CN104005759A - Resistivity simulation unit with stable physical properties - Google Patents

Abstract

The invention discloses a resistivity simulation unit with stable physical properties. Specifically, the resistivity simulation unit is used for simulating the resistivity of an underground target stratum. The resistivity simulation unit is an annular unit which comprises a central annular hole and the surface of the resistivity simulation unit and an internal hole are covered with or filled with insulation oil so as to ensure that the physical properties of the obtained resistivity simulation unit are stable.

Description

Physically stable resistivity analog unit body

technical field

The invention relates to geophysical detection technology, in particular to resistivity logging technology.

Background technique

In the process of geological drilling, different geophysical detection techniques can be used for formations with different depths and different lithologies downhole. Among various geophysical detection technologies, measuring the resistivity of the target formation is one of the important means to distinguish different lithologies and discover underground oil, gas and water resources.

With the continuous improvement of logging technology, a batch of downhole measurement instruments with large amount of information and small detection radius, such as downhole acoustic and electric imaging instruments, downhole micro-resistivity scanning instruments, etc., have been successfully developed. These downhole measuring instruments have high resolution and provide a large amount of downhole information, which provides an important basis for ascertaining the complex geological conditions downhole.

However, in the prior art, when calibrating and verifying the developed downhole measurement instruments to detect the reliability and consistency of these instruments, or when providing parameter basis for the preparation of corresponding interpretation software for the downhole measurement data of the instrument, it is necessary to to the actual wellbore site. Not only is this work costly and time-consuming, but the calibration, calibration, and provided parameter basis may not be ideal in terms of accuracy and consistency, and it may not even be possible to find an appropriate wellbore available to perform the work .

That is to say, how to calibrate and verify the developed downhole measuring instruments and provide parameter basis for the compilation of downhole measurement data interpretation software has become a major problem in this field that needs to be solved urgently.

Contents of the invention

An object of the present invention is to establish a set of devices for simulating various resistivities and different formation thicknesses in the ground, so as to easily calibrate and check the developed downhole instruments, and conveniently explain the downhole measurement data of the instruments. The programming of the software provides accurate and reliable parameter basis.

Another object of the present invention is to provide a unit that can accurately simulate the corresponding resistivity of different target formations downhole and its manufacturing method, which can be combined to simulate different resistivities of the entire downhole formation at any depth.

Another object of the present invention is to keep the resistivity of the unit for simulating the corresponding resistivity of different target formations downhole relatively stable during use, and minimize the influence of external humidity.

Another object of the present invention is to make the unit structure for simulating the corresponding resistivity of different target formations downhole simple, and it is convenient to form corresponding sections and to be relatively positioned easily.

Another object of the present invention is to enable the unit for simulating the corresponding resistivity of different target formations downhole to be used to detect one or more characteristic indexes of the downhole measuring instrument.

In order to achieve at least one of the above objectives, the present invention provides a resistivity simulation unit body for simulating the resistivity of the downhole target formation, which is an annular unit body with a central ring hole, and all surfaces and interiors of the resistivity simulation unit body The pores are covered or filled with insulating oil.

Preferably, the resistivity simulation unit body has one or more positioning holes axially penetrating through itself.

Preferably, the number of the positioning holes is three, and they are evenly distributed on the end surface of the resistivity simulation unit body along the same circumference.

Preferably, the surface of the inner hole of the resistivity simulation unit has at least one local calibration feature for detecting one or more characteristic indicators of the downhole measuring instrument.

Preferably, said local indexing feature comprises a plurality of grooves and/or holes having different geometrical sizes and/or orientations.

Preferably, the resistivity simulation unit body is made of cement, one or more conductive substances and water.

Preferably, the conductive substance is in the form of particles and/or powder.

Preferably, the conductive substance is graphite powder.

The ground calibration device for simulating the resistivity of downhole formations of the present invention can establish a set of devices for simulating various resistivities and different thicknesses of downhole formations on the ground. By using the device, the developed downhole instrument can be calibrated and verified conveniently, and an accurate and reliable parameter basis can be conveniently provided for compiling software for interpreting downhole measurement data of the instrument.

