No definite conclusions are drawn at this time, but it appears that by the proper selection of additives for cement, strength loss with age at high temperatures can be either eliminated or considerably lessened.Recent tests have shown that the strengths of cement will decrease with increase in temperature and age above a critical temperature. The critical temperature appeared to be approximately 220 0 to 240 0 F.

This paper presents the results of firing a number of different cementing compositions to the high temperatures which are expected to be encountered in thermal recovery wells. These compositions can be handled by ordinary cementing equipment and have sufficient thickening time to permit placement in wells to at least 6,000 ft in depth.Tests were conducted at temperatures of 700°, 1,000° and 1,500° F for periods of one, three and seven days, and at 2,000°F for one day in dry heat at atmospheric pressure. Physical appearance, weight loss, shrinkage, change of permeability and compressive strength were the properties recorded or calculated.These tests showed that a cementing composition can be designed for the most severe temperature conditions expected in the the thermal recovery process. These compositions will set hydraulically at low temperatures in one to two days and will retain most of their original physical properties after being heated to these extreme temperatures.

An increase in the number of deep wells being drilled where extreme bottom-hole temperatures are encountered, and the anticipated drilling of wells where temperatures in the range of 500°F or higher may occur, has brought about a comprehensive investigation of cementing materials and of the techniques involved in their proper usage at these elevated temperatures.Included are developments in cements, retarders, weighting materials and other cement additives which make it possible to formulate a variety of compositions to help resolve the cementing problems of these extreme well conditions. The problems associated with the selection and testing of cements are discussed, and a resume of field results is included.Previous studies on strength retrogression indicate that caution should be exercised in the selection of a cementing composition for use in high-temperature wells. It now appears that, by the addition of silica flour as a stabilizing additive to certain cements, compositions covering a wide range of slurry densities can be designed to meet extreme well conditions without strength retrogression.Improvements in cement retarders make it possible to produce a four-hour thickening time at static temperaturres up to 500°F. This temperature is considerably higher than conditions presently being encountered in drilling and completion work. Inert weighting materials, used to produce 20-lhl gal or heavier cement slurries, are reviewed.

The program of water inject~on at Elk Hills into the main Shallow Oil Zone'Sand, the SS~l, has been taking place since Feb-ruary 1955. Injection wells are loeated to of a water collection system, treating and shipping facilities, the drilling of two wells and the installation of a centrifugal water injection pump. The injection phase consists of three and one-half years of aquifer injection and the successful pressure build-up in the oil band.