The Use of Temperature Models for Well Heating and The Detection of In-Situ Combustion
Authors: El-Saleh Mudafar M. , Harmon Richard A. 
Published: December 2007

This paper was prepared for the 47th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in San, Antonio, Tex., Oct. 8–11, 1972 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 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. 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 discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Two methods of detecting ignition for in-situ combustion have been studied. The methods consider the temperature response at the ignition well when that well is either shut in or backflowed following the ignition period. A conduction-convection model of reservoir heating is used to determine the lowest temperature levels resulting from the ignition procedure. Ignition is confirmed if procedure. Ignition is confirmed if temperatures recorded by these tests exceed these minimum levels.

The conduction-convection model was also used to study the effects of two ignition process variables - air injection rate and process variables - air injection rate and heater size.

Introduction

Methods of detecting ignition of a well during in-situ combustion range from analysis of the gas composition at producing wells to measurement of reservoir temperatures at observation wells close to the ignition well. The method of backflowing an injection well in order to determine the air requirement for in-situ combustional implies that the ignition is confirmed by gas analysis. The methods of this paper consider the temperature response at the injection well in order to supplement the information gained by these other methods.

The temperature of the air injected into the reservoir during the ignition procedure can be controlled by the size of electrical heater and the air flow rate. The effects of these process variables and heat losses to the process variables and heat losses to the surrounding formation can be studied with existing conduction-convection models.

IGNITION DETECTION METHODS

Description of the Methods

Two methods of detecting ignition are presented. In the first method the ignition presented. In the first method the ignition well is backflowed and the temperature of the produced fluid is measured. This could be done produced fluid is measured. This could be done after a short period of dry combustion following an ignition period during which hot air is injected. For the second method the well is shut in immediately after the ignition heating and the temperature falloff is recorded.

The analysis of the temperature response in each of these methods is made by comparison with the predicted response assuming that no combustion has occurred. Prediction of temperature response is greatly simplified when there is no combustion. Existing mathematical models can be used to account for both conduction and convection in the reservoir and heat losses by conduction to the surrounding formation.