Gas lift disadvantages?

1) High back pressure on sandface due to fluid in the tubing restricting production.

- e.g. lifting a well with PI of 1 bpd/psi from 10000 ft with a static bottom hole pressure of 1000 psi is difficult;

- Flowing bottom hole pressures is greater than with e.g., Electric Submersible Pumps. This leads to potential loss of reserves.

2) Gas lift is inefficient in energy terms (typically 15-20%).

3) Gas compressors have a capital cost they require expensive maintenance & skilled operations staff. However, they may already be required fir gas sales.

4) Annulus full of hogh pressure gas represents a safety hazard.

5) High installation cost can result from top sides modifications to existing platforms e.g. compressor installation.

6) Adequate gas supply required throughout project life.

- decreasing BHP, increasing water cut etc;

- sufficient gas to start up First well;

- slow start after facility shut down;

- increased gas handling requirements in facilities.

7) Gas lifting of viscous crude (< 15 ̊ API) is difficult and less efficient

8) Wax precipitation problems may increase due to cooling from cold gas injection &subsequent expansion. &

9) Hydrate blocking of surface gas injection lines can occur during cold weather if gas inadequately dried.

10) Lifting of low fluid volumes is inefficient due to gas slippage.

11) Good data management and complete network modeling required for efficient/maximum profitability operation.