CN106761726A - Oil base drilling fluid is with brill lateral position well logging apparatus and method - Google Patents

Abstract

The invention discloses an oil-based drilling fluid lateral azimuth logging device and method while drilling. It includes: sinusoidal AC excitation source, lateral azimuth logging while drilling sensor, signal acquisition module and computer. The invention adopts the excitation method based on the principle of electromagnetic induction to replace the traditional direct excitation method and overcomes the limitations of the latter; establishes an equivalent circuit model of well logging based on the principle of capacitive coupling, and uses digital phase-sensitive demodulation technology to solve the problem of oil-based drilling The current signal detection problem under the liquid; the button-shaped electrode is used to detect the formation in different azimuths, and then the logging information such as formation resistivity imaging can be obtained during the drilling process. The invention has the advantages of simple and reliable structure, high measurement accuracy, large measurement range, etc., and provides a reference method for logging while drilling under the condition of oil-based drilling fluid.

Description

Lateral azimuth logging while drilling oil-based drilling fluid device and method

technical field

The invention relates to the field of petroleum well logging, in particular to an oil-based drilling fluid lateral azimuth logging while drilling device and method.

Background technique

Well logging refers to the method of measuring geophysical parameters by using the electrochemical properties, electrical conductivity, acoustic properties, radioactivity and other geophysical properties of rock formations. Well logging technology is used to explore oil and gas resources in formations, and plays a pivotal role in the petroleum industry. According to different logging methods, logging methods can be divided into two categories: wireline logging and logging while drilling. Geological parameters are measured while drilling. Due to its good real-time performance, accuracy of measurement data and low operating cost, LWD technology is gradually replacing traditional wireline logging and plays an important role in directional drilling.

Drilling fluid is the circulating flushing medium used in the wellbore during the drilling process. Drilling fluid is the blood of drilling, also known as drilling flushing fluid. Drilling fluid can be divided into clear water, mud, clay-free flushing fluid, emulsion, foam and compressed air according to its composition. Mud is a widely used drilling fluid. It is mainly suitable for unstable rock formations with loose walls, developed cracks, easy to collapse and drop blocks, and swelled and spalled when exposed to water. At present, with the advancement of drilling technology, oil-based drilling fluids are more and more widely used in drilling operations because of their advantages of reducing oil and gas layer damage and enhancing wellbore stability. However, the existence of oil-based drilling fluid means that an insulating medium is added between the detection electrode in direct contact with the formation to be measured, which blocks the direct flow path, making the logging-while-drilling technology under ordinary water-based drilling fluid no longer possible. Be applicable.

Based on the principles of capacitive coupling and electromagnetic induction, the present invention designs an oil-based drilling fluid lateral azimuth logging device and method while drilling. The device can overcome the problem that the traditional logging-while-drilling method cannot work in oil-based drilling fluid, and can further obtain azimuth formation information, which has important application value.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and provide an oil-based drilling fluid lateral azimuth logging device and method while drilling.

Technical scheme of the present invention is as follows:

An oil-based drilling fluid lateral azimuth logging device, characterized in that it includes a sinusoidal AC excitation source, a lateral azimuth logging while drilling sensor, a signal acquisition module and a computer, and the lateral azimuth logging while drilling sensor is Including drill collar, drill bit, helical annular excitation coil and several button electrodes; during logging operation, the lateral azimuth logging while drilling sensor is located in the borehole, and the gap between the lateral azimuth logging while drilling sensor and the well wall is filled with The oil-based drilling fluid is the formation to be measured outside the wellbore; the helical toroidal excitation coil is composed of a toroidal magnetic core and a coil wound on the toroidal magnetic core; the helical toroidal excitation coil is installed on the drill collar , which is insulated from the drill collar and connected to the sinusoidal AC excitation source. Several button electrodes are inlaid and installed at different heights on the lower part of the drill collar to form a button electrode array; each button electrode contains an insulating ring, which makes the drill collar No contact with the button electrode, the button electrode is connected to the lower part of the drill collar through the signal acquisition module, and the signal acquisition module is connected to the computer

In the present invention, the button electrodes are inlaid and mounted on the lower part of the drill collar. Each button electrode contains an insulating ring so that the electrodes do not directly contact the drill collar. The button electrodes are connected to the lower part of the drill collar through a signal acquisition module. The short principle keeps the potential of the button electrode consistent with the lower part of the drill collar.

