American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
This paper was prepared for the Oklahoma City SPE Regional Meeting, to be held in Oklahoma City, Okla., March 24–25, 1975. 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 presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request 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 discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.
When production from a well falls below the profitable level, usually due to declining profitable level, usually due to declining reservoir pressure, the producer must decide whether to abandon, recomplete, or begin secondary-recovery operations. Until recently, the choice was made very difficult by the scarcity of reservoir-rock information obtainable from the existing logs.
The development of new took and techniques for logging in cased holes has greatly improved this situation. A modern logging program for these old wells might consist of a Dual-Spacing Neutron Decay Time tog, a Compensated Neutron log, and, where applicable, a cased hole Formation Density log. These, in conjunction with the original open-hole logs (usually a vintage Electrical Survey or a Gamma Ray-Neutron log) permit much better accuracy and reliability in the determination of porosity, fluid saturation and in some cases the type of hydrocarbon behind the pipe.
This paper presents several examples of Mid-Continent wells which were logged by such modern techniques. In each, the cased-hole logs allowed the producer to select with confidence the most appropriate action for his well.
Developments in technique and equipment have brought a new order of reliability to log evaluation in cased holes. The key to these advances is the Dual-Spacing Thermal Decay Time device (TDT*-K). Also useful are the Compensated Neutron and Formation Density logs, which can be run in combination, and which under favorable conditions will provide good porosity determination and gas detection in cased holes.
