RU2770874C1 - Method for downhole directional survey and downhole system for implementation thereof - Google Patents

Abstract

FIELD: measuring.SUBSTANCE: invention relates to downhole directional surveying, in particular, to a method and system for downhole directional survey for the purpose of determining the spatial position of the wellbore with a ferroprobe inclinometer, including that in the process of drilling inclined and horizontal boreholes. The method includes pre-logging ground control implemented using two identical downhole tools, interconnected in series, wherein each tool comprises triads of accelerometric and ferroprobe sensors, sensitivity axes whereof match the axes of the bases of the first and second bodies of the downhole tools Rk1(x1,y1,z1)and Rk2(x2,y2,z2), respectively. Based on the results of the pre-logging control, a table of systems of inequalities characterising the sets of conditions of sensor operability is compiled. Further in the process of hoisting operations, the values of information signals of all accelerometric and ferroprobe sensors of both downhole tools are recorded, a comparative analysis of the recorded values with the table of systems of inequalities characterising the sets of conditions of sensor operability is performed, providing a possibility of identifying non-operating sensors, wherein, in case any of the accelerometric or ferroprobe sensors of one downhole tool fails, the sought zenith and sighting angles are determined based on the values of the second downhole tool.EFFECT: increase in the hardware and information reliability of the downhole system and increase in the accuracy of measurements of the spatial position of the wellbore.2 cl, 1 dwg

Description

The invention relates to well inclinometry, in particular to solving problems of determining the spatial position of the wellbore with a fluxgate inclinometer, including in the process of drilling inclined and horizontal wells.

When determining the parameters of the spatial position of the wellbore to measure the magnetic azimuth, ferroprobes are used, consisting of a triad of magnetic field strength sensors (magnetometers), the sensitivity axes of which are orthogonal and rigidly connected to the inclinometer body. The readings of each of the magnetometers contain information about the projections of the Earth's magnetic field strength, the value of which depends on the orientation of the sensitivity axes of the magnetometers relative to the Earth's magnetic field strength vector. Based on this information, the azimuth of the wellbore is determined at the location of the inclinometer.

Ferroprobe downhole inclinometers are known, which contain a triad of three accelerometers with orthogonal sensitivity axes and a triad of orthogonal fluxgates, the sensitivity axes of which are directed parallel to the axes of the inclinometer body (Isachenko V.Kh. Inclinometry of wells. M .: Nedra, 1987, p. 46.) - in various embodiments, they are presented in inventions, for example, patents RU No. 2235200, 2004, No. 2018646, 1994, No. 2204712, 2003, GB patent No. 2370361 A1 (Great Britain, 2003).

The disadvantage of these inclinometers is large errors in the measurement of the magnetic azimuth in the case when there are elements of the construction of the drilling complex, consisting of ferromagnetic materials, in the area of the location of the fluxgates. In the presence of interference due to the magnetization of the ferromagnetic elements of the drilling equipment (downhole assembly, pipe string), the readings of the magnetometers are distorted by the magnitude of the projections of the magnetic field from interference sources on the sensitivity axis of the magnetometers.

In instrument engineering, methods for separating a useful signal and constant interference by modulating the readings of information sources are widely used, as, for example, in a device for monitoring a set of parameters of well curvature (AS USSR No. 1208208, 1986), containing a triad of fluxgate sensors. In this device, one of the fluxgates of the triad is oriented along the longitudinal axis of the inclinometer body, and the other two are installed at an angle to the longitudinal axis of the body. However, to improve the quality of determining the parameters of the harmonic and constant components of the total signal, it is necessary that the modulation depth of the measured signal be maximum. This is due to the fact that errors in determining the parameters of the Earth's magnetic field vector and interference from the ferromagnetic elements of the drilling system, which are calculated from the readings of magnetometers, depend on the amplitude of the modulated signals and, therefore, on the depth of their modulation. But in the case of coincidence or parallelism of the sensitivity axis of the device and the axis of its rotation, the amplitude of the modulated signal is equal to zero. Therefore, the modulation of the signals of the ferroprobes, which are installed at an angle to the longitudinal axis of the inclinometer body, makes it possible to solve this problem. However, the modulation of signals from a fluxgate oriented in the device along the body axis is practically useless.

In addition, the reliability of the data obtained directly depends on the reliability and accuracy of the sensors themselves and the electronic units used, which can fail during the work on the well.

The objective of the invention is to improve the hardware and information reliability of the downhole system and improve the accuracy of measurements of the spatial position of the wellbore.

The problem is solved in the following way.

