The application of wavelet analysis in testing of subsurface safety valve

With the increase of oil and gas wells, the use of various types of subsurface safety valve is growing rapidly. Safety valve testing is an important step to check whether the safety valve is qualified. The accuracy of the test results is affected by the reliability of the test system, as well as the accuracy of the test signal interpretation and record. Therefore, it is necessary to accurately identify and record the test signal of the safety valve test system. From the characteristics of the pressure test signal of the subsurface safety valve, this paper extract the 8 nodes: pressure beginning, safety valve opening, safety valve full opening, pressure keeping, pressure reducing, safety valve closure, safety valve complete closure, pressure recovery. Among them, the full opening of the safety valve and the full closure of the safety valve are "record points". Wavelet transform method is applied to signal analysis. Biorthogonal wavelet with the symmetry is selected for Discrete Wavelet Transforming (DWT). The appropriate threshold is determined for denoising to the details of the signal. The results show that the wavelet analysis can be used to accurately identify and locate the “record points”. This paper provides an efficient and accurate method for the signal recognition of the safety valve test system.