Preferably, the helical annular excitation coil is installed on the upper part of the drill collar.

The steps of the lateral azimuth logging while drilling method for oil-based drilling fluid are as follows:

1) Set the excitation signal of the sinusoidal AC excitation source as Where U _i is the effective value of the sinusoidal AC excitation voltage, f is the frequency of the excitation voltage, the excitation mode of the LWD sensor is based on the principle of electromagnetic induction; the helical ring excitation coil can be regarded as the primary side of the transformer, The number of turns is N _t ; the drill collar is regarded as the secondary side of the transformer, and its number of turns is 1; under the action of the sinusoidal excitation voltage u _i , an induced electromotive force will be generated on the drill collar, and the helical ring excitation coil is used as the boundary , the potential of the upper part of the drill collar is defined as 0, and the potential of the lower part is defined as where k is the sensor coefficient defined taking into account electromagnetic losses;

2) The button electrode has the same AC potential as the lower part of the drill collar. Based on the principle of capacitive coupling, under the action of AC excitation, the button electrode and the wellbore wall form a coupling capacitance C ₁ through oil-based drilling fluid, and the formation is equivalent to an apparent resistance R _f , the well wall and the upper part of the drill collar form a coupling capacitor C ₂ , and the three are connected in series to form an AC measurement circuit; the AC current i ₀ starting from the button electrode flows through the AC measurement circuit path, and finally returns to the upper part of the drill collar. Note: Part of the current flows directly through the oil-based drilling fluid and directly returns to the upper part of the drill collar without passing through the formation, but the coupling capacitance C ₃ of the oil-based drilling fluid is relatively large, so it can be ignored.

3) Due to the existence of coupling capacitors C ₁ and C ₂ , the phase of the AC current i ₀ and the excitation voltage u _i are different in phase The alternating current i ₀ is converted into a digital signal sequence u ₀ (n) by the signal acquisition module and sent to the computer. On the host computer of the computer, the amplitude A ₀ and phase of u ₀ (n) can be obtained by using the digital phase-sensitive demodulation technology Therefore, according to the simplified logging equivalent circuit model, parameters such as formation apparent resistance _Rf can be obtained:

Then, based on the known apparent resistivity of formations in different azimuths, logging information such as formation resistivity imaging can be further obtained.

The present invention has the beneficial effect compared with prior art:

1) Using the capacitive coupling principle and digital phase-sensitive demodulation technology, a simplified logging circuit model is established to solve the current signal detection problem under oil-based drilling fluid.

2) The excitation method based on the principle of electromagnetic induction is used to replace the direct excitation method of traditional wireline logging, and the induced potential is generated on the drill collar and button electrode, which is simple and reliable. On the other hand, like button electrodes, drill collars also emit current. Since the potentials on the drill collar and the button electrode are the same, the drill collar current has a focusing effect on the electrode current, thereby increasing the formation detection depth of the button electrode.

3) Button-shaped electrodes are used to detect formations in different azimuths, and then to obtain logging information such as formation resistivity imaging during drilling.

Description of drawings

Fig. 1 is a structural schematic diagram of an oil-based drilling fluid lateral azimuth logging device;

Fig. 2 is a schematic structural diagram of a lateral azimuth logging while drilling sensor;

Fig. 3 is the installation diagram of button electrode;

Fig. 4 is a schematic diagram of an equivalent circuit of a logging sensor;

Fig. 5 is a schematic diagram of a logging equivalent circuit model;

Fig. 6 is a schematic diagram of a simplified logging equivalent circuit model.

In the figure: sinusoidal AC excitation source 1, LWD sensor 2, signal acquisition module 3, computer 4, drill collar 5, drill bit 6, helical ring excitation coil 7, button electrode 8, formation to be measured 9, Borehole 10, oil-based drilling fluid 11, insulating ring 12.

detailed description

As shown in FIG. 1 , the oil-based drilling fluid lateral azimuth logging device includes a sinusoidal AC excitation source 1 , a lateral azimuth logging while drilling sensor 2 , a signal acquisition module 3 and a computer 4 . The sinusoidal AC excitation source 1 provides excitation signals for the lateral azimuth logging while drilling sensor 2, and the measured current signal generated by the lateral azimuth logging while drilling sensor 2 is amplified and collected by the signal acquisition module 3, and transmitted to the computer 4 for processing. further signal processing.