The resistivity simulating unit body of the present invention can accurately simulate the corresponding resistivity of different target formations in the downhole, and these resistivity simulating units can be combined to simulate different resistivities of the whole downhole formation at any depth. Moreover, the resistivity simulation unit body can remain stable for a long time during use.

In addition, the resistivity simulation unit body of the present invention has a simple structure, is convenient for forming corresponding sections, can be relatively positioned easily, and can also be used to detect one or more characteristic indexes of the downhole measuring instrument.

According to the following detailed description of preferred embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will be more aware of the above and other objects, advantages and features of the present invention.

Description of drawings

Hereinafter, preferred embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings, in which the same reference numerals designate the same or similar components or parts. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the attached picture:

Fig. 1 shows a schematic side sectional view of a ground verification device for simulating downhole formation resistivity according to a preferred embodiment of the present invention;

Fig. 2 is a schematic end view of the resistivity simulation section in the downhole formation simulation body of the ground verification device shown in Fig. 1;

Figure 3 is a schematic side cross-sectional view of a portion of the resistivity simulation section shown in Figure 2;

Fig. 4 is a schematic end view of the borehole wall imaging detection section in the downhole formation simulation main body of the ground verification device shown in Fig. 1;

Fig. 5 is a schematic A-A cross-sectional view of a part of the wellbore imaging detection section shown in Fig. 4;

Fig. 6 is a schematic B-B sectional view of a part of the borehole wall imaging detection section shown in Fig. 4;

Fig. 7 is a schematic end view of an annular unit body according to a preferred embodiment of the present invention;

Fig. 8 is a schematic side sectional view of the annular unit body shown in Fig. 7 .

Detailed ways

Referring to Fig. 1 , the surface verification device for simulating the resistivity of downhole formations according to a preferred embodiment of the present invention includes a circumferentially closed outer wellbore 10 (for example, it may be a closed steel pressure-bearing barrel) and a The main body of downhole formation simulation 20 . Preferably, a centralizer 15 is provided between the outer wellbore 10 and the downhole formation simulation main body 20, so as to fix the downhole formation simulation main body 20 and the outer wellbore 10 together properly (usually on the same central axis), so as to avoid correction on the surface. During the use and hoisting of the test device, the whole or part of the downhole formation simulation main body 20 is displaced and/or deformed. As is well known to those skilled in the art, a plurality of centralizers 15 may preferably be arranged along the axial direction of the outer wellbore 10 . Each centralizer 15 itself can be, for example, an integral component, or can also be composed of a plurality of separate components, and its specific structure is well known to those skilled in the art, and will not be repeated herein.

In addition, as those skilled in the art can understand, for example, after the ground calibration device of the present invention is installed in the calibration site, before use, it needs to be installed in the wellbore 10 (including to the possible instrument space of the downhole formation simulation main body 20 and Into the gap between the downhole formation simulation main body 20 and the outer wellbore 10 ) to inject liquid for simulating the downhole formation liquid environment. These liquids can be, for example, Chinese national standard 35# diesel oil, or other hydrocarbon liquids with electrical insulation properties, or even oil-based mud drilling fluids proportioned according to actual needs, or other base drilling fluids, including water-based mud drilling fluid. For convenience of description, these fluids are referred to as "well fluids" in this application.

In general, the outer wellbore 10 has, along its axial direction, a first end 11 and a second end 12 axially opposite said first end. Apparently, in order to inject well fluid into the downhole formation simulation main body 20 and allow downhole measurement instruments to enter and exit, the first end is an open end.

