Upstream production operators face an assortment of challenges when it comes to optimizing their facilities. Increased maintenance costs, geographically dispersed operations, and day-to-day production challenges all impact the bottom line for facilities. To complicate matters, the use of modern technology, including subsea tiebacks, flexible risers, and nonassociated field production, has introduced new challenges such as increased slugging, instability, and changes in the gas/oil ratio.

In other process industries, many facilities are leveraging advanced process control tools such as model predictive control (MPC) to increase production rates, decrease operational costs, and optimize facility operations . Recently, some of the more progressive upstream operators have begun to follow the lead of other industries and are deploying MPC technology in their production assets with positive results.

Small production increases can have huge benefits, and new optimization techniques that maximize production rates and enhance operations can significantly improve an operation's bottom line. Most assets enable easy implementation of MPC technology over the top of existing controls infrastructure, which can be accomplished for relatively little investment when compared to alternative improvement options like equipment upgrades.

MPC in upstream operations

As an IT-based technology, MPC is suitable for remote collaboration and multi-asset scenarios that enable more sophisticated optimization, improving productivity levels across the whole asset supply chain. MPC also can stabilize production and greatly reduce the number of production trips. As a result, it should be on the change management checklist for any facility or asset transitioning to remote operations. MPC can help optimize many aspects of facility operations, including:

Better operation of topsides, resulting in reduced backpressure and increased production at the wellhead;

Reduction in energy consumption, which significantly reduces GHG emissions and carbon tax payments; Mitigation of slugging and stabilizing production to reduce the number of topsides facility trips;

Optimization of gas lift rates in real time to achieve maximum liquid production rates per well;

Optimization of constrained gas lift supply to achieve maximum production across wells; and

Modulation of well production in excess of topsides capacity to achieve maximum liquid production in gas/condensate fields. The flexibility of MPC makes it a useful fit for many scenarios and can help facilities increase production, remotely collaborate to improve issue support, and reduce operational costs.

Advanced process control technologies for offshore production facilities help decrease operational costs and improve production. (Image courtesy of Honeywell)

Challenges in slugging

Slugging flow regimes present a constant challenge to upstream operators by creating periods of constant all-liquid or all-gas flow for equipment designed to handle a continuous, three-phase flow of oil, gas, and water. Terrain with subsea tiebacks used for production can cause this slugging regime. Changes in a reservoir production profile can do so as well by creating specific conditions for the aggregating flow, which causes slugging. Traditional ways to prevent slugging include controlling pressure pulses from risers to avoid fluid agglomeration or controlling the riser choke valve to stop gas and liquid slugs from arriving rapidly in the separator. However, MPC technology presents an alternative option and can optimize level control valves to improve the ability of separators to handle surges in volume. In any normal upstream production site, hydrocarbon material moves through the sequential stages of three-phase separation, with each separator feeding the next. Each operates at a lower pressure, evolving more gas and removing water from the reservoir fluids. Subsequent separators are typically smaller than the preceding one, which results in level control problems. Level control algorithms on the separators are typically tuned for tight level control and maintain level stability at the expense of the outflow of liquid – especially when the inflow of liquid is highly variable, such as in a slugging situation. This results in rapid level fluctuations and regular trips in the last stage of separation.

MPC technologies can balance the inventories across the separators by optimizing the level control valve position. This, in turn, can model and control the relationship between the second- and third-stage separators, which enables smoother and easier management of inventory across the process. In advance of a slug of material arriving in the separator, the MPC algorithm can reduce the level in the separators to accommodate the surge in volume without approaching any of the trip limits. This results in deferment reductions and production increases.

Providing support remotely

Upstream operations, as in any industry, need support and maintenance to continue to operate as designed. Oftentimes, applications reside in remote oil production sites, which can make maintenance a challenge. However, the growth of remote access technologies now makes it possible to virtually bring experts on site to provide issue support – no matter how far or remote the site is.This enables experts to serve more sites. Leveraging this type of technology also enables experts to provide sites with the right information at the right time to improve overall operations, and facilities can achieve several objectives, including:

Increasing worker safety by keeping personnel out of harm's way, both at the operating facility and en route to and from the site;

Improving staffing and retention through work location flexibility;

Deploying expertise over multiple operating assets and avoiding time-consuming trips to specific sites; and

Sharing best practices and centralizing expertise. Implementing remote collaboration services correctly can achieve these objectives and lead to significant increases in production, recovery, and productivity.

Remote support for geographically dispersed operations can optimize workflow at upstream facilities.

Doing more with less

Challenges associated with slugging are just one of many optimization issues that upstream facilities face on a daily basis. And production complexes are often spread over vast geographical distances and hazardous environments, so sharing best practices and receiving maintenance support can be troublesome.

With the availability of advanced process controls and remote collaboration, optimizing production and collaborating across physical distances is much simpler. Leveraging these technologies and services can help facilities improve production capabilities and mitigate operational costs while adequately addressing the challenges of diminishing resources and workforce expertise.