Abstract

Trouble-shooting technique is an important part in artificial lift technology. Based on wave equation created by Gibbs from 1970s, dynamometer card method has been applied successfully in beam pumping well's trouble-shooting technique. As for PCP wells, there's no such the same parameter as beam pumping unit's dynamometer card which could indicate systems performance directly. In Daqing Oilfield, PCP trouble-shooting technique has been studied for more than ten years. Many methods were tried, such as operating current, effective power, rod string's operating torque and axial load, oscillation frequency, etc. Application indicated that, among all the above parameters, rod string's operating torque and axial load were the most effective ones to reflect PCP system's operating status to date. However, it was still difficult to give a clear description of a PCP system without the assistance of other parameters.

This paper overviewed the development history of PCP well's trouble-shooting technique in Daqing Oilfield. A comprehensive testing and trouble-shooting system was presented consisting of a loads sensor, a wireless signal processing system and the trouble-shooting software. The diagnose model was created on the basis of PCP well's operating loads and the related production data base, which could distinguish ten types of operating status of PCP system. In the past few years, this system has been applied in more than 300 PCP wells in Daqing Oilfield. Although the compatibility of the model for different driving methods needs to be improved for a wider application(such as ASP flooding), the system has been approved to be convenient and effective in water flooding and polymer flooding area which could apply a good reference for other issues.

Introduction

PCP was used in Daqing Oilfield from 1980s. To date, there are more than 3000 PCP wells in operation. With the increment of PCP number, the requirement for PCP trouble-shooting technique has been more and more urgent in the past ten years. In the initial stage of 1990s, PCP's trouble-shooting and diagnosis were based on empirical evaluation of production data such as production rate, dynamic level and operating current, most of which were the same as beam pumping system. The problem was that none of these parameters could describe downhole system's performance directly and exactly.

Referring to Gibb's wave equation theory and dynamometer card of beam pumping system, a new trouble-shooting method was created on the basis of PCP rod sting load measuring and analysis as well. And the polished rod load measuring device was the core of the technique. From the early of 1990s, several generations of devices were developed with higher accuracy and easier application. The diagnosis theory also developed from the simple experienced judgement to more scientific models.

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