] In a first aspect, the present application discloses a mine water recharge reservoir scaling trend prediction method, comprising the following steps:

[0006] Step S1, obtaining key hydrogeological parameters of mine water recharge reservoir;

[0007] Step S2: Set up monitoring wells around the reinjection well to obtain the conventional physicochemical properties of the water samples from the reinjection well and monitoring well; Step S3: For the conventional physicochemical properties of the water samples from the reinjection well and monitoring well, use the Reznoll index method to quickly determine the carbonate scaling condition, and use the relative saturation RS to quickly determine the sulfate and silicate scaling condition, in order to obtain the scaling condition; If it is determined that no scaling is found in the water sample, return to step S2 to continue monitoring; If scaling is found in the water sample, proceed to step S4;

[0008] Step S4: Predict the ion concentration and scaling amount at different locations in the reinjection reservoir, and analyze the changes in the porosity of the reinjection reservoir.

[0009] As a further improvement of the present invention, in step S1, the key hydrogeological parameters include reservoir depth, reservoir medium permeability coefficient, rock density, porosity, reservoir rock mineral composition, and reservoir pressure and temperature.

[0010] As a further improvement of the present invention, in step S2, the conventional physicochemical indicators include the temperature, mineralization, pH value and ion concentration of the water sample.

[0011] As a further improvement of the present invention, in step S3, the rapid prediction method specifically includes: Step S31, carbonate scaling condition: The Reznoll index method is used to determine the calcite, a representative carbonate, as follows:

[0012] RI = 2pH s -pH a (1)

[0013] pH s = -log[Ca 2+ ]-log[ALK]+K c (2)

[0014] In the formula, pH s It is the calculated pH value, pH a This is a geothermal fluid experiment to measure pH value; [ALK] is HCO3. - Ion molar concentration, [Ca 2+ [K] represents the molar concentration of calcium ions. c -constant;

[0015] Step S32, Sulfate Scaling: Qualitative estimation of the relative saturation RS of gypsum, a representative sulfate compound. The formula for relative saturation RS is as follows:

[0016]

[0017] In the formula, Ca is expressed in ppm.2+ Content, ppm SO4 is SO4 in ppm 2- Content, log K 石膏 is the solubility product of gypsum;

[0018] Step S33, silicate scaling condition: the size of the relative saturation R.S. of amorphous SiO2 quartz phase is used to determine, the formula is as follows:

[0019]

[0020] In the formula, T is the absolute temperature (K) of the recharge reservoir, and SiO2 is the content of soluble silicon in water (mg / L).

[0021] As a further improvement of the present application, in step S4, the ion concentration and scaling amount at different positions of the recharge reservoir are predicted, and the change of the void ratio of the recharge reservoir is analyzed, specifically:

[0022] Step S41, based on the key hydrogeological parameters of the recharge reservoir obtained in step S1, a conceptual model is constructed by using the hydrogeochemical numerical simulation software PHREEQC, and the process of the recharge well water entering the recharge reservoir is generalized as a one-dimensional water flow migration process extending outward from the recharge well as the center;

[0023] Step S42, a one-dimensional convection-dispersion equation is established to simulate the process of the mine water entering the reservoir water, and the equation is as follows:

[0024]

[0025] In the formula: c is the concentration of solute, mol / L; t is time; x is spatial coordinate; v is the seepage velocity of groundwater, m / s, indicating the overall flow speed of groundwater in the groundwater layer; D L is the hydrodynamic dispersion coefficient, m 2 / s; is the solute transport caused by convection, mol / (m 3 ·s); is the concentration change caused by dispersion, mol / (m 3 ·s); is the concentration change caused by water-rock reaction, mol / (m 3 ·s);

[0026] Step S43, based on the conventional mineralization index information collected by the recharge well in step S2, the ion concentration change caused by the reaction term is calculated by using the Transport module of the hydrogeochemical numerical simulation software PHREEQC; the mineral saturation index is obtained by using the Equilibrium_Phases module to verify the precipitation and dissolution of calcite, gypsum and quartz, and the measured value of the monitoring well and the numerical simulation data are compared and verified to improve the accuracy of the simulation;

[0027] Step S44, the ion concentration calculated in step S43 is substituted into the mineral precipitation and dissolution equilibrium chemical equation to obtain the reaction mass of mineral precipitation, and the reaction mass is substituted into formula (6) to calculate the porosity in the recharge reservoir, and the formula is as follows:

[0028] M 岩 =ρ 岩 (V 水 ÷∈ p (1-∈ p )) (6)

[0029] In the formula, M 岩 and ρ 岩 are the mass and density of the rock respectively; V 水 is the volume of the reaction water; ∈ p represents the porosity of the rock.

