Observations on the Primary Migration of Oil in the la Luna Source Rocks of the Maracaibo Basin, Venezuela

Kinetic modeling of petroleum formation in the Maracaibo Basin: Final report, Annex 12

“…This indicates that low porosity in the range observed in the La Luna Formation substantially increases the likelihood of source rock fracturing as well as improves the oil expulsion efficiency. Bitumen-filled microfractures are observed in the La Luna shale (Talukdar et al, 1987). This indicates that the compactionoverpressuring-fracturing approach in PYROL shows promise for predicting the conditions of migration though fractures.…”

“…Subsequent to the published studies, additional calculations addressed the effect of the porosity function. The porosity of the La Luna formation is substantially less than that assumed in the initial parametric studies, being only 1-3 percent in the oil window (Talukdar et al, 1987). The effect of porosity on overpressuring and oil expulsion efficiency for a lacustrine source rock is shown in Figure 22.…”

“…In Figure 49a the measured pore pressure at the location of the La Luna formation (approximately 4700 m -15,500 ft depth) is about 86 MPa (0.82 times lithostatic). Porosity is constrained by present-day measured values to be less than about 2% at depths of 4-5 km (Talukdar et al 1987). However, the measured presentday porosity is a function of the burial history of the formation because overpressuring and kerogen conversion can retard porosity development or even create new porosity.…”

“…These are the TOC of the source rock, EPSZ-the initial porosity, EPSC-the rock compaction coefficient, FLITH-the ratio of pore pressure to lithostatic pressure at which the rock is assumed to fracture, RLITH-the ratio of lithostatic pressure to hydrostatic pressure (dependent on rock density), the relative permeability coefficients, and KPRES-the hydraulic conductivity coefficient. The average present-day TOC of the La Luna shale is about 3.8% (Talukdar et al, 1987); INTEVEP provided measurements of the present-day TOC of the La Luna for ten wells in the Maracaibo Basin. Typical values of FLITH observed in hydrofractured rocks have been estimated to be between 0.8 and 0.9 (Palciauskus and Domenico, 1980;Lerche, 1990).…”

Potential petroleum source rocks in a tertiary sequence of the Eastern Venezuelan Basin

“…The Querecual Formation is considered to host the principal source rock of the basin (Talukdar et al, 1985(Talukdar et al, , 1988, whereas the shales from the San Antonio Formation are considered as secondary source rocks (López, 1997). Tertiary rocks of the basin may also contribute to the formation of hydrocarbons accumulated in this basin, making necessary the determination of the generation potential of this Tertiary (Late OligoceneeEarly Miocene) sequences.…”