Abstract

Wolfcamp unconventional reservoirs are an increasingly popular lower-cost oil opportunity during this time of market instability. Unfortunately, the Wolfcamp shale horizons can be unpredictable in acreages with limited well control and seismic data. Sedimentary organic matter analyses can define thermal maturity windows, determine kerogen types, and reflect depositional environments to assist in realizing hydrocarbon potential. Sixteen samples were palynologically processed at roughly three-meter intervals from the upper Wolfcamp section of the Collier-1201 well in Reeves County, TX. Prepared microscope slides were examined in transmitted light to quantify and describe the organic constituents in each sample. Organic geochemical data were integrated to corroborate palynofacies findings. The majority of observed organic matter particles were classified as highly degraded terrestrial phytoclasts. These phytoclasts, along with the inferred thermal alteration index and geochemical data, reflect a shallow marine, neritic environment with significant terrestrial influence, preserving mature to post-mature kerogen that had at one point passed through the oil zone of hydrocarbon generation. Lithofacies, palynofacies, and geochemical data indicate sea levels regressed as the studied interval was deposited. Terrigenous organic input (mostly kerogen type-III materials with some type-II from cuticular plant debris) was likely elevated during times of lower sea level as subaerially exposed reefs spatially expanded, while plank-tonic organisms (kerogen type-II) thrived in the same shallow marine environment, making the upper half of the studied interval a specially effective source rock.