Xia Yun, Tian Fang, Li Baoli
Abstract From the principles of scanning electron microscopy, X-ray diffraction, cathodoluminescence, electron microprobe, energy spectrum, fluorescence, inclusions and other analytical techniques, we systematically introduce the application of reservoir special analytical techniques in different fields of exploration technology, and describe the prospects for the combination of special analytical techniques in the identification of the threshold of oil production, establishment of high-precision stratigraphical grid, and fine description of the reservoir. The prospects of the combination of special analysis techniques in identifying oil thresholds, establishing high-precision stratigraphic grids and reservoir fine description are described, and the application effects of special analysis techniques in igneous exploration and reservoir protection are exemplified; meanwhile, it is also pointed out that the application of reservoir special analysis techniques in oil and gas exploration is at a preliminary stage and needs to be further explored.
Keywords: reservoir, special analysis technology, hidden reservoir, exploration, comprehensive evaluation
I. Introduction
The development of the instrumentation industry and the wide application of computer technology have led to the development of petroleum geology experimental analysis technology by leaps and bounds. In order to meet the needs of oil and gas exploration and development, in recent years, the world has successively proposed and developed a series of new reservoir analysis and testing technology, mainly in reservoir geochemistry, cathodoluminescence, inclusions, image processing, fractal technology, rock-forming mineral isotopes, rock-forming simulation experiments, and other experimental analysis technology has made some new progress. China's petroleum geology reservoir experimental analysis technology closely follow the world's advanced level, a variety of analytical testing program is relatively complete, in addition to micro-infrared spectroscopy analysis technology has not yet been carried out, the rest of the advanced technology in our country, some of which are also at the world's advanced level. In recent years, the stratigraphic office of Institute of Geological Sciences of Shengli Petroleum Administration has actively introduced advanced analytical technologies such as cathodoluminescence, inclusions, image analysis and electron probe and energy spectrum, and applied them to reservoir oil and gas exploration and research and oil layer protection research, forming a complete set of comprehensive evaluation technology of the reservoir and oil layer protection technology, which has provided many valuable research results for oil and gas exploration and development.
Figure 1 Methodological diagram of reservoir yield analysis technology
The reservoir experimental analysis technology includes three major parts: conventional analysis technology, special analysis technology and supporting or selective analysis technology (Figure 1). Conventional analysis can only meet the requirements of regional exploration, and special analysis projects must be carried out if fine description and comprehensive study of the reservoir is conducted.
Two, X-ray diffraction analysis technology
The basic principle of X-ray diffraction is to identify the type of minerals by determining the crystal spacing. X-ray diffraction is the most important means of analysis for fine-grained clay minerals, as well as minerals with great variations or even completely different faces.The application of X-ray diffraction analysis technology in petroleum geological research and oil and gas exploration includes mixing ratio calculations, whole-rock X-ray diffraction and quantitative analyses, in addition to qualitative and quantitative analyses of clay minerals.
1. Calculation of mixing ratio
The so-called mixing ratio refers to the percentage of montmorillonite content in the mixing mineral I/S (illite/montmorillonite) or C/S (chlorite/montmorillonite). Since there is an obvious correspondence between the transformation reaction of organic matter to hydrocarbons and the dehydration reaction in the transformation of montmorillonite to illite in oil-bearing rocks, the characteristics of the diagenetic transformation of mudstone clay minerals can be utilized to infer the degree of thermal evolution of organic matter, and be used to classify the stage of diagenesis, to estimate the geothermal temperature, to predict the oil-bearing reservoirs, and to judge the oil-bearing throttle limit.
Figure 2 Relationship between permeability and montmorillonite content in low-permeability reservoirs
2. Whole-rock X-ray diffraction qualitative and quantitative analyses
In addition to being mainly used to study the role of diagenesis and to deduce the evolution of hydrocarbons, the technique of X-ray diffraction clay analysis is mainly applied to research on the protection of hydrocarbon reservoirs in the exploration and development of oil and gas. Clay minerals in clastic reservoirs are the main source of material causing injury to the formation. The sensitivity injuries caused by clay minerals to reservoirs include five sensitivities such as water-sensitive and quick-sensitive. After a comparative study, it is found that water-sensitive injury is the main factor causing sensitivity injury in low-permeability reservoirs (permeability less than 50×10-3μm2). The intensity of water sensitivity mainly depends on the absolute content of montmorillonite, an expansive clay mineral in the reservoir (Fig. 2), and has little correlation with other physical parameters of the reservoir. The discovery of this law helps to accurately predict the potential sensitivity of low-permeability reservoirs, and then take effective protective measures to realize the low-injury or even no-injury exploration and development of low-permeability reservoirs.
