American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the SPE-European Spring Meeting 1976 of the Society of Petroleum Engineers of AIME, held in Amsterdam, The Netherlands, April 8–9, 1976. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal, provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract The development, theory, and testing of a new device to monitor liquid production in an oil well flowline are presented. The instrument is capable of measuring either all liquid flow on two-phase slug or plug flow common in gas lift or rod pumped wells. The results of several field tests are included to show the range of the system. Basic assumptions for the Production Surveillance Monitor (PSM) to work are discussed along with its estimated accuracy and repeatability. Introduction In the author's opinion, there has long been a need for a simple device that can estimate or measure the flow in the production line of an oil well. Absolute accuracy of such a device is not a major requirement for production surveillance. Errors as much as +ten production surveillance. Errors as much as +ten percent could even be tolerated if an percent could even be tolerated if an indication of flow could be determined. Since a lot of the production in the oil field is two-phase flow, the device should indicate the total liquid portion of this two-phase flow, or estimate the total amount of liquid flow in a single-phase line. Such an instrument must be reliable and rugged so that it will not fail under oil field conditions. Our concept was to develop a simple transducer and then use complex analysis to allow the surveillance of the wells. Considerable laboratory investigations were made into many types of flow meters and flow measuring techniques. This paper reports on a new flow measuring scheme which solves the problems discussed in this paragraph. This new system uses a dynamic pressure paragraph. This new system uses a dynamic pressure transducer to measure small pressure fluctuations that can be related to liquid flow. THEORETICAL DEVELOPMENT The phenomena observed in the laboratory experiments indicated that there was a relation between the output of the crystal pressure transducer measuring dynamic pressure pressure transducer measuring dynamic pressure and the flow rate (see Figure 1). If the flow is turbulent and single phase, the instantaneous value of velocity is: (1)where U = the average or mean velocity, and u = the instantaneous variation of velocity from U. A time average of u shows that it is zero.