[0030] Secondly, the application also discloses a descaling and permeability increasing method based on the mine water recharge reservoir scaling trend prediction method.

[0031] (1) Hydraulic fracturing and permeability increasing: for low permeability strata, the permeability of the strata is improved by fracturing technology;

[0032] (2) Acidification and permeability increasing: for carbonate rocks and sandstones containing acid-soluble cement, the mineral composition in the rock is dissolved by injecting acid solution or gas to increase the permeability of the strata;

[0033] (3) Injection-pumping-injection cycle flushing: regular reverse water injection or gas-water mixed flushing to remove particles in the fractures.

[0034] The technical effects of the application are:

[0035] (1) The present application sets a recharge well and a monitoring well, simultaneously collects water samples of the two wells, respectively determines the scaling indexes of carbonates, sulfates and silicates in the water samples through the Ryznar method and the relative saturation method, comprehensively and quickly judges the scaling condition of the recharge reservoir medium under the long-term recharge condition, so as to realize the regular monitoring of the recharge water; in the case that the recharge reservoir medium has a scaling trend, the conventional physical and chemical index information of the water sample of the recharge well is used, the ion change condition in the recharge well water of the recharge reservoir is simulated through the hydrogeochemical numerical simulation software, the change condition of the ion concentration on the migration path of the well water is revealed, the scaling amount of the injected well water and the change condition of the void of the reservoir permeation are obtained, then the conventional physical and chemical index of the water sample in the monitoring well is used for verification, so as to improve the accuracy of the simulation and provide a scientific data basis for the formulation and implementation of the reservoir permeation scheme.

[0036] (2) Since the construction of the monitoring well needs a high cost, the present application realizes the regular monitoring through the fast scaling prediction by establishing one (not multiple) monitoring well, judges the ion concentration change and the void change through the hydrogeochemical analysis, then the water sample data of the monitoring well are used for verification, so that the engineering cost of the mine water recharge can be saved and the continuous operation of the recharge work can be ensured. BRIEF DESCRIPTION OF DRAWINGS

[0037] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0038] Figure 1 is the process flow chart of the mine water recharge reservoir scaling trend prediction and descaling and permeation increasing method of the present application;

[0039] Figure 2 is the conceptual model schematic diagram of the mine water recharge in the embodiment;

[0040] Figure 3 is the mine water recharge mineral saturation index SI change graph in the embodiment;

[0041] Figure 4 is the ion concentration change graph of the water sample at different positions in the embodiment. DETAILED DESCRIPTION

[0042] As shown in Figure 1 , the mine water recharge reservoir scaling trend prediction method of the present application specifically comprises the following steps:

[0043] Step S1, obtaining the key hydrogeological parameters of the recharge reservoir.

[0044] The regional M coal mine water injection project is adopted, and the drilling information of the injection well and the monitoring well is obtained. The vertical depth of the injection well and the monitoring well is 1300 m, the distance between the monitoring well and the injection well is 50 meters, the thickness of the injection reservoir is 199-203 m, the permeability coefficient of the reservoir is about 2-2.4 m / d, the density of the reservoir rock sample is 2.84 g / cm 3 , the porosity is 3.06%, the main mineral of the reservoir rock is calcite (accounting for 65%), and the monitoring hole water level is measured to be stable at-31-30.5 m, and the reservoir temperature is 40℃.

[0045] Step S2, obtaining the conventional physical and chemical indexes of the water samples of the injection well and the monitoring well.

[0046] The water samples are regularly monitored and tested for their conventional physical and chemical indexes, including the pH value and the ion concentration of the water samples. The water quality characteristics of the Ordovician limestone water and the mine water are mainly high sulfate water with SO4 2- , Ca 2+ , Na + +K + as the main components. The water characteristics of the two are similar, and the mine water is better than the reservoir groundwater. The specific water sample physical and chemical indexes are shown in Table 1.

[0047] Table 1 Conventional physical and chemical indexes of mine water and reservoir water in eastern M coal mine

[0048]

[0049] Step S3, using the conventional physical and chemical indexes of the water samples in the injection well, adopting Ryzner index method and relative saturation R.S. to determine the scaling situation.

[0050] Step S31, predicting carbonate scaling, and the representative is calcium carbonate in calcite. The Ryzner index method formula is as follows:

[0051] RI = 2pH s -pH a (1)

[0052] pH s =-log[Ca 2+ ]-log[ALK]+K c (2)

[0053] In the formula, pH s is the calculated pH, pH a is the measured pH value of the injection reservoir water, [ALK] is the molar concentration of HCO3 - (mol / L), [Ca 2+ ] is the molar concentration of calcium ions (mol / L), and K c is a constant.

