Fairway

Key Takeaways

• Basin-scale petroleum system fairways are defined by the geographic intersection of the mature source rock kitchen (the area where the source rock has reached sufficient thermal maturity to generate and expel hydrocarbons), the effective carrier bed or fault network (the migration pathway connecting kitchen to trap), and the viable trapping configuration (where structural or stratigraphic closures exist in carrier bed-connected reservoirs); the fairway is the area within which all three elements are simultaneously present and correctly configured; source rock kitchens are mapped from burial history modeling constrained by vitrinite reflectance data and calibrated to regional seismic-well ties; migration pathways are inferred from the dip of carrier beds, the connectivity of fault networks, and hydrocarbon shows in wells along the expected migration corridor; the fairway boundary is drawn at the point where any one of the three elements becomes marginal or absent: the edge of the mature kitchen, the stratigraphic pinchout of the carrier bed, or the limit of structural closure; areas outside the fairway may have individual favorable elements but lack the full petroleum system configuration needed for a commercial accumulation.
• Unconventional play fairways for shale and tight formation resources are defined by a different set of parameters from conventional exploration fairways, because in unconventional plays the petroleum system elements of source, reservoir, and trap are all contained within the same formation rather than being spatially separated: the key parameters defining the unconventional fairway are total organic carbon (TOC, minimum typically 2-4% for commercial shale gas, 3-6% for liquids-rich shale), thermal maturity (vitrinite reflectance Ro, with the dry gas fairway typically above 1.2%, the liquids-rich window at 0.9-1.2%, and the oil window at 0.6-0.9%), net pay thickness (minimum productive interval thickness, typically 50-150 feet for commercial resource plays), reservoir quality (porosity, permeability, brittleness index from mineralogy that determines hydraulic fracture propagation efficiency), and current-day reservoir pressure (overpressured zones typically outperform normally pressured zones due to higher gas-in-place and better initial production rates); the intersection of all commercial thresholds for these parameters defines the sweet spot fairway within the broader geographic extent of the formation.
• Stratigraphic fairways in conventional exploration define the geographic limit within which a specific reservoir unit maintains the porosity, permeability, and net-to-gross ratio required for commercial production, bounded by facies changes rather than structural limits: fluvial channel sand fairways (the downstream extension of a sand-filled river valley or deltaic distributary channel system, within which channel sands of sufficient thickness and quality to form a commercial reservoir exist at the target depth) are classic examples, as are turbidite channel fairways (the laterally confined corridors within a deep-water fan system where channelized turbidite sands are thick enough and well enough connected to form a producible reservoir); the fairway boundary in stratigraphic plays is often gradational rather than sharp, as the reservoir quality deteriorates laterally as the facies transitions from proximal (coarser, better-sorted) to distal (finer, lower quality), requiring a net-pay cutoff to define the commercial edge of the fairway; mapping stratigraphic fairways requires dense well control or high-quality seismic facies analysis to track facies changes that may not be expressed as structural features on conventional time-structure maps.
• Fairway ranking and prospect generation within the fairway proceeds by identifying individual prospects (specific drilling targets with defined trap geometries and estimated resource volumes) within the statistically favorable area and ranking them by their probability of success (Pg) and expected net present value (NPV); the fairway concept provides the basis for portfolio management in exploration programs by defining the geographic area within which drilling capital should be concentrated, the total number of drillable prospects within the fairway (the inventory), and the statistical expectation of how many of those prospects will be successful given the assessed Pg values; a fairway with 20 prospects each with Pg = 0.25 provides a statistically diversified portfolio with a high probability that at least some wells will succeed; concentrating drilling outside the fairway (in areas where Pg is systematically lower because a key petroleum system element is marginal or absent) reduces the expected value of the exploration program without a compensating reduction in drilling cost.
• Fairway evolution over the life of a basin reflects the accumulation of geological knowledge from drilling results: the initial fairway definition is based on the geological model and analog basins, with significant uncertainty in the boundaries; each well drilled within or near the fairway constrains one or more of the key parameters (source rock richness, migration efficiency, reservoir quality, trap seal integrity) and either confirms the fairway as mapped or requires its boundaries to be updated; dry holes outside the fairway that confirm the geological reasoning for excluding that area increase confidence in the fairway model; discoveries inside the fairway that confirm expected petroleum system elements provide confidence that the remaining prospects within the fairway have similarly high geological potential; wells that fail inside the mapped fairway (due to unexpected sealing failure, reservoir quality deterioration, or trap breach) require analysis of whether the failure reflects a local geological heterogeneity (leaving the fairway model otherwise intact) or a systemic misunderstanding of one of the petroleum system elements that requires redrawing the fairway boundaries for the entire play.