RU2540770C1 - Stratal induction tiltmeter - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention suggests tiltmeter consisting of sealed dielectric body with scanning induction tool rotating inside it; the above tool includes one transmitting coil, two compensating and one receiving dipole coils with mutually perpendicular magnetic moments, high-frequency generator, amplifier, phase-sensitive detector, spectrum analyser and azimuth sensor. At that the transmitting coil is made of two identical sections interconnected in series through two paralleled quadrupole compensating coils. Besides, the transmitting coil is made as a hexagonal frame protruded intensely along the tool axis with at least 20-multiple ratio of length towards its width oriented by a shaper peak towards the receiving coil thus ensuring tilt of magnetic-moment vector distributed along the frame in regard to the tool axis per preset angle of 82°. Quadrupole compensating coils are mounted at the opposite sharp peaks of the hexagonal frame coaxially with the tool by opposite magnetic moments. At that magnetic moment of the receiving dipole coil is placed in magnetic moment plane of the transmitting coil and oriented towards the tool axis at angle of 8°.

EFFECT: expanding range of the tiltmeter sensitivity and selectivity.

3 dwg

Description

The invention relates to the field of geophysical research of wells and can be used to determine dip angles and dip azimuths of layers and cracks in sections of oil, gas, coal, ore and other mineral deposits.

Known reservoir induction tiltmeter [Patent No. 1393902 SU, MKI: E21B 47/02. Stated April 28, 84; Publ. 05/07/88. Bull. Number 17. Registered in the State Register of Inventions of the Russian Federation and is valid from 03.16.1993]. This inclinometer contains an induction probe uniformly rotating around the axis of the well, a high-frequency oscillation generator, an amplifier, a phase-sensitive detector, a spectrum analyzer and a flux-probe indicator of the azimuthal orientation of the probe, the induction probe being made in the form of a radiating coil, the magnetic moment of which is directed at an angle of 1-25 ° to the axis probe, and receiving dipole and quadrupole coil systems. The magnetic moment of the receiving dipole coil is perpendicular to the radiating magnetic moment, i.e. is directed at an angle of 65-89 ° to the axis of the probe, and the magnetic moments of the receiving quadrupole coils, compensating for the direct field of the radiating coil, are perpendicular to the axis of the induction probe or combined with it. For the noise-resistant version of the known tiltmeter, an optimum value of the direction of the magnetic moment of the radiating coil is recommended an angle of 8-12 ° to the axis of the probe.

The well-known formation induction tiltmeter provides reliable determination of the inclination angles of rock formations in well sections in the range of 0 ÷ 45 ° and azimuths of their fall in the range of 0 ÷ 360 °. In the same ranges, it also provides reliable detection of inclined cracks that cut the formation at other inconsistent angles that differ from the formation.

However, having a circular radiation pattern and receiving high-frequency electromagnetic waves, it is not sensitive enough to vertical and subvertical cracks with tilt angles in the range of 60 ÷ 90 °. Such fractures in the strata due to their greater openness compared to inclined horizontal sharply increase their reservoir (hydraulic) properties and, consequently, the productivity of oil and gas and hydrogeological wells. (From the geomechanics of rocks it is known that the greater openness of vertical and, accordingly, the closure of horizontal cracks in the rock mass is due to the regular excess of the vertical component of the rock pressure over the horizontal). At the same time, vertical and subvertical fracturing of rocks sharply reduces the strength and stability of roofs in coal mines and mines, the sides of coal and ore quarries, causes sudden emissions (soufflars) of explosive methane into mine workings and, therefore, reduces the safety of mining operations.

The aim of the invention is to eliminate this drawback. This goal is achieved by the fact that in the proposed formation induction tiltmeter, the radiating coil is made of two identical sections, connected to each other sequentially through two parallel quadrupole compensating coils, and the radiating coil is made in the form of an axisymmetric hexagonal frame strongly elongated along the probe axis with at least 20 a multiple ratio of its length to width, oriented by a sharper apex towards the receiving dipole coil and providing a slope distributed along the frame in is the magnetic moment of a given angle, for example, 82 ° to the axis of the probe, and quadrupole compensating coils are mounted on opposite sharp triangular vertices of the hexagonal frame coaxially with the probe in opposite directions of magnetic moments, while the magnetic moment of the receiving dipole coil is in the plane of the magnetic moment of the radiating coil and directed accordingly at an angle of 8 ° to the axis of the probe, i.e. oriented perpendicular to the magnetic moment of the radiating coil.

