This paper was prepared for the SPE Symposium on Mechanical Engineering Aspects of Drilling and Production to be held in Fort Worth, Tex., March 5–7, 1967. 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 PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made.
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Measurements of fluid movement in boreholes have been used to determine the porosity and permeability of exposed formations and the efficiency of the mechanical conditions of completions. Until the present time, all analyses using radioactive techniques have been based on calculations dependent upon an accurate knowledge of pipe or hole diameters.
A new technique has been developed, independent of diameters, to provide accurate measurements of fluid flow in casing, behind the casing, and in the open hole. This method measures the radiation intensity of a moving slug of radioactive material in the borehole. As material is lost to the formation, a decrease in intensity is observed providing information for constructing an accurate profile. Calculations are made based on the absorption factor of the rock compared to the borehole fluid and the method of measurement of the intensity of recorded radiation. Case histories are presented demonstrating the accuracy and improvements over other techniques.
Determining of the effectiveness of well completions, stimulate, remedial and secondary recovery techniques provides the engineer with information essential to obtain maximum petroleum reserves from the formations. The most used technique to provide this information has been studies of fluid movement from injected radioactive tracers. The tracer methods have provided general information on channels, thief zone locations, and stimulation effectiveness.
To obtain more detailed information, calculations were made from velocity recordings of the movement of radioactive tracer material in the borehole using hole diameter information at each section of a well. Such information was restricted to sections of wells where accurate caliper information was available. After stimulation, the hole diameters change both in open-hole sections and cased sections, restricting accurate fluid movement analysis to inside casing or undisturbed sections of uncased bore-holes.
In wells where abrupt changes in diameter occur due to casing programs or irregular bore-holes, the hydraulic flow diameter and calipered diameters vary directly with the degree of change. This is demonstrated by laboratory tests as shown in Fig. 1. In this test, a 2-in. section of tubing was swedged to a 7-in. OD casing section.