Reservoir evaluation instrument analysis project

The instrumental analysis of evaluation includes scanning electron microscope analysis, X-ray diffraction analysis, cathodoluminescence, fluorescence microscope and inclusion cold and hot bench determination. They are also very important basic analysis items in reservoir evaluation. The corresponding analytical standard methods at all levels are: GB/T18295—21 "Analysis method of sandstone samples in oil and gas reservoirs by scanning electron microscope", SY/T6189—1996 "Quantitative analysis method of rock minerals by energy spectrum", SY/T5163—1995 "X-ray diffraction identification method of relative content of clay minerals in sedimentary rocks" and SY/T5983—1994. T5614—1993 "Identification method of rock by fluorescence microscope", SY/T5916—1994 "Identification method of rock sample by cathodoluminescence" and SY/T61—1994 "Determination method of homogeneous temperature and salinity of sedimentary rock inclusions".

72.9.2.1 scanning electron microscope analysis method for sandstone samples in oil and gas reservoirs

Definition

Pores are spaces surrounded by solid rock parts and not filled with solid debris particles, impurities and cements.

the ratio of pore and throat area to the viewing area in the viewing area of face rate (%).

throat connects the narrow channel between two adjacent pores.

Clastic particles mainly refer to the granular original materials (including Shi Ying, feldspar and cuttings) that constitute sandstone.

cements are free minerals formed in intergranular pores by chemical precipitation.

fine-grained detrital materials deposited by hetero-groups in a mechanical way.

method summary

it is made according to different types of samples and analysis and identification requirements. The petroleum geological samples should be coated with a conductive film before being observed by electron microscope. Adjust the scanning electron microscope, the beam should be stable, the electron beam axis should be good, and the instrument should be in the best state. After the instrument is in normal and stable working condition, the sample can be observed, identified and measured. The contents include morphology observation, pore and throat characteristics observation, type determination, and measurement of surface pore and throat size; Observe the type and occurrence of cement.

instruments and devices

scanning electron microscope with image analysis software.

x-ray energy spectrometer.

the solid microscope has the functions of reflecting and transmitting light.

vacuum coating machine or sputtering instrument.

oven.

reagents and materials

chloroform.

latex, conductive adhesive or double-sided tape.

gold thread.

special spraying carbon rod.

sample preparation

oil-bearing samples need to be washed with chloroform by extraction or immersion.

the representative and flat fresh section is selected as the observation surface.

on the pile, use latex, double-sided tape or conductive adhesive to stick the sample on the sample pile.

dry it naturally or put it in a constant temperature box below 5℃ for drying.

the ear washing ball is used for dust removal to blow off the surface dust.

the coating is carbon plated in a vacuum coating machine or gold plated in a sputtering machine.

analysis step

after the scanning electron microscope is turned on and the instrument is in normal working condition, the sample can be analyzed according to the following steps.

1) morphology observation. Under the microscope of 2 ~ 2 times, observe the whole picture of the sample, including the size and distribution of debris particles, cement, heterobase and pore development, and take photos.

2) porosity. Observe the pore and its characteristics, determine the pore type and measure the pore size. Use the electronic scale provided by the instrument to measure the distance at the widest point of the short axis of general pores as the pore diameter value of the sample.

3) throat. Observe the characteristics of throat, determine the type and connectivity of throat, and measure the size of throat.

4) measure the face rate. Observe the development of pores under the magnification of 5 ~ 2, and select the measuring visual field to ensure that there are more than 3 pores in the visual field; Using image analysis software, the face rate is measured according to the threshold set by gray level, and the percentage of the areas of pores and throats within the threshold range to the viewing area is calculated. For each sample, at the same magnification, more than 4 viewing areas are selected for repeated measurement, and the average value is taken as the face ratio of the sample.

5) cement. Observe the type and occurrence of cement. The morphology of cement was observed under scanning electron microscope, and the characteristic elements of cement were determined by energy spectrometer. Cements are mainly clay minerals, carbonate, sulfide, sulfate and zeolite.

6) epigenetic changes of diagenesis. The epigenetic changes of diagenesis, such as secondary enlargement of Shi Ying, secondary enlargement of feldspar, dissolution leaching, transformation and metasomatism, were mainly observed under scanning electron microscope.

72.9.2.2 X-ray diffraction analysis method for relative content of clay minerals in sedimentary rocks

Summary of methods

According to Stokes law, clay minerals are separated by natural sedimentation method. The suspension with particle size less than 2μm is sucked for tabletting, and there are different tabletting methods for different minerals, different analysis purposes and sample size. The tabletting method is suitable for whole rock analysis; Basic analysis of X-ray diffraction of clay minerals by natural orientation sheet (N); The purpose of EG is to distinguish whether swelling minerals exist or not. Identification of chlorite by heating sheet at 55℃; The purpose of hydrochloric acid tablets is to remove chlorite and identify kaolinite; Thin section method is generally used for authigenic mineral identification. Adjust the X-ray diffraction pattern analyzer, and after the instrument is stable, the prepared sample slices will be qualitatively and quantitatively analyzed on the computer.

instruments and equipment

the angle measurement accuracy of polycrystalline x-ray diffractometer is better than .2; The resolution of the instrument is better than 6%, and the comprehensive stability is better than 1%.

centrifuge.

crusher.

electric drying oven.

electric water bath pot.

ultrasonic cleaner.

porcelain mortar, copper mortar, agate mortar.

high beaker, low beaker.

standard sieve.

high temperature furnace.

reagents and materials

sodium hexametaphosphate.