Preferably, a circumferentially closed liquid storage tank 40 is disposed on the first end 11 of the outer shaft 10, and the liquid storage tank has a first end face and a second end face axially opposite to the first end face along the axial direction of the liquid storage tank. Two ends. The first end surface and the second end surface of the liquid storage box 40 respectively have a first central opening and a second central opening, and the first central opening is used for injecting well liquid into the outer wellbore and for downhole measuring instruments to enter and exit, while the first central opening The two central openings are then sealingly secured (for example by welding) to the outer surface of the first end 11 of the outer wellbore 10 circumferentially along their edges. It is very advantageous that such a liquid storage tank 40 defines a temporary liquid storage space in it to contain the liquid that may overflow the outer shaft 10 when the calibration device of the present invention is in use, so as to prevent the overflowed liquid from flowing to the surroundings environment, and subsequently allow these liquids to flow back into the outer wellbore 10. For example, when the downhole measurement instrument to be tested is suspended into the outer wellbore 10 (specifically, it is usually placed in the possible instrument space of the downhole formation simulation main body 20), some of the previously injected well liquid may overflow, This part of the liquid that overflows can be contained temporarily in the liquid storage tank 40, and can not flow into the environmental space; It can flow back into the outer shaft 10 again.

In order to facilitate the hoisting operation of the ground verification device of the present invention by external hoisting equipment (such as a crane), preferably, a hoisting member 45 can be arranged near the first end 11 of the outer shaft 10 or at the first end surface of the liquid storage tank 40 adjacent to the circumferential edge. . In one embodiment, the hoisting member 45 may be a plurality of hoisting rings symmetrically fixed to the first end surface of the liquid storage tank 40 near the peripheral edge. For example, after the ground verification device is assembled, it can be hoisted on the hoisting ring by a crane, and the ground verification device is placed in an underground pit where the temperature environment is preferably kept relatively stable (usually the first end 11 of the outer shaft 10 faces upwards. , while the second end 12 faces down).

As can be understood by those skilled in the art, the so-called "underground pit" here is not an underground wellbore for actual geological exploration or resource extraction, but is excavated and/or constructed at the calibration site for accommodating the calibration of the present invention. A "container" for a device. It is preferable to build the "container" below the ground, but it is not necessary because of economic or environmental considerations. Therefore, although in some practical applications, the verification device of the present invention may be placed in the so-called "underground pit", for those skilled in the art, since it is no longer necessary to go to the actual geological exploration or resource extraction Calibration/verification of instruments is carried out in underground boreholes, so the verification device of the present invention is still considered a "surface verification device".

In the preferred embodiment shown in FIG. 1, the second end 12 of the outer wellbore 10 is also an open end, and a termination device 50 having a drain valve 51 is provided on it to close the opening of the second end 12, and The well fluid that has been injected into the outer wellbore can be discharged under the control of the drain valve 51, so as to be replaced with new well fluid according to the requirements of test and verification. Of course, those skilled in the art can understand that, alternatively, the second end 12 of the outer wellbore 10 can also be permanently closed. The pipe can be pumped, or the entire surface test device can be tilted or turned over so that the liquid can flow from the open first end 11 of the outer wellbore 10 .

Generally, the downhole formation simulation main body 20 includes a resistivity simulation section 21 and an optional borehole imaging detection section 22 and an extension section 23 .

Referring to FIGS. 2-3 , the resistivity simulation section 21 is preferably composed of one or more resistivity simulation unit bodies 30 , and the thickness can be determined as required. The resistivity simulation unit simulates the resistivity of different target formations downhole, so as to be measured by downhole measuring instruments (not shown). Since the resistivity simulation section 21 can be composed of units with different thicknesses and different resistivities according to requirements, the longitudinal resolution of the simulated downhole measuring instrument can be varied from, for example, 10mm-1000mm and other different resistivities of formations with different thicknesses, as The calibration of downhole measuring instruments and the compilation of corresponding interpretation software provide a scientific and true basis, and the reliability and consistency of the corresponding downhole measuring instruments can be checked regularly.

