Research Of State Assessment For The ESP Unit Based On The Statistics

ESP (electric submersible pump) is a kind of large displacement, high-head and no pole oilpumping equipment. It is one of the most important methods for making high and steadyproduction. At recent years, the ESP is very popular in each oilfield of our country. However, itsworking condition is atrocious and its cost is expensive. Once some key part exist failure, it willoccur considerable economy losses. Therefore, it has a very important practical significance totake research on the ESP unit quality reliability.By analyzing a large amount of the ESP unit failure data, the paper selects the mainpositions of the easily damaged as testing object. Combining with existing lab equipments,using advanced modern testing technique, research of vibration detection for the ESP unit intest-well are taken. Moreover, plenty of experiment data for the ESP unit are collected.The statistic theory, which is based on the probability and stat., is introduced in this paper.Systemic research that from low statistic to high statistic, from general statistic to cyclic statisticis taken based on the simulation results. The important characters of each statistic are analyzedand it is applied into the vibration state assessment for the ESP unit.Peak-peak value statistic and virtual value statistic can describe the amplitude in timedomain, so they are used for founding the relative vibration standard for the ESP unit accordingto the "3σ" principle of the probability and stat. theory. Power spectrum statistic can describe theamplitude in frequency domain, so they are used for assessing the vibration state for the ESPunit and the characters under different state are extracted. At last, bispectrum statistic,bicoherence spectrum statistic, cyclic mean statistic, cyclic spectrum density and cyclicbispectrum are also used for extracting the states for the ESP unit. The result demonstrate thatthe cyclic statistic and the high-order statistic have better resolution and include more usefulinformation than the general statistic and the low-order statistic correspondingly, so it can detectfault feature of the ESP unit more accurately and effectively. But its evaluation is still morecomplicated and the physical meaning is fuzzier, so it is difficult to formulate a uniformvibration assessment standard for the ESP unit.Finally, acorrding to the practical need of field and combining with the main researchcontents of this paper, the software system of vibration detection and state assessment for theESP unit is developed by using the abundant function tool box of MATLAB and the simplelanguage of VB. By the local test, well application effect has been gained and reliability ofsystem is verified.