EDTA sodium salt.

chloroform.

hydrochloric acid.

hydrogen peroxide.

ethanol.

ammonium hydroxide.

potassium chloride solution (1mol/L).

analysis steps

1) clay separation. The clay separation methods of different lithology samples are slightly different. Mudstone clay separation is to crush the sample to a particle size less than 1mm, then put it in a tall beaker, soak it in distilled water, promote dispersion by ultrasonic wave, and absorb the suspension with a particle size less than 2 μ m. After the sandstone clay is crushed, the oil-bearing sandstone is extracted with chloroform until the fluorescence level is below 4, and then the sample is soaked and dispersed in a high beaker to absorb the suspension with the particle size less than 2mm. For the separation of carbonate clay, 2% ~ 3% hydrochloric acid should be used repeatedly until there is no reaction. Then the carbonate-removed sample was washed repeatedly with distilled water to suspend the clay.

2) preparation of orient tablets.

a. dry sample method. Put 4mg of dry sample into a 1mL test tube, add .7mL of distilled water, stir well, fully disperse the clay particles with ultrasonic wave, quickly pour the suspension onto the glass slide, and air dry.

B. suspension method. Add a proper amount of distilled water to the clay obtained by centrifugal sedimentation, stir well, absorb ～.8mL of suspension on the glass slide, and air dry.

C. filtration method. Connect the vacuum pump with the suction bottle. Start the vacuum pump and put the soaked microporous membrane on the funnel. Pour the suspension in several times, and draw it out within 1min each time. When the clay membrane is 3 ~ 4μ m thick, take off the filter membrane, stick the filter membrane on the glass slide, and then put it in a Petri dish for drying.

3) natural orientation film processing.

a. ethylene glycol saturated tablets (EG). Using ethylene glycol steam at 4 ~ 5℃, keep the natural orientation sheet at a constant temperature for 7 hours and cool it to room temperature.

B. heating plate (55℃). Under the condition of (55 1)℃, keep the ethylene glycol saturated tablets at constant temperature for 2h, and naturally cool them to room temperature.

4) preparation of special tablet.

a. hydrochloric acid tablets (HCl). Add 6mol/LHCl into the 4 ~ 5mg sample, treat it in a water bath at 8 ~ 1℃ for 15min, cool it, then centrifuge and wash it until there is no chloride ion, and then make tablets by dry sample method.

B. potassium ion saturation tablet (KCl). Weigh 4mg sample into a test tube, add 7 ml of 1 mol/LKCl solution, saturate it for three times, wash it with distilled water until there is no chloride ion, and make tablets by dry sample method.

5) computer analysis. According to the pre-selected working conditions, adjust the X-ray diffractometer, and after the instrument is stable, make qualitative and quantitative analysis on the prepared samples.

6) x-ray diffraction spectrum (see fig. 72.19).

ordinate: diffraction intensity, expressed by I, s-1.

abscissa: diffraction angle, expressed by 2θ, ().

peak scale value: crystal plane spacing, expressed by d, 1-1nm.

d value is the basic data for identifying minerals, such as chlorite d(1)=14.26×1-1nm, kaolinite d(1)=7.2×1-1nm, and its d(1)=17×1-1nm will gradually decrease during the transformation from smectite to chlorite.

peak side symbol (hkl): diffraction index.

baseline BL: dotted line in the figure.

background b: the distance between the baseline and the abscissa, s-1.

full width at half maximum (FWHM): (), which can be used to indicate the crystallinity of illite. The full width at half maximum of authigenic kaolinite is very small. The full width at half maximum of clastic kaolinite is wider.

peak height h: the unit is s-1, which is often used in qualitative analysis. For the diffraction peak of a mineral, it should be converted into relative intensity, the maximum intensity of peak height is 1, and the rest should be converted in proportion.

peak area a: stands for integral strength, and the unit is numeration, and it can also be expressed in mm2, which is commonly used in quantitative analysis of clay minerals.

7) qualitative analysis. See table 72.29 for X-ray identification features of common clay minerals.

