For refineries, terminals & downstream operators
Every barrel. Every movement. Accounted for with
OAS connects your operations, scheduling, and accounting teams in a single system so nothing falls between the gaps.
The industry's leading refineries and downstream operators run on OAS.
When a refinery or terminal can't afford to lose track of a barrel, they choose OAS. Trusted by global majors and independent operators across three continents.
Learn HowFrom the first nomination to the final mass balance in one system.
Meet Maron Systems
OAS brings your operations, commercial, and accounting teams onto a single platform. No re-keying. No version conflicts. No gaps between the numbers your teams are looking at.
- Operations, commercial & accounting in one live view
- Modular by design, deploy the modules that match your operation
- Proven across 150B+ barrels of storage capacity globally



See what Maron can do for you.
Get Started
Explore how our software fits your workflows, teams, and existing systems — and how it can reduce risk, loss, and time to insight.
Where shipping, inventory and accounting
OAS
One live operational picture
Shipping, inventory, and accounting on the same screen. No more chasing figures across systems.
Decisions in real time, not next morning
When demurrage risk or stock variance emerges, OAS surfaces it. Before it costs you.
Fits how you already work
OAS connects with your existing ERP, trading, and port systems. No rip-and-replace required.
OAS
Less time reconciling. More time running your operation.
Nomination to Delivery
Close invoices faster. OAS tracks every movement from nomination through delivery with measurement data already attached, no chasing required.
Inventory Clarity
Actual stock, planned stock, and ownership - all visible, all sites, in real time. Know exactly what you have before someone asks.
Smart Scheduling
Berth conflicts flagged before vessels arrive. Drag-and-drop scheduling with built-in constraints, so your plan doesn't fall apart at the jetty.
Actionable Insights
OAS puts your KPIs, demurrage exposure, and shipment trends in one view, so management reporting takes minutes, not a morning.




Our Customers
See what our customers are saying
50% demurrage reduction, year one
OAS improved marine scheduling clarity and discipline across our operation cutting demurrage by 50% in the first year.
One version of the truth
Data now flows seamlessly across trading, shipping, and refining. The spreadsheets and the errors are gone.
A decade of continuous improvement
OAS has been a key part of our continuous improvement process in shipment handling and stock accounting for over ten years.
Our Blog
Blog & Articles
European Refineries Are Running Out of Time to Fix Their Oil AccountingÂ
European refineries are not operating in the same environment they were three years ago. More than three months into the Strait of Hormuz disruption, global oil supply has tightened significantly. Inventory buffers across multiple countries are eroding, with some approaching critical levels [S&P…

Maron & bp Castellón Project Spotlight: Bio-Feedstock Traceability for Customs Compliance
At bp Castellón, import duty classification on bio-feedstocks represents a significant and recoverable cost. The refinery uses biowaste-derived feedstocks — used cooking oil (UCO), soybean expeller oil (SBEO), and palm oil mill effluent (POME) — as inputs for HVO and…

Refinery Demurrage: Are You Solving the Right Problem?
A vessel runs over laytime. A claim arrives. It gets processed and closed. That’s usually the full arc of a demurrage event. That cycle is expensive because it feels manageable. Treating demurrage as a cost to handle rather than a problem to diagnose…

