CN100430719C - Rock Microelectronic Scanning Imaging System and Imaging Method - Google Patents

Abstract

The present invention relates to a rock microelectronic scanning imaging system and imaging method. The system includes: an electrode plate, on which a plurality of mutually insulated electrodes are distributed, and the electrode plate and the electrodes are connected to a signal generating device. The electrode is connected to the input end of the interface circuit through the current sampling resistor; a backflow plate is connected to the signal generating device. The imaging method is to process the sample into a saturated conductive fluid, then fix the sample between the reflow plate and the electrode plate, the signal generator sends the measurement signal, the system collects the current data of each electrode, and the current data is normalized by the system After processing and reconstructing the image, it will be displayed. The invention establishes the corresponding relationship between the image fracture width of the rock sample model and the actual sample fracture width by performing related measurement on the known rock sample model, and provides a calculation basis for back-calculating the real fracture width from the image measured by the imaging instrument on the well site.

Description

Rock Microelectronic Scanning Imaging System and Imaging Method

technical field

The present invention relates to a rock microelectronic scanning imaging system and imaging method, in particular to a rock microelectric scanning imaging that uses rock samples to provide back calculation basis for real fracture width calculation basis for imaging instruments on the well site in oil and gas exploration Systems and imaging methods.

Background technique

In oil and gas exploration, it is necessary to conduct corresponding surveys on the physical and chemical properties of the local geological rock formations, so as to provide sufficient geological data basis for future mining work.

For the research on the distribution of rock fractures in well logging, the full-bore formation micro-resistivity imager (FMI) is usually used to directly survey on the well site.

The key components of the full-bore formation micro-resistivity imager are four pushing arms that are perpendicular to each other and push against the well wall, and each pushing arm has a polar plate and a wing plate. There are 24 electrodes on each pole plate and wing plate to obtain 192 micro-resistivity curves. The diameter of the button electrode is 0.41cm, the outer diameter of the insulating ring is 0.61cm, and the electrode spacing is 0.76cm. During the measurement, the entire electrode plate maintains the same potential, and the total current is a fixed value. Measure the current of each button electrode, and then calculate the grounding resistance of each button electrode according to the plate potential and the current of each button electrode. After the resistance is normalized, it is converted into a gray value and displayed in the form of an image.

The existing full-bore formation micro-resistivity imager has some shortcomings in logging. In its work, it actually measures the distribution of resistivity anomalies in the detection range near the button electrode, not the rock formation on the borehole wall. Therefore, the full-bore formation micro-resistivity imager cannot effectively and accurately obtain the distribution parameters of rock formation fractures.

Because the plates of the full-bore formation micro-resistivity imager have radians, the measured current has a large divergence, and the number of button electrodes on each plate is small, so the full-bore formation micro-resistivity imager Relevant measurements cannot be made in the laboratory on known small-sample models of rocks.

In order to solve these problems, the present invention can carry out relevant measurement to the small sample model of known rock in the laboratory, establishes the corresponding relationship between the image fracture width of the small sample model of rock and the actual sample fracture width, and provides the best results for the well site. The measurement image of the imaging instrument is back-calculated to provide a calculation basis for the real fracture width, ensuring that the imaging instrument on the well site can accurately and effectively obtain the distribution parameters of rock formation fractures.

Contents of the invention

The first purpose of the present invention is to provide a rock microelectronic scanning imaging system for the above-mentioned deficiencies in the prior art. The real crack width is back-calculated from the instrument measurement image to provide calculation basis.

The second object of the present invention is to provide a rock microelectric scanning imaging method for the above-mentioned deficiencies in the prior art. Collect, process, and obtain images of the distribution of fractures in rock samples.

In order to achieve the above-mentioned first purpose, the present invention adopts a rock microelectronic scanning imaging system, which includes a computer, a signal generating device and an interface circuit; the signal generating device is connected to the computer through a universal parallel interface bus; the interface circuit Connected with the signal input end of the computer, it also includes:

An electrode plate, a plurality of mutually insulated electrodes are distributed on the electrode plate, the electrode plate and the electrodes are connected to the signal generating device, and the electrodes are input to the interface circuit through a current sampling resistor terminal connection; specifically, the electrodes are uniformly arranged on the electrode pad in a planar array, and the electrode pad is a metal plate;

A return plate, the return plate is connected with the signal generating device.