Three, scanning electron microscope analysis technology
Scanning electron microscope is the use of a certain energy of the electron beam bombardment of solid samples, so that the interaction between the electrons and samples, and then with the help of special detectors for the collection, processing, and imaging, you can intuitively recognize the sample's ultramicro morphology, structure and elemental composition. Scanning electron microscopy of rock minerals is characterized by three-dimensional graphics, high resolution and large depth of field, which can provide the following geological information for the study of reservoirs and their diagenesis: particle size, sorting, rounding, cement content, pore distribution and its content; to determine the type and morphology of authigenic cement and its distribution in the pores; to determine the type and geometry of rock pores, and to judge the reservoir performance; to determine the level of secondary enlargement of quartz; to determine the level of dissolution of quartz; to determine the level of secondary enlargement of quartz; and to determine the level of dissolution of quartz. secondary plus the judgment of the level; dissolution accounted for the judgment, etc..
Scanning electron microscopy can visually and qualitatively observe the particle size and pore space characteristics of rocks, but how to quantify the observed particle size and pore space information is an urgent technical challenge. Through the technical research in recent years, the author has successfully developed the quantitative analysis technology of reservoir particle size parameters and porosity parameters. The principle is to use computer technology to binarize the scanning electron microscope image, find out the value of particle and porosity parameters, and then draw the porosity and particle size distribution curve. This technical achievement is the first of its kind in the national scanning electron microscope analysis industry, and has a broad application prospect.
Four, cathodoluminescence technology
Cathodoluminescence is the cathode ray tube issued by the accelerated electrons on the sample bombardment, so that the electrical energy is converted into light radiation and luminescence, i.e., with the cathode ray tube accelerated electrons generated by the excitation and the production of a fluorescence. Its applications in petroleum geology and oil and gas exploration are as follows.
1. Judging the source and determining the nature of the parent rock
The luminescence characteristics of various quartzes are formed in the process of the formation of the parent rock, representing the temperature conditions of its rock formation, and quartz particles have three types of luminescence, i.e., violet, brown, and non-luminescence, and the three different luminescence types reflect the three different causes of the quartz.
Through the analysis of Bohai Deep 4, Lin95, Pile Deep 1 and Central 5 wells, it can be seen that the luminescence of detrital quartz in the deep reservoirs of Bohai South, Linnan and Weibei in Shengli Oil Zone is generally brownish, light brown, etc. There are two kinds of temperature conditions for the formation of the quartz with brownish luminescence, one of them is greater than 573℃, and the other is from 300 to 573℃, and its mother rock is high and intermediate grade metamorphic rock, and it is inferred that there are three kinds of luminescence of the detrital quartz grains in the deep reservoirs in Bohai Deep 4, Linnan and Weibei of Shengli Oil Zone. Combined with the petrological characteristics, it is inferred that the parent rocks of the three depressions are mainly the old metamorphic rocks of Taiguyu; secondly, purple light is seen in the quartz grains of Lin82 and Lin45-11 wells, and the parent rocks of them are the Mesozoic ejecta rocks.
2. Inferring the depositional environment, studying various rock-forming roles, and dividing the sequence and period of rock-forming roles
(1) Inferring the change of depositional environment
According to the research, the luminous intensity and color of the carbonates are controlled by the ratio of [Fe2+]/[Mn2+]. When [Fe2+]/[Mn2+] is less than 0.5, it shows yellow color; when the ratio of [Fe2+]/[Mn2+] is 0.5-1, it shows orange color; when the ratio of [Fe2+]/[Mn2+] is 1-2, it shows orange-brown color; when the ratio of [Fe2+]/[Mn2+] is 2-10, it shows brown-dark brown; and when the ratio of [Fe2+]/[ Mn2+] is greater than 10, it does not glow. Combined with the research on elemental geochemistry, the [Fe2+]/[Mn2+] ratio is one of the markers for judging the paleoenvironment, and different ratios represent different paleodepositional environments. The oolite seen in the thin section of 3871.00m sample from Lin82 well, the oolite core is a mesoclast, with the change of environment, the composition and luminescence characteristics of its oolite ring also change, the color and brightness of cathodoluminescence are different, the oolite ring from the inside to the outside of the color of bright yellow-yellow-brown-brown-red, the brightness of the light-darker From this, we know that the [Fe2+]/[Mn2+] ratio in the environment during the formation of the oolite is low-high-medium, and the change of the ratio indicates that the ancient salinity in the depositional environment is high-gradual-low-medium, and Fe2+ is not easy to change. Fe2+ is not easy to migrate, while Mn2+ is easy to migrate, and the change of the color of the oolite reflects the change of the distance of the sediment from the shore, which may be related to the advancement and retreat of the lake water at the time of deposition.
