CN108427657B - Effectiveness analysis and regulation and control method for underground water seal oil reservoir water curtain system - Google Patents

Effectiveness analysis and regulation and control method for underground water seal oil reservoir water curtain system Download PDF

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CN108427657B
CN108427657B CN201810168774.3A CN201810168774A CN108427657B CN 108427657 B CN108427657 B CN 108427657B CN 201810168774 A CN201810168774 A CN 201810168774A CN 108427657 B CN108427657 B CN 108427657B
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curtain system
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王者超
孙华阳
乔丽苹
黄安达
岳伟平
杨磊
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Northeastern University China
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Abstract

The invention discloses an effectiveness analysis and regulation method for a water curtain system of an underground water-sealed oil reservoir, which is a method for judging the effectiveness of the water curtain system by analyzing the similarity of chemical characteristics of water samples in different areas and water supply water of the water curtain system and regulating and controlling the water curtain system by regulating the water supply water of the water curtain. The method collects groundwater samples at different positions before, during and after the oil depot is built, analyzes the water chemical characteristics, classifies the water chemical characteristics of the water samples by combining a clustering analysis method and a principal component analysis method, obtains the hydraulic connection condition between the water supply of the water curtain system of the reservoir area and the groundwater at different positions, can further accurately judge whether the water curtain system of the underground water-sealed oil depot can effectively operate, and regulates and controls the water curtain system by adjusting the water curtain water supply components according to the analysis result. The invention provides an effectiveness analysis and regulation method of an underground water seal oil depot water curtain system based on underground water chemical characteristics.

Description

Effectiveness analysis and regulation and control method for underground water seal oil reservoir water curtain system
Technical Field
The invention relates to a method for analyzing and regulating effectiveness of a water curtain system of an underground water-sealed oil depot, in particular to a method for judging whether water supply of the water curtain system can cover the whole depot area or not by analyzing similarity of the chemical characteristics of underground water at different parts based on the chemical characteristics of underground water at different parts of an underground water-sealed oil depot site area and regulating and controlling the performance of the water curtain system according to generated chemical reaction. The invention belongs to the field of underground engineering.
Background
With the development of economy and society, the demand of petroleum is increasing day by day, and the significance of petroleum storage is great. Among various ways of storing petroleum, the underground water-sealed oil depot has the characteristics of small occupied area, large reserve, high safety and the like, so that the underground water-sealed oil depot is more and more widely applied. The oil storage function of the underground water-sealed oil depot is established on the following 3 basic conditions: 1) the relative density of oil is less than that of water; 2) the petroleum is not decomposed and dissolved when meeting water; 3) the water pressure around the oil depot is greater than the stored pressure. When storing oil, the underground water-sealed oil depot relies on the water curtain system to prevent oil leakage. Therefore, the evaluation of the effectiveness of the water curtain system plays a crucial role in the safe and stable operation of the oil depot. But currently, an effective technical means is still lacking.
Disclosure of Invention
In order to solve the problems in the prior art, the invention mainly aims to construct an effectiveness analysis and regulation method for an underground water-seal oil depot water curtain system with extremely high application value.
The method collects groundwater samples at different positions before, during and after the oil depot is built, analyzes the water chemical characteristics, classifies the water chemical characteristics of the water samples by combining a clustering analysis method and a principal component analysis method, obtains the hydraulic connection condition between the water supply of the water curtain system of the reservoir area and the groundwater at different positions, can further accurately judge whether the water curtain system of the underground water-sealed oil depot can effectively operate, and regulates and controls the water curtain system by adjusting the water curtain water supply components according to the analysis result.
The purpose of the invention is realized by the following technical scheme:
the effectiveness analysis method for the water curtain system of the underground water-sealed oil reservoir specifically comprises the following steps:
(1) collecting samples: rock samples and underground water samples are respectively collected according to the determined sampling time and sampling points, and geological features of reservoir areas of the oil depot can be reflected.
(2) Sample detection: XRD (X-ray diffraction) analysis is carried out on the collected rock samples to obtain mineral compositions of rocks in the reservoir area, and water chemical reaction which possibly occurs is judged according to the mineral compositions of the rocks and regional hydrogeological conditions to select a corresponding water sample detection index.
(3) And (3) data analysis: the method comprises the steps of combining two mathematical statistical methods of cluster analysis and principal component analysis, converting water sample detection indexes with high correlation into new variables which are mutually independent or irrelevant to obtain water sample principal components, drawing a scatter diagram of each underground water sample principal component, and obtaining main influence factors which are dissolution of rocks and seepage of underground water respectively. And grouping the sampling points on the main component scatter diagram, and grouping the points at the closer positions on the main component scatter diagram into a group.
(4) Discussion of Water curtain effectiveness: and analyzing the chemical characteristics of the water supplied by the water curtain, and judging the effectiveness of the water curtain system by analyzing the distribution condition of the sampling points similar to the chemical characteristics of the water supplied by the water curtain.
