On the status and application of downhole electronic pressure gauge

Abstract: The electronic pressure gauge is widely used to measure and record the value of the electronic equipment of the pressure and temperature of the layers of oil and gas fields, oil, gas, water, and other media, but also a high real-time, high-accuracy, high-resolution three high "The the wellsite pressure and temperature testing device. This paper is to start from the principle and application status of electronic manometer on the failure modes of the pressure gauge the downhole testing process often appears simple analysis of the reasons and the main factors that led to the failure of the electronic manometer and a summary of the system proposed a targeted improved method and VALID preventive measures.

Keywords: electronic pressure gauge, principle, application status, and failure modes of influencing factors, preventive measures

1 Introduction

Oil field exploration and development process, testing and monitoring of the pressure and temperature of the oil and gas fields layer oil test, trial mining work important task is also to develop a the wellsite production system to determine the yield of the well site and the cornerstone of the the calibration completion of data, so in order to properly evaluate the mineral formation of oil and gas equivalent, timely and accurately measure the oil content, the pressure and temperature of the gas-bearing value has a very important practical significance. pressure gauge and thermometer is the equipment used by the testing process, and its development has also gone from With the rapid development of electronic Electrotechnical initial low accuracy, a single species of pure mechanical structure to the complex changes in the electronic structure. has a high-precision, high sensitivity, high integration performance electronic manometer mushroomed. Currently, the National major oil fields is widely used electronic manometer up to dozens, many manufacturers of the manometer, complex models, different instrument battery detection, identification and mode of operation, in the course of very confusing. In addition, in the mineral layer of oil and gas exploration and development in the production process, the electronic pressure gauge long-term work in the harsh environment, coupled with the selection of the instrument properly, the performance of the components are not reliable and human operational errors can cause electronic manometer failure, and even lead to the failure of the trial mining process. downhole electronic pressure gauge failure analysis and prevention has a very important practical significance.

2, the working principle and performance indicators


2.1 works electronic manometer is a major high-precision electronic instruments used in the oil and gas field seam measurement of pressure and temperature values. Its core components of pressure and temperature sensors, due to poor working conditions and changing pressure gauge, the sensing element making the need to use the deep downhole high-temperature, high-pressure special materials to ensure the accuracy and reliability of the electronic voltmeter under the joint effect of pressure and temperature of downhole formation according to the principle of strain bridge pressure sensor and a temperature sensor, the oscillation circuit of the manometer, the the seam pressure value under test, the temperature value converted to resistance values ​​and the voltage of the circuit system identification value, by the oscillation circuit for the entire frequency conversion to the computer identifying the frequency of the current value signal, and then translated into correction processing via software, the downhole pressure and temperature data of the tester needs to be seen from the above composition principle, the core circuit of the electronic manometer of contains two measurement circuits: a pressure measuring circuit and the temperature measurement circuit.

2.2, the performance technical indicators electronic pressure gauge with high sensitivity, high accuracy, high reliability, performance, technical indicators are as follows:
2.2.1, precision manometer when no error of the ideal state, a manometer of the standard curve should be one curve, but affected by many factors in the formation, the actual map of traces of the manometer for the quadratic or cubic curve. under normal operating conditions, a pressure gauge measuring the accuracy allowed error is +-4psi.

2.2.2, hysteresis Hysteresis refers manometer the maximum difference of the data, hysteresis error manometer sensor uses material from both directions close to the same target measured value in the measurement process, manufacture and installation level and use the environment under normal operating conditions, the pressure gauge allows the hysteresis measurement error of ± 2 psi.

2.2.3, repeatability repeatability error is the pressure gauge in the whole measuring range and under the same working conditions, the same operator on the same input pressure value from the same direction for several consecutive measurements obtained by random error, repeatability error and manometer formation and sensor materials. the repetitive measurement error under normal operating conditions, the pressure gauge allows for +-3psi.

2.2.4 Resolution Resolution refers to the amount of change value of the target pressure when the measured value change, a pressure gauge can be identified by the smallest input under normal operating conditions, a pressure gauge resolution 0.02psi.

3, the electronic manometer application status


3.1, electronic manometer classification


Electronic manometer can be divided in accordance with the well testing, well logging technology the ground direct reading electronic manometer, underground storage electronic manometer and new direct-reading electronic manometer.

3.1.1, the ground direct reading electronic manometer the ground direct reading manometer direct-reading test technology refers to the use of the ground electronic manometer been logging a total invested along with the logging tools after docking into the signal cable from the wellhead, The electronic manometer the measured seam of pressure and temperature changes is transmitted through the signal cable to the computer system on the ground, on the computer display by operating software, reads out and were processed and analyzed in real time on the data of the measured ledge.

3.1.2, underground storage the electronic manometer underground storage manometer is the test by the SCM system, underground storage storage logger and power supply battery with integrated electronic pressure gauge bundle and accompanying test tool inputs are logging pressure and temperature changes stored in the memory storage logger microcontroller system the electronic manometer induction acquisition stored procedures in accordance with pre-set to the ledge after the end of the test tasks, the electronic manometer removed from the wellhead and computer connected to the system will be in accordance with a predetermined operating program stored pressure and temperature data logger for playback.