(2) Inferring the change of salinity of stratum water after deposition
According to the characteristics of the evolutionary sequence of carbonate rock formation in the Bohnan Depression, early calcite (brownish yellow) -late calcite (bright yellow) -iron calcite (yellowish brown) -dolomite (rose red) -Fe-bearing dolomite (non-luminous), reflecting the change from high to low paleosalinity in sedimentary-early diagenetic-late diagenetic environments.
3. For identification of secondary pores
When intergranular pores are present in clastic rocks, it is sometimes difficult to distinguish and confirm whether they are primary or secondary. For example, calcite, dolomite or other mineral-filled pores, in the process of diagenesis, all or most of the cement was dissolved, the formation of secondary intergranular pores and primary intergranular pores are sometimes difficult to distinguish between under the conventional microscope, while under the cathodoluminescence microscope, as long as there is a bit of calcite residue in the edges of the particles, it can be found. Therefore, if residual calcite, dolomite, rhodochrosite and other collodion can be seen at the edge of the particles, it can be inferred that they are secondary pores.
Rock samples of quartz fragments in the edge of the irregular or jagged, the use of cathodoluminescence can clearly distinguish between the account of the dissolution produced or local increase caused by the irregular shape. The former form secondary pores, the latter is narrowed primary pores.
4. Study of crystal growth ring and cement generation
Cathodoluminescence microscopy can be used to solve the carbonate cement generation and study its ring structure.
5. Restoration of the original rock structure
Rocks undergo a series of changes when they are transformed by diagenesis, often altering the original structure of the rock. Cathodoluminescence microscopy can, to a certain extent, reproduce the structure of the original rock.
6. Research on tectonic microcracks
The study of rock cracks is an important part of reservoir research, due to the modification of diagenesis, many cracks can not be observed. Through the cathodoluminescence microscope can be more clearly observed crack development, including the size, width and filling of cracks, especially for multiple groups of cracks cross relationship between each other and the formation order can be studied.
V. Electron probe and energy spectrum analysis technology
Electron probe is a large precision instrument to analyze the surface morphology and material components. Under the bombardment of the electron beam, different elements produced by the X-ray wavelength and energy are different. Electron probe wave spectrometer and energy spectrometer through the determination of the chemical composition of minerals and achieve the purpose of accurately determining the type of minerals. Electron probe analysis area is small, the electron beam spot can be in the range of 1 ~ 100 μm arbitrary choice, the analysis of micro-fine minerals and veins and the analysis of the composition of fine samples is extremely effective means of identification. Electron probe can directly determine the components of the sample on the optical thin section. The micro-fine minerals of the thin section can be analyzed by point, line and surface. Energy spectrum analysis is generally carried out in conjunction with scanning electron microscope observation, that is, by detecting the energy intensity of the characteristic X-rays of the element for qualitative and quantitative analysis of the element. Energy spectrometer in the measurement of the same point, can be detected at the same time the composition of the various elements of the point, and displayed on the fluorescent screen, giving a variety of elements of the spectrum, the more content, the higher the peaks, and vice versa, the spectrum is very intuitive.
Electron microprobe spectroscopy and energy spectrum analysis technology in petroleum geology is mainly used in the following aspects: combined with cathodoluminescence microscopy, can reveal the principle of luminescence of minerals; combined with X-ray diffraction analysis, can be accurately identified various types of clay minerals of the chemical composition; but also accurately identify the zeolite minerals, as well as paleontology, rock-forming minerals and authigenic minerals to accurately identify the composition.
