A SIMPLE RETARDER RESPONSE TEST FOR OILWELL CEMENTS AT HIGH-TEMPERATURES

A simple retarder response test for Class G and Class H oilwell cement s at high temperatures has been developed to assist with well cementin g operations. This test is based upon the Schedule 29L7 thickening tim e examination given in API Specification 10, which has a bottom hole c irculating temperature (BHCT) of 126-degrees-C (258-degrees-F). It is very discriminating and has proved to be a useful guideline for cement selection and quality control purposes. Cements giving long (200-300 minutes) and very long (above 300 minutes) thickening times are the mo st suitable to consider employing in wells at high BHCT's such as appr oximately 126-degrees-C. Cements with moderate (100-200 minutes) or ev en shorter (less than 100 minutes) thickening times may be able to be used in such high temperature wells, but the additive requirements (pa rticularly for suitable retarders) are likely to be much greater and t hus more expensive than for the cements which demonstrate long or very long thickening times under the test conditions.