Petroleum reservoir

About: Petroleum reservoir is a research topic. Over the lifetime, 5403 publications have been published within this topic receiving 83535 citations. The topic is also known as: petroleum deposit.

A Model of Hydrocarbon Generation from Type I Kerogen: Application to Uinta Basin, Utah

Abstract: We have developed a computer model that can predict when and how much oil and gas are generated from a source rock during its burial and later uplift. Kinetic parameters for the oil and gas generation reactions are obtained from high-pressure pyrolysis experiments carried out over a wide range of heating rates and temperatures. In our kinetic model, which applies only to Green River shale, we use a single activation energy of 52.4 kcal/mole and different pre-exponential factors for different products of primary pyrolysis, which allows us to extrapolate laboratory-derived kinetics to geologic heating rates. This model is in contrast to the wide distributions of activation energies or artificially low apparent activation energies used in some models of petroleum formation. hen extrapolated to geologic heating rates on the order of 10°C/m.y., our kinetics show that the temperature of the maximum rate of oil generation (Tp) changes by about 15°C when the heating rate is changed by an order of magnitude. Changes in pressure have relatively minor effects on the kinetics of oil generation but are important for gas generation reactions. We used geophysical data from oil fields in the Uinta basin of Utah to develop a thermal history model of Green River Formation source rocks. This time-temperature history was used to predict the maturation level of the kerogen at a given depth and to predict changes in the compositional characteristics of the oil. The shape of calculated oil generation rate curves, as a function of depth in the basin, mimics the shape of the overpressure curves; this similarity suggests that oil-gas generation may be an important cause of overpressuring. Maturation levels and compositional characteristics of the oil predicted by our model agree very well with characteristics of the oil recovered from the basin.

Petroleum Microseepage at Cement, Oklahoma: Evidence and Mechanism

Abstract: Striking mineralogic and chemical changes occur in outcrops of a Permian redbed sequence overlying oil-productive parts of the prolific multireservoir oil accumulation at the Cement anticline, Oklahoma. Gypsum beds along the flanks are altered abruptly to erosion-resistant carbonate rocks at the crest of the fold in the Keechi Hills. Associated sandstones, typically red and friable in the surrounding region, are altered to pink, yellow, and white on the flanks of the anticline and to hard carbonate-cemented gray sandstone at the crest. The zone of cementation, confined to sandstone intervals, extends to a depth of at least 2,500 ft. Calcitized gypsum exceptionally deficient in C13 and light-carbon/heavy-oxygen cements directly overlie petroleum-productive zones near regions where fluids have superior vertical avenues of communication (faults and an unconformity at shallow depths and of limited extent along the crest). Away from these avenues of leakage, the influence of hydrocarbons on the isotopic composition of the carbonate cements decreases systematically. Color changes in the sandstones are related to reduction and dissolution of iron in the presence of hydrocarbons. Much of the hydrocarbons leaked from Missourian reservoirs beneath the crestal unconformity. Dense crude oil from stratigraphically discontinuous reservoirs along the basinward flank of the structure are associated with low-salinity pore water. Paraffinicity and salinity of waters decrease systematically with increasing depth of burial; these salinity variations, initially effected by ingress of water squeezed from expandable clays in the bordering basin, may have played a role in the selective solution of low-molecular-weight fractions. Water, vertically expelled along the crest, was desalted in passing from sandstone to shales. Large volumes of sandstone thereby were cemented off in shallow Permian rocks in places over the crest; the uncemented sandstones are petroleum-productive do n the flanks.