Gamma Ray Spectrometry Logs Research Articles

The determination of sedimentary environment and associated energy in deep-buried marine carbonates: insights from natural gamma ray spectrometry log

The determination of sedimentary environment and associated energy in deep-buried marine carbonates: insights from natural gamma ray spectrometry log

GEOLOGICAL PETROPHYSICAL EVALUATION OF YAMAMA FORMATION SUBBA FIELD

The main purpose of this study is to estimate hydrocarbon potentialities of Yamama Formation (Valanginian–Early Hauterivian) by using assessment technique links up between gamma ray spectrometry logs and other conventional open hole logs for determining the petrophysical properties of Yamama units in Subba oil-field and oil water contact as well. The Lower Yamama (YB); is considered the main reservoir unit, aptly composed of shallow high depositional energy levels of oolitic to bioclastic grainstone facies reflecting low clay-content, thus these properties had gave a fruitful chance as for immigrated oil to accumulate in the porous bodies of this reservoir units. The non-improved petrophysical properties of upper Yamama member (YA) due to far-deep depositional conditions reflected by well-developed dense-compact sub-tidal open-shelf lagoonal benthic foram / algal wackestone facies and sparse-fossiliferous lime mudstone intercalated with bioclastic wackestone facies, are clearly displayed sedimentary intervals of high clay-content that is, the reduction potential depositional conditions are highly affected on these facies.YB-unit have attained (22-29m) net pay thickness with porosity (9.35-10.9%) and water saturation ranged (40-40.6%),whereas the YA-unit net-pay thickness is reached to (7.5-16.5 m) with (6 % phi) and (35.3%Sw). The oil water contact at the lower Yamama member may assign at depth 3573m (MSL) of southern dome on basis of electrical logs monitoring, well log interpretation and test results carried out the formation units.

A new method of deep carbonate lithology identification at the Tadong uplift in the eastern section of the Tarim Basin

The lithology identification of deep carbonate rocks has always been a difficult field of research. The deep carbonate rock formations in the eastern section of the Tarim Basin have complex tectonism, deposition, and diagenesis. Therefore, it is difficult to use conventional logging information to identify the lithology of deep carbonate rocks. In this study, a natural gamma ray spectrometry log in unconventional logging was used to discover a new method (comprehensive superposition method) for the lithology identification of deep carbonate rocks. The research results showed that the TH, U, K, and KTH information in a natural gamma ray spectrometry log can reflect the lithological characteristics of carbonate rocks extremely well. In addition, this new identification method was able to optimize the typical logging parameters which could best reflect the lithology of the carbonate rocks after analyzing the original record curve and a variety of combined curves of the natural gamma ray spectrometry. This new method could comprehensively superpose the typical logging parameters and was capable of finally quantitatively identifying the lithology of dolomite, micrite, calcarenite, and finely crystalline limestone in deep carbonate rocks, with an identification accuracy of more than 79 %. On the basis of the above research results, a special statistical method was made to analyze the typical logging parameters of natural gamma ray spectrometry and to assist and test the identification of a comprehensive superposition method, in order to improve the lithology identification accuracy. This new method for the lithology identification of deep carbonate rocks, based on a natural gamma ray spectrometry log, achieved good application effects in the eastern section of the Tarim Basin.

Gamma ray spectrometry logs as a hydrocarbon indicator for clastic reservoir rocks in Egypt

Petroleum oil is an important source for the energy in the world. The Gulf of Suez, Nile Delta and South Valley are important regions for studying hydrocarbon potential in Egypt. A thorium normalization technique was applied on the sandstone reservoirs in the three regions to determine the hydrocarbon potentialities zones using the three spectrometric radioactive gamma ray-logs (eU, eTh and K% logs). The conventional well logs (gamma-ray, deep resistivity, shallow resistivity, neutron, density and sonic logs) are analyzed to determine the net pay zones in these wells.Indices derived from thorium normalized spectral logs indicate the hydrocarbon zones in petroleum reservoirs. The results of this technique in the three regions (Gulf of Suez, Nile Delta and South Valley) are in agreement with the results of the conventional well log analyses by ratios of 82%, 78% and 71% respectively.

