Log Correlation Research Articles

A log correlation of the Rotliegend of the northern Cleaver Bank High: the search for controls on reservoir sand distribution

Gamma ray log correlations of some 50 Open File wells were used to investigate the distribution and relative age of aeolian Leman Sandstone developments across the northern Cleaver Bank High. The correlations led to a sequence stratigraphic interpretation based on a depositional record of climatically forced fluctuations in the level of the Silverpit Formation playa lake system. This confirmed the widely reported diachroneity of the Leman Sandstone and identified the onlapped Base Permian palaeotopography and climatically forced, generally positive, changes in the water budget of the Silverpit Lake as the chief controls on aeolian sand distribution. However, a ‘1/f n ’ power law distribution of changes in water budget is preferred to the idea of strictly cyclic climatic control. On this basis, the transgression of the northern Cleaver Bank High and the occurrence of aeolian and lacustrine end-member facies within depositional sequences of uniform thickness can be understood. Interval isochores were used to derive palaeotopographic maps of the Base Permian. Taken in conjunction with the observed facies of the onlapping depositional sequences, the maps locate under-explored basal aeolian Leman Sandstone play fairways.

Abundances of 30 Elements in 23 Metal‐Poor Stars

We report the abundances of 30 elements in 23 metal-poor ([Fe/H] <-1.7) giants. These are based on 7774 equivalent widths and spectral synthesis of 229 additional lines. Hyperfine splitting is taken into account when appropriate. Our choice of model atmospheres has the most influence on the accuracy of our abundances. We consider the effect of different model atmospheres on our results. In addition to the random errors in Teff, log g, and microturbulent velocity, there are several sources of systematic error. These include using Teff determined from FeI lines rather than colors, ignoring NLTE effects on the FeI/FeII ionization balance, using models with solar [alpha/Fe] ratios and using Kurucz models with overshooting. Of these, only the use of models with solar [alpha/Fe] ratios had a negligible effect. However, while the absolute abundances can change by > 0.10 dex, the relative abundances, especially between closely allied atoms such as the rare earth group, often show only small (<0.03 dex) changes. We found that some strong lines of FeI, MnI and CrI consistently gave lower abundances by ~0.2 dex, a number larger than the quoted errors in the gf values. After considering a model with depth-dependent microturbulent velocity and a model with hotter temperatures in the upper layers, we conclude that the latter did a better job of resolving the problem and agreeing with observational evidence for the structure of stars. The error analysis includes the effects of correlation of Teff, log g, and microturbulent velocity errors, which is crucial for certain element ratios, such as [Mg/Fe]. The abundances presented here are being analyzed and discussed in a separate series of papers.

Permo–Triassic rocks in boreholes in the Annan-Canonbie area, Dumfries and Galloway, southern Scotland

Synopsis Recent boreholes provide new data on the sequence, age, lithology and geophysical log stratigraphy of Late Permian and Early Triassic strata on the northern edge of the Carlisle Basin. Late Permian evaporites (gypsum-anhydrite) and microfloras are recorded and described for the first time in onshore Scotland. The lower, argillaceous and evaporite-bearing strata are assigned to the Eden Shales Formation and are divided into three informal lithostratigraphical units, in ascending order ES1, ES2 and ES3. The Eden Shales grade upwards into the St Bees Sandstone Formation. The strata closely resemble those in neigh-bouring Cumbria, and help to refine some details of regional palaeogeography and correlation. Regional log correlation suggests that a significant evaporite-bearing Late Permian section is missing, probably cut out by faulting, in the Silloth-1A Borehole, the main deep borehole penetrating the Carlisle Basin.