Referring to Figs. 4-6, the optional wellbore imaging detection section 22 is composed of one or more wellbore imaging detection units 35, and the thickness can be determined as required. The borehole wall imaging detection unit body simulates the resistivity of different target formations downhole for downhole measuring instruments (not shown) to measure it, and at least a part or each borehole wall imaging detection unit body 35 faces outward At least one local calibration feature is provided on the inner surface of the central axis of the wellbore 10 to detect one or more characteristic indicators of the downhole measuring instrument. The local indexing feature includes a plurality of grooves 37' and/or holes 37'' having different geometric sizes and/or orientations. More specifically, holes of different diameters and depths may be formed in the inner hole wall, grooves of different sizes extending parallel to the transverse direction, grooves extending perpendicular to the transverse direction and/or at other angles of inclination relative to the transverse direction The extended inclined groove is used, for example, to detect characteristic indicators such as imaging resolution and/or detection depth of the corresponding downhole measuring instrument. So far, it can be understood that the wellbore imaging detection unit body 35 is essentially a special resistivity simulation unit body with local calibration features.

As shown in FIG. 1 , the resistivity simulation section 21 can be arranged to be adjacent to the first end 11 of the outer wellbore 10 in the axial direction, and the borehole wall imaging detection section 22 can be arranged to be adjacent to the resistivity in the axial direction. Rate simulation section 21. Or alternatively, the wellbore imaging detection section 22 can be arranged to be adjacent to the first end 11 of the outer wellbore 10 in the axial direction, and the resistivity simulation section 21 can be arranged to be adjacent to the wellbore wall in the axial direction Imaging detection section 22 .

In addition, the optional extension section 23 may also consist of one or more extension section units 39 and be disposed adjacent to the second end 12 of the outer wellbore 10 in the axial direction. As those skilled in the art can understand, since the downhole measuring instrument does not detect the extension section 23, the resistivity of the section unit body may not be particularly limited.

Preferably, the resistivity simulation section 21, the borehole wall imaging detection section 22 and the extension section 23 are respectively defined with instrument spaces 32, 36, 38 capable of receiving downhole measuring instruments, shown as Round central bore. As mentioned above, the extension section 23 is not measured by the downhole surveying instrument, so the instrument space 38 therein is, for example, used to provide an extended accommodating space for the operation of the downhole surveying instrument.

More preferably, these instrument spaces 32, 36, 38 all have the same central axis and cross-sections of the same shape, thus these instrument spaces 32, 36, 38 constitute the complete instrument space 25 of the downhole formation simulation main body 20 .

Of course, those skilled in the art should also understand that if there is no instrument space defined in the resistivity simulation section 21, the borehole wall imaging detection section 22 and/or the extension section 23, then the downhole measuring instrument will be lowered into these areas. Measurements are made in the space defined between the inner surface of the section and the outer wellbore 10. Therefore, it can be said that the instrument space for receiving downhole measuring instruments in the ground verification device of the present invention for performing measurement operations can be further defined by the downhole formation simulation main body 20 itself in the outer wellbore 10, or can also be defined by the downhole formation simulation main body 20 and the outer wellbore 10 common limits are given.

In some embodiments, the resistivity simulation unit body 30 , the wellbore imaging detection unit body 35 and the extension section unit body 39 can be made into any suitable shape, such as a brick body that is roughly rectangular or roughly sector-shaped. These bricks are assembled into sections in the outer wellbore preferably end-to-end in the circumferential direction or with a certain interval, and stacked in the axial direction, and define corresponding instrument spaces therein.

More preferably, the resistivity simulation unit body 30 and/or the wellbore imaging detection unit body 35 and/or the extension section unit body 39 can be an annular unit body with a central annular hole, and at this time, the instrument space of each section is composed of these annular unit bodies. The central ring hole of the unit body is formed along the axial direction. It should be noted here that the term "ring" used in this application includes but is not limited to a circular ring, other rings with a closed or non-closed periphery and a closed or non-closed hollow inner hole, such as a closed or non-closed ring with a roughly elliptical outline. Closed rings, or closed or non-closed rings with a generally rectangular outline, etc. are also possible; and it is not required that the central ring openings of these rings have the same shape as their peripheral contours. The ring-shaped unit body itself can be made integrally, and can also be composed of smaller unit bodies.