Taking the sample of 3090.5m from Luo 151 well in Luojia area of Zhanhua Depression as an example. The lithology of the sample is medium-fine-grained pyroxene, in which there is a micro-zone ring zone plagioclase feldspar, for which micro-zone specific elemental K, Na, Ca facies analysis was done, and the results are shown in Fig. 3. From Fig. 3, it can be visualized that the distribution of elemental ring zones has a pattern of distribution, with the outer layer being orthoclase feldspar (potassium facies distribution), the intermediate layer being a point of calcium-bearing plagioclase feldspar (calcium, sodium facies distribution), and the innermost layer being minerals containing iron, silicon, and aluminum, which are similar to the chlorite's elemental composition, i.e., feldspar gradually decreases in calcium ions and increases in sodium ions from the center to the edge. On the one hand, this indicates that feldspar was formed over a long period of time; on the other hand, it indicates that the magma was basal when it began to crystallize the minerals, and then gradually transitioned to acidic. At the same time, it shows that the cooling time of the magma is very long, and the crystals formed by it tend to be coarser. In the later stage, if there is a fault cutting, the formation water is easy to dissolve the crystals, and form the oil and gas reservoirs with the main storage space of cracks-soluble holes, such as the igneous oil reservoir of Shang741 block in Shanghe Oilfield.
Figure 3 Luo 151 well 3090.50m annular feldspar surface analysis element distribution morphology
Six, fluorescence microanalysis technology
Fluorescence microscopy principle is to use ultraviolet light as a source of light, irradiated by the objective lens to the thin film, the thin film samples contained in the organic matter and asphaltene will be stimulated by the fluorescence, according to the luminescence of the sample characteristics as well as luminous material and rock structure, tectonic interrelationships, and so on. Based on the luminescence characteristics of the sample and the correlation between the luminescent material and the rock structure and structure, the type of organic matter, maturity, effective storage space, oil and gas transportation can be judged. There are several applications of fluorescence thin section analysis technology in oil and gas exploration.
1.Evaluation of oil-bearing layer
Fluorescence microscopy can provide information for the study of the type of organic matter, morphology, casein maturity, source of organic matter, so as to evaluate the oil-bearing layer.
2. Research on the direction of oil transport and transport time
Fluorescence microscopy to study the direction of transport of hydrocarbons, mainly relying on the intensity of luminescence (on behalf of the content of hydrocarbons) in the longitudinal or transverse changes in the comparison of the information, as long as the determination of the formation of the pore space time, combined with the range of the luminescence can be the study of the time of transport of oil.
3. Determine the validity and oil content of reservoir storage space
Take carbonate rock as an example. To determine the validity of carbonate reservoir space is based on the following: (1) cracks are percolation channels, while holes are often reservoir space; (2) the oil content of the matrix around the slit holes has nothing to do with the production of oil; (3) the latest formation of the reservoir space containing asphalt material is the most effective; (4) when there is a third generation of slit holes in the filling of the third generation of the filling of the filling of the hole, only early filling of the first two generations of the filling of the filling of the first generation of the filling of oil content is ineffective.
Carbonate rock oil law is: ① secondary effective cracks, holes, good or bad luminescence and oil production has a close relationship with the oil, seams and holes in the oil can be oil, if not oil only matrix oil is not oil; ② along the secondary effective seams and holes with oil, and to the matrix dip the wider, the more color halo, the more bright the better, the better, the prediction of obtaining a high yield of oil streams; ③ matrix luminescence is unrelated to the production of oil, the substrate luminescence, seams, holes Not luminous not oil production, substrate does not glow, the seam holes glow can still produce oil.
4. Judgment of oil-water layer interface
General oil layer section of rock samples luminescence show good, all pores contain oil, suture, intergranular holes, intergranular holes, crystals, such as the dissolution of the seam dip dyeing luminescence is very good; oil and water near the wells section of luminescence shows uneven phenomenon, matrix luminescence is poor, part of the pore luminescence; and the water layer samples of its seams and the rock do not luminescence. According to the longitudinal changes in oil content can be judged oil-water layer interface.