As shown in FIG. 2 , the LWD sensor 2 includes: a drill collar 5 , a drill bit 6 , a helical ring excitation coil 7 and several button electrodes 8 . During logging operations, the lateral azimuth logging while drilling sensor 2 is located in the wellbore 10 , and the gap between them is filled with oil-based drilling fluid 11 . Outside the wellbore 10 is the formation 9 to be measured. The helical annular excitation coil 7 is composed of a high magnetic permeability annular magnetic core and a coil wound on the magnetic core. The helical ring excitation coil 7 is installed on the drill collar, insulated from the drill collar 5, and connected with the sinusoidal AC excitation source 1. A plurality of button electrodes 8 are inlaid and installed at different heights on the lower part of the drill collar 5 to jointly form a button electrode array. Each button electrode 8 contains an insulating ring 12 and is connected to the lower part of the drill collar 5 through the signal acquisition module 3 . The signal acquisition module 3 is connected with a computer 4 . The helical annular excitation coil 7 is installed on the top of the drill collar 5 .

As shown in FIG. 3 , the button electrode 8 is inlaid and mounted on the lower part of the drill collar 5 . Each button electrode 8 contains an insulating ring 12 so that the electrode does not come into direct contact with the drill collar 5 . The button electrode is connected to the lower part of the drill collar 5 through the signal acquisition module 3, and the potential of the button electrode 8 is kept consistent with the lower part of the drill collar 5 by using the virtual short principle.

As shown in FIG. 4 , the process of using the device and method to detect formation information in different azimuths is as follows: the sinusoidal AC excitation source 1 applies the excitation signal to the helical ring excitation coil 7 . The spiral ring excitation coil 7 is used as the primary side of the transformer, and its number of turns is N _t , and the drill collar 5 is used as the secondary side of the transformer, and its number of turns is 1. Under the action of the sinusoidal excitation voltage u _i , an induced electromotive force will be generated on the drill collar (5). With the helical ring excitation coil (7) as the boundary, the electric potential on the upper part of the drill collar (5) is defined as 0, and the electric potential on the lower part defined as Where k is a sensor coefficient defined in consideration of electromagnetic loss; the button electrode 8 obtains the same potential as the lower part of the drill collar 5 by using the virtual short principle of the signal acquisition module 3 . The detection current i ₀ emitted from the button electrode 8 flows through the oil-based drilling fluid 11 and the measured formation 9, and returns to the upper part of the drill collar 5 through the oil-based drilling fluid 11, forming an AC channel. i ₀ is amplified into u ₀ by the operational amplifier of the signal acquisition module 3, and then transmitted to the computer 4 after being collected. The computer 4 uses a digital phase-sensitive demodulation algorithm to obtain the real part and imaginary part of the detection current, thereby obtaining the apparent resistance of the formation, and then obtaining information such as formation resistivity imaging.

The steps of the lateral azimuth logging while drilling method for oil-based drilling fluid are as follows:

1) Set the excitation signal of the sinusoidal AC excitation source as Among them, U _i is the effective value of the sinusoidal AC excitation voltage, and f is the frequency of the excitation voltage. The excitation method of the sensor is based on the principle of electromagnetic induction. The spiral ring excitation coil can be regarded as the primary side of the transformer, and its number of turns is N _t ; the drill collar is regarded as the secondary side of the transformer, and its number of turns is 1. Under the action of the sinusoidal excitation voltage u _i , an induced electromotive force will be generated on the drill collar (5). With the helical ring excitation coil (7) as the boundary, the electric potential on the upper part of the drill collar (5) is defined as 0, and the electric potential on the lower part defined as where k is the sensor coefficient defined taking into account electromagnetic losses;

2) As shown in Fig. 5, based on the capacitive coupling principle, under the action of AC excitation, the button electrode 8 and the wellbore wall pass through the oil-based drilling fluid 11 to form a coupling capacitance C ₁ , and the formation 9 can be equivalent to an apparent resistance R _f , The well wall and the upper part of the drill collar 5 form a coupling capacitor C ₂ , and the three are connected in series to form an AC measurement circuit. The alternating current i ₀ starting from the button electrode 8 flows through the alternating current path, and finally returns to the upper part of the drill collar 5 . Note: A part of the current flows directly through the oil-based drilling fluid and directly returns to the upper part of the drill collar without passing through the formation, but the oil-based drilling fluid coupling capacitance C ₃ is relatively large, so it can be ignored. The simplified logging equivalent circuit model is shown in Fig. 6.