According to the technical scheme, preferably, the rock sample is collected before the oil depot is built, and the water sample collection is carried out before the oil depot is built, during the construction and after the oil depot is put into operation, so that the chemical change characteristics of underground water in the whole process can be reflected.
According to the above technical solution, preferably, the sampling time should avoid sampling in the abnormal weather periods such as rainstorm period and drought period. The water sample collection process is completed within 1-3 days, so that the problem that the timeliness is lost and adverse influence is caused on an analysis result is avoided.
According to the technical scheme, preferably, the sampling points are key areas such as a hydrogeological unit, a bad fault body, an engineering construction affected area and an oil and gas pollution area, so that the obtained sample is representative.
According to the technical scheme, the arrangement of collection points is encrypted in key areas of an oil and gas pollution area including a ventilation vertical shaft and a sewage port, and the influence of oil depot construction on the environment is mainly evaluated.
Hydrogeological unit is aquifer, relative water barrier, supply area and the zone of discharging and an underground water flow system of constituteing promptly, bad disconnected layer body is rock stratum or rock mass and takes place obvious displacement's position along the fracture face promptly, the engineering construction affected area is the region that the structure construction probably influences peripheral geological conditions promptly, oil gas pollution area is the region that probably produces the pollution to the surrounding environment because of oil gas reveals in the oil storage process promptly.
The water chemical reaction types mainly comprise dissolution reaction, oxidation-reduction reaction and hydrolysis reaction of rocks. The silicate minerals including feldspar, pyroxene, amphibole, mica and olivine mainly undergo hydrolysis reaction. Silicates containing low-valent iron and other minerals can be oxidatively destroyed to become high-valent iron. Dissolution of rock has occurred, with calcite and dolomite being susceptible to dissolution reactions.
The water sample detection indexes are as follows: k+、Cl-、Na+、Ca2+、Mg2+、HCO3 -、Al3+、SO4 2-、CO3 2-、NO3 -Mineralization, full hardness and pH value. Wherein the dissolution reaction of the rock is mainly to detect K+、Cl-、Na+、SO4 2-、CO3 2-Hydrolysis reaction should detect mainly Ca2+、Mg2+、K+、Na+、Al3+And pH value, etc. Degree of mineralization, NO3 -The full hardness has great effect on detecting the water quality pollution degree.
According to the above technical solution, preferably, the water sample detection indexes with high correlation are converted into new variables which are independent or unrelated to each other, that is, if the number of the water sample samples is n and the number of the selected water sample detection indexes is p, then the matrix X ═ X (X) can be obtained from the original data of the water sampleij)n×pWherein x isijThe j-th index data of the ith sampling point is represented, the index data is standardized to obtain a standardized matrix, and covariance matrixes R and R are established according to the standardized data matrixij(i, j ═ 1, 2, …, p) as the original variable XiAnd XjThe calculation formula of the correlation coefficient is as follows:
Figure BDA0001585220550000021
wherein
Figure BDA0001585220550000022
Represents the average of the different indices at the ith sample point,
Figure BDA0001585220550000031
denotes the average value of the j index, xkjAnd (4) representing the index value of the kth sampling point j, solving the characteristic value, the principal component contribution rate and the accumulated variance contribution rate according to the covariance matrix R, and determining the number of the principal components.
According to the above technical solution, more preferably, the eigen equation | λ E-R | ═ 0 is solved, where E denotes an identity matrix, the eigenvalues λ i (i ═ 1, 2, …, p) are obtained and arranged in order of magnitude, i.e., λ 1 ≧ λ 2 ≧ … ≧ λ i ≧ 0, and the contribution of the principal component Zi
Figure BDA0001585220550000032
Wherein λjThe characteristic value of the index is represented by the cumulative contribution rate
Figure BDA0001585220550000033
Selecting the main component with high accumulated contribution rate, wherein the accumulated contribution rate reaches 1, 2, …, m (m is less than or equal to p) corresponding to characteristic values lambda 1, lambda 2, … and lambda m of 78-95%, and the integer m is the number of the main component.
According to the technical scheme, under the preferable condition, if the chemical components of the water samples classified into a group of internal sampling points are similar to those of water supplied by the water curtain, the water curtain system is in hydraulic connection with the part, the water seal effect of the water curtain system is good, and the water curtain system can effectively operate; otherwise, the water curtain system is still to be improved.
If the water chemical characteristics of the underground water sample of the sampling point of the reservoir area can be similar to those of the water sample of the water curtain water supply, the water curtain water supply can be fully permeated into the sampling point and is positioned in the water supply range of the water curtain hole, the water sealing effect of the water curtain system is good under the condition, oil leakage can be effectively prevented, and the water sealing effect of the water curtain system is good under the condition.
The invention also provides an effectiveness regulation and control method of the water curtain system of the underground water-sealed oil reservoir, which regulates and controls the water curtain system by changing chemical components of water supplied by the water curtain system to regulate the water-rock reaction process according to the judged main water chemical reaction type based on the effectiveness analysis result of the water curtain system.
