Ejectors are an effective tool to increase production, enhance recovery and extend the the life of mature fields. This is achieved by lowering the back-pressure on a well (or a number of wells) imposed by the downstream pipeline and process equipment.
The reduction in the flowing wellhead pressure (FWHP) will result in an increase in production. In many cases, it is also expected that the reduction in the FWHP will help to stabilise production and improve the flow regime of fluids passing through the well bore.
Each well will have its own characteristics. Some high pressure wells decline very fast, some very much slower. The good news is that even with a fast-declining high pressure well, the economics of an Ejector project are compelling. The energy can be used efficiently and effectively to boost production from a low pressure, well, providing a significant payback of extra production.
The increase in production depends on two main factors;
- The productivity index (PI) of the LP wells
The PI value is provided by the Operator, but in many cases an accurate value for the PI at the reduced FWHP is not available. The only way to establish the PI of the well at the reduced FWHP is to test the well at the reduced FWHP, using a Test Separator, for example. Alternatively, Operators can provide best-estimates, based upon their experience and understanding of their field.
- The amount of reduction in the FWHP
The achievable drop in FWHP is dependent on factors such as the HP / LP pressure ratio and flow ratio (across the Ejector) and other factors such as the type of motive flow (gas or liquid) and the amount of liquids in LP gas (in gas production applications) and, in the case of the oil production, the combined flow rate of LP gas and liquids.