Published in Petroleum Transactions, Volume 207, 1956, pages 59-64.
A new pozzolanic composition has been developed for cementing oil wells where moderate to high temperatures prevail. This material is an entirely different concept to other oil well cementing materials, such as portland cements, cements containing additives, or liquid resins. Its characteristics are such that it is not, at present, recommended for use at temperatures less than 140°F. It can be either accelerated or retarded across a wide range of well conditions.
This new cement is composed of a pozzolanic material, hydrated lime, and a chemical activator to give it early initial strength. This material can be used in wells from 6,000 to 18,000 or more feet where temperature conditions are similar to those along the Gulf Coast. This cement, when set, has no soluble portion subject to leaching or any compounds that should be attacked by sulfate waters or brines. For this reason, it should be permanent when placed adjacent to formations carrying any type of fluid.
The compressive strengths in 24 hours are more than adequate for wells where temperatures are 140°F and higher. These values are in excess of many other types of cementing composition presently in use in the field. This pozzolanic composition does not retrogress in strength at high temperatures as do some other types of cementing materials.
The slurry weights of this material will vary slightly according to the specific gravity and water requirements of the pozzolan itself. The materials covered herein will mix from 13.5 to 14.3 lb/gal, and will have a waiting-on-cement time comparable to other materials used under the same conditions.
Economically speaking, this composition is less expensive than either portland cements or retarded cements presently being used under deep well conditions.
Pozzolans are "siliceous material which, though not cementitious in themselves, contain constituents which at ordinary temperatures will combine with lime in the presence of water to form compounds which have a low solubility and possess cementing properties.'' The use of pozzolanic materials dates back many hundreds of years and both the ancient Greeks and Romans were aware that certain volcanic deposits, if finely ground and mixed with lime and sand, yielded a mortar which possessed special properties. Generally, the early strengths of such materials were rather weak and were considered insufficient for modern commercial usages.