Potential For Oil Exploration Research Articles

Lithological and facial features of organogenic structures of the second carbonate stratum of the eastern flang of the Pre-Caspian depression on Zharkamys uplift

The Pre-Caspian Basin is the major oil and gas basin in Kazakhstan. It contains huge hydrocarbon reserves within pre-salt carbonate deposits. There had been numerous discoveries of oil and gas-condensate fields associated with pre-salt carbonate complexes in the Eastern part of the Caspian Basin.
 The object of this study is the second carbonate stratum (CS-II) of the Late Visean Early Moskovian age of the Eastern part of the Pre-Caspian Basin. The formation of the Eastern part of the Pre-Caspian Basin took place in the zone of the junction of the East European craton and folded structures of the Urals. These conditions predetermined the complexity of sedimentation processes, variety of lithological types of rocks and diagenesis processes with the formation of reservoir heterogeneity.
 CS-II will retain the leading role as the main reservoir of hydrocarbons and it has further potential for oil exploration in the region for two to three decades. It has been proven by the discovery of large oil and gas-condensate fields in the CS-II, such as Zhanazhol, Urikhtau, Kozhasai, Alibekmola, etc.

Fracture evolution in oil-rich rhyolitic lavas of the Hailar Basin, northeastern China

Rhyolitic lavas can hold considerable oil exploration potential which is inferred to be controlled by fracture systems. The need for a better understanding of fracture properties and related petroleum systems for such rocks is the principal motivation of this study. We investigate the fracture evolution of this play type by an analysis of the Early Cretaceous oil-rich rhyolitic lava outcrops, located in the Hailar Basin, northeastern China, integrating multiscale fracture data from field investigation, optical microscopy, fluorescence imaging, and scanning electron microscopy. Six main types of volcanic-related and tectonism-induced fractures are identified. Aperture, spacing, and length of these fractures predominantly show power-law distributions, and in most cases, the dimension of these three parameters follows that columnar joints > platy cooling fractures ≈ tectonic fractures ≫ conjugate shear fractures ≫ perlitic fractures. In addition, the fracture orientation patterns are commonly predictable. Small fractures usually make significant porosity contribution and are excellent reservoir spaces, while large fractures control the permeability and act as channels. The early Early Cretaceous NW–SE extension (D2 of the five phases of basin deformation) dominated the fracture evolution of the lavas. Although the seal of the reservoir is probably not extensively damaged by the reactivation of fractures during the multistage deformation of the basin, the likelihood of reactivation of fracture sets C1, C3, and T1 needs to be carefully evaluated during the exploration and recovery, as the reactivation tendency factors (fa) of these sets are > 1 at a certain stage of deformation. We suggest that the observed patterns may be extrapolated to similar rhyolitic lavas in many parts of the world.

Depositional environment, hydrocarbon generation and expulsion potential of the middle Permian Pingdiquan source rocks based on geochemical analyses in the eastern Junggar Basin, NW China

ABSTRACTAs the most important source rocks in the eastern Junggar Basin, the middle Permian Pingdiquan (P2p) source rocks have attracted increasing attention after the discovery of tight oil in the Shazhang uplift. The P2p source rocks are widely distributed (up to 7546 km2) and have an elevated thickness in the eastern Junggar Basin. To explore the P2p tight oil resource in the eastern Junggar Basin, 113 core samples from 34 exploration wells were analysed geochemically and re-examined for their organic matter abundance, type and thermal maturity, hydrocarbon potential and sedimentary environment. Geochemical analysis results indicate that the P2p source rocks are fair to good source rocks dominated by Type II kerogen, presently in a low mature–mature stage, and biomarkers and trace elements indicate deposition in a terrestrial to coastal environment under oxic to dysoxic, and fresh to brackish conditions, with possible intermittent seawater influence, implying proximity to the open sea. Based on hydrocarbon expulsion modelling, hydrocarbon expulsion began at 0.87% Ro, and the peak expulsion occurred at 1.1% Ro. Hydrocarbon generation intensities in the Shazhang uplift and the Wucaiwan sag are relatively large, with values centred at 4–6.5 million t/km2 and 4–6 million t/km2, respectively, with total hydrocarbon generation and expulsion from the P2p source rocks approximately 4.56 × 109 t and 1.44 × 109 t, respectively, indicating significant tight oil exploration potential in the eastern Junggar Basin. The Shazhang uplift and the Wucaiwan sag are two hydrocarbon expulsion centres in the study area with the largest hydrocarbon expulsion intensity centred around the Shazhang uplift, exceeding 3 × 106 t/km2. We suggest that the area with high hydrocarbon expulsion intensities is a favourable target for tight oil accumulation and exploration.

Characteristics of petroleum geology of the Baise Basin in Guangxi, China

Baise Basin, which covers an area of 830 km2 (320 mi2) with a length of 109 km (70 mi) and a width of 7–14 km (4–8 mi) and strikes northwest, is a Paleogene lacustrine-faulted basin. Its formation experienced synrift, regional subsidence, and uplift and erosion. Its Paleogene depositional environments experienced changes from flood-plain or alluvial-fan facies to fluvial facies, delta facies, lacustrine (fan-delta facies), and then fluvial facies, all of which combine to reflect the evolution from individual fault-controlled depocenter through maximum areal development and subsidence and then shrinkage. The Nadu Formation lacustrine mudstones, with thickness ranging from 300 to 600 m (980 to 1970 ft), are the main source rocks. The in-place potential resources in the Baise Basin have been estimated to be 73 106 t (540 million bbl) of oil and 77 108 m3 (270 bcf) of gas. Three biodegraded oil pools, seven oil fields, and five gas pools have been discovered. Oil and gas pools are characterized by thin reservoirs, small area distributions, and shallow burial depth and can be classified into three types: structural, stratigraphic, and combined structural stratigraphic. The proven reserves of oil total 123 105 t (91 million bbl), and those of gas total 7.7 108 m3 (27 bcf). The ratio of proven oil reserves to in-place potential oil resource is about 16.9%, suggesting that the basin still has considerable potential for oil exploration. Reservoirs deeper than 2000 m (6500 ft) in stratigraphic and subtle traps have a major potential for exploration and are the favorable targets of the future.