James D. Tucker

Microbial reservoir characterization: An integration of surface geochemistry and developmental geology data

Microbial Reservoir Characterization (MRC) integrates measurements of hydrocarbon microseepage escaping from petroleum reservoirs with developmental geologic and engineering data for an enhanced identification of the subsurface reservoir fabric. Studies from mature producing fields demonstrate MRC technology can monitor subsurface fluid withdrawal patterns with microseepage patterns identified from surface soil samples. Areas of the reservoir in contact with producing wells, by-passed production, and reservoir heterogeneity characteristics can be identified. Microbial ER microseepage links the distribution of hydrocarbon traps with the continuity (compartments) of a reservoir, as well as locates areas prone to higher quality reserves. Upward, buoyancy driven forces controlling hydrocarbon microseepage is altered along pressure pathways streaming to production wells. In these cases, microseepage is essentially shut down and lower concentrations of gases reach the surface environment. Case studies from a variety of basin environments will be presented.

Comparison of Microbial And Sorbed Soil Gas Surgace Geochemical Techniques With Seismic Surveys From the Southern Altiplano, Bolivia

Yacimientos Petroliferos Fiscales Bolivianos (YPFB) undertook a large seismic evaluation in the southern Altiplano, Bolivia in 1994. As an additional layer of information, sorbed soil gas and Microbial Oil Survey Technique (MOST) geochemical surveys were conducted to evaluate the hydrocarbon microseepage potential. The Wara Sara Prospect had 387 sorbed soil gas samples, collected from one meter depth, and 539 shallow soil microbial samples, collected from 15 to 20 centimeter depth. The sorbed soil gas samples were collected every 500 meters and microbial samples every 250 meters along geochemical traverses spaced 1 km apart. The presence of anmalous hydrocarbon microseepage is indicated by (1) a single hydrocarbon source identified by gas crossplots, (2) the high gas values with a broad range, (3) the high overall gas average, (4) the clusters of elevated samples, and (5) the right hand skewed data distributions.

Surface geochemical hydrocarbon signature of the eastern Colorado and western Kansas Morrow Formation

Meandering fluvial deposition, combined with valley-fill stratigraphic and combination traps, makes the Pennsylvanian Morrow Formation sandstones of eastern Colorado and western Kansas a very challenging exploration target. Surface geomicrobial analysis of shallow soil samples enhances and ranks geophysical and geological leads by identifying hydrocarbon microseepage patterns. Productive versus nonproductive Marrow traps are delineated by microbial prospecting which locates and measures concentrations of specific microbial populations associated with hydrocarbon gases leaking from buried reservoirs. We provide examples of microbial signature profiles over known production and prospect locations prior to drilling, including the Moore-Johnson state-line field.