5. Application of fluorescence thin section analysis technology in oil and gas exploration in Hotan Prospect, Xinjiang
(1) Fluorescence characteristics of reservoir and oil content analysis
Since the outcrops of outcrop oil-bearing samples in Hotan Prospect have been weathered and filtered for a long time and the oil has been heated up and evaporated, and most of the light petroleum fractions in the pore spaces in the rocks have been taken away or volatilized, the outcrops are observed with fluorescence microscope to determine if the samples are once oil-bearing or not. The fluorescence microscope observes these outcrop samples and judges whether they are once oil-bearing rocks, mainly looking for the remaining asphalt traces of oil-bearing rocks, i.e., the color and brightness of luminescent substances in the pore crevices and whether they have colored fluorescence. Accordingly, it is inferred that the quartz sandstone of the Carboniferous Kalawuyi Formation and the tuff of the Azgan Formation, as well as the rock-chip sandstone of the Permian Psig Formation and the dolomite of the Kozlichman Formation, are favorable oil- and gas-bearing reservoir rocks of the Carboniferous-Permian System.
(2) Characteristics of oil-bearing rocks and judgment of maturity
Generally speaking, good oil-bearing rocks must have three conditions: ① a large number of organic residues distributed in the rock, the higher the abundance of organic residues, the higher the potential for oil and gas; ② good quality of the organic matter, the humified casein is stronger than humified casein in terms of the ability to produce oil and gas; ③ the maturity of oil-bearing rocks. In addition, the fluorescence intensity produced in shallow immature samples is large, and the luminescence intensity is weakened in the main oil-forming zone because some hydrocarbons have been excluded. The dry gas zone shows no fluorescence.
Hetian Prospecting Area oil-bearing rock characteristics are as follows: ① lithology for mudstone, sandy mudstone and gray mudstone three categories (excluding carbonate rocks); ② three lithology are different degrees of organic matter body, organic body in two states exist, one is a filamentous body along the layers of the long, sporadic distribution or concentration of the layer, mainly distributed in the mudstone and sandy mudstone, and the other organisms in the form of particles, sporadic or dispersed in the matrix; ③ organic body is granular, scattered or dispersed in the matrix; ③ according to the organic matter residue judgment, the organic matter content is generally 4% to 20%; ④ organic residue luminescence color for the dark orange-brown predominantly, a small amount of orange-yellow, for the colloidal and asphaltene asphalt (Table 1).
Table 1 Characteristics of raw oil rocks in Hotan Prospect
Based on the above analysis, it can be seen that the abundance of raw organic matter residues in Hotan Prospect is not ideal, and its luminescence color indicates that the organic matter has reached a high level of maturity, but the residues of the organic matter for the heavier asphaltene, the organic matter of the exhaustion of hydrocarbons is sufficient, and contributes to the larger. If the thicker oil-bearing rock is found, although the abundance is not high, there can be exploration prospects.
Seven, inclusions analysis technology
Inclusions are rock-forming minerals during or after the growth process, in the defects within the mineral crystals, nests or secondary microcracks are wrapped in the solid, liquid or gas. Inclusion analysis technology can be applied to the following aspects of oil and gas exploration research: ① restoring paleogeothermal temperature and remodeling thermal history; ② studying the environment of rock-forming and the history of rock-forming; ③ studying the history of pore evolution; ④ determining the relative time and direction of oil and gas transport; ⑤ researching the nature and source of water in the field, and determining the conditions of oil and gas transport.
Deep oil and gas layer exploration is the hot spot of current oil and gas exploration in Shengli oil area, but it is also a difficult point. In recent years, with the deep oil and gas exploration, the scientific researchers in the stratigraphic room have carried out useful exploration and research in this area by using the special analysis technology of inclusions, and have achieved some understanding and results.
1.Determine the depth of oil destruction, predict the favorable depth of natural gas exploration
The temperature of oil destruction is 118~121℃, Weibei depression with this temperature section of the inclusions are seen at a depth of 3150m, Bohanan area is seen at 3600m, the two depths represent the depth of the two depressions (depressions) of the depth of the oil destruction, above the depth of the two is a favorable target for oil exploration, below this depth, the depth of oil is the depth of the inclusions, and the depth of oil destruction is the depth of the inclusions, and the depth of oil destruction is the depth of the inclusions. Above these two depths, it is a favorable target for petroleum exploration. Below this depth, the petroleum is gradually cracked, generating light components and methane and so on. Therefore, below 3600m in Weibei Depression is the target for deep natural gas exploration, which has been confirmed by exploration and inclusions composition. In the inclusions of the sample of Chang67 well 3157m in Weibei Depression, the percentage of methane mole number is 19.9%, and in the two inclusions of the sample of 3701.08m in Yang5 well, the percentage of methane mole number is 43.9% and 57.6% respectively, which indicates that with the increase of depth, the deeper the degree of petroleum destruction, and the content of methane is also gradually increased.