The invention has the beneficial effects that:
according to the method, the similarity of the water chemistry characteristics of underground water in the reservoir site area of the underground water-sealed oil reservoir is taken as a judgment basis, rock sample water samples capable of representing geological conditions are adopted in different construction periods, and a proper water chemistry data index is selected according to rock mineral composition and hydrogeological conditions; grouping the sampling points by using another mathematical statistical method to obtain a distribution range of the sampling points similar to the chemical characteristics of the water supply of the water curtain system, thereby judging the effectiveness of the water curtain system; and (3) combining the main water-rock reaction type of the reservoir area, and adjusting the water supply quality of the water curtain system to regulate and control the effectiveness of the water curtain system. The method can comprehensively and accurately judge whether the water curtain system of the underground water-seal oil depot can operate effectively or not, and can regulate and control the effectiveness of the water curtain system according to the analysis result.
1. An effectiveness analysis method of an underground water seal oil depot water curtain system based on an underground water chemical principle is established;
2. the method can judge the type of the water chemical reaction which possibly occurs according to the obtained chemical characteristics of the groundwater sample in the oil depot site area, and regulate and control the water curtain system by regulating the water supply components of the water curtain.
Compared with the prior judgment method, the method can effectively avoid various interference factors, and the obtained conclusion is more reliable, thereby having great significance for judging the safety of the underground engineering under the composite condition. Meanwhile, the invention has wide application range, and is also suitable for underground projects such as nuclear waste storage, carbon dioxide underground sealing, garbage underground landfill, natural gas storage and the like besides the underground water-sealed oil depot.
Drawings
FIG. 1 is a diagram of an underground engineering structure of an underground water-sealed oil depot;
FIG. 2 is a diagram showing the distribution of underground water sampling points in an underground water-sealed oil depot site area;
FIG. 3 is a graph of the change in the concentration of the predominant cations in the water over a monitoring period of time;
FIG. 4 is a graph of the change in anion concentration in groundwater over a monitoring period of time;
FIG. 5 is Cl during the monitoring period-The concentration variation of (2);
FIG. 6 shows NO during the monitoring period3 -The concentration variation of (2);
FIG. 7 is a graph of pH change over a monitoring period;
FIG. 8 is a Piper plot of water samples taken at 7 months of 2015;
FIG. 9 is a graph of the Piper of a water sample taken at month 1 of 2016;
FIG. 10 is a graph of the Piper of a water sample taken at month 7 of 2016;
FIG. 11 is a dendrogram of a system clustering analysis;
FIG. 12 is a lithograph of principal component analysis;
FIG. 13 is a scatter plot of principal components of samples of groundwater taken at different sampling points at 7 months of 2016, with principal component 1(PCA1) indicating rock dissolution and principal component 2(PCA2) indicating seepage.
Detailed Description
The following non-limiting examples will allow one of ordinary skill in the art to more fully understand the present invention, but are not intended to limit the invention in any way.
Examples
1 engineering background
1.1 general overview of the engineering
With the first large underground water-sealed oil depot project in China as background, the cavernous region of the reservoir is spread in the 5-degree direction from north to west, the east-west width is about 600m, the south-north length is about 838m, and the reservoir capacity is 300 multiplied by 104m3The design lifetime is 50 a. The underground water-sealed oil depot engineering mainly comprises an underground engineering part and an overground auxiliary facility part, wherein the underground engineering part mainly comprises a main cavern, a construction roadway and a water curtain roadway, and the engineering structure diagram is shown in figure 1. 9 main chambers are arranged in parallel according to the north-south and the west, and each 3 main chambersThe chambers are connected through 4 branch holes to form 1 tank body, and the tank body is divided into 3 tank groups. The elevation of the designed bottom plate surface of the cavern is-50 m, the length of the designed bottom plate surface of the cavern is 500-600 m, and the designed distance between the two caverns is 30 m. The design distance between the wall of the tunnel cavity and the wall of the adjacent construction roadway is 25 m. The project was started in 11 months in 2010, completed in 4 months in 2014, and put into operation in 6 months in 2015.
1.2 general overview of weather and geomorphology
The climate type of the area where the reservoir area is located is a northern China warm and warm season wind type continental climate, the air is humid, the climate is mild, and the annual average temperature is 12.2 ℃. The average precipitation for many years is 711.2-798.6 mm, the precipitation for 6-9 months accounts for 70-76% of the whole year, and the precipitation is mostly concentrated in several times of rainstorm. The annual average land evaporation was 1410mm, the average peak monthly at 5 months, 175 mm.
The reservoir area belongs to the landform of low hills and hills, the nearly east-west trend of the mountain body of a cave depot, the elevation of a ridge is 280-350 m, the north side of the ridge is a cliff, the south side is a steep slope, the terrain slope is generally 35-55 degrees, and the south-north and north-south two sides of the ridge develop nearly south-north ditches and north-east ditches. The cave depot main body is positioned on the south side of the mountain, the average elevation of the ground is about 220m, the elevation of the highest position is 350.9m, the elevation of the lowest position is 97.5m, and the relative height difference is 253.4 m.