Failure of an industrial wastewater lagoon in a karst terrain and remedial action

Failure of a wastewater lagoon, caused by development of a sinkhole underneath the lagoon at a site in the Lehigh River Valley near Allentown, Pennsylvania, allowed waste water to enter into the underlying karstified carbonate aquifer, a source of public water supply in the area. Identification of the contamination and development of an appropriate site-specific remediation plan required understanding of site geology, stratigraphy, hydrogeologic setting and aquifer characteristics. Information on site geology and hydrogeology, including aquifer geometry and matrix, occurrence and flow of groundwater were collected and evaluated. Core holes were drilled, geophysically logged, and correlated to define stratigraphy and structural controls to the movement of groundwater and pollutants. Monitoring wells were installed. Water level data collected on a continuous basis were used to determine the direction and gradient and also correlated with climatic changes to define amplitude of fluctuations of groundwater. Correlation of lithologic logs and interpretation of geophysical logs identified five water-producing zones separated by semi-confined layers within the carbonate aquifer. Water samples were collected from different water producing zones and analyzed to delineate vertical and horizontal extent of contamination. Pentaerythritol (PE), which was directly linked with the failure of lagoon, was identified as a pollutant in groundwater. PE was found to be present in the lower water-producing zones. Based on a geologic and hydrogeologic model of the site and understanding of flow regime and presence of PE in the lower water producing zones, a remedial plan (a pump-and-treat system) was developed and implemented to remediate the aquifer. This remedial action has reduced the PE level in groundwater and also created a pressure trough as a barrier to off-site migration.

Nonlinear free energy relationship in the general-acid-catalyzed acylation of rat kidney gamma-glutamyl transpeptidase by a series of gamma-glutamyl anilide substrate analogues.

The gamma-glutamyl transpeptidase (GGT) purified from rat kidney reacts with a series of eight parasubstituted L-glutamyl gamma-anilides, in the presence of Gly-Gly, catalyzing the formation of gamma-Glu-Gly-Gly (pH 8.0, 37 degrees C). The transpeptidation reaction was followed through the discontinuous colorimetric determination of the concentration of released parasubstituted aniline. Steady-state kinetic studies were performed to measure k(cat) and K(M) values for each anilide substrate. A Hammett plot constructed by the correlation of log(k(cat)) and the sigma(-) parameter for each anilide substrate displays statistically significant upward curvature, consistent with a general-acid-catalyzed acylation mechanism in which the geometry of the transition state changes with the nature of the para substituent. Kinetic isotope effects were measured and are consistent with a reaction involving a proton in flight at the rate-limiting transition state. The pH-rate profiles measured over pH 7.0-9.5 are bell-shaped with kinetic pK(a) values that may be attributed to the active site nucleophile (or its general-base catalytic partner) and the active-site general acid. The variation of the latter pK(a) value as a function of temperature is consistent with an enthalpy of ionization expected for an ammonium ion acting as a general acid. Examination of the variation of k(cat) as a function of temperature gave values for the enthalpy and entropy of activation that are similar to those determined for the general-acid-catalyzed breakdown of the tetrahedral intermediate formed during acylation of chymotrypsin by similar amide substrates.

Determination of octanol–water partition coefficients of pesticides by microemulsion electrokinetic chromatography

Microemulsion electrokinetic chromatography (MEEKC) was evaluated as a screening tool for the indirect measurement of octanol–water partition coefficients (log P o/w) of pesticide compounds. Over 80 pesticide compounds representing a variety of structural characteristics were studied, and good correlation of log P o/w with the logarithm of the retention factor was found. The microemulsion system studied allowed the separation of compounds in the log P o/w range of −1 to 7. In addition, a smaller set of simple organic molecules that vary in structural features was evaluated and compared to the pesticide log P o/w calibration. The pesticide and simple organic molecule log P o/w calibration lines were statistically similar. This suggests that a universal set of standard compounds may be employed for the log P o/w calibration to provide measurements for a variety of compounds with good accuracy.