In accordance with the downhole inclinometry method, which includes the operation of pre-logging ground control of the performance of sensors of a downhole tool containing two triads of accelerometric and fluxgate sensors, and subsequent logging in the process of tripping operations with binding of the obtained data to the depth of the well, according to the invention

- pre-logging ground control is carried out using two identical downhole tools connected in series with each other, each of which contains triads of accelerometric and fluxgate sensors, the sensitivity axes of which coincide with the axes of the bases of the first and second bodies R _{k1 (x1, y1, z1)} and R _{k2 (x2,y2,z2)} respectively,

- in the process of pre-logging ground control with arbitrarily set values of sighting angles ϕ _1i , ϕ _2i determine the values of zenith angles θ _1i , θ _2i , azimuth angles α _1i , α _2i and magnetic inclination angles υ _1i , υ _2i sensors of both downhole tools and obtained comparative values make up a table of the system of inequalities:

where:

- вектор ускорения свободного падения;

- вектор индукции геомагнитного поля; g_ij - сигнал акселерометрических датчиков;

- сигналы феррозондовых датчиков,μ _m , η _m , λ _m , ε _{k(m, θ, ϕ, α, υ)} - a priori specified values determined by the marginal error values, which are normalized by the metrological characteristics of the first and second downhole tool;

- free fall acceleration vector;

- geomagnetic field induction vector; g _ij - accelerometric sensor signal;

- signals of fluxgate sensors,

further, in the process of tripping operations of the downhole tool, the values of the information signals of all accelerometric and fluxgate sensors of both downhole tools are recorded, they are compared with the table of the system of inequalities, and the performance of the downhole system sensors is diagnosed and the information received is corrected.

To implement the proposed method, a downhole system is used, containing a housing inside which two triads of accelerometric and flux-gate sensors are placed, an electronic block for converting information signals and a device for transmitting data to ground equipment, which is additionally equipped with a second housing with two triads of accelerometric and flux-gate sensors placed inside, an electronic a block for converting information signals and a device for transmitting data to ground equipment, identical to the first one. Both housings are sequentially joined to each other along the longitudinal axis in such a way that the sensitivity axes of all sensors coincide with the axes of the bases of the first and second housings R _{k1 (x1, y1, z1)} and R _{k2 (x2, y2, z2),} respectively.

The proposed method of well inclinometry makes it possible, based on the results of pre-logging checks of the well system during well logging operations in the well, in real time to compare the information received with the table of the system of inequalities, quickly identify non-working sensors and, in the event of failure of any of the accelerometric or flux-gate sensors of one downhole tool, determine the desired anti-aircraft and sighting angles according to the measured values of the second downhole tool and thereby promptly correct the information received, increasing the measurement accuracy.

Along with this, in the event of implicit failures of any of the sensors (departure of parameters, change in the linearity of static characteristics, etc.), a comparative analysis of all the conditions of the system of inequalities with the information obtained makes it possible to identify a specific inoperative sensor directly during the operation of the equipment in downhole conditions without the use of technological operations with additional time costs, thereby increasing the manufacturability and efficiency of operation of the proposed downhole system for the implementation of the present method of downhole inclinometry.

The proposed method of downhole inclinometry and the downhole system for its implementation are economical, do not require special equipment and materials for practical implementation, which corresponds to the criterion of the invention "industrial applicability".

The figure shows a diagram of a variant of the downhole system for implementing the downhole inclinometry method.

The downhole system contains a downhole tool 1 and a downhole tool 2 connected to each other by means of a threaded connection 3. Each of the downhole tools 1 and 2 contains a triad of fluxgate sensors 4 and 5 - (TFD-1 and TFD-2), respectively, and a triad of accelerometric sensors 6 and 7 - (TAD-1, TAJ-2), respectively.

, числовое значение которого выражается постоянной величиной, то есть ϕ₀=const. то есть обеспечиваются условия α=const; θ=const, а ϕ=var. Затем для различных произвольных значений визирного угла

определяют значения зенитных углов θ_1i, θ_2i, визирных углов, азимутов, а также и углов магнитного наклонения

. По измеряемым информационным сигналам с датчиков для каждого из скважинных приборов 1 и 2 выполняют сравнение полученных результатов и составляют таблицу системы неравенствIn practice, a pre-logging control of the performance of the proposed well system is preliminarily performed. To do this, a "bundle" of downhole tools 1 and 2 is located in such a way that its spatial orientation does not change (for example, in a position close to horizontal), and there is the possibility of free rotation around its own longitudinal axis. Since the downhole tools 1 and 2 are rigidly connected to each other by means of a threaded connection 3, the basis R _k2(x2,y2,z2) and the body of the downhole tool 2 in the apsidal plane with respect to the basis R _k1(x1,y1,z1) of the downhole tool body 1 occupies a position shifted to the sighting angle

, the numerical value of which is expressed by a constant value, that is, ϕ ₀ =const. that is, the conditions α=const are provided; θ=const and ϕ=var. Then for various arbitrary values of the sighting angle

determine the values of zenith angles θ _1i , θ _2i , sighting angles, azimuths, as well as magnetic inclination angles

. According to the measured information signals from the sensors for each of the downhole tools 1 and 2, a comparison of the results obtained is performed and a table of the system of inequalities is compiled

where μ _m , η _m , λ _m , ε _{k(m, θ, ϕ, α, υ)} are a priori specified values determined by the marginal error values, which are normalized by the metrological characteristics of downhole tools 1 and 2.

