Hartzog Draw Field, discovered in 1975 in the Powder River Basin of northeastern Wyoming, is the largest known accumulation in the Upper Cretaceous Shannon sandstone. The field is long and narrow — roughly twenty-two miles by one to four miles — because it follows a buried sand-ridge complex deposited on an ancient marine shelf rather than a fold. It was unitized in 1980, drilled on one hundred and sixty acre spacing, and has been waterflooded since, making it one of the basin’s few large conventional flood units.
The 1975 discovery came late in the era of conventional Rocky Mountain exploration, and it was a genuinely different kind of target. Rather than testing a structure, operators were chasing a stratigraphic body — a shelf sand ridge encased in marine shale at roughly nine thousand feet. The find defined the Shannon as a play in its own right in the Powder River Basin, and the field’s narrow, sinuous outline on a map still looks unlike the rounded anticlinal fields that dominate Wyoming’s earlier oil history.
Development followed quickly. More than one hundred and seventy wells were drilled on one hundred and sixty acre spacing along the trend, and in 1980 the field was unitized so that pressure could be managed across the whole sand body rather than lease by lease. Waterflooding began under that unit structure. Unitization at this scale is what makes a stratigraphic reservoir workable, because the sand ridge is a single connected system and producing it competitively would have wasted much of the drive energy available.
Since then the story has been engineering rather than exploration. Core-based studies documented the field’s internal facies architecture — porosities near fifteen percent in the best sand and falling sharply into poorer facies — which controls how injected water actually moves through the reservoir. Carbon dioxide miscible flooding has been considered for the field as a further recovery stage. The surrounding Campbell County acreage has meanwhile seen an entirely separate wave of horizontal drilling in other formations, which owners should not confuse with activity in the Shannon unit itself.
Hartzog Draw produces from the Upper Cretaceous Shannon sandstone at roughly nine thousand to nine thousand six hundred feet, in a stratigraphically controlled trap formed by a large mid- to outer-shelf sand-ridge complex. The reservoir is elongate, about twenty-two miles long and one to four miles wide, and its quality varies systematically by facies: core porosities reach about fifteen percent in the best sand and decline markedly elsewhere, with permeabilities measured in tens of millidarcies at best. Sweep efficiency in a body like this depends entirely on understanding that internal architecture.
Waterflooding under the 1980 unit is the field’s established recovery method, maintaining pressure across a sand ridge that has no strong natural drive. Because permeability changes sharply between facies, injected water tends to move preferentially through the better sand, and the practical work of operating Hartzog Draw has been placing injection to sweep the poorer rock as well. Carbon dioxide miscible flooding has been evaluated as a subsequent stage. Owners should treat that as a studied option rather than an operating project unless the operator has confirmed otherwise.
Hartzog Draw interests are unit interests, which changes the arithmetic: your income depends on unit participation factors and on an injection program rather than on any single well near your tract. The production is mature flood output, declining slowly, with a possible but unbooked CO2 phase behind it. The trend crosses the Campbell and Johnson County line, so title work sometimes lands in both. We buy minerals and royalties in Campbell and Johnson Counties and provide free written offers.
County-level well data, production charts, and selling guides for the counties this field spans:
It is an Upper Cretaceous marine shelf sandstone that forms elongate sand-ridge bodies encased in shale. Hartzog Draw is the largest known Shannon accumulation, which is why the field is twenty-two miles long and only one to four miles wide.
Because the field was unitized in 1980 so the whole sand ridge could be waterflooded as one reservoir. In a unit, production is allocated to tracts by a participation formula rather than by which well happens to sit nearest your acreage.
Not directly. The horizontal activity across the Powder River Basin targets other formations entirely. Your Shannon unit interest responds to the waterflood, not to those wells, unless your minerals also cover the intervals being drilled — which is worth checking in your deed.