RU2486338C1 - Method of transmitting measurement data by cable-free telemetric system during well drilling - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: disclosed is a method of transmitting measurement data by a cable-free telemetric system when drilling wells, involving encoding and transmitting information via a phase-shift keyed signal in form of a sequence of pulses, synchronising the signal and receiving the encoded information by a land receiver. One-time (initial) phase synchronisation of precision quartz-crystal oscillators of the transmitter of the bottom telemetric system and the land receiver is carried out by accumulating data on the transitioning of the signal through zero and one-time synchronisation of signals using a priori information on the bottom telemetric system at the current moment in time is also carried out. Prolonged stability of synchronisation of said oscillators is ensured by adjusting the phase of the quartz-crystal oscillator of the land receiver relative to the statistically determined transitioning through zero of the signal of the transmitter of the bottom telemetric system.

EFFECT: higher capacity of the communication channel and high noise-immunity thereof.

1 dwg

Description

The present invention relates to the field of well drilling and is intended to transmit geophysical information via an electromagnetic or hydraulic communication channel.

When using a wireless electromagnetic or hydraulic communication channel, downhole parameters are measured, encoded and transmitted to the surface. The transmission is carried out by encoding information, for example, by a noise-like signal using phase-shift keying of a signal whose frequency is in the range from fractions to units of hertz.

Known methods for synchronizing data transmission between the receiver and the transmitter suggest the presence of sync.

The known program of character-by-character and word-by-word synchronization using a pilot signal (Mukhametov Z.V., Rosenshmidt O.M., Sabaev E.A. Tokarsky V.R. and Kuznetsov G.F. Information and computing structure of the equipment ZIT - 1 // Geophysical surveys during drilling and well testing (Tr. VNIIneftepromgeofiziki) - Ufa, 1989. - Issue 19, p. 102).

In this method, synchronization takes 16% of the entire transmission cycle time and is a phase-shifted signal consisting of 61 characters. A message with bottomhole information follows immediately upon completion of the sync sending. Entering synchronism is carried out by sequential step search. At each step, the correlation sum of the received and reference signal is calculated. The decision on the presence or absence of a clock in the received signal is made by comparing the correlation sum with two thresholds, and the position of the clock in the received signal is determined by the maximum of this sum. Since with a coordinated reception, the maximum of the correlation sum falls at the time the sync message is finished in the received message, its finding means that the downhole information transmitted follows. Symbol-by-word and word-by-word synchronization is carried out by counting the discrete from the end of the clock. At the end of the entire message, consisting of 5 words, the process is repeated anew, starting with the search for the sync package.

A disadvantage of the known method is the presence of synchronization in each block of transmitted data, which reduces the channel throughput, as well as the need for re-synchronization in conditions of unstable reception, which requires not only the reception of the synchronization block, but also the entire package of geotechnological data.

A known method of forming data packets measurement cableless telemetry system in the process of drilling a well (US Pat. RF №2351960, publ. 04/10/2009).

The method includes encoding every four bits of information with a noise-like signal (BSS) of 16 bits in length and transmitting the encoded information using a phase-shifted signal. Carrier frequencies 10.17 can be used to transmit information; 5.09; 2.54; 1.27 or 0.64 Hz, phase modulated. Each transmitted packet contains at the beginning a clock package consisting of four SHPS, which are not found among SHPS, which encoded measurement data. The zenith, azimuth, and divergence bits are separated into different groups, independently encoded in the NPS. Information is transmitted in the following sequence: clock transmission, diverter, zenith, diverter, azimuth, diverter, additional parameter, diverter. Each diverter value is transmitted in two sequences of four bits. The value of the zenith angle and azimuth are transmitted in three sequences of four bits. The value of the additional parameter is transmitted in two sequences of four bits. In an additional channel, the generator speed, temperature, frame number of the static metering, a sign of the battery discharge of the device, or one of the logging parameters can be transmitted.

A known method of generating data packets of measurements of a cableless telemetry system during well drilling, including encoding every four bits of information with a noise-like signal of 16 bits in length, transmitting information using a phase-shifted signal, each transmitted packet contains synchronization, zenith, azimuth, rejector and an additional parameter, when This information transfer occurs in blocks containing two types of packets: a regular packet and special packets transmitted in bits (RF Patent No. 2394257, Prior November 12, 2008, published July 17, 2010, ЕВВ 47/12) (adopted as a prototype).

A disadvantage of the known method is the presence of sync, which reduces the bandwidth of the communication channel.

