In the fast-paced world of oil and gas, well time and cost planning is a high-stakes balancing act. With countless variables—from formation pressures and rig performance to logistics and unpredictable weather—planning a well with confidence is no small feat. 

 

Relying solely on deterministic models, which use single-point estimates, can lead to unrealistic expectations, budget overruns, and delays across drilling operations.

 

This is where probabilistic modelling steps in, offering a smarter, more transparent approach to managing uncertainty in drilling. When combined with Monte Carlo simulations, it empowers teams to navigate complexity, reduce risk, and improve decision-making across entire drilling campaigns.

Understanding probabilistic modelling in drilling

Probabilistic modelling allows engineers to replace fixed values with distributions—realistic ranges of possible outcomes based on offset data, expert judgment, or historical trends.

Drilling doesn’t follow a script. ROPs fluctuate, equipment can fail, and weather delays happen. Instead of asking, “What’s the number?”, probabilistic modelling asks, “What’s the range?”

By using distributions to represent possible outcomes, drilling engineers can model uncertainty more accurately. This shift from deterministic to probabilistic well time and cost estimates makes forecasts more realistic and actionable.

Monte Carlo simulation: test-driving your plans

Once you’ve set up your input ranges—you run a Monte Carlo simulation. Think of it as test-driving your time and cost plans 10,000 times to see all the ways the operation could go.

This simulation produces valuable outputs for each well or across an entire drilling campaign:

 

• P10, P50, and P90 scenarios for time and cost estimates (best-case, most likely, and worst-case),
• Probabilistic delivery timelines for well operations,
• Insight into the most significant drivers of variability or risk.

 

These results allow for better stakeholder communication and data-driven decisions, replacing guesswork with clarity.

From chaos to clarity in well time and cost planning

Planning a well isn’t about getting it perfect—it’s about getting it real.

With probabilistic modelling and Monte Carlo simulations, drilling and well teams gain the ability to anticipate and prepare for uncertainty. And when you do that, well planning becomes a little less chaotic and a lot more strategic.

In multi-well drilling campaigns, probabilistic modelling becomes even more powerful. Running simulations across a series of wells helps identify patterns, bottlenecks, and cumulative risks that might not be visible when wells are planned in isolation.

With a well engineering tool like iQx PLANS, automation accelerates the entire process. You can adjust inputs, rerun simulations, and update your plan within minutes. This kind of agility is essential when millions of dollars and tight schedules are at stake.

Final Thought

Well time and cost planning will always involve uncertainty—but probabilistic approach offers clarity. By embracing probabilistic modelling, supported by Monte Carlo simulation and automation, drilling teams can deliver more accurate forecasts, optimise resources, and reduce costly surprises.

 

Reach out to our team to walk you through how we’ve implemented these methods in our PLANS software — used by operators globally to improve forecast accuracy, compare scenarios, and make smarter planning decisions.