Figure 72.19 X-ray diffraction spectrum

Table 72.29 X-ray identification of clay minerals

Continued table

8) Quantitative analysis. The formula for calculating the mass fraction when the mineral assemblages are S, I/S, It, Kao and C is: < P > Investigation and Analysis Technology of Resources and Environment in Volume IV of Rock Mineral Analysis < P > where: w(Kao) is the mass fraction of kaolinite; W(C) is the mass fraction of chlorite; W(S) is the mass fraction of smectite; W(It) is the mass fraction of illite; W(I/S) is the mass fraction of illite-smectite mixed layer; I.7nm(N) is the diffraction peak intensity of .7nm on the N spectrum; I1.nm(55℃) is the diffraction peak intensity of 1.nm on the 55℃ spectrum; H.358nm(EG) is the diffraction peak intensity of .358nm on the EG spectrum; H.353nm(EG) is the diffraction peak intensity of .353nm on the EG spectrum; I1.7nm(EG) is the diffraction peak intensity of smectite at 1.7nm on the EG spectrum; I1.nm(EG) is the diffraction peak intensity of .7nm on the EG spectrum; H.7nm(N) is the diffraction peak intensity of .7nm on the N spectrum; .7nm (EG) is the diffraction peak intensity of .7 nm on the eg spectrum.

when there is only Kao without C, or only C without Kao, its mass fraction is calculated according to the following formula:

Rock Mineral Analysis Volume IV Resources and Environment Investigation and Analysis Technology

When there is only S without I/S, or I/S without S, its mass fraction is calculated according to the following formula:

Rock Mineral Analysis Volume IV Resources and Environment Investigation and Analysis Technology

Fluorescence microscope uses ultraviolet light as light source. Ultraviolet light can excite hydrocarbon substances in oil storage rocks to produce fluorescence. Observe and analyze the changes of these luminescent substances themselves and their relationship with rock structure and structure, so as to judge the types of organic matter, metamorphic degree, effective storage space, oil and gas migration and other issues.

instruments and equipment

a fluorescence microscope is equipped with a transmission light system, a reflection light system and photographic equipment, as well as ultraviolet and blue laser filters and absorption filters.

polarizing microscope.

refrigerator.

reagents and materials

potassium ferricyanide.

glycerol.

hydrochloric acid.

chloroform.

alizarin red.

analysis steps

1) selection. Core and cuttings samples must be selected with representative parts according to analysis items under ultraviolet light. Samples used for fluorescence microscope identification shall not be soaked in organic solvents before production. Select a piece of cuttings with the same lithology as the fluorescent sample and make polarizing film to facilitate the comparative observation of fluorescent thin slices.

2) production. If cracks develop or rocks are loose, T-2 or K-2 type 52 glue is used to cement the samples for making fluorescent flakes. K -1 type 52 glue can be used for oil sandstone with poor glue permeability. If the glue still can't penetrate, purify the paraffin cementation plane instead. Then rough grinding, fine grinding, fine grinding, grinding into a mirror. The slide must be ground glass. Slide the slide after the water in the sample is dry. When the oil-bearing sample contains bubbles, it should not exceed 3% of the rock area; Generally, the bubble content in the rock slice of the sample shall not exceed 1% of the rock slice area. Fluorescent flakes are generally not covered, but samples that are easily deliquescent and volatile must be covered.

3) identification under the microscope. The identification contents under fluorescence microscope include:

a. The relationship between the luminous color and wavelength of asphalt and its composition. In order to solve this problem, the standard oil sample is selected to determine the relationship between its luminous color and wavelength, and determine what kind of asphalt it belongs to, as shown in Table 72.3. From the table, it can be seen that the main colors of oily asphalt are yellow, green and blue, with the wavelength range of 45 ~ 6 nm, the main colors of colloidal asphalt are orange and brown, and the main colors of asphaltene asphalt are brown.

table 72.3 luminous color, wavelength and composition of asphalt

B. quantitative luminous intensity. Luminescence intensity mainly reflects the oil content in rocks. The higher the oil content in rocks, the greater the fluorescence intensity of oil. In the fluorescence image processing, the luminance value is used to quantitatively represent the luminous intensity of asphalt (Table 72.31).

table 72.31 relationship between luminous intensity and asphalt content

C. quantification of oil-bearing range. (1) all kinds of asphalt content (oil, gum, asphaltene). ② Oil-bearing area ratio, which reflects the oil-bearing range of oil-bearing rocks to some extent. It can approximately replace the pore content, but this value is higher than the pore content, because it also includes the range of oil impregnation.

D. see table 72.32 for the difference between true and false oil-bearing display.

table 72.32 shows the difference between true and false oil bearing

the judgment of oil-water interface by fluorescence microscope and the prediction of oil bearing effect

1) the judgment of oil-water interface. In general, the luminescence of rock samples in oil-bearing wells is good, all pores are oil-bearing, and the suture, intergranular pores, intergranular pores and crystal cleavage are excellent by impregnation. The luminescence of the well section near the oil-water interface shows uneven phenomenon, the matrix luminescence is poor, and some pores glow; However, the cracks and rocks of water-bearing samples do not emit light. The oil-water interface can be judged from the longitudinal change of oil content.

2) Prediction of oil-bearing effectiveness. Through the fluorescence geological work, fully understand the geological conditions of this area and this well, and comprehensively consider relevant data, such as core (cuttings), drilling, gas logging, mud logging, caliper, geophysical logging, field fluorescence analysis and other data, we can judge whether there is oil or not.

72.