Strength Of Oil Well Cements And Additives Under High Temperature Well Conditions

Abstract

Abstract 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 degrees to 240 degrees F. This paper presents results of tests which were designed to determine, if possible, the cause and means for overcoming this strength loss. Various types of cements and additives were evaluated in this investigation. These data are the results of tests made to date in this investigation. 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. Introduction The strength of oil well cement is usually considered to increase with increasing temperature under the normal conditions prevailing in an oil well. Only recently the fact that the strength of the cement decreases rapidly with high temperature and age was brought to the attention of the industry. The data presented in a paper, prepared by the API Mid-Continent District Study Committee on Cementing Practices and Testing of Oil Well Cements, given at the 1954 Spring Meeting of the Mid-Continent District showed that all types of Portland and oil well cements tested had much less strength when cured at 320degrees F than when cured at 200 degrees F. Also this paper contained data showing some cements had a retrogression of strength with time as the cement was cured at 320 degrees F, with some cements losing more than 50 per cent of their one-day strength after 14 days. This paper offered no explanation as to what remedies might be taken to alleviate or eliminate this strength retrogression.