3) Due to the existence of oil-based drilling fluid coupling capacitance, the phase difference between the AC current i ₀ and the excitation voltage u _i is different in phase The alternating current i ₀ is converted into a digital signal sequence u ₀ (n) by the signal acquisition module and sent to the computer. On the host computer of the computer, the amplitude A ₀ and phase of u ₀ (n) can be obtained by using the digital phase-sensitive demodulation technology Therefore, according to the simplified logging equivalent circuit model, parameters such as formation apparent resistance _Rf can be obtained:

Then, based on the known apparent resistivity of formations in different azimuths, logging information such as formation resistivity imaging can be further obtained.

A series of simulation experiments have been carried out on the designed oil-based drilling fluid lateral azimuth logging device to verify the feasibility of the method. When there are horizontal high-resistivity target formations, inclined high-resistivity target formations, and high-resistance target rock masses in the measured formation, this method can clearly distinguish the formation resistivity image, and the measurement results are ideal.

Claims (3)

1. an oil-base drilling fluid lateral orientation logging while drilling device, is characterized in that comprising sinusoidal alternating current excitation source (1), lateral orientation logging while drilling sensor (2), signal acquisition module (3) and computer ( 4), the lateral azimuth logging while drilling sensor (2) includes a drill collar (5), a drill bit (6), a helical annular excitation coil (7) and several button electrodes (8); , the LWD sensor (2) is located in the borehole (10), the gap between the LWD sensor (2) and the borehole wall is filled with oil-based drilling fluid (11), and in the borehole ( 10) outside is then measured formation (9); Described helical toroidal exciting coil (7) is made of toroidal magnetic core and the coil wound on the toroidal magnetic core; This helical toroidal exciting coil (7) is installed in On the drill collar (5), it is insulated from the drill collar (5) and connected to the sinusoidal AC excitation source (1). Several button electrodes (8) are inlaid and installed at different heights on the lower part of the drill collar (5) to form a Button electrode array; each button electrode (8) contains an insulating ring (12), the insulating ring (12) makes the drill collar (5) and the button electrode (8) not contact, and the button electrode (8) passes through the signal acquisition module (3 ) is connected to the bottom of the drill collar (5), and the signal acquisition module (3) is connected to the computer (4). 2. The lateral azimuth logging while drilling oil-based drilling fluid device according to claim 1, characterized in that said helical annular excitation coil (7) is installed on the top of the drill collar (5). 3. a kind of oil-based drilling fluid lateral azimuth logging while drilling method using device as claimed in claim 1, is characterized in that its steps are as follows: 1) Set the excitation signal of the sinusoidal AC excitation source (1) as Where U _i is the effective value of the sinusoidal AC excitation voltage, f is the frequency of the excitation voltage, the excitation mode of the LWD sensor (2) is based on the principle of electromagnetic induction; the helical ring excitation coil (7) can be seen As the primary side of the transformer, the number of turns is N _t ; the drill collar (5) is regarded as the secondary side of the transformer, and the number of turns is 1; under the action of the sinusoidal excitation voltage u _i , the drill collar (5) will generate Induced electromotive force, with the helical ring excitation coil (7) as the boundary, the potential on the upper part of the drill collar (5) is defined as 0, and the potential on the lower part is defined as where k is the sensor coefficient defined taking into account electromagnetic losses; 2) The button electrode (8) has the same AC potential as the lower part of the drill collar (5). Based on the principle of capacitive coupling, under the action of AC excitation, the button electrode and the borehole wall form a coupling capacitance C ₁ through the oil-based drilling fluid (11) , the formation is equivalent to an apparent resistance R _f , the borehole wall and the upper part of the drill collar (5) form a coupling capacitor C ₂ , and the three are connected in series to form an AC measurement circuit; the AC current i ₀ from the button electrode (8) flows through The AC measurement circuit path finally returns to the top of the drill collar (5); 3) Due to the existence of coupling capacitors C ₁ and C ₂ , the phase difference between AC current i ₀ and excitation voltage u _i The alternating current i ₀ is converted into a digital signal sequence u ₀ (n) through the signal acquisition module (3), and sent to the computer (4), and on the computer (4), the digital phase-sensitive demodulation technology is used to obtain u ₀ (n ) magnitude A ₀ and phase Obtain formation apparent resistance R _f : Then, based on the known apparent resistivity of formations in different azimuths, formation resistivity imaging information can be obtained.