Characteristics of Milankovitch Cycles in the Mid‐Permian Liangshan and Qixia Formations of the Sichuan Basin—Examples from Well‐Long17 and Well‐Wujia1

AbstractThe Liangshan and Qixia formations in the Sichuan Basin of central China were formed in the earlier middle Permian. Based on outcrop observation of the Changjianggou section at Shangsi, Guangyuan region and 3rd‐order sequence division in typical drillings, one‐dimensional spectrum analysis has been used to choose the better curve between the natural gamma ray spectrometry log(ln (Th/K)) in Well‐Long17 and the gamma ray log(GR) in Well‐Wujia1, respectively, for identifying Milankovitch cycles in Sequence PSQ1 which comprises the Liangshan and Qixia formations, and then to identify the variation in the Milankovitch cycle sequences. On this basis, the system tract and 4th‐order sequence interfaces in Sequence PSQ1 were found via two‐dimensional spectral analysis and digital filtering. Finally, a high‐frequency sequence division program was established. Among these cycles, long eccentricity (413.0 ka) and short eccentricity (123.0 ka) are the most unambiguous, and they are separately the major control factors in forming 4th‐order (parasequence sets) and 5th‐order (parasequences) sequences, with the average thicknesses corresponding to the main cycles being 11.47 m and 3.32 m in Well‐Long17, and 14.21 m and 3.79 m in Well‐Wujia1, respectively. In other words, the deposition rate in the beach subfacies is faster than that of the inner ramp facies. The ln(Th/K) curve is more sensitive than the GR as the index of relatively ancient water depth in carbonate deposition. One‐dimensional spectrum analysis of ln(Th/K) curve could distinguish the Milankovitch cycle sequences that arose from the Precession cycle (20.90 ka), with a much higher credibility. Sequence PSQ1 in Well‐Long17 contains 10 4th‐order sequences, and the growth span of Sequence PSQ1 consisting of the Liangshan and Qixia formations is about 4.13 Ma. The single deposition thickness of the long eccentricity cycle sequence has the characteristics of thinning and then thickening in the two‐dimensional spectrum, which could be used to identify the system tract interface of the 3rd‐order sequence. The precession sequence thickness remains stationary. As a result, the early deposition rate in the mid‐Permian of the Sichuan basin was very slow, remaining nearly stationary, and this reflects a sustained depositional environment. Whole‐rock carbon and oxygen isotope curves could also prove this point Milankovitch cycle sequence studies provide a basis for paleoenvironmental analysis and, as such, can be used to analyze ancient climate change, calculate deposition rate and deposition time, and carry out fine isochronous stratigraphic correlation.

Ancient subaerial exposure and freshwater leaching in sandstones

Research Article| December 01, 1990 Ancient subaerial exposure and freshwater leaching in sandstones D. Emery; D. Emery 1BP Exploration Company, Ltd., Britannic House, Moor Lane, London EC2Y 9BU, England Search for other works by this author on: GSW Google Scholar K. J. Myers; K. J. Myers 1BP Exploration Company, Ltd., Britannic House, Moor Lane, London EC2Y 9BU, England Search for other works by this author on: GSW Google Scholar R. Young R. Young 1BP Exploration Company, Ltd., Britannic House, Moor Lane, London EC2Y 9BU, England Search for other works by this author on: GSW Google Scholar Author and Article Information D. Emery 1BP Exploration Company, Ltd., Britannic House, Moor Lane, London EC2Y 9BU, England K. J. Myers 1BP Exploration Company, Ltd., Britannic House, Moor Lane, London EC2Y 9BU, England R. Young 1BP Exploration Company, Ltd., Britannic House, Moor Lane, London EC2Y 9BU, England Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1990) 18 (12): 1178–1181. https://doi.org/10.1130/0091-7613(1990)018<1178:ASEAFL>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation D. Emery, K. J. Myers, R. Young; Ancient subaerial exposure and freshwater leaching in sandstones. Geology 1990;; 18 (12): 1178–1181. doi: https://doi.org/10.1130/0091-7613(1990)018<1178:ASEAFL>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We present an example of leaching by meteoric water in the Jurassic Magnus Sandstone Member of the northern North Sea. The interpretation is based on information from several independent techniques, including downhole natural gamma-ray spectrometry, detailed petrographic analysis, and cross-sectional time-slice reconstructions from seismic data. The initial lines of evidence that prompted further investigation into freshwater involvement in the Magnus Sandstone Member were brackish formation-water compositions and a potassium depletion shown by the gamma-ray spectrometry log, in sandstone beneath the unconformity at the base of the Cretaceous section. Subsequent detailed petrographic study confirmed that the potassium depletion had been brought about by potassium feldspar dissolution, resulting in precipitation of kaolinite and creation of secondary porosity, the latter also revealed by conventional core-analysis porosity and permeability measurements. Finally, cross-sectional time-slice reconstructions from a regional seismic line across the Magnus oilfield strongly suggested subaerial exposure of the Magnus Sandstone Member in Early Cretaceous time and consequent freshwater leaching of the Magnus Sandstone Member and generation of the unconformity at the base of the Cretaceous. The combination of several lines of evidence from the Magnus field supports the process of subaerial exposure and freshwater leaching to create secondary porosity in sandstones. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Relation between source rock properties and wireline log parameters: An example from Lower Jurassic Posidonia Shale, NW-Germany