[0054] The data in Table 1 is substituted into the above formula to calculate the RI index, and the scaling judgment is made according to Table 2:

[0055] Table 2: Calcium carbonate scaling trend identification table

[0056] Ryznar index (RI) Scaling tendency RI < 4.0 Very severe 4.0 < RI < 5.0 Severe scaling 5.0 < RI < 6.0 Moderate scaling 6.0 < RI < 7.0 Mild scaling RI > 7.0 No scaling

[0057] Step S32, sulfate scaling prediction: The mine water usually has the characteristics of high sulfate, and the calcium sulfate scaling trend in the recharging reservoir can be qualitatively estimated by the relative saturation R.S. of gypsum (CaSO4-2H2O), which is defined as follows:

[0058]

[0059] In the formula, ppm Ca— Ca content in ppm; ppm SO4— SO4 content in ppm; log K— solubility product of gypsum, which is calculated according to the relative solid TDS (in ppm) and temperature. 2+ 2- 石膏

[0060] Sulfate scaling trend determination basis: When the R.S. of gypsum is ≤1, it indicates that it is not saturated and will not cause gypsum scaling; when the R.S. is >1, it indicates that it is supersaturated and will produce sulfate scaling.

[0061] Step S33, silicate scaling prediction: The relative saturation R.S. of amorphous SiO2 quartz is used to determine the silicate scaling trend, and the formula is as follows:

[0062]

[0063] Silicate scaling trend determination basis: When R.S. is ≤1, no silicate scaling is generated; when R.S. is >1, it indicates that it is supersaturated and will produce silicate scaling.

[0064] In this embodiment, the silicate content in the water sample composition is low, so it is not necessary to predict the silicate scaling trend, and the final scaling condition is shown in Table 3. In Table 3, the water samples of the recharging well and the monitoring well are the mixed water of the mine water and the original reservoir water.

[0065] Table 3: Scaling trend prediction

[0066]

[0067] Step S4, calculation of the scaling amount at different positions of the recharging reservoir and analysis of the change of the void fraction.

[0068] ​​​Step 41, in the PHREEQC software, the key hydrogeological parameters obtained in step S1, i.e. the drilling information about the recharge well and the monitoring well, including the reservoir depth, the reservoir medium permeability coefficient, the rock density, the void ratio, and the reservoir rock mineral composition, the pressure and temperature information, are used to build a conceptual model, and the process of the recharge well water entering the reservoir is generalized as a one-dimensional water flow migration process extending outward from the recharge well, as shown in Figure 2 FIG. 1D refers to one dimension, and r is the mineral ion diffusion radius centered on the recharge well.

[0069] Step S42, a one-dimensional convection-dispersion equation is established to simulate the process of well water entering the reservoir water, and the equation is as follows:

[0070]

[0071] In the formula, c is the concentration of the solute (unit: mol / L), t is the time, x is the spatial coordinate, v is the groundwater seepage velocity (unit: m / s), which represents the overall flow velocity of groundwater in the groundwater layer, D L is the hydrodynamic dispersion coefficient (unit: m 2 / s);

[0072] is the solute migration caused by convection, mol / (m 3 ·s); is the concentration change caused by dispersion, mol / (m 3 ·s); is the concentration change caused by water-rock reaction, mol / (m 3 ·s).

[0073] Step S43, the conventional materialization index information of the recharge well and the monitoring well obtained in step S2 is used to calculate the ion concentration change caused by the reaction term by using the Transport module of the hydrogeochemical numerical simulation software PHREEQC and formula (5). The Equilibrium_Phases module is used to obtain the mineral saturation index (SI) to verify the precipitation and dissolution of calcite and gypsum. In this step, the numerical simulation obtains the mineral saturation index SI, which is an index for measuring whether a certain mineral in the aqueous solution reaches a saturated state. When SI>0.5, it means that a certain mineral in the groundwater is in a saturated state and will precipitate from the water, and vice versa; when SI is between -0.5 and 0.5, it is in a dissolution equilibrium state. As shown in Figure 3As shown, the mineral saturation index SI of calcite is >0.5, indicating that calcite precipitation occurs, consistent with the scaling observed in step S3 above. The simulation results show that calcite is in a state of precipitation, while gypsum and sodium salts are in a state of dissolution equilibrium. Table 4 compares the measured values ​​from the monitoring well with the numerical simulation results, showing that SO4 exhibits the smallest simulation error. 2- The error was 0.14%, with the largest error occurring in HCO3. - The error between the measured values ​​of the monitoring well and the numerical simulation results is less than 5%, which shows that the numerical simulation results of this embodiment have high accuracy.