N-Arylhydroxamic Acids as Novel Oxidoreductase Substrates

N-Arylhydroxamic acids (AHAs) are promising novel N−OH mediators for oxidoreductase catalysis. They are electrochemically active compounds with a redox potential of 0.31−0.41 V vs. SCE. Representative oxidoreductases, e.g. fungal peroxidase from Coprinus cinereus (rCiP), catalyze the oxidation of AHAs with apparent bimolecular constants (kox) of 7.1·103 to 1.5·107M−1s−1 at pH = 8.5 and 25 °C. The limiting step in substrate oxidation was the reduction of compound II (Cpd II). The oxidation constants of N-hydroxyacetanilide (1a) and N-hydroxy-N-phenylbenzamide (2a), determined by a stopped-flow and steady-state method, were similar. The decrease in the reduction rate of Cpd II reduction rate decrease occurred at pKa = 8.5 for 1a and 7.7 for 2a. The nitroxyl radical of 1a, an intermediate in the oxidation, shows decreasing stability at alkaline pH. The structure−activity relationships (SARs) of these AHAs were analyzed within the framework of Marcus cross-relationship, and by using ab initio quantum chemical calculations. A linear correlation of log(kox) vs. redox potential was only indicated for benzamides, as predicted by electron transfer theory. Acetamides showed the opposite tendency: the constant (kox) increased if the potential of substrate increased. The correlation between log(kox) and HOMO (Highest Occupied Molecular Orbital) energy revealed that for benzamides the reactivity decreased with decreasing HOMO energy, whereas for acetamides the reactivity increased if the HOMO energy decreased. The rather low reactivity of these AHAs and the unexpected dependence on the redox potential and the HOMO energy could be explained by the electronic structure of the AHAs and the substrates docking in the active center of the enzyme.

Electron ionization mass spectra of 3,4-disubstituted-1,2,4-oxa(thia)diazole-5(4H)-thione(ones). Substituent effects on the mass spectrometric rearrangement of 3-aryl-4-(p-tolyl)-1,2,4-oxadiazole-5(4H)-thiones to the corresponding oxo compounds.

The fragmentation behaviour of ten 3,4-disubstituted 1,2,4-oxadiazole-5(4H)-thiones and seven 3,4-disubstituted 1,2,4-thiadiazole-5(4H)-ones studied here confirmed the earlier observations about the partial rearrangement of the former after ionization into the latter before further fragmentation. In the case of eight 3-(substituted phenyl)-4-(p-tolyl)-1,2,4-oxadiazole-5(4H)-thiones the fragmentations reflecting the above-mentioned molecular ion rearrangement show a clear correlation on the substituent sigma values. The electron-withdrawing substituents destabilize the molecular ion, so higher amounts of the rearranged ion [R(1)NCO](+.) are obtained. A good correlation of log[R(1)NCO](+) against sigma was obtained (r = 0.96). Only a satisfactory correlation prevailed for log([R(1)NCO](+)*/[R(1)NCS](+)*) against sigma(r = 0.87).

Kinetic studies of guinea pig liver transglutaminase reveal a general-base-catalyzed deacylation mechanism.

Guinea pig liver transglutaminase (TGase) reacts with 0.1 mM N-Cbz-L-Glu(gamma-p-nitrophenyl ester)Gly (5, prepared herein, K(M) = 0.02 mM) to undergo rapid acylation that can be followed spectrophotometrically at 400 nm (pH 7.0, 25 degrees C). Deacylation of the transiently formed thiolester acyl enzyme intermediate via catalytic aminolysis was studied in the presence of six primary amines of widely varying basicity (pK(NH+) = 5.6-10.5). Steady-state kinetic studies were performed to measure k(cat) and K(M) values for each amine substrate. A Brønsted plot constructed through the correlation of log(k(cat)/K(M)) and pK(NH+) for each amine substrate displays a linear free-energy relationship with a slope beta(nuc) = -0.37 +/- 0.08. The shallow negative slope is consistent with a general-base-catalyzed deacylation mechanism in which a proton is removed from the amine substrate during its rate-limiting nucleophilic attack on the thiolester carbonyl. Kinetic isotope effects were measured for four acceptor substrates (water, kie = 1.1 +/- 0.1; aminoacetonitrile, kie = 5.9 +/- 1.2; glycine methyl ester, kie = 3.4 +/- 0.7; N-Ac-L-lysine methyl ester, kie = 1.1 +/- 0.1) and are consistent with a proton in flight at the rate-limiting transition state. The active site general-base implicated by these kinetic results is believed to be His-334, of the highly conserved TGase Cys-His-Asp catalytic triad.