The relationships between source rock quality and wireline log parameters were established for the Lower Jurassic Posidonia Shale, the most prolific petroleum source rock of Central Europe. Wireline logs used are the gamma ray spectrometry, density, sonic and various resistivity logs. The organic geochemical parameters considered include the organic carbon content, hydrogen index, and the hydrocarbon potential expressed by pyrolysis yield. The case history presented is based on a continuous core through the entire Posidonia Shale interval from a location where this source rock is immature. Care was taken to detect and to avoid samples and log values influenced by bore hole roughness and fractures. Fair correlations were observed only between uranium content from gamma ray spectrometry log and organic carbon content. No correlation was recognized between uranium content and kerogen type as defined by hydrogen indices. For various reasons density, sonic, and resistivity logs did not provide useful data in this study. Three rock units with irregular, high and low uranium contents could be differentiated. Possible causes for this tripartition are different environments during deposition and postdepositional redistribution of uranium during early diagenesis and in association with fractures.

Depositional Environments and Invasion Profiling in Heavy Oil Sands, Eastern Venezuela: A Case Study: ABSTRACT

A comprehensive study of a single well for INTEVEP and Meneven in the Faja Petrolifera del Orinoco--an extensive (570 × 140 km, 350 × 90 mi) east-west trending heavying oil belt located immediately north of the Orinoco River, eastern Venezuela--resulted in an interpretation of an invasion profile dependent on depositional environments. The data base was derived from: (1) 400 ft (121 m) of whole core (67% recovery) and 124 sidewall cores taken from the 1,500-1,900 ft (457-579 m) interval of the upper Tertiary Oficina Formation, which, in this area, overlies the Precambrian metamorphosed igneous basement. (2) A logging suite of 22 conventional, experimental, and prototype wireline logs. In this area, the Oficina Formation is a complex series of stacked, heavy oil-saturated, sand-dominant, fluvially-transported, unconsolidated sediments overlain by lignite- and mud-dominant backswamp and estuarine sediments. Bedding, mineralogy, lithology, and paleontology define fluvial-channel fills, channel-lag deposits, crevasse splays, overbank levees, swamps, estuarine lagoons, and estuarine-channel fills in a delta-plain environment. Reservoir geometry and facies analyses suggest that several short, wide, deep-channeled, meandering rivers flowed generally northward across a tropical-subtropical plain of low relief carrying the bulk of the sediment in bedload traction (channel fills) and a smaller fraction in density suspension (crevasse splays). A unique logging suite permitted the measurement of invasion in this heavy-oil environment. The invasion of the mud filtrate was measured at varying depths of investigation using, from shallowest to deepest depths: (1) gamma ray spectrometry log, (2) microspherically focused log, (3) nuclear magnetism free fluid index, and (4) deep Laterolog. In addition, water trapped in the fine-grained sands was characterized by comparing the porosity from the electromagnetic propagation log to the free fluid index from the nuclear magnetism log. Identification of the depositional facies coupled with these log responses produced an innovative interpretation of the invasion profile. From an oil-bearing gross interval of 262 ft (80 m) 9 sand units were defined according to their primary and secondary (steam processing) production capability. End_of_Article - Last_Page 516------------