1.3 geological conditions
The area of the reservoir site shows that the main growth of the flexible shear band and the brittle fracture structure of the mountain making band, and the fold structure is not very grown. According to the difference of geological times, cause lithology and engineering properties, the lithology of strata in the reservoir area can be divided into 4 categories: the fourth system is the residual slope, the surging layer, the second growth granite of early chalkiness, the granite of late primordial ancient world, the rock vein of the brilliant spots of early chalkiness and the twinkling rock vein. Wherein, the main stratum is the granite sheet gneiss of late Yuan ancient boundary, accounts for more than 80% of the cave depot rock mass, is light flesh red to light grey, and the main minerals are: quartz, potash feldspar, albite, anorthite, amphibole, biotite, etc. and the fine granite flake has a blocky structure, and the rock mass is relatively broken and relatively complete and belongs to hard rock.
In order to find out the hydrogeological condition of the reservoir area, the total of about 50km for the reservoir area and the periphery2The region is subjected to hydrogeologyAccording to investigation and survey results, the water-containing medium in the reservoir area is granite gneiss in the ancient late Yuan province, the main types of underground water are bedrock fracture water and loose rock pore water, and the rock fracture water can be divided into superficial reticular fracture water and deep vein-like fracture water. The reservoir area is a hilly area, and the underground water takes atmospheric precipitation as a main supply source. The artificial wetland system has the advantages that the granite cracks grow, the terrain is steep, the slope of the ground is large, so that atmospheric rainfall is mostly discharged in the form of surface runoff, the infiltration amount is small, the supply is poor, according to the demonstration report of water resources of the underground water seal cave depot engineering, the average rainfall infiltration supply amount in the region is 53.8mm during the 1980-2000 years, the average rainfall infiltration amount in the region is 736.2mm for years, and the rainfall infiltration coefficient in the region is only 0.073.
According to geotechnical engineering survey investigation on the underground water-sealed oil depot in the design stage, the water chemistry types of underground water in the reservoir site area before the cave depot is built are all SO4+HCO3-Ca + Na type water, and the underground water is colorless, tasteless, transparent, low in mineralization degree, good in water quality, and can be used as domestic water and water during construction and operation.
2 research methods
2.1 Water sample Collection and detection
In order to research the chemical characteristics and the evolution law of underground water in the underground water-sealed oil depot site region, underground water samples are collected from the region of the oil depot site region in 7 months in 2015, 1 month in 2016 and 7 months in 2016 respectively, and 37 parts of water samples are collected in total. When water samples are collected, the water samples are strictly executed according to relevant regulations in DD2008-01 and GB12999-91, the position distribution situation OF sampling points is shown in figure 2, and the sampling points respectively comprise engineering construction affected areas and comprise 5 permanent water level monitoring holes (OF 1-OF 5); selecting a temporary drilling hole ZK009 by the hydrogeological unit; selecting a temporary drilled hole ZK013 from the poor fracture layer body; the oil gas pollution area comprises 3 ventilation vertical shafts (VT 1-VT 3), 3 sewage ports (SF3, SF6 and SF7) and water curtain water supply, and water samples taken at the sampling points can reflect the water quality change condition of underground water in the reservoir area in the running process of the oil reservoir. And after the water sample is collected, the water sample is timely sent to a geological environment monitoring station of Shandong province for detection. The detection index is the concentration of common ions in the underground water, including K+、Na+、Ca2+、Mg2+、Al3+、Cl-、SO4 2-、HCO3 -、CO3 2-、NO3 -And the ions are rich in the groundwater and widely distributed, and the chemical type and the characteristics of the groundwater can be basically determined. Wherein the cation (K)+、Na+、Ca2+、Mg2+) The concentration of (A) is detected by a flame yard absorption spectrophotometer, NO3 -Concentration was measured using an ultraviolet spectrophotometer, HCO3 -、CO3 2-The concentrations were determined by HCl titration. In addition, the detection indexes also comprise mineralization degree, full hardness, pH value and the like, which are important indexes for reflecting water quality in chemical components of underground water and have important influence on the chemical properties of the underground water.
2.2 rock mineral composition analysis
In order to research the mineral composition of the rock in the reservoir area, core samples are taken back at sampling points of the underground water-sealed oil reservoir, then slices are cut on the taken different core samples respectively, 5 rock slices are taken in total, and the mineral components of the taken rock slices can represent the mineral composition of the rock in the reservoir area. The dried rock slices were then subjected to XRD experiments to obtain the rock mineral composition.
