Early oilfield well testing systems included application electronics in the United States, HP 1000 logging systems from France Geological Services, and electrical testing equipment from Dresser. The application electronic system generates a series of continuous small regular pulse signals through a dedicated sensor through the well pipe connection. After the signal is converted into a sound through its equipped external circuit, the worker calculates the well depth based on the total number of sounds heard. In the application electronic system test process, the interference signal generated by the change of the network pressure or other factors such as the collision wall of the sensor is converted into sound, which results in a small accuracy of the well depth test result.
The Geological Service's HP 1000 logging system and Dresser's electrical measuring equipment use optical encoders to calculate the well depth of the double-pulse signal phase-detection phase-phase difference of 90 degrees during the rotation of the sensor. The ordinary phase discrimination method is to first latch a pulse through a D flip-flop and compare it with another pulse to determine the direction of rotation. This method has a very difficult to overcome. When the sensor vibrates back and forth in one direction, such as frequent jumps, the phase detector is often out of control and causes misdetection. If there is no software to judge the control, the cumulative error after long-term use. It is quite big. Therefore, this method must be combined with a computer to perform high-precision depth measurements.
Cables are also used to measure well depth in the petroleum industry. Taking into account the mechanical pull of the cable, flying elastic deformation, temperature, buoyancy, mud pressure, tidal effect, measurement methods and other factors, the measurement accuracy will be constrained, and many related error methods are used to correct the Sichuan. In the case where cable type, instrument weight, and mud density are known, the absolute error in cable measurement depth is a function of depth, which increases with depth. In practice, it has been found that after correction, the absolute error of the cable is about 1 / 1000, but in fact this accuracy becomes worse when the following factors occur. For example, the depth control step is not strictly observed, and the distance between the cable drum and the drill floor is not considered, or the cable is new, and permanent stretching is performed, or the scale of the depth measuring device is poor. Therefore, although many related error methods are used in the measurement to correct, the measurement results will be inaccurate due to the difference in actual operation.
Nowadays, with the development of science and technology and the wide application of computer technology, many high-precision logging equipments have appeared in foreign countries. Some scientific and technological development companies and geological scientific exploration technology research institutes in China have also designed and produced their own advanced testing equipment, such as Y. A tester, a logging tool, a dynamic gyro inclinometer, a high-precision inclinometer, and the like. These instruments are highly accurate and fully functional, allowing many of the dynamic parameters of the well to be measured at one time during the test, but their high prices make it difficult for many oilfield companies to accept.