If all the conditions for matching the system of inequalities (1) are met, the well system is suitable for operation.

Further, during logging operations, the well system is lowered on a cable along the wellbore to the bottom, and then, during the lifting process, measurements are made in accordance with the traditional method of inclinometric logging with depth referencing. At the same time, the received values of all twelve information signals received from the sensors 4-7 of both downhole tools are recorded and the measured values are analyzed step by step.

At the initial stage, the signal modules are evaluated by the measured projections from all three-component sensors of the downhole system. If the first two conditions of the system of inequalities (1) are met, then the next stage of the analysis is performed.

If the first two conditions of the system of inequalities (1) are not met, then the analysis is already directly measured signals from accelerometric sensors g _ij and fluxgate sensors t _ij .

When analyzing the values of the measured signals from accelerometric and fluxgate sensors, a failure classifier is used, the essence of which is as follows. Since the information electrical signals from sensors 4-7 are further converted into a form convenient for transmission via a logging cable to ground equipment, then in case of obvious failures of any of the sensors or electronic units of the secondary signal conversion, situations may arise when digital codes, corresponding to each of the values of g _ij and t _ij will be identified as zero values U _0, or values equal to the values of bipolar supply voltages of downhole tools U _m and Un, which, as a rule, exceed the limiting values of the dynamic ranges of changes in analog signals from sensors:

Then, in case of failure, for example, of one of the sensors 6 (for example, accelerometer A _x1 in TAD-1), the desired zenith and sight angles are determined from the measured values of g _i2(x,y,z) of sensors 7 in TAD-2. The same is done in cases of failure of any of the fluxgate sensors 4 or 5 in TFD-1 or TFD-2, respectively.

In addition, latent (implicit) failures of sensors may also occur during operation (departure of parameters, change in the linearity of static characteristics, etc.). Analysis of all the conditions of the system of inequalities (1), , based on the registration of unreliable information signals from accelerometric and fluxgate sensors 4-7, allows you to identify a specific sensor with a hidden defect and carry out further repair and restoration of a failed downhole tool that is already subject-oriented.

Thus, the proposed method of downhole inclinometry and the downhole system for its implementation make it possible to increase the accuracy of measurements with a fluxgate downhole inclinometer by determining and compensating for interference that occurs in magnetometers due to the influence of magnetized structural elements of the drilling assembly when using methods of modulating the readings of magnetometers.

Along with this, in the course of work, based on the registration of unreliable information signals from accelerometric or fluxgate sensors, it is possible to identify sensors with hidden defects, thereby providing the possibility of repair and restoration of failed devices already subject-oriented, without technological operations with additional time costs. .

Claims (9)

1. The method of downhole inclinometry, including the operations of pre-logging ground control of the performance of sensors of a downhole tool containing two triads of accelerometric and flux-gate sensors, and subsequent logging in the process of tripping operations of a downhole tool with binding of the data obtained by the depth of the well, characterized in that pre-logging ground control is carried out with using two identical downhole tools connected in series with each other, each of which contains triads of accelerometric and fluxgate sensors, the sensitivity axes of which coincide with the axes of the bases of the first and second bodies of downhole tools R _{k1 (x1, y1, z1)} and R _{k2 (x2, y2 ,z2)} respectively; at arbitrarily set values of sighting angles ϕ _1i , ϕ _2i determine the values of zenith angles θ _1i , θ _2i , azimuth angles α _1i , α _2i , magnetic inclination angles υ _1i , υ _2i of the sensors of both downhole tools and, using the obtained comparative values, make up a table of systems of inequalities , characterizing the totality of the conditions for the operability of the sensors:

where μ _m , η _m , λ _m , ε _{k(m, θ, ϕ, α, υ)} are a priori given values determined by the marginal error values, which are normalized by the metrological characteristics of the first and second downhole tool;

- free fall acceleration vector;

- geomagnetic field induction vector; g _ij - accelerometric sensor signal; t _ij - signals of fluxgate sensors; further, in the process of tripping operations, the values of information signals of all accelerometric and fluxgate sensors of both downhole tools are recorded, a comparative analysis of the recorded values is carried out with a table of systems of inequalities characterizing the totality of sensor performance conditions, which makes it possible to identify non-working sensors, while in the event of failure of any of the accelerometric or fluxgate sensors of one downhole tool determine the desired zenith and target angles according to the values of the second downhole tool. 2. A downhole system for implementing the method of downhole inclinometry according to claim 1, containing a housing inside which two triads of accelerometric and flux-gate sensors are placed, an electronic unit for converting information signals and a device for transmitting data to ground equipment, characterized in that it is additionally equipped with a second housing with placed inside by two triads of accelerometric and fluxgate sensors, an electronic unit for converting information signals and a device for transmitting data to ground equipment, identical to the first one and connected in series with it along the longitudinal axis in such a way that the sensitivity axes of all sensors coincide with the axes of the bases of the first and second bodies of downhole tools R _k1(x1,y1,z1) and R _{k2(x2,y2,z2),} respectively.

Images