Pennel Field lies in Fallon County, Montana, on the crestal portion of the Cedar Creek Anticline — the long, narrow structural high running southeast out of the Williston Basin that carries roughly fifteen separate oil fields across eastern Montana and southwestern North Dakota. Pennel has produced more than forty-one million barrels from Mississippian, Silurian, and Ordovician carbonate reservoirs, with the Ordovician Red River as its principal pay. Like its neighbours on the anticline, it is a waterflood field: low rates, long life, and production governed by injection.
The Cedar Creek Anticline was producing long before Pennel was drilled. Shallow gas was found on the structure in 1913 and oil in 1936, well ahead of the North Dakota discoveries that made the Williston Basin a major province in the 1950s. Deeper drilling into Paleozoic carbonates followed, and it revealed that the real volumes lay in the Ordovician and Silurian section rather than in the shallow Cretaceous zones that had drawn the first wells. Pennel belongs to that deeper generation of anticline fields.
Development established a stacked producing column: the Ordovician Red River, roughly five hundred and twenty-five feet thick in this area and composed of several depositional cycles from marine through supratidal facies, along with Silurian and Mississippian carbonates above it. Because those cycles behave as distinct flow units, the field has been managed as a set of separately engineered pools rather than as one reservoir. Waterflood units were established to hold pressure, and the Pennel waterflood remains the mechanism by which the field produces today.
The anticline’s ownership has consolidated repeatedly. Shell’s historic Cedar Creek position passed to Encore Acquisition around the turn of the century, then to Denbury Resources about 2010 with carbon dioxide flooding of the Red River units in view, and to ExxonMobil with its acquisition of Denbury in 2023. In the mid-1980s Meridian Oil drilled vertical wells on the field flanks that proved uneconomic — a useful reminder that not every extension of a good field is a good well.
Pennel produces from Paleozoic carbonates on the crest of the Cedar Creek Anticline: chiefly the Ordovician Red River, with Silurian and Mississippian carbonate reservoirs also contributing. The Red River here runs about five hundred and twenty-five feet thick and consists of several cycles grading from marine into supratidal deposits, so porosity and permeability are organized in layers rather than distributed evenly. That layering is why the field is developed as multiple units and why injection response varies markedly between them, even in wells only a short distance apart on the same structure.
Waterflooding has been the working method at Pennel, maintaining reservoir pressure across the Red River and the carbonates above it. In cyclic carbonates of this kind, injected water follows the most permeable layers, so recovery depends on how carefully injection is distributed between flow units rather than on volume alone. Carbon dioxide flooding of the Red River units along the Cedar Creek Anticline has been studied and planned for years as a further recovery stage. Implementation has advanced in stages across the anticline rather than everywhere at once.
A Pennel interest is a long-duration conventional asset with decades of operating history and a shallow decline supported by injection, plus the possibility of a further carbon dioxide phase if it advances on the anticline. Owners here often receive more than one payment from a single tract because their acreage participates in several units. Interests are commonly fractionalized among heirs at some distance from the property. We buy minerals and royalties in Fallon County and provide free written offers.
County-level well data, production charts, and selling guides for the counties this field spans:
Published figures place cumulative production at more than forty-one million barrels from Mississippian, Silurian, and Ordovician carbonate reservoirs. Larger totals are sometimes attached to the field in summary lists, and we would not rely on those without seeing the underlying accounting.
Because the field is developed as multiple units in different formations, and your acreage may participate in more than one. Each unit calculates its own allocation and issues its own payment, which is why owners here often see several small checks rather than one.
Carbon dioxide recovery in the Red River units along the Cedar Creek Anticline has been evaluated and held as a development option for years. It has advanced in stages rather than all at once, so treat it as possible upside rather than as scheduled activity.