2.3 mathematical statistics
In order to judge the hydraulic connection condition between the water seal effect of the water curtain system of the underground water seal oil depot and the sampling points of the reservoir site area, the SPSS software is used for carrying out cluster analysis and principal component analysis on the water sample taken in 2016, 7 months, wherein the formula is as described above. The basic idea of cluster analysis is to observe the relationship between samples according to the numerical characteristics of things, the relationship between samples is measured by the distance between samples, and the close distance represents the small difference degree between samples, so that the samples with close distance are classified into one class when the cluster analysis is carried out. The sample data of the analysis is not much, so the system clustering analysis is adopted. The basic idea of principal component analysis is to use fewer variables to explain most of the variables in the original data, and convert the original variables with high correlation in the data into new variables which are independent or unrelated to each other, and these new variables which are independent or unrelated to each other are the principal components. When the original variable with high correlation is converted into a new variable which is not correlated, the total variance of the variable is kept unchanged, and the first variable obtained by conversion has the maximum variance, which is called as a first principal component; the second variable has the second largest variance and is uncorrelated with the first variable and is called the second principal component; by analogy, 1 variable has 1 principal component.
3 water chemical characterization
3.1 groundwater chemistry characteristics
The water quality test results of the water samples taken at different monitoring periods are shown in table 1, and it can be seen from table 1 that the main ions in the groundwater include Na+、Ca2+、Mg2+、Al3+、Cl-、SO4 2-And HCO3 -In the cation, Na+、Ca2+Has high content of Na+Is the most predominant cation; in the anion, Cl-And HCO3 -Has high content of HCO3 -Is the most predominant anion. During the operation of the oil depot, the water chemistry characteristics of the underground water can be changed to a certain extent, and the change conditions of the main anion and cation concentrations in the underground water within the monitoring time period are respectively drawn according to the results shown in table 1 and are shown in fig. 3 and 4+、Na+、Ca2+、Mg2+、HCO3 -The ion concentration is generally in an increasing trend, SO4 2-The ion concentration generally decreases.
TABLE 1 Water quality test results of Water samples taken within test time periods
Figure BDA0001585220550000071
As shown in FIG. 5, the oil depot was operated with Cl in the groundwater-The concentration of the water-soluble salt is not more than 100mg/L (except water curtain water supply in 2016 and 1 month), and the water corrodes the steel bars in the reinforced concrete according to geotechnical engineering investigation code GB50021-2001The performance evaluation index belongs to weak corrosion, so that the underground water has no obvious corrosion effect on anchor rods, steel arch ribs, reinforcing meshes and the like adopted by the cave depot support.
NO in groundwater during operation of oil depot3 -The concentration of (c) is shown in fig. 6. As can be seen from FIG. 6, NO is monitored during the monitoring period3 -The ion concentration of the total water sample tends to increase first and then decrease, namely NO of the water sample taken in 2016 (1 month)3 -The ion concentration is higher and lower during other monitoring periods. Since the hydrogeological conditions of the reservoir site are less affected by humans and atmospheric precipitation is the main source of groundwater in the site, NO in the groundwater of the site3 -The ion concentration is mainly related to precipitation. 6-9 months per year in the area are rich water period, the rainfall is sufficient, and the rainwater seeps into the ground to cause NO3 -The ion concentration decreases. In addition, the winter of each year is the low water period of the area, and the precipitation of water in the area is insufficient in the next half year of 2015, so NO is generated3 -The ion concentration is at a higher level. NO in drinking water according to sanitary Standard for Drinking Water GB5749-20063 -The ion concentration needs to be lower than 10 mg/L. Therefore, NO in Water samples taken from OF2 and SF6 in 7 months OF 20153 -The ion concentration exceeds the standard; NO OF water curtain water supply and water samples taken from OF2, VT 1-3 in 20163 -The ion concentration exceeds the standard.
In the initial operation stage after the underground water oil-sealed reservoir is put into operation, the mineralization degree of underground water in the reservoir area is not high, the mineralization degree is mainly concentrated between 200mg/L and 400mg/L, and in the operation process of the oil reservoir, the mineralization degree of underground water mainly tends to rise, but does not exceed 1000mg/L, and still belongs to fresh water. Meanwhile, the underground water in the reservoir area is mostly weakly alkaline, as shown in fig. 7, most of the pH values of the water samples taken in the monitoring time period are between 7 and 8.5, and the pH values in the underground water generally fall along with the operation of the oil reservoir. Furthermore, the pH of the water samples taken at 1/2016 VT3, ZK009 and 7/2016 VT1 did not meet the standards.
3.2 groundwater chemical type evolution characteristics
To visually express the water chemistry characteristics of underground water in reservoir areas andand (3) respectively drawing a Piper three-line graph of the underground water in the reservoir area of the water-sealed petroleum cavern at different times by utilizing the AquaChem according to the relative content of main ions. Piper graph of the groundwater sample taken at 7 months of 2015 as shown in FIG. 8, the cations in the groundwater were predominantly Na in 9 samples taken at 7 months of 2015+、Ca2+Mainly, the anions in the groundwater are mainly HCO3 -Predominantly, the predominant groundwater chemistry type is HCO3-Ca + Na form of water. The Piper graph of a sample of groundwater taken at 1 month 2016 is shown in FIG. 9, where the cations in the groundwater are predominantly Na+、Ca2+Predominantly, anions predominantly being HCO3 -And Cl-Mainly comprises the following steps. K in groundwater+、Na+The relative abundance of K is improved compared with that of the K in 2015 month 7, which shows that the dissolution and filtration effect in underground water systems in reservoir areas can cause K to be generated+、Na+The concentration of (c) increases. The predominant groundwater chemistry type at this stage is HCO3Water of the Ca + Na type and SO4+ Cl-Na form of water.