3.2, the failure of electronic manometer electronic pressure gauge needs long-term use in high pressure, high temperature and other harsh geological conditions, together with its components is easy to aging, these external factors and internal factors that can lead to the manometer measurement error. oil test, trial mining process manometer accuracy, resolution and stability parameters have higher requirements, so using the larger measurement error in the process will make a serious deviation from the actual value of the measurement value of the pressure gauge, resulting in the failure of electronic pressure gauge manometer lead to failure in the course of the main reasons are the following:

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(1, unstable performance of the core components of the electronic manometer pressure sensors, temperature sensors, microprocessors, memory, main components of the circuit: signal amplification circuit data conversion circuit, oscillation circuit. these electronic components and circuits will lead to the failure of the electronic manometer rattling.

(2), immature and circuits of the measurement data disorders electronic manometer Data Interface Operation Software built-in battery energy will cause the pressure and temperature data collected by the manometer and the test time corresponding to the non-sexual relations, such Moreover called electronic pressure gauge data disorder.

(3, non-point electronic manometer another VALID form non-point, is a the manometer the collected data, i.e., temperature values, the pressure value serious distortion, a significant deviation from the normal, resulting in distortion of the manometer measurement curve. in the actual testing process, there are two kinds of non-point form: one can be amended by deleting part of the distortion point and non-point normal test curve minority, another can not modify, delete points and other technical means to eliminate the influence non-point normal test curve. former non-point can be called mining point deviation latter case we call non-point failure of the electronic manometer.

(4, the data is not written to or has not wholly disposable electronic manometer data processing core components with fixed storage capacity of the microprocessor, thus in programming manometer hardware, must be reasonable set the timing of the counter and considering the the register storage capacity, so that the system is capable of sequential read and write in the planned acquisition time, at the same time to ensure that the number of data deposited prevent overflow, to avoid the failure of the test.

(5), and the the overrange overrange use is another cause of failure of the electronic manometer before testing choosing a suitable pressure gauge logging segment conditions may cause damage to the sensor in the process of testing Sham Tseng which led to the failure of the electronic manometer.

(6), the power supply apparatus of the electronic manometer of the battery passivation is usually high temperature lithium batteries, while at the factory in order to prevent the battery from natural discharge to be formed in its characteristic surface layer of passivated protective film, but this characteristic of the lithium battery cause to measure downhole data at both the low voltage instability is often caused by mining point exception, even to the point of failure can not be repaired and data disorder.

(7), leaked from a technical analysis leaked main factors led to the failure of the electronic manometer. Downhole pressure gauge in the practical application of the process three prone to leaking phenomenon: The first is near the sensor on pressure points, followed by sealing the core circuit board sealing positions, third at the the instrument logging rope connected part. guide pressure point near the seal by the manufacturing process to ensure that, usually in high-precision machining center, through a well-designed structure parameters, to ensure the guide pressure point near to withstand the high pressure of the underground without leaking a sealed chamber with the O-ring seal technology, the same high-precision machining, to ensure Sham Tseng pressure capacity of the pressure gauge; instrument with rope connection part is the most prone to leak place during the installation process instruments and wire connection, we usually call it the "armored" This process must ensure that the following points:
a rope instrument signal connections must be flexible connection, and not subjected to axial tension.
b, anti-the normal rotation device, to avoid signal connection is broken, between the rope and the instrument.
c, wire rope, and the instrument is connected points should be sunk in the insulating filler material, the external pressure can only be applied to the filler material, and ensure that the electrical signal with an external insulation.

(8) human factors human factors of electronic manometer has two main aspects: First, the novice operation resulted in the the manometer assembly process parts damage, electronic pressure gauge is a precision instrument, so for the operating level of the testers and expertise requirements are relatively high. during transport due to improper care caused by the disorder caused by damage to the internal circuitry of the instrument data and data not adopt the whole phenomenon.

4, failure prevention measures


4.1, due to the more sensitive electronic pressure gauge for the formation of high temperature, high pressure and severe vibration, in order to reduce the sensor instantaneous force strength, designers should set a pressure buffer device in the circuit of the hardware or software systems. Addition to high temperatures, with sulfur strata should change manometer sealing structure to prevent the leaks caused by corrosion and damage of the cable, the circuit and sensor member.

4.2 choice of appropriate scale, in accordance with the preferred match and performance characteristics of the pressure gauge, pressure gauge of appropriate storage capacity. Due to instability manometer performance, selection should be consolidated and reliability of product problems can arise in the course of analysis, the complementary combination. example, for a sampling point density is relatively dilute well area, generally used in low storage capacity manometer measured gas and fracturing of wells is generally used in a large number of process plant due to the sampling point more high storage capacity manometer. generally used for special well-type deep well and deep well fracturing process high accuracy, good seismic performance SPAR manometer, and measured gas wells, associated as well should be used DDI, the SEI new electronic manometer .

5 Conclusion:

Understand and analyze electronic manometer works, performance indicators and failure modes of rational selection with pressure gauge, to ensure the maintenance and calibration of the instrument in place to improve the success rate of electronic pressure gauge downhole test, the actual test mining process already achieved remarkable results. various failure modes of electronic manometer well supporting the process of design and innovation, is constantly effective way to full potential in the oil and gas test mining mining test instrument. Currently, due to the the electronic manometer test technology and processes in complex geological formations are not very comprehensive, so we still have to strengthen theoretical study work and study in the future, continue to accumulate experience and optimize the design for oilfield exploration and developed to provide more effective technical support.

References:

[1] Jia Shih Hsin. The oil test mining process, Beijing: Petroleum Industry Press .1999.8.1
[2] Feng Chao. Electronic manometer, Zhejiang: Electronic Industry Press 2003
[3] Han Jian. Electronic Technology, Beijing: Chemical Industry Press .2004.6.1

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