In old, mature fields with declining production and timeworn facility equipment, transient flow problems like slug and surge issues tend to appear during operations, especially during platform start up (PSU) processes where flowrates, pressures, and temperatures are constantly and significantly changing, which can lead to unstable production. Such situations may cause longer production stabilization time and potentially trip the entire facility if not managed properly. To mitigate this, a methodology for an integrated transient modelling advisor (ITMA) is introduced to assist engineers in determining a suitable well start up sequence at reduced risk. With ITMA, engineers can automate the determination of a well start-up sequence and simulate results of the proposed well start up sequence. This provides critical data for users to identify potential transient flow issues in advance prior to implementation. In addition, ITMA can give better clarity to operations on unseen risks that could lead to facility trips and eventually incur production loss. The ITMA we discuss here has three components integrated to work as a complete system.
First, the data retrieval step is where the most recent historical well test data are retrieved from the database, and hierarchical analysis is performed to propose the most suitable well line up (WLU) sequence. The determination of WLU is produced based on pre-set well performance priority criteria and equipment capacity constraints and the proposed WLU is passed to the ITMA simulation engine.
Second, the transient modelling engine simulates PSU scenarios based on proposed WLU. The baseline scenario can be modified to account for other factors, and multiple scenarios can be configured and tested. Some input data (such as choke opening and casing head pressure incremental versus time) can be modified before the run prior to simulation initiation.
Third, at the end of the simulation, engineers are able to obtain and visualize critical output results such as platform production rates, separator liquid level, flowline slug/surge severity, and compressor/pump trip potential via trend plots. This result can be used to evaluate potential transient issues between scenarios and finalize the most suitable plan for use.
ITMA assists engineers in planning and making proactive decisions for effectively managing PSU challenges and adding value in various areas –
Operation Efficiency: Reduces risk of facility trips/shut-downs due to surge issues and slug issues during startup/ramp up stage
Proactiveness: Improves team ability to forecast and plan for potential problems during PSU situations and make decisions with increased operability assurance
Production recovery: A system that assist operation to achieve normal production conditions from shutdown state in a stable and quick manner.
The use of such an ITMA system in designing and proactively evaluating start up procedures can help reduce the unstable production period and minimize risk of flow assurance issues and facility trips that could lead to production loss.