In a preferred embodiment, the resistivity simulation unit body 30, the borehole wall imaging detection unit body 35 and the extension section unit body 39 can all be made into the central ring hole and the peripheral contour as shown in Figures 7-8. All are in the form of a circular ring-shaped unit body 60 . At this time, the resistivity simulation unit body 30, the borehole wall imaging detection unit body 35 and the extension section unit body 39 can all have the same outer diameter and inner diameter, and the thickness of each unit body can be set according to needs, and can be the same as each other. Can be different. In a specific example, the inner diameter can be, for example, 200 mm, and the outer diameter can be, for example, 800 mm (the maximum outer diameter can reach 1.5m or more); each unit body is preferably stacked in sequence (for example, from bottom to top) to form The extension section 23, the borehole imaging detection section 22 and the resistivity simulation section 21 constitute the entire downhole formation simulation main body 20; the entire length of the downhole formation simulation main body 20 may be about 7.5 m, for example. The annular unit body 60 preferably also has one or more positioning holes 64 axially passing through itself. It should be noted that, for the sake of clarity, the positioning hole 64 is only marked in FIGS. 7-8 , but not shown in other drawings. When assembled, adjacent annular units 60 are properly positioned relative to each other by inserting locating pins in corresponding locating holes 64 . In one embodiment, the number of positioning holes 64 is preferably three, and they are evenly distributed on the end surface of the annular unit body 60 along the same circumference. Further, when stacking the annular unit bodies 60 , an adhesive may be applied on opposite end surfaces of two adjacent annular unit bodies 60 to bond and fix the two annular unit bodies 60 together. In the present invention, the binder is preferably sodium silicate, commonly known as "water glass".

In particular, in each section of the downhole formation simulation main body 20, especially in the resistivity simulation section 21 and the borehole wall imaging detection section 22, each unit body can preferably be made of cement, one or more conductive substances and water Made to simulate the specific resistivity of a certain formation of interest. The conductive substance is preferably in the form of particles and/or powders, such as graphite powder, carbon nanotube particles, particles or powders of certain conductive metals, and the like.

In a particularly preferred embodiment, the present invention uses graphite powder as the conductive substance. Wherein, the ratio of cement and graphite powder is preferably selected in the range of 60:40 to 83.5:16.5 according to the resistivity of the target formation to be simulated. For example, when the ratio of cement and graphite powder is 60:40, the resistivity of the fabricated resistivity simulation unit is roughly 0.2ΩM; while when the ratio of cement and graphite powder is 83.5:16.5, the resistivity The resistivity of the analog unit body is approximately 2000ΩM. As can be understood by those skilled in the art, when the unit body of simulated resistivity is manufactured, graphite powder is used as a conductive substance therein, so if the proportion of graphite powder is reduced, the resistivity of the unit body obtained will decrease Correspondingly increased; On the contrary, if the proportion of graphite powder is increased, the resistivity of the obtained unit body will be correspondingly reduced. Accordingly, when implementing the present invention, it is also possible that the ratio of cement and graphite powder exceeds the preferred range given above according to actual needs, for example, the ratio may be selected within the range of 50:50 to 90:10.

It should also be noted here that, when the present invention manufactures the resistivity simulation unit body (including the borehole wall imaging detection unit body), it is preferable not to use sand and gravel as the aggregate as in the manufacture of conventional concrete components. This is because, if sandstone is used, the number of irregularities and/or larger pores in the unit cell will be greatly increased, making it difficult to obtain the desired resistivity more accurately; And/or the physical properties (such as electrical resistivity) of larger-porosity units are also difficult to keep stable during use. However, as disclosed in this paragraph, in an alternative embodiment, sand and gravel can also be used to participate in the manufacture of the resistivity simulation unit body.