A Piper graph of a groundwater sample taken at 7 months of 2016 (shown in FIG. 10), in which the cations in the groundwater are Na+、Ca2+Predominantly, anionic with HCO3 -And Cl-Mainly comprises the following steps. SO in groundwater between 1 month of 2016 and 7 months of 20164 2-The relative abundance of (A) is reduced, indicating that SO is consumed by leaching in groundwater systems in reservoir sites4 2-Furthermore, evaporative concentration in groundwater can lead to Cl-The relative abundance of (a) increases. The predominant groundwater chemistry at this stage is HCO3Water of the Ca type and SO4+ Cl-Na form of water.
By combining the water quality detection results of the underground water in each stage and the Piper graph of the taken water sample, the water chemistry type of the underground water is HCO in the initial operation stage of the underground water-sealed oil depot3Water of the Na + Ca type and SO4+ Cl-Na type water, the most predominant of which is HCO3-Na + Ca type water. Formation of chemical components of underground water is mainly based on leaching and evaporation concentration, wherein leaching can cause K+、Na+、Ca2+And HCO3 -Has improved relative abundance, SO4 2-The relative abundance of (a) is in a downward trend; concentration by evaporation results in an increase in the relative abundance of Cl-.
3.3 Water-rock interaction characteristics
XRD experiments were performed on the obtained rock sample chips, and the chemical element composition of each rock sample chip was calculated from the results of the XRD experiments and is shown in table 2. From table 2, it can be seen that the number percentages of atoms such as Si, O, Al, K, Na, and C in the rock in the reservoir site area are relatively large, and the rock in the reservoir site area conforms to the characteristics of typical granite, and in combination with the geotechnical engineering survey and investigation of the underground water-sealed oil reservoir at the design stage, it can be seen that the rock minerals in the area mainly include potassium feldspar, albite, and anorthite, and when the potassium feldspar, the albite, and the anorthite in the rock minerals contact with the underground water, they are partially dissolved, and the reaction equation is as follows:
2KAlSi3O8+2H2CO3+9H2O→Al2Si2O5(OH)4+2K++2HCO3 -+4H2SiO4 2-(Potassium feldspar)
2NaAlSi3O8+2H2CO3+9H2O→Al2Si2O5(OH)4+2Na++2HCO3 -+4H2SiO4 2-(albite)
2Ca0.5AlSi3O8+2H2CO3+9H2O→Al2Si2O5(OH)4+Ca++2HCO3 -+4H2SiO4 2-(anorthite)
From the above reaction equation, it is known that K is generated when underground water dissolves potassium feldspar, albite and anorthite in surrounding rocks+、Na+、Ca2+、HCO3 -Causing an increase in the concentration of these ions and a decrease in the pH of the groundwater with concomitant formation of kaolinite. In addition, when in ground waterCa2+When the concentration is relatively high, part of Ca is present2+Will react with SO4 2-The reaction produces CaSO which is slightly soluble in water4Thereby causing SO in the groundwater4 2-The concentration is in a descending trend, and the reaction equation is as follows: ca++SO4 2-→CaSO4↓
TABLE 2 chemical element composition of each rock sample slice
Figure BDA0001585220550000091
Figure BDA0001585220550000101
4 Water curtain System effectiveness analysis
Whether the underground water-sealed oil depot can normally operate is directly related to the water-sealed effect of a water curtain system of the underground water-sealed oil depot. When the water curtain system can effectively operate, water in the water curtain roadway can fully permeate into the underground, and because the density of the water is higher than that of the oil, and the oil is insoluble in water, the water curtain formed by underground water in the reservoir area can prevent the oil from leaking when the water curtain system can effectively operate, and the normal operation of the oil reservoir is ensured. In order to judge whether the water curtain system can effectively operate, the invention utilizes a statistical method to carry out statistical analysis according to the detection result of the water quality of the underground water so as to judge the effectiveness of the water curtain system. In order to judge the real-time water sealing effect of the water curtain system of the underground water-sealed oil depot, the data of a water sample taken in 2016, 7 months are taken for cluster analysis and principal component analysis.
