Thermal neutron capture gamma rays have been observed in boreholes drilled in shales, sandstones, and limestones. A capsuled source of neutrons and a scintillation crystal detector, connected through 5,000 ft of logging cable to a transistorized, multichannel, pulse‐height analyzer, were used. Resolved peaks were identified on the basis of the known energies of expected gamma rays and results obtained in models where conditions of porosity, casing, and fluid were controlled. To properly interpret borehole spectral data a system with good energy resolution and an accurate means of energy calibration are necessary. This is accomplished by using hydrogen and iron to give prominent gamma‐ray peaks at opposite ends of the energy range of interest. On field spectra, identification was made of gamma rays from chlorine, silicon, calcium, hydrogen, and iron. On the basis of chlorine gamma rays, salt water can be differentiated from oil or fresh water. Gamma rays from iron casing are an undesirable background and reduce the sensitivity of the method compared to that possible in an uncased hole. Two examples of natural gamma‐ray spectra show well resolved lines from uranium‐radium and thorium.
A method has been developed for using a logging tool in wells with sand problems to develop information on (1) producing rates above which sand production occurs, (2) the location of the sand-producing interval in a zone, and (3) the flow rate contributions of various segments of a perforated interval. Introduction In any area subject to sand production problems, it is desirable to know what production rate will precipitate sand movement and at what formation depth precipitate sand movement and at what formation depth the sand is being produced. These questions are particularly important in multiple-completion gas particularly important in multiple-completion gas wells in which produced sand from an upper formation can strike the tubing that reaches to the lower formation. Tubing failure often occurs in such blast zones unless some preventive measure is taken, such as (1) using blast-resistant material in the tubing string, (2) using some form of sand control, or (3) restricting production rate. Knowledge of the sand-producing tendencies of the formation can be helpful in applying any of these measures. Theoretical Considerations Produced fluids striking tubing will generate noise. Produced fluids striking tubing will generate noise. Sand carried in fluid moving at a given velocity will contribute additional noise. A well log can be made that reflects generated noise per unit of time recorded as a function of production rate and depth. Relation Between Total Noise and Production Rate We assume that the generated noise is proportional to the kinetic energy of the materials produced into the wellbore per unit of time. Then(1) However, (2) and (3) Substituting Eqs. 2 and 3 into Eq. 1 gives (4) For a given toad productive interval in a well, A and L can be included with the other constants in a new constant, C2. Thus,(5) Taking the logarithm of the terms on each side of Eq. 5, then taking the derivative of each term with respect to log q, gives(6) Eq. 6 can be used to define the fluid production rate at which sand production begins. A plot of thei logarithm of Nd vs the logarithm of q for ad=1 single-phase fluid at two levels of q results in a straight line with a slope of 3 if no sand is produced. JPT P. 803
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the 49th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Texas, Oct. 6–9, 1974. 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 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 discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Emphasis on maximum petroleum production rates, operational economy and safety, and antipollution has led to the development of an acoustic sand-detection system capable of continuously monitoring the production of solid Designed to mount in surface flowlines, output from the device reflects the kinetic energy of entrained solids which, coupled with an independent measurement of velocity, can be used to calculate the rate of sand production and the mass concentration of solids in the flow stream. Such information can warn operators of dangerous erosive conditions, can help establish the maximum safe producing rate, and can confirm the effectiveness of completion practices. The "surface sand detector," practices. The "surface sand detector," formulation of results, and example applications are described. We came to the following conclusions.We have established that flow noise in the 0.65 to 0.75 Mhz band is due to solids in the flow stream.A device that is very sensitive to detection of small solids concentrations has been successfully used to establish maximum sand-free production rates for a given completion state of procedure.If fluid or gas production rates are known, the rate of sand production and concentration can be determined within a factor of 2 by the surface sand detector.Insofar as rate of metal erosion depends on the kinetics of impinging sand, the surface sand detector can provide a measure of potential erosion wear. potential erosion wear Introduction Sand production can lead to extremely costly problems, particularly in high-rate wells where down-time for even minor well or production facility repair can defer production production facility repair can defer production of thousands of barrels of oil. Yet it is the goal of all operators to establish and maintain maximum safe well producing rates. The surface sand detector described herein was developed to assist in establishing a well's maximum sand-free producing rate. The device is basically an acoustic probe, which is inserted into the flow stream. The probe responds to entrained solids and produces an output proportional to the kinetic energy of the sand proportional to the kinetic energy of the sand striking it. The detector is insensitive to flow noise and other noises, except in two- or three-phase liquid/gas slug flow. However, even in this situation, the low background slug flow noise has not prevented the detection of solids.
should provide much better oil saturation information in waterflmded cores than iS pOS-Two sandstone fields which are approaching sible using conventional core barrels. the economic limit for waterflooding were considered as locations for improved water-
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