The electrodes are evenly arranged in the manner of dislocation between two adjacent rows, and the electrodes are button electrodes, and the sides of the electrodes are covered with insulating rings.

The rock microelectric scanning imaging system of the present invention adopts a plurality of button electrodes to be evenly arranged on the electrode plate in a plane array, and the button electrodes are insulated from the surrounding electrodes, so that the button electrodes and the sample to be tested can be fully Contact, the measurement current is relatively concentrated, which can ensure accurate scanning and imaging of the fracture distribution of small rock samples in the laboratory. By measuring the known small sample model, the corresponding relationship between the image crack width and the actual sample crack width is established. Therefore, a calculation formula is provided for back-calculating the real fracture width from the measurement image of the imaging instrument on the well site.

In order to achieve the above-mentioned second purpose, the present invention adopts a rock microelectronic scanning imaging method, which performs the following steps:

Step 1. Processing the rock to be tested into a plate-shaped body, soaking it in an electrolyte solution to reach saturation, and making a sample to be tested;

Step 2, setting the sample to be tested between the electrode plate and the return plate;

Step 3, the computer issues a signal sending command to the signal generating device, and the signal generating device transmits a measurement signal to the electrode plate and the electrode, so that the electrode sends a measurement current to the sample under test at an equal potential;

Step 4, the current sampling resistor collects the signal of the measured current on the electrode, and transmits the signal to the interface circuit;

Step 5. The computer performs real-time normalization processing and reconstructed image processing on the collected signals.

The imaging method of the present invention fully utilizes that the button electrodes arranged on the electrode plate have equal voltages to the surrounding button electrodes and plates, and can form a current focusing effect, so that the supplied current is almost perpendicular to the contact surface and penetrates The rock sample reaches the return plate on the opposite side of the sample, so that the collected current value can accurately reflect the resistivity of the tested sample, and the imaging map of the crack distribution of the tested sample can be obtained after corresponding processing.

Description of drawings

Fig. 1 is the constitution block diagram of a specific embodiment of rock microelectric scanning imaging system of the present invention;

Fig. 2 is the structural representation of electrode pad in the embodiment shown in Fig. 1;

Fig. 3 is a flow chart of a specific embodiment of the rock microelectronic scanning imaging method of the present invention;

Fig. 4 is the schematic diagram of the artificial rock sample with fracture;

Fig. 5 is a schematic diagram of the specific process of step 3 in the imaging method shown in Fig. 3;

Fig. 6 is a diagram of the scanning imaging results of the rock sample shown in Fig. 4 .

Detailed ways

The rock microelectric scanning imaging system of the present invention is composed of a computer, a signal generating device, an electrode plate and its upper electrode, a return plate, an interface circuit and other parts connected in sequence, and Fig. 1 is a rock microelectric scanning imaging system of the present invention The block diagram of the specific embodiment, the system computer 1 and the signal source 2 are connected by the general parallel interface bus GPIB bus, the return flow plate and the electrode plate 3 are connected with the output terminal of the signal source 2 by common wires, and the electrode plate Common electric wires are used to connect the electrodes on the top and the input end of the interface circuit 4, and ordinary electric wires are used to connect the output end of the interface circuit 4 and the signal input end of the computer 1.

The electrodes are arranged on the electrode plate. The shape, size, distance and arrangement of the electrodes are extremely critical, which directly affect the imaging effect. The electrode of the present invention is a button electrode, and its side is covered with an insulating ring. The button electrodes are evenly arranged on the electrode plate in a planar array, and the two adjacent rows are misaligned with each other. This arrangement can make the electrodes fully contact with the sample to be tested, and the measurement current is relatively concentrated to ensure the accuracy of the measurement.

