Managing Coalbed Methane Wells Feeding LNG Plant

Emerson’s Michael Calvert


LNGIndustry-Santos-GLNGLiquefied natural gas (LNG) facilities require careful pressure management on their incoming gas pipelines. In a recent LNG Industry article, Turn it Up (and Down), Emerson’s Michael Calvert describes the challenges and solutions around the Santos Gladstone LNG (GLNG) project.

One of the big challenges is that the source gas is from coal-bed methane (CBM) fields instead of traditional gas production wells. In these conventional gas fields:

…the wells are on pressure control. If the LNG plant shuts in, the pressure rises and the wells shut in. When the pressure drops, the wells come back online.

The approach does not work effectively in a CBM application, because:

…if the coal bed wells shut in, 20-30% of the wells will not come back online due to ingress of water at the coal bed, resulting in a shortage of supply for the LNG plant.

Another challenge is the time it would take to shut in hundreds of wells manually in the event of a major problem.

Typically it would take up to 16 hours to turn all the wells down manually, one-by-one, and Santos GLNG could not afford that kind of time.

Emerson, as the project’s main automation contractor, teamed with the engineering, construction and procurement (EPC) and Santos engineers to define the project requirements.

The solution developed used the Syncade operations management software for:

…resource management, operations optimisation, integrated information, and quality and regulatory compliance support.

The team designed the solution to:

…imitate the operator with largely manually initiation for changes. The capability for rapid shut-in was also added. In case of a field-based incident or issue, all wells on the line or in the hub could be shut-in, or set to ‘minimum gas’ or ‘minimum water.’

The well management system needed to track the produced water along with the gas to better control the amount of water produced. Other key information required included:

…well number, flow line, compressor station, minimum/maximum speed of down-hole pump, minimum/maximum pressure, minimum/maximum flow, ‘pumped’ or ‘free flowing’ well, information on water, and wells on maintenance that should be excluded.

Wells were organized into three gas-processing hubs and the well management solution required the capability to:

…make simultaneous flow set-point adjustments by priority group, potentially adjusting hundreds of wells at a time, while building in capability for local control to override the software if needed.

Santos-GLNG-ProjectBy taking an integrated operations (iOps) approach, six operators:

…control the entire gas field from Brisbane, which is hundreds of kilometers away from the field. As such, Santos GLNG’s technicians can remotely manage the turn-up, turn-down or rapid shut-in of up to 2000 wells at a time.

In addition to the Syncade software, the solution included:

DeltaV distributed control systems, and ROC units.

In testing the Well Management solution:

…within 90 sec. after a turn-down, turn-up or shut-down event was initiated, the software had calculated all new set-points and broadcasted them to the distributed control system for implementation. It would previously have taken a single operator 16 hours to manually turn down 500 wells, but the operator is now able to perform the same operation in two minutes, up to 600 km from the wells.

You can connect and interact with other oil & gas and operations management experts in the Oil & Gas and Operations Managements groups in the Emerson Exchange 365 community.

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