Petrography and palynology of quartzites in the Sirte Basin, central Libya

Petrographic and palynological analysis and wireline log correlations of the so-called pre-Upper Cretaceous ‘quartzites’ in the central Sirte Basin permits, for the first time, the recognition of the development of six types of quartzites and sandstones of Late Cambrian, Late Devonian, Devonian-Carboniferous and Early Cretaceous age. The Late Cambrian section age, dated by the presence of associated marine acritarchs Vulcanisphaera turbata and Retisphaeridium dichamerum, comprises two shallow marine quartzite units separated by a varicoloured argillaceous feldspathic sandstone unit (Red Beds). The two quartzite units show tidal bedding and mud couplets. They were probably deposited in a subtidal environment. They form fractured reservoirs in the giant Attahaddy Gas Field. The varicoloured sandstone unit (Red Beds) is rich in Skolithos and was probably deposited in an intertidal environment. A Late Devonian (Strunian) shallow marine to continental sandstone unit age dated by the marine acritarch Gorgonisphaeridium solidum and the land-derived spore Verruciretusispora cf. famenensis has been identified in wells V1-59 in the southwest of the study area and EE1-59 in the southeast. A Carboniferous (Visean) sandstone unit age dated by the land-derived spores Aratrisporites saharaensis and Calamospora sp. has been identified in wells C3-6, KKKK1-6, BBBB2-6 and V1-59. The Early Cretaceous continental fractured quartzite unit dated by tricolpate pollen produces oil in the Wadi Field. The study reveals that the Devonian and Carboniferous sandstones, with good primary porosity, previously considered Nubian and Cambro-Ordovician, respectively, form an attractive hydrocarbon-bearing trend in the southern part of the study area.

Ketene reactions with the aminoxyl radical tempo: preparative, kinetic, and theoretical studies.

Tetramethylpiperidinyloxy (TEMPO, TO*) reacts with ketenes RR(1)C=C=O generated by either Wolff rearrangement or by dehydrochlorination of acyl chlorides to give products resulting from addition of one TEMPO radical to the carbonyl carbon and a second to the resulting radical. Reactions of phenylvinylketenes 4b and 4f, phenylalkynylketene 4c, and the dienylketene AcOCMe=CHCH=CHCMe=C=O (11) occur with allylic or propargylic rearrangement. Even quite reactive ketenes were generated as rather long-lived species by photochemical Wolff rearrangement in isooctane solution, characterized by IR and UV, and used for kinetic studies. The rate constants of TEMPO addition to eight different ketenes have been measured and give a qualitative correlation of log k(2)(TEMPO) = 1.10 log k(H(2)O) -3.79 with the rate constants for hydration of the same ketenes. Calculations at the B3LYP/6-311G//B3LYP/6-311G level are used to elucidate the ring opening of substituted cyclobutenones leading to vinylketenes and of 2,4-cyclohexadienone (17) forming 1,3,5-hexatrien-1-one (18).

Correlation between migration behaviors of antiozonants and temperature

AbstractMigration behaviors of antiozonants depending on temperature were studied using a carbon black‐filled NR vulcanizate containing N‐phenyl‐N′‐isopropyl‐p‐phenylenediamine (IPPD) and N‐phenyl‐N′‐(1,3‐dimethylbutyl)‐p‐phenylenediamine (HPPD) as antiozonants. The experimental temperatures were 100, 90, 80, and 70°C. Migration rates of them increased steeply by increasing the temperature. The correlation between the migration rates and the temperature was investigated using the half (t1/2)‐ and quarter (t1/4)‐lifetimes of the migrants remaining in the vulcanizate after the migration. The plot of log t versus 1/T was well fitted by the linear equation: The correlation coefficients were higher than 0.995. It was found that the migration behavior and temperature had a correlation of log t = b/T + c, where t and T are the migration time and temperature, b is Ea/R, and c is the constant. The activation energies for the migration were 36.48 and 37.93 kJ/mol for IPPD and HPPD, respectively. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 80: 1566–1570, 2001