2.Judging the oil and gas exploration potential at a certain depth
There is no oil and gas display below 3900m in the central 5 wells of Weibei Depression, is it that no good favorable phase zone has been found or there is no potential for anger? From the gas-liquid inclusions in the fracture of 4244m in the central 5 wells, it can be shown that there are a large number of hydrocarbons from C1 to C4 in the formation below this depth, and the inclusions or gases are always transported from the bottom to the top, which proves that the oil-generating parent material below the depth of 4244m in the wells has a high oil-generating capacity, and if the deep part of the Weibei Depression can find a good reservoir rock layer, then this kind of reservoir sandstones may have a good capacity of oil and gas storage.
3. Speculation on the evolutionary history of the basin
The measured paleo ground temperature of the 4244m parcel in the central 5 wells of the Weibei Depression is 168℃, and the measured bottomhole temperature is 139℃, with a difference of 29℃ between the two. According to the calculation, the minimum geothermal gradient of Weibei Depression is 3.39℃/100m, and the maximum geothermal gradient is 3.7 C/100m, and the relative uplift height or paleo-stripping thickness of the calculated value compared with the present depth is 855m or 765 m. In addition, in the calcite vein of different periods at 3701.08m of central 5 wells, the homogeneous temperature of the inclusions of the early calcite inclusions and the inclusions of the late calcite inclusions is 164℃, and the homogeneous temperature of the late calcite inclusions is 164℃. The mean temperature of late calcite inclusions is 153℃, with a difference of 11℃. This also indicates that after the formation of the rift, the Weibei depression was gradually uplifted as a whole, and did not gradually sink until after the Late Tertiary.
VIII. Application of reservoir special analysis technology in igneous reservoir exploration
The intrusive rocks of the Jiyang depression are mainly distributed in the Shasan section of Shanghe and Luojia areas, and are intruded in dark mudstone, shale and marl. According to the observation of thin section, the rock structure is pyroxene green structure, pyroxene long pyroxene green structure, X-ray diffraction analysis of the main components are plagioclase feldspar and pyroxene, and the secondary components are magnetopyrite and black mica minerals. Due to the different speed of heat dissipation in each part of the rock body and the effect of crystallization differentiation, the center part is coarsely crystallized and the feldspar content is also high. In the rock, CaO content accounts for 8.7%-9.9%, Al2O3 accounts for 14.57%-15.7%, FeO+Fe2O3 accounts for 10.25%-11.79%, and Na2O+K2O accounts for 3.86%-5.09%. It can be seen that the rock has a high content of Ca, Fe and Al oxides. According to the analysis of ICP elemental spectra, the content of cation Fe in pyroxene is 6.91%-10.22%, Mg is 2.43%±, Al is 7.4%-7.30%, Na is 2.77%±, K is 4.34%±, and Ca is 5.61%-7.15%. After the intrusion of the intrusive rock in the invasion of the position, the high temperature formation of minerals by the influence of the third system of aqueous media, become very unstable, or fibrous amphibole or ettringite, or clay, carbonate, and so on, and ultimately into the low-temperature aqueous media under the conditions of stability of the alteration of the clay minerals or carbonates. The types of these clay mineral compositions are basically similar to those in the pores of Tertiary sandstones from the present assay and analytical data, but the content is relatively different, constituting a special clay mineral assemblage in igneous rocks. The altered clay minerals analyzed by thin-section observation and X-diffraction are chlorite, ilmenite/montmorillonite, illite, and kaolinite. The total clay mineral content is 15% to 24%, and the main clay minerals are chlorite and ilmenite interlayer minerals, with a relative content of 37% to 47% chlorite, 25% to 41% ilmenite interlayer, 0 to 23% other illite, 12% to 15% kaolinite, and a ratio of ilmenite to ilmenite interlayer of 60% to 70%. The intrusive rock body itself is dominated by cracks and pores, and the cracks are more developed in the edge phase zone and transition phase zone, while the cracks in the center phase zone are poorly developed; the primary cracks, i.e., joints and seams, are more developed than the surrounding rocks which are mudstone and the surrounding rocks which are of other lithology (e.g., marl), and the cracks are more developed than those far away from the cracks (e.g., cracks are more developed in the Shang 743 wells than in the Luoyang 151 wells). Fracture development zone is more developed dissolution pore, especially near the fault matrix is easily affected by the acidic water medium, the formation of solution holes and caverns, etc.; on the other hand, if the intrusive body of the various phases of the zone fracture development degree is equal, the center phase of the zone solution holes are the most developed.