Specifically, the method for manufacturing the aforementioned resistivity simulation unit body (including the wellbore imaging detection unit body) includes the following steps:

a. Provide cement, one or more conductive substances in granular and/or powder form (preferably graphite powder), and water.

b. Stir the conductive substance, the cement and the water to make a mixture.

c. Molding the mixture into a green body. The shape of the green body is preferably a ring with a central inner hole, and the specific size is determined according to specific testing needs.

d. Place the molded green body in a correspondingly shaped blank for shape maintenance for a period of time. This period of time is preferably greater than 24, 36, 48 or 60 hours, more preferably greater than 72 hours.

e. Drying the green body after the conformal curing. When performing this treatment, the green body is preferably placed in an environment at a certain temperature for more than a period of time, the temperature is preferably 100°C or above 120°C, more preferably above 150°C, and the period of time is preferably 1, 2 , 3, 4, 5, 6 or 7 hours or more, more preferably 8 hours or more.

The green body after drying treatment can already be used as a resistivity simulation unit body. However, in order to keep the resistivity of this unit body relatively stable during use and minimize the impact of external humidity on the resistivity, it is preferable to continue with the following steps:

f. Carry out saturated immersion insulating oil treatment on the green body after the drying treatment.

What needs to be specially explained here is that in the context of this application, the term "insulating oil" does not mean that the substance is liquid at normal temperature. Those insulating substances that are liquid and still retain their electrical insulating properties. In the present invention, the insulating oil is preferably high melting point paraffin, and the liquid formed after melting can be called paraffin oil. When carrying out the saturated immersion insulating oil treatment, the high-melting point paraffin wax is heated and melted into paraffin oil, and then the body that has undergone the drying treatment is completely immersed in the paraffin oil. The immersion time should not only allow the paraffin oil to cover all the surfaces of the green body, but also allow the paraffin oil to fully immerse into the green body and fill the pores therein, so as to ensure the stability of the physical properties of the obtained resistivity simulation unit body. Specifically, the soaking time may preferably be between 0.5-2.0 hours, more preferably about 1 hour. In a specific example, the depth of the paraffin oil may be about 1 meter, which of course can be properly set according to the immersion requirements. After the saturated immersion insulating oil treatment, the resistivity of the unit body can remain relatively stable, thus ensuring the calibration accuracy of the tested downhole measuring instrument.

The present invention particularly preferably uses graphite powder as the conductive medium, because the physical and chemical properties of graphite are very stable below 250°C, and will not react with cement, adhesives, etc. to affect the service life and Its resistivity is stable. Other conductive substances with stable physical and chemical properties and uniform particles can also be used as a conductive medium and mixed with other materials such as cement to make a resistivity simulation unit.

So far, those skilled in the art should recognize that although a number of exemplary preferred embodiments have been shown and described in detail herein, without departing from the spirit and scope of the present invention, the content disclosed in the application can still be Numerous other variations or modifications consistent with the principles of the invention are directly identified or derived. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims (8)

1. the resistivity simulation cell cube of formation at target locations resistivity under a simulation well, it is characterized in that, described resistivity simulation cell cube is the annular element body with central annular distance, and covers or be filled with insulating oil in the hole of all surface of described resistivity simulation cell cube and inside.

2. resistivity simulation cell cube according to claim 1, is characterized in that,

Described resistivity simulation cell cube has the one or more locating holes that axially run through itself.

3. resistivity simulation cell cube according to claim 2, is characterized in that:

The quantity of described locating hole is three, and along same circumference uniform distribution on the end face of described resistivity simulation cell cube.

4. resistivity simulation cell cube according to claim 1, is characterized in that,

On the bore area of described resistivity simulation cell cube, there is at least one local feature of demarcating, for detecting one or more characteristic index of described device for subsurface measuring.

5. resistivity simulation cell cube according to claim 4, is characterized in that,

The described local feature of demarcating comprises multiple grooves and/or the hole with different geometrical size and/or orientation.

6. resistivity simulation cell cube according to claim 1, is characterized in that:

Described resistivity simulation cell cube is made up of cement, one or more conductive materials and water.

7. resistivity simulation cell cube according to claim 6, is characterized in that,

Described conductive materials is particle and/or powder type.

8. resistivity simulation cell cube according to claim 6, is characterized in that,

Described conductive materials is graphite powder.