Incubation periods and nest contents of three species of chelid tortoises in northern Victoria were recorded. Mean incubation period for eggs of Emydura macquari (Cuvier) was 75 days and average number of eggs per nest was 15.7; for Chelodina longicollis (Shaw), 138 days and 10.7 eggs per nest; for Chelodina expansa Gray, normally exceeding 324 days and 15.4 eggs per nest. In abnormal seasons C. expansa hatchlings may emerge from the nest in less than 193 days or more than 522 days after eggs were deposited. Eggs artificially incubated at 30�C consistently develop more quickly than those at lower temperatures under natural conditions. In the field nest temperatures closely approximate the mean daily air temperature. Embryos of C. expansa are tolerant to nest temperatures ranging from 4.9�C minimum to 29.6�C maximum. The other species are subject to variations of about 15 degC with up to 8.5 degC variation being recorded in 1 day. Development of early embryos approximated that recorded for cryptodire tortoises. However, there are large individual differences in the period of incubation needed for specific stages to be reached, especially between embryos of the short-necked and long-necked species of these pleurodire tortoises. It is suggested that differences in the anatomy of their eggs are the main factors in the different incubation periods between short-necked and long-necked species.
Permeabilities of cementing compositions have become of increasing interest during the last few years due to the growing use of underground reservoirs for gas storage. This paper presents data on water permeabilities and limited data on gas permeabilities for some of the more common oilwell cementing compositions. These data were obtained in the laboratory using both water and air permeameters with Hassler-sleeve specimen cells. The liquid permeameter was designed to operate at pressures up to 100 psi; the air permeameter was designed to operate at a maximum pressure of 3,000 psi. The study was made at the temperature range normally encountered in gas-storage reservoirs. Results obtained in this study indicate that, in obtaining permeability data on cements, liquid permeability tests should be run instead of gas. Also, permeability of any sort is probably not of significant importance when planning a cementing program of a low-temperature gas-storage reservoir since there is little to choose among cements as to permeability after seven days' curing time. Introduction Due to the growth in the number of underground gas-storage reservoirs in recent years, an increased interest in permeabilities of oilwell cementing compositions has been shown. When leakage of gas in storage wells is discussed, the question of permeability of cements always seems to arise. Therefore, the purpose of this study was to obtain these data. Some previous work has been done by Morgan and Dumbauld on water permeabilities of cements, but very little information could be found on gas permeabilities. This is particularly true for the wide range of cementing compositions available to the oil industry today. Questions have also arisen as to bonding of the cement to pipe and formation, and what practices should be observed in order to obtain a good bond for sealing wells in LPG-storage reservoirs. Bonding of cement to pipe has been discussed at length by Winn, Anderson and Carter in their paper. A survey of cementing practices among the companies utilizing underground storage for natural gas indicated that two types of reservoirs are being usedaquifers, or formations that originally contained water; andformations that originally contained oil and gas as well as water. In multiple-zone storage some small leaks have occurred, but investigations indicate these are located between the mud cake-cement interface where poor bonding occurs and are not due to the permeability of the cement. Nevertheless, a comprehensive permeability study of a variety of cements has been made. Experimental Determinations The two instruments used in obtaining permeability data were an air permeameter (Fig. 1) and a liquid permeameter (Fig. 2). JPT P. 851^
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