American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Improved Oil Recovery Symposium of the Society of Petroleum Engineers of AIME, to be held in Tulsa, Okla., March 22–24, 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 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 A nuclear logging method to determine the presence of hydrocarbons behind casing regardless of water salinity has been developed. This log, referred to (is the Carbon Log or Carbon/Oxygen Ratio Log, is commercially available on a limited basis in the United States and Canada.. For most of us in the oil production industry, the Carbon Log principle, including the technique, terminology and method of operation, is new. This paper is written and presented for those who desire an introduction to Carbon Logging. The intent of this paper is to cover the basic nuclear principles involved, instrument operation and how use is made of the nuclear reactions. Examples of interpretation techniques for the determination of oil saturation, lithology, salinity and the presence of gas are shown. Introduction The nuclear reactions from which the Carbon Log measurements are obtained are not new. Reactions that occur when certain elements are bombarded with high energy neutrons are well documented. Fortunately, a number of the elements that are present in the rock matrix and the fluid contained therein do react in some identifiable way to neutron bombardment. The Carbon Log is made possible due to the fact that Dresser Atlas has a monoenergetic neutron source that can be controled so as to provide a desired amount of neutrons in periodic bursts, i.e. the neutrons produced are of one specific energy level---14.2MEV.
For many years, wireline tracer surveys have been used to determine the height of fractures created during hydraulic stimulation procedures. A recent advancement in fracture evaluation technology has been to tag different stages of a fracture operation with multiple radioactive tracers, providing the capability to discern between created and propped fracture heights in one or more zones of interest. In this research, a wireline instrumentation and data analysis system is implemented to identify and separate the individual yields from multiple radioactive tracers, with an additional feature that determines whether the tracer material is inside of the borehole or distributed throughout the created fracture zone. A single postfracture pass of the logging instrument is used to accumulate gamma ray spectra at each 7.6 cm interval along a borehole. A weighted least‐squares spectrum unfolding algorithm calculates the radioactive intensities as a function of depth, while the peak‐to‐Compton down‐scatter ratio determines the proximity of the tracer material to the wellbore. Field examples illustrate the effectiveness of the system for the evaluation of multistage fracture operations.
1978 Rocky Mountain Regional Cody Wyoming May 17–19, 1978 Abstract A new pulsed neutron logging technique has been developed to unambiguously identify the presence of the element carbon. The Carbon/Oxygen Log is currently available on a limited commercial basis in North America and has been tested under a wide variety of field conditions. This paper covers the theory of the log's response and shows examples of what is available in the way of taped output. The basics of interpretation by a simplified pattern recognition technique are reviewed along with test pit measurements and verified field response. pit measurements and verified field response Introduction During the past three years, a Carbon/Oxygen logging device has been commercially available and has been used to survey several hundred wells. Despite the fact that a great many of these applications have been made as a "last resort" when definitive answers could not be derived from other more conventional logging methods, the device has scored a very high success ratio in predicting the type of fluid ultimately produced. Also complicating these initial efforts is the fact that development and improvement of the instrumentation has been continuous over this period of time and even now, a significant advance is on the verge of commercial introduction. The Dresser Atlas Carbon/Oxygen Log is made possible by an electro-mechanical device that can be pulsed in extremely short, concentrated bursts of 14 Mev neutrons and a detector system that can selectively discriminate and count the high energy gamma rays that result from the inelastic collisions of these neutrons with the atoms of carbon and oxygen. Figure 1 schematically reviews the source and time frame of neutron bombardment induced gamma radiation. Note that the inelastic or prompt gamma rays exist only while the very high energy neutron source is on and for a very few microseconds following the cessation of the pulse. From this period of time until the neutron source is reactivated, only gamma rays of thermal neutron capture, and to a lesser degree, activation gamma rays, are present. This is an extremely important point, as the 4.43 Mev inelastic carbon gamma ray is the only unambiguous nuclear indicator of that element in nature.
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. 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 Formation evaluation of clastic formations in Cased Hole uses the principals and logics of Sandstone II and Complex Reservoir Formation Analysis. Included in the Program are analysis from Open Hole Surveys, when available, along with analysis of the Carbon Oxygen Ratios, Silicon Calcium Ratios, Gamma Ray, Silicon, Calcium, Compensated Neutron, Neutron Lifetime Sigmas, near detector curve from the Lifetime Log, and for detector curve from the Lifetime Log measurements. The Cased Hole Clastic Evaluation will allow analysis of possible hydrocarbon bearing zones regardless of water salinities through casing. Matrix constants, formation salinities, clay volumes, formation fluid parameters, i.e., water, gas, and oil, are determined from comparison of a series of checks and balances of the survey responses and their material balance equations. The analysis is presented in analog form along with a printed report and commentary. Examples are shown from the Gulf Coast, California, Red Desert, and East Texas of the analysis along with tested results. Introduction Evaluation of clastic formations in cased holes uses pattern recognition in (addition to the principals and logic of Dresser Atlas' evaluation programs for Sandstone and Complex Reservoir formations. The evaluation technique allows analysis through casing on possible hydrocarbon bearing zones regardless possible hydrocarbon bearing zones regardless of water salinities. Data are utilized from Gamma Ray Logs, Silicon/Calicum (Si/Ca) ratios, Silicon/Calcium (Si/Ca) continuous curves, Carbon/Oxygen (C/O) ratios, Inelastic Neutron Logs, Compensated Neutron Logs, Dual Detector Neutron Lifetime Logs and open hole surveys. Matrix constants and formation salinities are determined from crossplots. Shale volume parameters are calculated. Then the data is parameters are calculated. Then the data is compared in a series of checks and balances using crossplots of porosities that are shale volume corrected. Data output is in analog and tabulated form. The analog plot is the Cased Hole Exploration Service Epilog, (Figure 8C). Displayed on a four track grid, the curves are recorded as follows: Track I Lithologic characteristics - Shale% of Bulk Volume, Permeability Index, and C/O Ratio measurements.
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