The large amount of thermal energy carried by the intruding rock will form a contact metamorphic zone around the intruding rock, resulting in chemical reactions between the minerals and the synthesis of low-density minerals into high-density minerals. Analyzed by electron microprobe and X-ray diffraction, this high-density minerals are garnet, the formation of garnet is bound to reduce the solid volume of the rock per unit volume, the effective pore space increases, the casting of thin-section observation of this pore space for garnet intergranular pore space, and the rock from sedimentary rocks into contact metamorphic rocks, such as Luo 151, Luo 152, Luo 151-4 wells of contact metamorphic rocks, the physical properties of the determination of porosity of up to For example, Luo 151, Luo 152, Luo 151-4 wells, the porosity of which is 25%-36%, the reservoir is equivalent to the sandstone reservoir of Tiantao Formation, and the output of a single well is 15-90t/d. For the formation of this kind of contact metamorphic reservoirs, it is believed that two basic conditions are needed: ① there must be high-energy intrusive rocks; ② the magma must be invaded into the grey mudstone and muddy greywacke, which can make it metamorphic and produce effective pore space. Therefore, for future exploration of contact metamorphic reservoirs, we should not only look for igneous rocks, but also look for large-scale and regional distribution area of marl (i.e., when marl distribution area intrudes into gabbro), then we may find this kind of contact metamorphic reservoirs. The discovery of contact metamorphic reservoirs in Jiyang depression fills the blank of similar reservoirs found at home and abroad, and provides the basis for future search of this kind of special oil and gas reservoirs.
Nine, exploratory well sandstone reservoir conventional geological parameters and sensitivity prediction technology
In order to avoid oil and gas layer damage during exploratory well drilling, the author developed the exploratory well sandstone reservoir conventional geological parameters and sensitivity prediction software, which realizes the prediction of exploratory well conventional geological parameters and sensitivity parameters. The realization of this prediction is based on the research results in three aspects: ① within two years, a 50MB oil reservoir protection database was built, and according to the distribution of the data surface in the database, the oil area was divided into dozens of blocks, and the longitudinal pattern of change and trend of the parameter was found out according to the blocks; ② through the correlation research, the petrochemical and sensitivity injury indices that may be caused by the various mineral components and the relationship of the change of the size of the value between the parameters were determined; ③ a module was compiled; and the prediction software was developed. ②Through the correlation study to determine various mineral components may cause lithology and sensitivity injury index and the relationship between the values and magnitudes of various parameters; ③Establishment of the module; ③Programmed prediction software, the prediction method is: first of all, according to the coordinates of the exploratory wells to be predicted to determine the software coding block to which the exploratory wells belong to be predicted (according to the database parameter regression established by the homogeneous block), through the regression equation of the blocks as the basis for the development of the software, to carry out the parameter prediction. The predicted parameters are mainly lithology and physical properties, and there are 24 of them***. Based on the 24 predicted parameters, the sensitivity parameters and related critical values that are important for the protection of oil and gas reservoirs can also be predicted.
By comparing with the actual analyzed data after sampling of 8 exploratory wells, it is found that the predicted parameters basically match with the measured parameters, with an accuracy of 70%. Since the prediction of conventional geological parameters and sensitivity of exploratory well reservoirs was carried out in October 1998, the prediction of more than 90 exploratory wells has been completed. This work saves a large amount of costs required for actual measurement and has significant economic benefits.
X. Concluding Remarks
From the above analysis, it can be seen that reservoir special analysis technology and reservoir sensitivity prediction technology play a very important role in oil and gas field exploration and development, and its application prospect is very broad. However, it should also be seen that, due to the introduction of cathodoluminescence, electron microprobe and energy spectroscopy, inclusions and other analytical techniques for a short period of time, is still in the early stage of technological development and mid-stage, the application of the oil and gas exploration belongs to the exploration stage, the application of the effect is not significant enough. This is related to the short time of technology development, but also related to the limitations of reservoir microanalysis technology. Only the organic combination of reservoir micro-specific analysis technology and macro-analysis technology can achieve significant exploration results and benefits.