[0074] Table 4 Errors between Measured Values ​​and Numerical Simulation Results from Monitoring Wells

[0075]

[0076] Error = |Measured value - Simulated value| / Measured value * 100%

[0077] Based on the simulation results, the changes in ion concentrations within the range from the reinjection well to the monitoring well were obtained, such as... Figure 4 As shown. By Figure 4 It can be seen that, with the reinjection well as the center, the distance from the monitoring well to Ca... 2+ Mg 2+ Na + SO4 2- Cl - First decrease, then increase, with Ca within the range of 0–30m. 2+ The fastest downward trend was observed in Na. + The most gradual decrease, HCO3 - Overall, it is in an upward phase.

[0078] Step S44: Substitute the ion concentration calculated in step S43 into the chemical equation for the mineral precipitation dissolution equilibrium (see Table 5) to obtain the reaction mass M of the mineral precipitation. 岩 ;

[0079] Table 5 Common Dissolution and Precipitation Reactions in Mine Water Reinjection

[0080]

[0081] **T(K)=℃+273.15

[0082] Substitute the mineral quantity into formula (6) to calculate the change in porosity in the reinjection reservoir, as shown in the following formula:

[0083] M 岩 =ρ 岩 (V 水 ÷∈ p (1-∈ p (6)

[0084] In the formula: M 岩 and p 岩 respectively the mass and density of the rock; V 水 is the volume of the reaction; and p is the porosity of the rock.

[0085] The water chemical simulation reaction volume is calculated according to 1L of water, and the mineral mass change is limited to the area within a radius of 0.5m from the well, the mineral precipitation mass is calculated according to the mineral precipitation dissolution equilibrium reaction and the percentage of the mineral in the formation sample composition, the generated calcium carbonate precipitate is 38.7mg, the maximum porosity corresponding to the void ratio in this embodiment is calculated according to formula (6), and the maximum void ratio is reduced to 1.84%, the void ratio (porosity) before the recharge is 3.06%, and the mineral precipitation transformation may cause the heterogeneity of the reservoir to increase. The void ratio is used to represent the permeability of the recharge layer, and the smaller the void ratio, the smaller the permeability.

[0086] As Figure 4 shown, the effect of this simulation can be found that the precipitation occurring in the mine water recharge is mainly concentrated in the area centered on the recharge well, and the influence is relatively small, but the influence of the scaling needs to be considered in the actual engineering. Therefore, the application also discloses a descaling and permeability increasing method, which specifically comprises:

[0087] Hydraulic fracturing to increase permeability: for low permeability formations, the permeability of the formation is improved by fracturing technology;

[0088] Acidification to increase permeability: for carbonate rocks, the mineral composition in the rock is dissolved by injecting an acidic solution (gas) to increase the permeability of the formation;

[0089] Injection-pumping-injection cycle: periodic backwashing, regular reverse water injection or gas-water mixed flushing, and removing particles in the fracture.

[0090] The application realizes the periodic monitoring of the mine water recharge process by setting the recharge well and the monitoring well to quickly judge the scaling of the water sample, so that the recharge work can be smoothly carried out; when scaling is judged to occur, the ion change of the recharge reservoir water sample, the precipitation mass and the void ratio of the recharge reservoir are obtained by using the hydrogeochemical numerical simulation analysis method, so that scientific guidance can be given to subsequent permeability increasing operation. And the conventional physical and chemical indexes of the water sample obtained in the monitoring well are used to verify the data of the hydrogeochemical numerical simulation analysis, so as to ensure the accuracy of the simulation.

[0091] The embodiments of the present application are described in detail above with reference to the accompanying drawings, but the present application is not limited to this, and various changes that can be made within the knowledge of those skilled in the art without departing from the spirit of the present application are within the scope of the claims of the present application.

Claims

1. A method of predicting scaling tendency of a mine water recharge reservoir, characterized in that, The method comprises the following steps: Step S1, obtaining key hydrogeological parameters of the mine water recharge reservoir; Step S2, setting up monitoring wells around the recharge well to obtain the conventional physical and chemical indexes of the water samples in the recharge well and the monitoring wells; Step S3, based on the conventional physical and chemical indexes of the water samples in the recharge well and the monitoring wells, using the Latsyno index method to quickly determine the carbonate scaling, and using the relative saturation R.S. to quickly determine the sulfate and silicate scaling, so as to obtain the scaling conditions; if the water sample does not appear scaling, return to step S2 for continuous monitoring; if the water sample has scaling conditions, execute step S4; Step S4, predicting the ion concentration and scaling amount at different positions of the recharge reservoir, and analyzing the change of the void ratio of the recharge reservoir.

