The Evaluation of Effects of Anti Gas Migration Additive on Cement Slurry Physical and Mechanical Properties at Real Well Conditions

Formation fluid migration to the cement column is one of the most common and costly problems occurring in most gas and some oil wells, which could lead to some hazardous consequences. Some major oil companies have designed special additives to mitigate or preferably eliminate the phenomena of gas migration. With respect to most Iranian oil and gas fields, the use of anti gas migration additives is highly required. In one gas filed as a case study, despite the application of anti gas migration additive to the cement recipe, the problem of gas migration through cement is still occurring. In this investigation, the process of quality control of the additive by use of FMA utility has been done and the effects of using this special chemical on all cement properties have been studied. Results showed that adding anti gas migration additives is not the only solution to overcome gas migration problem in cements. The main key in using anti gas migration additives is to optimize additive consumption and design slurry with acceptable properties such as zero free water, total API fluid loss value less than 50 cc, early compressive strength development in less than 5 hours, right angle set pattern in thickening time test (time between 30 and 70 BC must not exceed 25 minutes) and rapid gel strength development between 250 to 500 lb/100 ft2. Fortunately, by use of special anti gas migration additive from domestic source which is called PK-90 all aforementioned criteria had been met.