Joint Meeting of the Rocky Mountain Petroleum Sections of AIME, 3–4 March, Denver Introduction It has been recognized for many years that velocity measurements in the various formations provide useful information for both geologists and geophysicists. As early as 1934, patent applications were made for a two-receiver sonic logging device. However, in the past, the predominant application of velocity measurements has been in the field of geophysical problems -not in formation logging. The interpretation of seismic records is enhanced by accurate velocity data. Now, recent improvements in instrumentation have developed velocity measurements into an engineering tool which is helpful to both geologist and engineer in oil-well completion. The modern velocity, or sonic, logging tool will still provide the geophysicist with valuable velocity data, but its more important application will be in geological studies and reservoir evaluation. Correlation problems, sometimes difficult with conventional electrical and radioactive logs, may be improved with sonic logs, however, the main advantage of sonic logs over, other logging devices appears to be the accurate detection and measurement of porosity. Equipment Description The sonic logging device described in this paper is based on a development by the Humble Oil and Refining Co. It features a two-receiver system and a short spacing (Fig. 1). The spacing used is generally 1 ft. A third receiver at an interval of 3 ft provides an alternate spacing, which can be utilized where more suitable to local geological conditions. Sound pulses are emitted by the transmitter at the rate of 10 or more per second, and the first arrival of energy at each receiver triggers the response system. The two-receiver system eliminates some deficiencies of the single receiver used on several experimental and commercial tools. In the two-receiver system, the time consumed in the passage of the sound pulse from transmitter to wall of hole, and from wall of hole to receiver, is not added in the recording to the formation transit time. This hole effect is simply eliminated by recording the difference in arrival times at the two receivers. The influence of the mud character and hole size is, therefore, negligible in this system as long as the tool is held parallel to the wall of the hole. Centralizers are provided for this purpose.
Published in Petroleum Transactions, AIME, Volume 210, 1957, pages 260–267. Abstract A formation tester run on logging cable is now available to the oil industry. It offers a method of safely and rapidly testing possible producing formations in uncased holes. These tests can be made up the hole after running the electric log. Reservoir pressure data is continuously recorded at the surface as the fluid sample is extracted. The tester may be assembled with a reservoir of 1−, 2.75−, or 55-gal capacity. A retaining pad on the body of the tool is expanded against the wall of the hole at the exact depth desired; this depth is determined by electrical log control. Two bullets are then fired through the center of the retaining pad which create a connection between the formation and a flow line to the sample chamber. When the chamber is filled, a valve is closed and the fluid sample sealed at maximum pressure. The tool is retracted to minimum diameter and brought out of the hole. Electrical circuits permit a complete recording at the surface of the mechanical operations of the tool as well as the formation pressure build-up and the hydrostatic mud pressure. The tool was introduced commercially during the latter part of 1955 in the Gulf Coasts of Louisiana and Texas. Over 1,000 operations have been made to date (Sept. 1, 1956); 50 per cent of which resulted in successful tests. Failures have been due mostly to ineffective sealing in unconsolidated sands. One major company had 41 successful tests out of 80 attempts with 23 ineffective pad seals. Results for this company were very gratifying as to pinpointing gas-oil ratios, indicating productive permeabilities and aiding in determination of fluid content where electrical log and side-wall coring information were inconclusive. Eight typical pressure curves are discussed (including misruns). Six types of fluid recoveries are interpreted. Eight actual field examples of electric logs, showing the problems solved by the formation tester, are illustrated.
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