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.

Reservoir Characterization of the Hollin and Napo Formations, Western Oriente Basin, Ecuador

Abstract: The Oriente basin of Ecuador has produced a substantial amount of oil over the past 20 years. Nearly 3 billion bbl of oil have been recovered from the principal reservoirs in the Cretaceous Napo and Hollin formations. Subtle north-south structures, commonly associated with Andean-related faulting, have trapped much of the recoverable hydrocarbons in the thicker sandstones deposited within the Hollin and Napo reservoirs. East to west thinning of these reservoir units also contributes to the formation of stratigraphic traps. Both the Hollin and Napo formations comprise successions of eastward-sourced fluvial and deltaic sedimentary deposits that prograded westward into shoreline and marine shelf parasequences. The Albian Hollin reservoir interval consists of a dominant alluvial plain sandstone sequence (Main Hollin sandstone) that occupies much of the Oriente basin. In the western Oriente, the uppermost Hollin section grades vertically into open marine strata with isolated tidal- and storm-influenced sandstone bodies. The overlying Napo stratigraphy also consists of sand-rich fluvial and deltaic deposits in the eastern Oriente and abruptly changes to marine shales and limestones and lowstand valley-fill sandstones in the western part of the basin. Extensive structural and stratigraphic trap potential remains within the Napo and Hollin strata in the Oriente basin. High-resolution geophysical techniques and detailed geologic reservoir characterization facilitate successful exploitation of these remaining reserves.

Diagenetic quartzarenite and destruction of secondary porosity: An example from the Middle Jurassic Brent sandstone of northwest Europe

Abstract: Significant amounts of feldspar have been dissolved from Middle Jurassic sandstone oil reservoirs in the North Sea (northwest Europe) during burial diagenesis Sandstones of the Middle Jurassic Brent Group become increasingly quartzose with increasing burial depth. At Statfjord field (2500 m depth), sandstones are arkose to subarkose; at Hutton field (3050 m depth), they are subarkose to quartzarenite, and at Lyell field (3500 m depth), sandstones are typically quartzarenite. In spite of extensive feldspar dissolution, the abundance of secondary porosity due to feldspar dissolution is similar for all fields, averaging 2.9% of the total rock volume. Thus, far more feldspar has been dissolved than is recorded as secondary porosity. The limit on preservation of secondary porosity may be largely the effect of the mechanical strength of the rock. An excessive number of large secondary pores lowers the rock strength below the point at which the rock can withstand overburden stress, thus causing collapse of some of the secondary pores.

Stratigraphic Architecture of the Tonganoxie Paleovalley Fill (Lower Virgilian) in Northeastern Kansas

Abstract: Lower Pennsylvanian paleovalley-confined sandstones are important petroleum reservoirs in the Midwest. In Kansas, such reservoirs have produced approximately 220 million bbl of oil and 1.7 tcf of gas. Valley-fill successions tend to become muddy upward, but there can be considerable local heterogeneity in which reservoir sandstones pass laterally into muddy sandstones or nonreservoir shales. The lack of understanding of this reservoir heterogeneity can lead to low drilling success rates. The Tonganoxie paleovalley (Upper Pennsylvanian, northeastern Kansas) contains facies very similar to Lower Pennsylvanian (Morrowan) valley fills, and can provide an outcrop- and subsurface-based model of sandstone deposition. The Tonganoxie paleovalley was incised during lowered sea level and filled during the subsequent transgression. The main paleovalley is approximately 41 m deep, 11 km wide, and 240 km long, and was fed by 1-km-wide tributary valleys oriented roughly normal to the trunk valley. Sandstones occur in four distinct architectural elements that were deposited during different phases of transgression. Type I sandstone consists of a belt of sandstone and conglomerate 3-18 m thick and confined to the trunk valley and wider portions of tributary valleys. Type I sandstone consists of amalgamated channel fills, has little or no mud, and has the highest porosity and permeability. The type I sandstone is overlain by estuarine deposits of sandstone (type II sandstones), rippled argillaceous sandstone to sandy mudstone, and coal. Most of the paleovalley was filled during this stage. The type II sandstones are narrow (1.5 km wide) arcuate bodies up to 8 km long and were likely deposited in tidal point bars near the fluvial to tidal transition, are either isolated sandstone bodies or are incised into type I sandstone. The higher mud content is expected to reduce porosity and permeability compared to fluvial facies. Type III sandstone bodies occur at the upstream limits of narrow tributaries and are probably bay-head deltas. Well logs indicate a range of mud content. Type IV sandstone is a thin (3 m) discontinuous sheet of marine sandstone deposited after most of the paleovalley had been filled.

A new type of reservoir rock in volcaniclastic sequences

Abstract: Development of pronounced secondary porosity and permeability, accompanied by dramatic changes in wave propagation velocity and other physical properties, in laumontite tuffs occurs in the oil fields of eastern Georgia, Soviet Union. These rocks originated during intense hydrothermal alterations of andesite tuffs and comprise local (few meters thick), commonly lens-shaped bodies. Hydrothermal alteration was lithologically and structurally controlled, resulting in the formation of specific reservoir rocks identifiable on geophysical logs and capable of producing oil and gas. The considerable relief of the in-situ stress within these bodies was estimated from differential velocity analysis using sonic-log and laboratory data. This stress relief, as well as borehole enlargem nts (accompanied by the development of zones of nonelastic deformation around the hole) tends to enhance near-well permeability and, hence, the productive potential of these uncommon and poorly studied reservoirs.