Paper ID : 20100298 EVALUATION AND IDENTIFICATION OF WATER SEALANT PRODUCTS AS GAS BLOCK ADDITIVES FOR HPHT WELLS

Drilling through gas formations poses unique risks such as annular gas flow after cementing. Annular flow related to cementing has been credited mostly cause of poor cement bond resulted annular casing pressure in outer casing strings. When zonal isolation of gas wells is not achieved, gas can migrate behind the casing, thus charging shallow formations. These shallow gas formations become a costly problem when they are drilled into unexpectedly. They can also become a formidable challenge when the fracture gradient and pore pressure become nearly equal. In these situations, gas can broach the casing and cause a blowout. Clearly, well plug-and-abandonment is complicated when casing annulus squeeze cementing becomes necessary to eliminate gas migration. To address this problem effort has been made to identify and evaluate the indigenously available latex based water sealant products, used in large scale in concrete industry as gas tight sealant/gas block additives, applicable to oil well cementation of HPHT wells. Comparison of conventional and nonconventional gas tight additives were evaluated for specific gravity (2.1 and 2.3) cement slurries for high bottom hole temperature (BHST 145 and 175 0 C) and pressure conditions. The laboratory study revealed that 3-5% gas block latex based additives does not provide the gas tight cement slurry with conventional and non-conventional latex based gas block additives (Tapecrete, Super Latex, Raintite), even keeping the API fluid loss below 50 ml/30 min. Increase in gas block additives to 6-10% in cement slurry enhanced the capability of slurry to control gas migration. This study revealed that indigenous non conventional gas block additives gave similar results as obtained with conventional gas block additives, are techno-economic. This paper also elaborates the use of three component process to eliminate the gas migration.