In an effort to determine if lithology-shales, sands, or a mixture of both-can be inferred from interval seismic velocity values, probability theories of statistical inference were applied to data from 16 wells shot for velocity information and from electric logs of the wells in the San Joaquin Valley, California, area. Average velocities, velocity functions, and probability ratios were derived for the three classes of lithology, for all data, for the two general areas, and for three individual oil fields: Wasco, Rio Bravo, and Coalinga. * Manuscript received by the Editor June 11, 1962. t Independent Research, Dallas, Texas. (Figures 1 and 2). Bravo, and GreeleyWhile the quantity of the data at hand is obviously insufficient for any absolute statistical inference, or any test of significance, the design of the experiment may be of use to geophysicists to whom sufficient data are available, in their efforts at. lithologic interpretations of seismic velocities. The mathematical conventions used in the computations are based on the addition rule, the product rule, the method of least squares, and the probability integral and error function (see, for example, DeMoivre, Legendre, Laplace, Gauss in Smith, 1959; and Mellor, 19.55).All interpretation of subsurface data requires imagination and daring, coupled with commonsense application of such inference we might develop to what we already know-. We continue to grasp at any straw which may be of help in our interpretations. Of such are probability ratiosstraws of reasonable belief based on available experimental data-no more and no less.Haskell (1941) published an analysis of the effect of increasing overburden in this area, using velocity surveys of the CWVSG. He selected five stratigraphic zones, the average velocity within each zone, and l,OOO-ft depth intervals. He suggested that 78 percent of the rate of increase of velocity with depth is due to overburden, and computed a total mean velocity gradient for this area of 0.464 ft/sec, with a maximum depth range of 13,500 ft. Our study yielded a total mean velocity gradient of 0.357 ftjsec for the Wasco-Rio Bravo-Greeley area and 0.580 ft/sec for the Coal- 46
The purpose of this study has been the interpretation of the most probable structure producing the slightly subcircular anomaly at Crosbyton, as mapped by the pendulum, torsion balance, magnetometer, and dip needle. Work was begun in 1935 under the direction of Dr. Barton, who was to have written the geological considerations. All calculations were completed in 1938, but unfortunately the geological interpretation was not written by Dr. Barton before his death, July 8, 1939. At my request, since he had discussed the Crosbyton anomaly with Dr. Barton many times, and was quite familiar with the work we were doing, Mr. Weaver kindly consented to write the geological interpretation and help me with the completion of the paper. It is due to his knowledge and able assistance that the paper has been brought up to date in the light of subsequent drilling by the Gulf Oil Corporation.
Regarding President Cox's article (September 1978 EOS, page 835): AGU membership and services have always been ‘accessible’ to women. Some of us have been members and recipients of benefits therefrom for more years than most present male members. Nonetheless, except for the challenging support of a few civilized members who have also been leaders in AGU, in our daily work and association with male colleagues we have been made to feel unwelcome, unwanted, intrusive, and downright inferior. This attitude has been doubly reinforced in AGU publications and AGU efforts to acquire and retain for members taxpayer (female and male) money for the support of male geophysicists. All protestations to the contrary, such efforts have of necessity been political. We love our work, and thanks to millions of less fortunate humans who pay the bill, we are allowed to pursue it in relative comfort.
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Abstract Flow closing coefficients and a function for prediction of orifice size, given the pressure drop and flow rate, were derived from pressure drop and flow rate, were derived from an analysis of water flow tests made on subsurface controlled safety valves. A pressure-drop function, the mass flux function, and four pressure-drop function, the mass flux function, and four Buckingham pi-number functions, were investigated, using the test data, as possible equivalents to the Bernoulli flow equation. The Euler function gave the highest probability of minimum error in prediction of the flow closing coefficients and orifice size. Introduction Subsurface controlled safety valves (SSCSV) are installed down hole in the tubing by wireline. They are frequently referred to as velocity closing valves or Storm Chokes. When they are installed in oil or gas wells, their purpose is to shut the well in when a disaster purpose is to shut the well in when a disaster occurs at the surface causing the wellhead to be partially or completely removed. The sudden partially or completely removed. The sudden increase in production rate resulting from such an event causes the safety valves to close because of an increased pressure drop across the bean or choke. This increased pressure drop acting against a differential area formed by the bean diameter and a sealing element diameter produces a force that overcomes a spring force produces a force that overcomes a spring force acting to keep the valve open during normal production. production. Fig. 1 shows a common type of SSCSV usually referred to as a "poppet type". The valve is shown in both open and closed positions. It is in the open position during normal production and is closed immediately after a disaster production rate occurs. production rate occurs. Fig. 2 shows a ball-type SSCSV in both the open and closed position, and Fig. 3 illustrates a third type called a "flapper valve" in both positions. The operating principle is the same positions. The operating principle is the same for all three valves; that is, a pressure drop acting against a differential area causes a force greater than a preset spring force tending to keep the valve open, therefore the valve closes. Fig. 4 shows the derivation of the force-balance equation. This is a general derivation and is assumed to apply to all types of safety valves although a ball type is shown in the schematic. Fig. 5 shows the position of the pressure taps used to measure the effective or valve-closing pressure drop across the valve.
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