4.1 Cluster analysis
The water quality test results of the water samples taken in 2016 and 7 months are subjected to systematic clustering analysis, and a dendrogram of the systematic clustering analysis is shown in fig. 11. According to the dendrogram obtained by systematic clustering, the groundwater collected in 2016 and 7 months can be divided into 5 groups, and the grouping result is shown in Table 3. Wherein, the water curtain water supply system comprises a water curtain water supply system OF1, an OF2, an OF3, an OF4, an OF5 and a ZK013, an SF3, an SF6 and an SF7, a VT1, a VT2 and a VT3 and a ZK 009. The groundwater samples in the same group have similar water chemical compositions, so that hydraulic connection between sampling points can be judged.
TABLE 3 systematic clustering analysis grouping results
Figure BDA0001585220550000102
4.2 principal Components analysis
The water quality test results of the water samples taken in 2016 and 7 months were subjected to principal component analysis, and the lithotripsy graph obtained was shown in fig. 12. According to the composition diagram and the rotation composition matrix, 2 principal component factors exist after principal component analysis, the accumulated variance contribution rate reaches 79.4%, and most information of original variables can be represented. The component score coefficient matrix is shown in table 4.
TABLE 4 component score coefficient matrix for principal component analysis
Figure BDA0001585220550000103
Figure BDA0001585220550000111
According to the result of the principal component analysis, the factor score of each water sample can be obtained, and then the factor score of each water sample is multiplied by the square root of the characteristic value of the corresponding principal component to obtain the principal component score of the water sample. A scatter plot of the principal component scores of the various groundwater samples plotted according to the calculation results is shown in fig. 13. In the scatter diagram of the principal component score of the groundwater sample, if the positions of the points for representing the water samples are close, the water chemistry properties between the points are close, namely, the hydraulic connection exists between the water samples. Therefore, as shown in FIG. 13, the groundwater collected in 2016 and 7 months can be divided into 4 groups. Wherein, the water curtain water supply port, the OF1, the OF2, the OF3, the OF4, the OF5 and the ZK013 obtain one group OF water samples, the SF3, the SF6 and the SF7 obtain one group OF water samples, the VT1, the VT2 and the VT3 obtain one group OF water samples, and the ZK009 obtain a single group OF water samples. The water chemistry characteristics of groundwater within the same group have a higher similarity, i.e. there is a hydraulic connection.
4.3 Water curtain effectiveness discussion
The results OF cluster analysis and principal component analysis were combined, and the results OF grouping are shown in table 5, in which groundwater samples taken in water curtain supply, OF1, OF2, OF3, OF4, OF5, and ZK013 were grouped together, groundwater samples taken in SF3, SF6, and SF7 were grouped together, groundwater samples taken in VT1, VT2, and VT3 were grouped together, and groundwater samples taken in ZK009 were grouped together.
From the grouping results shown in table 5, it can be seen that the groundwater in the permanent water level monitoring holes OF 1-OF 5 and the temporary drilling hole ZK013 distributed around the underground water sealed oil depot has similar water chemical characteristics to those OF the water curtain water supply, i.e. they are hydraulically connected to each other. The water in the water curtain system can fully permeate into the ground to form a water curtain, so that the leakage of petroleum can be effectively prevented, the water sealing effect is good, and the water curtain system can effectively operate. In addition, group 2 was a water sample in the shaft, similar to each other in water chemistry; the group 3 is a sewage water sample, and the chemical components of the three water samples are similar because the properties of the stored oil in the three hole tanks are consistent; and the 4 th group is a far-field underground water sample of the reservoir site and is not influenced by the operation of the cavern.
TABLE 5 statistical analysis of the groundwater classification results and sample point types at each sample point
Figure BDA0001585220550000112
In conclusion, with the first large underground water-sealed oil depot in China as the background, rock samples and underground water samples are respectively collected according to determined sampling time and sampling points, and XRD analysis is carried out on the collected rock samples to obtain the mineral compositions of rocks in the depot area, namely quartz (9.5%), albite (18.1%), anorthite (59.3%), potassium feldspar (8.1%) and biotite (5%). According to the mineral composition of rock, in combination with geotechnical engineering survey on the underground water-sealed oil depot in the design stage, judging that the main water chemical reaction occurring in underground water system of reservoir site area is hydrolysis reaction of feldspar (potassium feldspar, albite and anorthite), and further judgingThe water chemistry data index adopted when carrying out statistical analysis comprises K+、Na+、Ca2+、Mg2+、Al3+、Cl-、SO4 2-、HCO3 -、CO3 2-、NO3 -Etc.) concentration, degree of mineralization, full hardness, pH, etc. Detecting a water sample to obtain a water quality detection analysis result of the water sample as shown in table 1; and selecting a main component for the related water chemistry index, wherein the main component 1 represents the dissolution of rock, and the main component 2 represents the seepage of underground water. The association clustering analysis grouped the water chemistry similarities into a group as shown in FIG. 12. According to the cluster analysis result, the water sample distribution is listed as shown in table 5, and as can be seen from table 5, the groundwater in the permanent water level monitoring holes OF 1-OF 5 and the temporary drilling holes ZK013 distributed around the underground water sealed oil depot has similar water chemical characteristics to those OF the water curtain water supply, namely, the groundwater has hydraulic connection with each other. The water in the water curtain system can fully permeate into the ground to form a water curtain, so that the leakage of petroleum can be effectively prevented, the water sealing effect is good, and the water curtain system can effectively operate.