Fig. 2 is the concrete structure diagram of electrode pad in the embodiment shown in Fig. 1, and electrode pad B is the rectangular metal plate of 6cm * 7cm, and the diameter of button electrode D is 0.4cm, and the insulating ring J that its periphery wraps tightly The width is 0.1cm, and the electrode array adopts a planar array, which is composed of 64 button electrodes, distributed in 8 rows, 8 in each row, the distance between rows is 0.76cm, and the distance between electrodes in a row is 0.59cm , the horizontal dislocation between two adjacent rows is 0.25cm, and the dislocation directions appear alternately. The electrode array is located in the center of the electrode pad B, with a length of 5.92 cm and a width of 4.98 cm. The upper and lower margins of the electrode pad B are 0.54 cm, and the left and right margins are 0.51 cm.

In order to allow the tested sample to be in better contact with the electrode on the electrode pad, a holder is provided on the electrode pad and the return pad, and the holder can clamp the electrode pad and the backflow pad against each other. When measuring, the sample to be tested is placed between the electrode pad and the return pad, so that the sample to be tested can be fixed between the electrode pad and the backflow pad by using the holder, so that the relative distance between the measured sample and the electrode pad The position will not change, ensuring the accuracy of the measurement.

Fig. 3 is a flow chart of a specific embodiment of the rock microelectronic scanning imaging method of the present invention, and the specific steps are:

Step 1. Process the rock sample. The rock sample is processed into a thin plate with a length of 8 cm, a width of 8 cm, and a height of 2.5 to 3.5 cm. The sample can also be natural rock, artificial rock or conductive rubber. In this example, artificial rock samples are used; as shown in Figure 4, Figure 4 is a schematic diagram of an artificial rock sample with a crack, and there is an artificial crack on it, the sample height H is 8cm, the width W is 8cm, and the thickness T is 3cm. The middle shaded part is the resistivity anomalous body, its resistivity Rt=0.01Ω·m, the opening degree of the shaded part APERTURE=0.2cm, the depth DEPTH=1.5cm, the resistivity of the non-shaded part Rb=30.3Ω·m, the processed rock The sample is immersed in the electrolyte solution to reach saturation. The electrolyte solution can be a saturated saline solution, and the rock sample is made into a saturated and conductive fluid as the sample to be tested;

Step 2. Fix the sample to be tested, and set the sample to be tested between the electrode pad and the reflow pad. This process is divided into two steps. First, set the sample to be tested between the electrode pad and the reflow pad, and then, Use the holder to make the electrode plate closely adhere to the surface of the reflow plate and the sample to be tested. During the measurement, the holder can ensure that the electrode plate is in good contact with the sample and keep its relative position unchanged;

Step 3. The computer sends a signal command to the signal generating device, and the signal generating device transmits a measurement signal to the electrode plate and the electrode, so that the electrode sends a measurement current to the sample to be measured at an equal potential; the signal is transmitted using an electrode array, and each electrode Maintain the same potential to transmit measurement signals to the sample under test, and the transmitted signals reach each electrode and plate at the same time. The system can control the magnitude of the transmitted signal current by detecting the electrode voltage; for a certain electrode, it is related to the surrounding electrodes and plates It has equal voltage, thus forming a current focusing effect, so that the current supplied by it is almost perpendicular to the contact surface and penetrates the rock sample to reach the return plate opposite to the sample; since the voltage between the electrode plate and each electrode is constant, therefore, every The size of the current flowing out of each electrode depends on the size of the medium resistance on the path it flows through. In this way, because there are cracks in the sample and it contains water, the resistance is smaller than the surrounding ones, resulting in a larger current flowing out of the corresponding electrode. , so that the current size distribution can be used to reflect the existence of rock cracks; during the process of the electrode emitting measurement signals, the computer also needs to detect the electrode voltage;

Fig. 5 is the specific process schematic diagram of step 3 in the imaging method shown in Fig. 3, and step 3 includes:

Step 3.1, the computer issues a signal transmission command to the signal generating device;

Step 3.2, the computer detects the electrode voltage, if it exceeds the value, continue to step 4; if it does not exceed the value, adjust the measurement signal, and then perform step 3.1;

