Lacustrine depositional environments in the Green River Formation, Uinta Basin: Expression in outcrop and wireline logs

Abstract

Lacustrine basins are key oil-productive areas of the world. Because fewer lacustrine exist than marine basins, lacustrine systems are relatively less well studied. This paper investigates fluvial-lacustrine depositional environments and their representation in wireline logs in the lower part of the Green River Formation, Uinta Basin, Utah. The five principal depositional environments of the lower Green River Formation are (1) deep lacustrine, (2) shallow lacustrine, (3) lacustrine delta, (4) coastal plain, and (5) alluvial plain. Deep-lake environments are characterized by laminated oil shales and fine-grained carbonates. These facies exhibit anomalously high neutron porosity, and low bulk density relative to other settings. Shallow-lake environments are dominated by weakly laminated to massive gray mudstones, and limestones, with occasional thin high-bulk-density sandstones. Lacustrine deltas (both sand-prone and mud-prone) grade from shallow-lake muds to ripple-laminated to cross-bedded sandstones. The upward decrease in clay can be seen in the gamma-ray, neutron-porosity, and bulk-density profiles of deltaic intervals. Coastal plain mudstones have a greenish hue, and frequently contain organic matter. Channels in coastal plain settings are typically thin, isolated, and heterolithic. Alluvial plain channels tend to be sandier, thicker, and less isolated than coastal plain channels. Alluvial mudstones are reddish with abundant pedogenic features. The vertical association of depositional environments in the lower Green River indicates both high-amplitude and high-frequency lake-level fluctuations. However, the macroscale trend shows a rapid deepening of the lake lower in the

Controls on the stratal architecture of lacustrine delta successions in low‐accommodation conditions

“…Diagnosis of deltaic deposits in the Green River Formation has been controversial. Eocene Lake Uinta delta deposits of the Green River Formation have been described in detail in many previous studies (Remy, 1992, Keighley et al ., 2002, Pusca, 2003, Burton et al ., 2014). However, there has been little emphasis and poor focus/definition on the lake deltas themselves in previous studies (except for the carbonate shoreline facies) either because they were thought to be eroded by the downcutting of subsequent distributary channels (Figs 1, 9B and 11F) or because their facies characteristics were difficult to identify.…”

A review of carbonates as hydrocarbon source rocks: basic geochemistry and oil–gas generation

“…For example, the Paleogene lacustrine carbonate source rocks in the western Qaidam Basin have generally low organic matter abundance (TOC generally < 0.4%; Su et al 2006;Wang et al 2009). However, the Paleogene lacustrine carbonate source rocks of the Green River Formation in the Uinta Basin (USA) and the Hetaoyuan Formation in the Biyang sag (China) contain relatively high amounts of organic matter with TOC ranging at 1.0%-20.0% and 0.5%-7.6%, respectively (Tissot et al 1978;Tuo et al 1997;Burton et al 2014). This may reflect that complex factors influence the variability of organic matter abundance of these source rocks.…”

Sedimentary facies of Paleogene lacustrine dolomicrite and implications for petroleum reservoirs in the southern Qianjiang Depression, China

“…Lacustrine carbonates are generally deposited in shallow water areas, which are located opposite a delta and away from the provenance regions [47][48][49][50]. Due to less provenance influence, the lake waters in these areas have high salinities that are favorable for the deposition of carbonates, whereas in the shallow water areas adjacent to the deltaic deposits, carbonates are poorly developed due to the high-energy, low concentration conditions resulting from greater provenance influence.…”