Figure 1 shows a block diagram of the proposed reservoir induction tiltmeter: 1 - dielectric body (rod) of the probe; 2 - upper and lower bearings; 3 - drive uniform rotation; 4-receiving dipole coil; 5 and 6 - the left and right sections of the radiating coil; 7 and 8 - lower and upper quadrupole compensating coils; 9 - fluxgate; 10 - high-frequency generator; 11 - amplifier; 12 - phase-sensitive detector; 13 - spectrum analyzer; 14 - frequency-modulated generator; 15 - frequency detector.

Figure 2 - conditional image of the design of the radiating and quadrupole coils: 5 - winding of the left section of the radiating coil without a frame; 6 - frame of the right section of the radiating coil without winding; 7 and 8 are the lower and upper quadrupole compensating coils in section.

Figure 3 - vector representation of the magnetic moments of the coils of the induction probe: 4 - receiving dipole coil; 5-6 - emitting coils; 7 and 8 - lower and upper quadrupole (compensating) coils; 9 - flux-gate coils; α and β are the angles of inclination, respectively, of the vectors of magnetic moments of the receiving and radiating coils.

The plastic induction tiltmeter (Fig. 1) contains an induction probe mounted on a dielectric (plastic) rod 1, rotating inside a dielectric (ceramic) sealed casing (not shown in the block diagram) in bearings 2 using an electric drive 3. On the dielectric rod 1 are placed receiving dipole coil 4, wound on a ferrite rod and mounted on the axis of the rod 1 at an angle, for example, 8 ° relative to it, sections 5 and 6 of the radiating coil, wound on a common frame in the form of strongly elongated along the axis of the eraser 1 hexagonal frame with at least a 20-fold ratio of its length to width, oriented by a sharper peak towards the receiving dipole coil 4, quadrupole (compensating) coils 7 and 8, wound in the form of conical solenoids, are mounted on opposite sharp triangular vertices of the hexagonal the frames 5, 6 are aligned with the dielectric rod 1, parallel to each other by the opposite leads of the windings and connected in series between sections 5 and 6 of the radiating coil. The sensor azimuthal orientation of the probe is made in the form of a single-element flux probe 9, the coil of which is wound on a magnetic (permalloy) core mounted perpendicular to the axis of the rod 1 in the vertical plane of the magnetic moments of the receiving and emitting probe system. The system of radiating-compensating coils 5-7 is connected to a high-frequency generator 10 with an operating frequency, for example, 225 or 450 kHz, i.e. in the non-working broadcasting range, and the receiving coil 4 is connected to an amplifier 11 connected to a phase-sensitive detector 12, the output of which is connected to the input of the spectrum analyzer 13. The reference voltage to the phase-sensitive detector 12 is supplied from a high-frequency generator 10. A flux probe 9 is connected to a frequency-modulated generator 14 and a frequency detector 15, the output of which is connected to the second input of the spectrum analyzer 13.

The proposed design of the radiating coil is significantly different from that in the known tiltmeter feature of its geometry and orientation relative to the axis of the probe (figure 2). Its original shape in the form of a hexagonal frame strongly elongated along the probe axis, narrowed towards the receiving coil and divided into two identical sections 5 and 6, wound on a common frame and connected to each other in series with quadrupole compensating coils 7 and 8, provides focused (conditionally “ slit ") the directional pattern of the excitation of the electromagnetic field distributed predominantly vertically (Fig. 3), which maximally covers the vertical vertically distributed magnetic moment of the coil (5-6) hydrochloric fracture along its length. Due to this, an electrically conductive (fluid-conducting) vertical crack concentrates the radiated electromagnetic energy, increasing the selectivity of the inclinometer mainly to vertical cracks. Such a concentration of radiated energy also increases (although to a lesser extent) the selectivity of the inclinometer to subvertical cracks.