2. The mine water injection reservoir scaling trend prediction method of claim 1, wherein, In step S1, the key hydrogeological parameters include the reservoir depth, the reservoir medium permeability coefficient, the rock density, the void ratio, the reservoir rock mineral composition, and the reservoir pressure and temperature.

3. The mine water injection reservoir fouling trend prediction method of claim 1, wherein, In step S2, the conventional physical and chemical indexes include the temperature, the salinity, the pH value, and the ion concentration of the water sample.

4. The mine water injection reservoir scaling trend prediction method of claim 1, wherein, In step S3, the carbonate scaling is determined by using the Latsyno index method, and the sulfate and silicate scaling is determined by using the relative saturation R.S., so as to obtain the scaling conditions; specifically: Step S31, carbonate scaling condition: using the Latsyno index method to determine the representative carbonate calcite, and the formula is as follows: （1）， （2）， wherein pH s is the calculated pH value, pH a is the experimental pH value of the geothermal fluid, [ALK] is the molar concentration of HCO3 - , [Ca 2+ ] is the molar concentration of calcium ions, and K c is the constant. Step S32, sulfate scaling condition: qualitatively estimating the relative saturation R.S. of the representative sulfate gypsum, and the formula of the relative saturation R.S. is as follows: （3）， where ppm Ca is the Ca content in ppm 2+ ppm SO4 is the SO4 content in ppm 2- log K 石膏 is the solubility product of gypsum; Step S33, silicate scaling condition: judging from the size of the relative saturation R.S. of the amorphous SiO2 quartz, and the formula is as follows: （4）， In the formula, T is the absolute temperature (K) of the recharge reservoir, and SiO2 is the content of soluble silicon in water (mg / L).

5. The mine water injection reservoir fouling trend prediction method of claim 1, wherein, In step S4, the ion concentration and scaling amount at different positions of the recharge reservoir are predicted, and the change of the void ratio of the recharge reservoir is analyzed, specifically: Step S41, based on the key hydrogeological parameters of the recharge reservoir obtained in step S1, using the hydrogeochemical numerical simulation software PHREEQC to construct a conceptual model, and generalizing the process of the recharge well water entering the recharge reservoir as a one-dimensional water flow migration process extending outward from the recharge well; Step S42, establishing a one-dimensional convection dispersion equation to simulate the process of the mine water entering the reservoir water, and the equation is as follows: （5）， wherein: c is the concentration of the solute, mol / L; t is time; x is the spatial coordinate; v is the groundwater seepage velocity, m / s, representing the overall flow speed of groundwater in the groundwater layer; D L is the hydrodynamic dispersion coefficient, m 2 / s; is the solute transport due to convection, mol / (m3s); is the concentration change due to dispersion, mol / (m3s); is the concentration change due to water-rock reaction, mol / (m3s); Step S43, based on the conventional physical and chemical index information of the recharge well collected in step S2, using the Transport module of the hydrogeochemical numerical simulation software PHREEQC to calculate the ion concentration change caused by the reaction term; using the Equilibrium_Phases module to obtain the mineral saturation index to verify the precipitation and dissolution of calcite, gypsum and quartz, and comparing and verifying the measured value of the monitoring well and the numerical simulation data to improve the accuracy of the simulation; Step S44, substituting the ion concentration calculated in step S43 into the mineral precipitation and dissolution equilibrium chemical equation to obtain the reaction mass M generated by mineral precipitation 岩 The reaction mass is further substituted into formula (6) to calculate the void fraction in the recharging reservoir, and the formula is as follows: （6）， where p 岩 is the density of the rock; V 水 is the volume of the water reacted; and p represents the porosity of the rock.

6. A descaling and permeability enhancement method based on the mine water recharge reservoir scaling tendency prediction method according to any one of claims 1-5, characterized in that, The method comprises: (1) Hydraulic fracturing to increase permeability: for low-permeability formations, the permeability of the formation is improved by fracturing technology; (2) Acidizing to increase permeability: for carbonate rocks and sandstone containing acid-soluble cement, by injecting acid solution or gas to dissolve the mineral composition in the rock, increase the permeability of the formation; (3) Injection-extraction-injection cycle flushing: regular reverse water injection or gas-water mixed flushing to remove particles in the fracture.

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