Abstract The potential for gas hydrate production is always present in deep water operation. It will cause hazardous impact if gas hydrate plug formed during drill stem testing. This paper takes a case from south china sea, with about 1500 meters water depth gas field, to describe hydrate prediction and prevention during drill stem testing.
This paper will discuss:
The method to predict what depth the gas hydrate may be formed in the testing string.
Procedure optimization to reduce the risk of gas hydrate
Key technique to prevent gas hydrate formation
The result of execution
The study indicated it is viable technique to predict gas hydrate formation by simulating fluid flow in testing string, as well as hydrate inhibitor selection and the amount of inhibitor can be simulated and optimized. The procedure of one flow period and one build-up period reduced the operational risk to form gas hydrate. Downhole methanol injection and closely production monitor prevented gas hydrate production. As a result of this practice, six times of DST has been successfully implemented in deep water gas field in south China sea. The well productivity and fluid sample has been accurately obtained for future overall development plan.
The result of this study are most applicable to DST design in deep water gas field, however, they also may also be appropriate for shallow water DST.