Wellsite Intelligence with the Gas Lift Optimization Solution

Weatherford's wellsite intelligence includes single or dual wells for injection control and parameter monitoring. The gas lift functions are logged for retrieval by the host. Integration with intelligent desktop applications assures seamless connection between the desktop and the wellhead. Programmable well start up algorithms insure proper unloading of the well. Robust pressure heading detection provides data that assures accurate analysis, well stability determination, lift gas allocation, and production parameters.

Firmware solutions offered by Weatherford include:

• Well pad remote terminal unit (RTU)
• Various forms of continuous flow gas lift such as:
  • Injection pressure operated
  • Production pressure operated
  • Differential pressure operated

Weatherford has moved more intelligence to the remote gas lift well site to facilitate gas lift optimization. The gas lift RTU not only provides the standard monitoring and control capabilities expected in a remote RTU but also utilizes a unique heading detection scheme that detects repetitive oscillation of the injection and/or production pressures. Once heading is detected an alarm is set which alerts the central host operators to a possible problem so that they can focus their attention on problem well sites.

Benefits of Wellsite Intelligence

• Access to continuous real-time data
• Twenty-four hour local optimization
• Production increases of two to five percent (typical)
• Optimized use of available injection gas
• Well stability profile (heading detection)
• Single point interface to SCADA/MIS

Features of Wellsite Intelligence

• Eight digital inputs and eight digital outputs
• Eight analog inputs and two analog outputs
• Two RS-232 serial ports expandable to four or six RS-232/ RS-485 ports
• One AGA-3 flow calculation with AGA-8 Method 2 compressibility
• Eight channel data logger with up to 240 records-per-channel
• Supports communications via radio (licensed, spread spectrum and Cellular Digital Packet Data (CDPD)
• User programmable via Automatic Control Logic (ACL)
• Modbus scanner can be used for polling local smart peripherals to retrieve and store data. Specific support is provided for the StarPac II single-loop flow measurement and control system
• Trend buffers for injection pressure, production pressure, differential pressure and production temperature for two wells
• Heading detection on the injection and/or production pressure trend buffers
• Low power design permits solar operation where required
• Local display and keypad.

Heading Detection

Once a minute, the RTU saves the average values of the injection pressure, production pressure, differential pressure and production temperature into separate 1500 record trend buffers for each input. If two wells are connected a total of eight buffers will be used. The RTU then analyzes the trend buffers for repetitive oscillation of the injection and/or production pressures for the wells. If oscillation is occurring an alarm is set alerting the central host operator to a potential problem. The determination of this oscillation condition is called heading. Heading detection is done continuously over a user specified time window. Heading data is also captured at a daily "Gauge-Off" time.

Standard Alarm Generation

All sensor inputs are monitored continuously for failure conditions. Depending on the degree of the failure, alarms are set for a high fail or low fail condition as well as a high-high fail or low-low fail condition. This alerts the central host operator that service must be done at that well site.

Interface to Smart Peripherals

The gas lift RTU is provided with a Modbus Scanner capable of communicating with other smart devices. Specific support is provided for the StarPac II single-loop flow measurement and control system. This allows the RTU to act as a data concentrator so that a single radio can be used to retrieve all the necessary information from the well site.

Data Logger

A flexible eight channel data logger that permits logging at different sample rates on the various channels is provided that allows up to 240 values to be stored per channel. Critical values can be stored for historical review.

PID Control

A single PID control loop is provided that can use internal process parameters or a value from an external transmitter as the control variable. The PID parameters can be tuned to provide rapid control with minimum overshoot.

ACL (Automatic Control Logic)

This feature allows the operator to add custom logic to the gas lift RTU to handle special applications. ACL allows the operator to read any parameter and if a read/write parameter, it can be modified. Standard math functions including add, subtract, multiply and divide are supported. Logical operators AND, OR, XOR and NOT are available so that decisions can be made on levels or state. A simple application may be the setting of an alarm based on some special conditions.

AGA-3 Gas Flow Calculation

One gas flow calculation using the industry standard AGA-3/ AGA-8 Gross Method 2 flow calculation is supported. Current and previous days total accumulations are maintained for local and remote recovery.

Software Compatibility

The gas lift RTU uses standard Modbus protocol so that it can be used with any of the typical industry SCADA packages including csLIFT.

Gas Lift Hardware Options

Platform 1 - this currently implemented product is specifically designed to log relevant pressures and temperatures for gas lift diagnostics and optimization. It features robust data logging capabilities as well as a unique proven heading detection algorithm to enable the alarming of gas lift instability based on pre-defined user input variables. The unit also supports a wide variety of local and remote communication capabilities as well as additional I/O. The platform consists of the following:

• EXS-1000 Gas Lift Optimization (GLO) RTU
• Data logging
• Heading detection
• Remote communication

Platform 2 - this RTU combines the features of Platform 1 with the additional features of gas flow measurement and PID valve control for a single or dual gas lift well. The system supports both turbine and conventional meter run measurement calculations and, based on a pre-defined injection gas set point, will control a pneumatic valve to maintain a constant injection volume. In addition to control, the RTU has special functional parameter inputs and control algorithms to assist in gas lift operation and optimization. The components of this platform consist of:

• EXS-1000 GLO RTU with PID control functionality and gas flow calculation
• Data logging
• Heading detection
• Remote communication
• PID loop control
• Gas flow measurement - turbine or orifice
• Special gas lift functions
  • Shut in parameter based on low injection line pressure
  • Standby time
  • Start up time
  • Ramp up time during restart

Platform 3 - this RTU has the features of Platform 1 as well as special gas lift functions and is integrated with the Flowserve StarPac to provide robust data logging and remote communications. Platform components are:

• EXS-1000 GLO RTU
• Data logging
• Heading detection
• Remote communication
• Integrated with Flowserve Starpac control valve
• Special gas lift functions
  • Shut in parameter based on low injection line pressure
  • Standby time
  • Start up time
  • Ramp up time during restart

Combined with the integrated software suite, well allocation priority and overall field lift efficiency can be accurately monitored.

The integrated control package supports numerous radio communications packages and has Class I, Division II, Group D classification. Solar-cell and battery provide adequate power because of the controller's low power consumption design.

Gas Lift Overview
Wellsite Intelligence
Gas Lift Solution Specifications