The triangular shape of the sharp peaks (ends) of the emitting frame (5-6) provides a more complete (compared to the round) compensation of its direct electromagnetic field along the axis of the probe with quadrupole coils 7-8, and therefore, a more complete suppression of this field as interference at the output receiving coil 4. As a result, the sensitivity (ratio of the useful signal to interference) of the tiltmeter as a whole increases. Elongated along the axis of the probe, the hexagonal frame forms (Fig. 3) a radiation pattern of magnetic moments distributed along its length, at an angle of inclination of the conditional "gap" of 82 °. For example, with a probe length of 1 m, i.e. the distance between the centers of the emitting and receiving coils is 1 m, the optimal length of the frame is 500 mm with a cross section of no more than 25 mm. Such probe sizes provide a sufficiently large (0.5 m) radial depth of scanning near-wellbore space and the identification of vertical and subvertical cracks in it. In addition, the small transverse dimensions of the probe coils make it possible to design small-sized downhole tools with a diameter of 36 mm or more.

The proposed reservoir induction tiltmeter works as follows.

The high-frequency electromagnetic field excited by the radiating coil 5-6 induces in the rocks of the near-wellbore space with a radius of up to 0.5 m the secondary magnetic field of eddy currents, which is received by the receiving dipole coil 4. In this case, the direct electromagnetic field of the radiating coil is compensated by quadrupole coils 7-8. The received signal of the secondary field is amplified by the amplifier 11 and detected by the frequency of the emitted field by the phase-sensitive detector 12. Due to the rotation of the coils of the induction probe, the detected signal is modulated by the harmonics of the rotation frequency and the envelope voltage appears at the output of the detector 12, which is transmitted to the first input of the spectrum analyzer 13. When the flux probe 9 in the Earth’s magnetic field, its inductance periodically changes, causing the frequency modulation of the frequency-modulated generator 14. Frequency detector 15 the modulated voltage of the generator 14 is converted into a sinusoidal voltage, synchronous and in-phase with the rotation of the probe, and fed to the second input of the spectrum analyzer 13. The output signals of the spectrum analyzer 13 are the amplitude of the zero harmonic (constant component of the input signal) and the amplitude and phase of the harmonics of the rotation frequency, according to which tilt angles and dip azimuths of reservoirs and fractures are calculated.

Technical effect. The main advantage of the proposed induction reservoir dipmeter is an expanded range of sensitivity and selectivity, which allows to identify and determine the occurrence elements (inclination angles and dip azimuths) of both gentle and inclined and steeply falling rock formations, vertical and subvertical cracks, and to identify areas of vertical anisotropy of electrical conductivity, and therefore , hydraulic conductivity of rock formations in sections of wells, to predict structural and geological, geological and mining and geological e conditions for the development of oil and gas, coal, ore and other deposits.

Claims (1)

A formation induction tiltmeter comprising a sealed dielectric housing with an induction probe rotating inside it, including a radiating and receiving dipole coils with mutually perpendicular magnetic moments, quadrupole coils compensating the direct field of the probe, an electric drive for uniform rotation of the probe, a high-frequency generator and an amplifier whose output is connected to a phase-sensitive a detector and spectrum analyzer, a flux-probe sensor of azimuthal orientation of the probe, characterized in that emitting to the coil is made of two identical sections connected in series through two parallel parallel quadrupole compensating coils, the radiating coil made in the form of an axisymmetric hexagonal frame strongly elongated along the probe axis with at least 20 times its length to width ratio, oriented by a sharper vertex in side of the receiving dipole coil and providing a slope of the magnetic moment distributed along the frame of the vector by a given angle, for example, 82 ° to the probe axis, and quadrupole compensations uyuschie coils mounted on opposite acute vertices of the hexagonal frame coaxially with the probe oppositely directed magnetic moments, wherein the magnetic dipole moment of the receiving coil is in the magnetic moment of the coil and the radiating plane is directed at an angle of 8 ° to the axis of the probe.

Images