Casing failure in production wells stimulated with steam presents economic and technical limitations in the application of the method. Completion of a steam injection well must be designed so that saturated steam can be injected into an oil reservoir at the desired rate, pressure or temperature and heat content. During the injection of steam, heat is lost to the surrounding well bore, equipment and the earth due to the high temperature of the steam. It is therefore desirable to design the completion so that heat loss is minimised and the casing temperature is kept low enough to prevent casing damage whilst ensuring that most of the steam goes into the productive formation. productive formation
The Upper Cruse sands of the Guapo Field have been under thermal exploitation, 'Huffing n Puffing', since August 1968 when a pilot project was initiated using a portable steam generator. Early results from the pilot indicated that economic production could be obtained from these viscous (1600 cp at 100 deg. F) oil reservoirs as production rates were increased from 15 bopd up to 100 bopd and in some cases up to 200 bopd.
As a result of the successful pilot a major expansion programme was vigorously embarked upon. Over 100 programme was vigorously embarked upon. Over 100 wells were drilled from the period mid 1971 to present and fixed generators installed.
After 3 years of 'huffing n puffing' it was found that many of the wells had parted casing and damaged gravel pack liners. To date, 15 casing and 50 gravel packed liner failures have been positively identified. packed liner failures have been positively identified. The text that follows outlines some of the procedures adopted and problems encountered procedures adopted and problems encountered and suggests principles that should be taken into account when designing steam injection - production wells of this nature.