Issue link: http://yearbook.epmag.com/i/671218
ARTIFICIAL LIFT TECHBOOK: CASE STUDY 38 | May 2016 | hartenergy.com and ratio/volume computations for variables like injected gas lift, wellhead casing/tubing pressure, wellhead output volume, gas-to-liquid ratio and others. Emerson also offers automated well test solutions to support the data requirements for a GLO. Periodic well test data for each well at different gas-lift fow is the key to obtaining good results from a GLO. The well test data need to be validated by an experienced production engineer or equivalent before it is sent to the optimizer. A GLO has a scheduler that can trigger well test notifcation. It has the capability to determine which wells are fow- ing freely, lifted by gas or shut in. This is essential to allocate avail- able resources. The GLO solution builds on the real-time-data foundation and includes an online multivariable optimizer that handles complex- ities like dynamically changing operating constraints for all wells located in the area (Figures 4A and 4B). The objective is to maximize operating margins for the entire area by equalizing incremental costs for each well vs. lift gas con- sumption. What that means in simple terms is that no improve- ment can be obtained by moving an increment of lift gas from one gas-lifted well to another. The optimizer dynamically allocates available lift gas to each well based on overall proftability while hon- oring all constraints. For example, the gas-lift allocation between the wells is changed automatically in response to changes in constraints such as reduction in gas-lift supply or water disposal capacity. If the available supply is further limited, the optimizer reprioritizes the wells and the lift gas is reduced from the lowest least marginally proftable wells and reallocated to the most marginally proftable. Abnormal events, such as blockage resulting from fow line freezing or hydrate formation, are detected and the gas-lift allocation is automatically adjusted. Emerson's GLO solution also includes a simulator module that compares simulated per- formance vs. actual performance for each well to fag excessive deviations. The GLO solution, which might include valves, measurement devices, hard- ware, software and services, is customized for each site and is easily integrated with any existing auto- mation infrastructure. n Production rate Injection rate WELL #3 WELL #4 WELL #1 WELL #2 Optimal gas distribution FIGURES 4A and 4B. Emerson's GLO solution builds on the real-time-data foundation and includes an online multivariable optimizer that handles com- plexities like dynamically changing operating constraints for all wells located in the area.