Step 4. The current sampling resistor collects the signal of the measured current on each electrode, and transmits the signal to the interface circuit. Each electrode transmits the signal of the current magnitude through the current sampling resistor connected in series at its input end, and transmits it to the interface circuit input After being amplified and filtered by the interface circuit, it is sampled and received by the computer, and the computer can selectively sample the signal of the current measurement on the electrode;

Step 5. The computer performs real-time normalization processing on the collected current value, reconstructs the image processing, and performs cyclic measurement as required, and finally displays it on the screen in grayscale or color form, thus obtaining the tested sample The surface resistivity image of ;

As shown in Figure 6, Figure 6 is the result of scanning and imaging the rock sample shown in Figure 4. The image can be a grayscale image or a color image, and the grayscale image represents the resistivity of the measured sample with the grayscale The color image represents the size of the sample resistivity in different colors. In the middle part of Fig. 6, there is a dividing line with significantly different gray levels, indicating that there is a crack in the rock sample shown in Fig. 4, which proves that the imaging method of the present invention can detect A crack with a width of 2mm.

If the fracture width and resistivity are constantly changed, and the relationship is established with the fracture display width of the formed image, an inversion model can be provided for the quantitative evaluation of fractures in the borehole electrical imaging logging data in oil and gas exploration.

Claims (9)

1. A rock microelectronic scanning imaging system, which includes a computer, a signal generating device and an interface circuit; the signal generating device is connected with the computer through a universal parallel interface bus; the interface circuit is connected with the signal input end of the computer , characterized by also including: An electrode plate, a plurality of mutually insulated electrodes are distributed on the electrode plate, the electrode plate and the electrodes are connected to the signal generating device, and the electrodes are input to the interface circuit through a current sampling resistor terminal connection; specifically, the electrodes are evenly arranged on the electrode pads in a planar array, and the electrode pads are metal plates; A return plate, the return plate is connected with the signal generating device. 2. The rock microelectronic scanning imaging system according to claim 1, characterized in that: the electrodes are evenly arranged in a manner of dislocation between two adjacent rows. 3. The rock microelectronic scanning imaging system according to claim 1 or 2, characterized in that: the electrode is a button electrode, and its side is covered with an insulating ring. 4. The rock microelectronic scanning imaging system according to claim 1, characterized in that: the electrode plate and the return plate are also provided with a clamp for clamping the electrode plate and the return plate to each other. Holder. 5. A method for performing microelectronic scanning imaging of rocks based on the rock microelectronic scanning imaging system of any one of claims 1-4, characterized in that the following steps are performed: Step 1. Processing the rock to be tested into a plate-shaped body, soaking it in an electrolyte solution to reach saturation, and making a sample to be tested; Step 2, setting the sample to be tested between the electrode plate and the return plate; Step 3, the computer issues a signal sending command to the signal generating device, and the signal generating device transmits a measurement signal to the electrode plate and the electrode, so that the electrode sends a measurement current to the sample under test at an equal potential; Step 4, the current sampling resistor collects the signal of the measured current on the electrode, and transmits the signal to the interface circuit; Step 5. The computer performs real-time normalization processing and reconstructed image processing on the collected signals. 6. The method according to claim 5, characterized in that: in the step 1, the rock to be tested is processed into a plate-shaped body with a thickness of 2.5-3.5 cm. 7. The method according to claim 5, characterized in that the step 2 is specifically: First, the sample to be tested is placed between the electrode plate and the return plate; Then, the electrode pad is closely attached to the surface of the tested sample and the reflow pad by using the holder. 8. The method according to claim 5, characterized in that said step 3 specifically performs the following steps: Step 3.1, the computer issues a signal transmission command to the signal generating device; Step 3.2, the computer detects the electrode voltage, if it exceeds the value, continue to perform step 4; if not, adjust the measurement signal, and then perform step 3.1. 9. The method according to claim 5, characterized in that the process of collecting the current measurement signal on the electrode in step 4 is to use a computer to selectively sample the current measurement signal on the electrode.

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