How to measure piston flowmeter

Contents

The invention belongs to the technical field of measuring the flow rate of associated gas produced by crude oil wells and wet gas produced by natural gas wells, and the invention relates to a measuring method of a constant volume pipe piston type wet gas flow meter for natural gas.

Background of the Invention

In most cases during the exploitation of oil and gas fields, the production of natural gas is always accompanied by the production of liquid hydrocarbons, free water and saturated water vapor. Therefore, wet gas metering is involved in the process of natural gas from single-well exploitation to multi-well gathering, purification, and pressurized transportation. Since the production measurement of a single well is closely related to the economic interests of the exploiter, and the metering data of a single well is also important data for the oil and gas field management to understand the production capacity and production status of the gas well. Therefore, improving the accuracy and reliability of wet gas metering has also attracted more and more attention from major oil companies in the world. Since the early 1990s, the International Gas Flow Laboratory and major international oil companies have successively carried out relevant research on wet gas metering technology. Wet gas metering technology has experienced more than 20 years of development. Developed countries such as Europe and the United States, especially the United States and Norway, have made some achievements in the research on the accuracy, stability and versatility of wet gas flow meters, and have gained a lot of experience in the selection, testing, calibration, use and maintenance of flow meters and the applicability of various working conditions. Daqing Oilfield in my country also conducted research on wet gas metering technology at the end of the 20th century, and some scientific research institutions and flow meter manufacturers also conducted research in this area on a small scale.

Generally speaking, natural gas that has been dehydrated, purified and recovered from light hydrocarbons to extract liquefied gas and light oil is called dry gas. Untreated natural gas extracted from oil and gas fields often contains a small amount of condensate water or oil, saturated water vapor and light hydrocarbons, and contains droplet components, which is called wet gas. Wet gas belongs to the category of multiphase flow. Compared with single-phase flow, wet gas metering technology is more complicated and difficult. The main reasons are as follows: the flow pattern of wet gas in the pipeline varies due to the gas pressure, flow rate, liquid content and pipeline installation position (horizontal, inclined or vertical) in the pipeline, and the flow pattern is relatively complex; the on-site working conditions of wet gas metering vary relatively greatly. If the flow meter is not selected reasonably, it is easy to cause the flow meter used to be unsuitable for the working conditions of the metering site, and even cause damage to the flow meter; most of the flow meters used for wet gas metering adopt the offline calibration method, but the calibration medium and working conditions of the general calibration or calibration laboratory are very different from the actual medium and working conditions, making it difficult to guarantee the metering performance of the flow meter on site.

In recent years, although some flow meter manufacturers have developed some types of wet gas flow meters (or multiphase flow meters), the current wet gas measurement at home and abroad still mainly adopts the traditional one-way flow technology. Due to the existence of liquid phase in the pipeline, the flow state in the pipeline seriously affects the metering performance of the flow meter. According to the latest experimental research, the maximum metering error can reach 15%.

Summary of the invention

The object of the present invention is to provide a measuring method of a constant volume pipe piston type natural gas wet gas flow meter which can overcome the influence of a small amount of liquid droplets contained in the natural gas mist fluid on the natural gas wet gas flow metering.

In order to solve the above problems, the present invention provides a measurement method of a constant-capacity piston-type natural gas wet gas flowmeter, wherein the flowmeter includes a constant-volume cylindrical metering tube with a built-in piston that can move up and down; two electric valves are connected to each end of the metering tube to control the reversal of intake and exhaust, and the metering tube can be controlled to respectively realize the metering of lower intake and upper exhaust, as well as the metering of upper intake and lower exhaust; the metering tube is also equipped with a temperature and pressure transmitter to realize the volume flow measurement of the natural gas wet gas.

Compared with the prior art, the present invention has the following technical effects: the constant volume tube piston type natural gas wet gas flowmeter provided by the present invention is a flowmeter based on volume measurement, which can overcome the influence of the mist fluid of a small amount of droplets contained in the natural gas on the measurement of the natural gas wet gas flow rate. Therefore, the measurement process is independent of the physical parameters of the measured natural gas wet gas and the flow parameters such as flow velocity and flow state. The measured flow rate is not easily affected by flow fluctuations and has higher accuracy.