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.

Dating diagenesis in a petroleum basin, a new fluid inclusion method

Abstract: The final porosity and permeability of sandstone petroleum reservoirs is greatly affected by the diagenetic growth of minerals after deposition. For example a sand may be deposited with a porosity of 25% and a permeability of 5,000 mdarcy (mD)1; diagenetic growth of quartz around detrital sand grains may leave a rock with only 10% porosity, and later growth of clays may partly fill these remaining pores and block inter-pore connections, reducing permeability to 100 mD (ref. 2). If the depth and timing of such diagenetic alteration can be measured and the extent of diagenesis estimated, then prediction of the diagenetic state of undrilled sandstones may become possible and diagenesis related more closely to the timing of hydrocarbon migration and the formation of hydrocarbon traps. We present an example of a new method for estimating the date of quartz diagenesis using a combination of techniques from thin section petrography, fluid inclusion thermometry, organic geochemical thermometry and sedimentary basin stratigraphic analysis. These results suggest that quartz in the Beatrice oilfield was precipitated from moving and cooling pore fluids, at a temperature between 68 °C and 94 °C in the late Jurassic.

Sealing mechanisms in volcanic faulted reservoirs in Xujiaweizi extension, northern Songliao Basin, northeastern China

Abstract: Distribution of volcanic reservoirs in Xujiaweizi half graben is controlled by both faults and sealing layers where their integrity could have been compromised. This paper documents the distribution of sealing units of the Denglouku and Yingcheng Formations based on seismic and well-log data to delineate all of the reservoirs with proper cap rocks within the volcanic Yincheng Formation via the relationship between the fault system and reservoir rocks. Based on the regional sealing effect of Denglouku Formation, two hydrocarbon traps are identified: the lower primary and upper secondary gas reservoirs where the formation with a mudstone percentage of more than 50% within the second member seals the primary reservoirs. The upper secondary trap is controlled by faults that have been activated during the structural reversal phase, causing the regional sealing layers in the Denglouku Formation to get displaced with a cap rock juxtaposition thickness of less than 35 m. This has created a series of fault-seal, dual-control reservoirs. The local seals within the Yingcheng Formation consist of mudstone, tight volcanic rock, and clayey breccia covering each volcanic eruption cycle. These local seals separate the volcanic gas reservoirs with a minimum thickness of 20 m. The local top seals in this tectonically active zone were placed on the hanging wall via the juxtaposition of the reservoir and overlying mudstone and/or clayey breccia. It was concluded that gas has migrated vertically through the faults and accumulated in the fault-controlled traps where sharp changes in the lithology (juxtaposition) form the seal, whereas the gas-water contact is controlled by the depth of the reservoir rock. Finally, this study concludes that the primary reservoirs are distributed in a sinusoidal configuration around the fault zone because of the dolphin effect of the Xuzhong strike-slip fault system that has connected the source and reservoir rocks.

Evolution of the Northeastern Arabian Plate Margin and Shelf: Hydrocarbon Habitat and Conceptual Future Potential

Abstract: About 98% of the huge recoverable hydrocarbon reserves of the Arabian Plate are concentrated in the Northeastern Margin Shelf extending from NW Iraq through the Gulf to Central Oman. The plate tectonic evolution of this region is reviewed as background for its enormous hydrocarbon productivity. This is intimately linked to a near-continuous passive margin history and gentle subsidence of an extraordinarily wide epeiric shelf, which allowed repeated regional development of source rocks in large intra-shelf basins frequently in optimal juxtapositional relationships with good regional reservoirs and seals; these events are discussed. Although currently reported reserve figures relate to Mesozoic and Tertiary reservoirs, it is concluded that several pre-Mesozoic regional sources have generated enormous volumes of hydrocarbons, the bulk of which still await discovery in up-dip Paleozoic reservoirs, and that future ultimate recoverable reserves could conceivably double.

Correlation between rock fabrics and physical properties of carbonate reservoir rocks

Abstract: Three carbonate core samples from an oil and gas reservoir of the NW German basin were chosen to study the correlation between rock fabrics and physical properties of reservoir rocks. Detailed fabric analyses and texture investigations were carried out as well as laboratory measurements of different physical properties, e.g. density, porosity, permeability, electrical conductivity, seismic compressional and shear wave velocities. Although the three core samples come from a similar depositional facies, they show great differences in the occurrence and three-dimensional distribution of the rock fabric elements. These heterogeneities are the result of various diagenetic and tectonic processes. For the correlation between the rock fabrics and the physical properties four main rock fabric types have to be considered: (a) major constituents, e.g. fossils, ooides, peloides and crystals; (b) pore space with different pore types; (c) fractures; and (d) stylolites. The results of the correlation clearly show that the values and anisotropies of the petrophysical properties are fairly related to the observed fabric elements, with their different arrangements, spatial distributions and preferred orientations. These results also provide a fundamental understanding of the petrophysical responses, such as seismics, to the different geological features (e.g. fractures) and their dynamic changes with pressure, which can be converted to different depths. The knowledge gained from such correlations may lead to an improved interpretation of geophysical data for hydrocarbon exploration and production and therefore to an advanced reservoir characterization.

Carbon dioxide and carbonate cements in the otway basin: implications for geological storage of carbon dioxide

Abstract: Understanding CO2 source and carbonate cements in natural gas accumulations is important for predicting the behaviour of anthropogenic CO2 in a reservoir system. The Otway Basin offers an excellent opportunity to examine late CO2-derived cements as an analogue for mineralogical storage of CO2. Understanding Otway Basin diagenesis and carbonate cement distribution is also of great significance to petroleum production in the region. Elemental and textural examination of Otway Basin cements has identified five carbonates in reservoir rock from CO2-rich gas accumulations. These carbonates show an overall increase in Fe2+ and Mg2+ relative to the calcites in CO2-free reservoir rock, indicating cation derivation from CO2 interaction with labile minerals. δ13C isotopes of 2.18‰ to -6.7‰ PDB from late carbonate cements in reservoirs containing CO2, confirm an inorganic CO2 origin. 3He/4He gas isotopic ratios of R/Ra > 1 indicate a predominantly mantle input for the CO2-rich accumulations. Degassing of magma associated with Pleistocene to Recent volcanics is suggested as the dominant, CO2 source for the existing CO2 accumulations. CO2 influx from the magmatic source was rapid, and is the most analogous scenario to injection of anthropogenic CO2. Natural influx of CO2 and the opportunity for mineralisation of CO2 is variable, with CO2 dissolving some original carbonate and precipitation dependant on pH, ρCO2, and available cations. Positive mineralogical CO2 storage occurs in the Pretty Hill Formation, due to a higher content of labile lithic minerals, with ~36 kg/m3 of CO2 (~48 kg/m3 carbonate) stored in the Ladbroke Grove Field from the current CO2 phase. The Waarre Sandstone has negative mineralogical storage of CO2, with less carbonate than similar reservoir rock without CO2, and therefore more CO2 being released from dissolution of early carbonates.