The present invention solves the problem of increasing the bandwidth of the communication channel and increasing its noise immunity.

This problem is solved by the fact that in the method of transmitting measurement data by a cableless telemetry system (downhole telemetry system) during drilling, including encoding and transmitting information with a phase-shifted signal in the form of a sequence of pulses, the signal is synchronized, the encoded information is received by the ground receiver, one-time (initial) synchronization phases of precision quartz oscillators of a downhole telesystem transmitter and a ground-based receiver by accumulating statistics of transition through zero and one-time synchronization of signals using a priori information of the downhole television system at the current time, for example, values of the zenith angle, gamma radiation level, vibration level, battery voltage, while the long-term synchronization stability of these generators is provided by phase correction of the crystal oscillator of the ground receiver relative to a statistically determined transition through zero of the downhole telesystem transmitter signal.

The figure shows a diagram of a device for implementing the method.

The device comprises a ground part and a downhole telesystem.

The downhole telesystem consists of blocks: a precision crystal oscillator 1, controller 2, transmitter 3, power supply 4, placed in the housing 5 of the telesystem emitting a dipole 6.

The ground part contains: an information signal receiver 7 (ground receiver), a controller 8, a computer 9, a precision crystal oscillator 10 with an autonomous power supply - a battery.

When implementing the proposed method, two precision quartz oscillators 1 and 10 are used in the downhole transmitter 3 and the ground receiver 7, which must be constantly turned on and synchronized. From the ground receiver 7, data is transmitted to the computer 9.

To transmit information, a carrier frequency in the range of 0.3 Hz ÷ 10 Hz, phase modulated by a noise-like signal in the form of a sequence of sinusoids, phase-shifted 180 ° is used.

For normal correlation signal reception, a phase shift of up to a quarter of the period is allowed. Currently, the frequency instability of thermally compensated quartz reaches 0.5 · 10 ^-6 and is further improved. The stability of thermostated quartz is still 1-2 orders of magnitude higher. At a carrier frequency of 2.5 Hz and thermally compensated quartz, the synchronization of the downhole transmitter 3 and the ground receiver 7 is maintained for more than 5 days.

Synchronization is performed only once on the surface, when the signal is not distorted by noise, in two stages: first, the signal is synchronized in phase, then synchronization occurs according to the received parameters. Phase synchronization is performed when the signal passes through zero, i.e. by changing his sign. The necessary statistics are collected for transitions through zero to increase the accuracy of the transition moment. Since the signal synchronization is maintained for days, the transition statistics can be collected over long periods. When the downhole telesystem is operating in the well, the moment the signal passes through zero is constantly monitored and the phase of the ground receiver 7 is adjusted, adjusted to the quartz generator 1 of the downhole telesystem. A number of algorithms are used that increase the accuracy of determining the moment of transition of a signal through zero, i.e. increasing the accuracy of phase synchronization. Thus, the downhole transmitter and the ground receiver are constantly synchronized.

The second stage of synchronization consists in finding the expected (known) values with a given corridor of tolerance of the zenith angle, vibration level, gamma radiation level, battery voltage and other known parameters. The coincidence of the accepted values with the expected means the completion of the synchronization procedure. At the same time, reception stability is ensured by binding to a specific current bit time of each parameter.

The difference between the proposed method and the prototype is the lack of synchronization in each block of transmitted data, and the synchronization procedure is performed only before starting work and only once according to known parameters at the current time. The stability of signal reception is provided not by receiving the clock, but by the stability of the crystal oscillators of the downhole transmitter and the ground receiver and the adjustment of their phases taking into account the zero crossing points.

In the implementation of the proposed method, the parameters are available for reception and processing immediately after any failure (lack of data under conditions of unstable reception, cable breakage at the input of the ground receiver, power failure of the receiver, ground computer failure, power failure in general at the rig), and not as a result of resynchronization , which requires time to receive the entire sync block together with geotechnological data.

Claims (1)

A method for transmitting measurement data by a cableless telemetry system (a downhole telesystem) during a well drilling process, including encoding and transmitting information with a phase-shifted signal in the form of a sequence of pulses, synchronizing a signal, receiving encoded information by a ground receiver, characterized in that they perform a one-time phase synchronization of the precision crystal oscillators of the downhole transmitter telesystem and terrestrial receiver by accumulating statistics of signal transition through zero and one-time sync ization signals using a downhole telemetry system a priori information on the current time, and the prolonged stability of synchronization of said generators provide phase correction of the quartz oscillator with respect to ground receiver statically defined zero crossing signal a downhole telemetry system transmitter.