Claims (9)

1. The effectiveness analysis method for the water curtain system of the underground water-sealed oil reservoir is characterized by comprising the following steps:
(1) collecting samples: respectively collecting rock samples and underground water samples according to the determined sampling time and sampling points;
(2) sample detection: carrying out XRD analysis on the collected rock sample to obtain mineral composition of the rock in the reservoir area, and judging the generated hydrochemical reaction according to the mineral composition of the rock and regional hydrogeological conditions to select a corresponding water sample detection index;
(3) and (3) data analysis: combining two mathematical statistical methods of cluster analysis and principal component analysis, converting water sample detection indexes into new variables which are mutually independent or irrelevant to obtain the principal components of the water sample, drawing a scatter diagram of the principal components of each underground water sample, obtaining influence factors which are respectively dissolution of rocks and seepage of underground water, grouping sampling points on the principal component scatter diagram, and grouping points at a close position on the principal component scatter diagram into a group;
(4) discussion of Water curtain effectiveness: and analyzing the chemical characteristics of the water supplied by the water curtain, and judging the effectiveness of the water curtain system by analyzing the distribution condition of the sampling points similar to the chemical characteristics of the water supplied by the water curtain.
2. The method for analyzing the effectiveness of the water curtain system of the underground water-sealed oil depot according to claim 1, wherein the rock sample is collected before the construction of the oil depot, and the water sample is collected before the construction of the oil depot, during the construction and after the operation, so that the chemical change characteristics of underground water in the whole process can be reflected.
3. The method for analyzing the effectiveness of the water curtain system of the underground water-sealed oil depot according to claim 1, wherein the sampling time is set to avoid sampling in the weather abnormal period of rainstorm and drought, and the water sample collection process is completed within 1-3 days.
4. The method for analyzing the effectiveness of the water curtain system of the underground water-sealed oil depot, as recited in claim 1, wherein the sampling points are critical areas such as hydrogeological units, bad fault bodies, engineering construction affected areas, and oil and gas pollution areas.
5. The method for analyzing the effectiveness of the water curtain system of the underground water-sealed oil depot according to claim 4, wherein the arrangement of collection points is encrypted for key areas of a ventilation shaft and a sewage port of an oil-gas polluted area.
6. The method for analyzing the effectiveness of the water curtain system of the underground water-sealed oil depot according to claim 1, wherein the water sample detection indexes are converted into new variables which are independent or unrelated to each other, that is, if the number of the water samples is n, and the number of the selected water sample detection indexes is p, a matrix X-X (X-X) can be obtained from the original data of the water samplesij)n.pWherein x isijThe j-th index data representing the i-th sampling point, i, j is 1, 2, …, p, and a covariance matrix R, R is establishedijIs the original variable XiAnd XjThe calculation formula of the correlation coefficient is as follows:
Figure FDA0002958612560000011
wherein
Figure FDA0002958612560000012
Represents the average of the different indices at the ith sample point,
Figure FDA0002958612560000013
denotes the average value of the j index, xkjAnd (4) representing the index value of the kth sampling point j, solving the characteristic value, the principal component contribution rate and the accumulated variance contribution rate according to the covariance matrix R, and determining the number of the principal components.
7. The method for analyzing the effectiveness of the water curtain system of the underground water-seal oil depot is characterized in that a characteristic equation | λ E-R | ═ 0 is solved, wherein E represents an identity matrix, a characteristic value λ i is obtained, wherein i ═ 1, 2, …, p is arranged according to the size sequence, namely λ 1 is more than or equal to λ 2 is more than or equal to … is more than or equal to λ i is more than or equal to 0, and the contribution rate of the main component Zi is
Figure FDA0002958612560000021
Wherein λjThe characteristic value of the index is represented by the cumulative contribution rate
Figure FDA0002958612560000022
Selecting the main components with high accumulated contribution rate, wherein the accumulated contribution rate reaches 1, 2, … and m corresponding to characteristic values lambda 1, lambda 2, … and lambda m of 78-95%, wherein m is not more than p, and the integer m is the number of the main components.
8. The method for analyzing the effectiveness of the water curtain system of the underground water-sealed oil depot according to claim 1, wherein if the chemical components of the water samples classified as a group of internal sampling points are similar to those of the water supplied by the water curtain, the water curtain system is in hydraulic connection with the part, the water sealing effect of the water curtain system is good, and the water curtain system can operate effectively; otherwise, the water curtain system is still to be improved.
9. An effective regulation and control method for a water curtain system of an underground water-sealed oil reservoir is characterized in that based on the effectiveness analysis result of the water curtain system by the method of claims 1-8, the water curtain system is regulated and controlled by changing the chemical components of water supplied by the water curtain system according to the judged water chemical reaction type.
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