Automated Gas Lift Injection System Improves Cash Flow!

Problem Area

Gas Lift operations require constant supervision to insure stable gas lift injection to all production wells.

For a gas lift well to produce at its maximum rate, injection gas must remain stable. Unstable injection rates result in:

- Reduced production from wells with too much gas
- Uncontrollable heading effects with too little gas
- Return gas venting at production facilities
- Wells loading up and unable to lift

Mechanically choking the well with a fixed sized choke is the manual method for setting an injection rate. Unfortunately a couple of common problems occur with fixed chokes resulting in unstable injection rates:
- The chokes freezes off, forcing too much gas down other gas lift wells
- a gas lift well develops downhill mechanical problems, increasing injection rates and robbing injection gas from other wells

Solution

Install a self contained electronically adjustable choke capable of adjusting gas injection rate based on actual real time gas measurements. Sentry's SCADA 3000 and Baker SPD's BTE Choke used together, continuously measure and control gas lift injection rates based on a target rate.

SCADA 3000 features both voice and data formats for real-time flows, pressures, and status. Field personnel are able to call into the unit as well as receive alarms by voice when conditions have changed at your site. Engineers can call into SCADA 3000 via modem and remotely program a desired injection rate, and review historical trending and real time status. The BTE Choke design minimizes the potential of freezing, and requires minimum torque up to 5000 psig differential. In addition top entry design enables replacement of internal parts while in the well flow line.

Equipment Operation

To automate an injection application the SCADA 3000 static and differential pressure sensors are installed in parallel to the existing mechanical recorder. If a thermowell connection is available, a temperature sensor may be installed as well. The Baker choke is installed in line or at 90º and wired directly into the SCADA 3000.

Both external power and communication are not required to automate gas lift. If communication is installed to SCADA 3000 the gas lift application can be controlled and monitored remotely.

To operate, the user programs SCADA 3000 with the desired flow rate and acceptable tolerance range. The SCADA 3000 will measure the gas flow and compare the actual rate to the target rate. If the actual flow is outside the tolerance range, SCADA 3000 adjusts the BTE Choke accordingly. Following an user defined wait time to give the altered flow time to stabilize, SCADA 3000 will recheck flow and adjust again if needed. This logic is repeated 24 hours a day, 7 days a week.

In the event the compressor goes down, SCADA 3000 will attempt to increase the choke size and after ten consecutive adjustments will stop. This logic allows the compressor to achieve the needed back pressure when it is restarted. If the choke attempts to freeze and measured flow begins to drop, SCADA 3000 will adjust the flow until the ice block clears.