Formation Productivity Evaluation From Temperature Logs

Abstract

Abstract A brief review is presented of the methods of quantitative evaluation of borehole temperature logs as applied to gas flow measurements. A method for evaluation of the formation productivity is introduced, making use of a temperature log of the flowing gas well, the reservoir temperature and pressure and the Joule-Thomson expansion temperature of the gas. A method is discussed for applying a scale to the temperature log. Its use for obtaining a better understanding of both natural and man-made formation fractures is proposed Introduction In previous work on the quantitative evaluation of borehole parameters through the use of temperature logs, Bird and others made use of a function delta of the variation of the earth's and the borehole fluid temperatures with depth. Kunz and Tixier have referred to this function as the subtangentAfter a brief review of the use of temperature logs for measuring the volume of gas flow in a borehole, this paper deals with the application of temperature logs to evaluate the mechanism of gas production. Determination of Gas Volume From a Temperature Log Fig.1 illustrates a graphical method of determining the quantity delta. This figure shows the shape of a standard temperature log in a gas producing zone. Delta is defined as where T, is for practical purposes the earth temperature, Tg, is the gas temperature and is the rate of change of gas temperature with depth. Fig. 2 is a plot of delta vs gas production rate. This figure was taken from Schonblom. The dots represent data taken in boreholes less than 5 1/2-in. diameter, the circles for boreholes between 5 1/2 to 7 1/2-in. and the squares for boreholes greater than 7 1/2-in. diameter. Schonblom, on a theoretical basis, concluded that the curve had to be discontinuous. The straight line on the left side represents the laminar portion and the curve on the right side represents the turbulent mode. Admittedly, the distribution of points in this figure looks distressing. JPT P. 301ˆ