Structural core analysis from the Gullfaks area, northern North Sea

Comprehensive analyses of more than 8 km of core data from the Gullfaks area, northern North Sea, have proven invaluable for a thorough understanding of the detailed deformation characteristics. In addition, the integration of the results with analyses of dipmeter data, well log correlation data, seismic data and field analogue data yields important information on the general structural characteristics and reservoir properties. Microanalyses show that all faults in the reservoirs are associated with abundant shear bands (deformation bands) clustered in a narrow damage zone that seldom exceeds a few tens of metres in width. Where mica is abundant, the bands are dominated by phyllosilicate framework structures, whereas disaggregation structures dominate cleaner sandstones. Permeability reduction across the shear bands depends on the amount of phyllosilicates present and is generally negligible in clean sandstones. Only minor amounts of cataclasis are observed. The width of the shear bands increases with increasing grain size. Orientation analyses of the dip of shear bands associated with minor faults show that these are symmetrical around a vertical axis. Since the general bedding rotation as observed in well data and seismic data is 10° towards the west, most shear bands must have formed after the rotation of bedding. This is likely because minor faults formed as (late) accommodation structures during slip along the main faults. The reservoir rocks are affected ductilely (by fault drag) in a zone wider than that affected by shear bands. This shows that part of the deformation was by a homogeneous redistribution of individual grains rather than by shear bands or discrete faulting. The integrated analyses of core data with seismic data demonstrate that most (curvi-)linear and fault-like features observed on seismic attribute maps are in fact noise-related.

N-Aryl-N-Hydroxy Urethanes as Peroxidase Substrates

N-Aryl-N-hydroxy urethanes (AHUs), which are promising N*OH mediators for oxidoreductase catalysis, are electrochemically active redox compounds with a redox potential of 0.35–0.40 V vs. SCE (0.59–0.64 V vs. NHE). Alkyl substituents in the carbamic acid residue have, as expected, only little influence on the redox potential. The highest potential was noticed for N-hydroxy-N-(4-cyanophenyl)-carbamic acid methyl ester. Recombinant Coprinus cinereus peroxidase (rCiP) catalyzes oxidation of the AHUs with apparent bimolecular constants k ox of 2.5ċ104–7.5ċ104 M −1s−1 at pH = 8.5 and 25°C. Structure-function connectivities of the substrates were analysed within the framework of the Marcus cross relationship and by using ab initio quantum chemical calculations. An excellent correlation of the redox potentials and the HOMO energies could be found. However, no correlation of log(k ox) with redox potential and HOMO energy was indicated as predicted by theory. This was explained by specific docking of the substrates in the active center of rCiP.

Evidence for Strike-Slip Faulting in the Smackover Formation of Northeast Texas and South Arkansas and Its Geological Implications

ABSTRACT Surface expression, seismic profiles, gravity and magnetic mapping, and well control provide evidence for strike-slip faulting in the Smackover Formation of East Texas and South Arkansas. The faulting that occurred after the deposition of Smackover and during the deposition of Buckner Anhydrite appears to be an extension of the South Florida shear zone. Evidence includes drainage patterns; lineaments on Lansat imagery; seismic lines with flower structure fault patterns; magnetic data with ridges broken by right lateral offsets; and well log correlations with abrupt termination of horizons. The strike-slip faulting triggered significant geological events. The faulting breached the mountains and highlands surrounding the ancient Gulf, initiating the drainage systems that subsequently filled the basin. Fault breaks in the Buckner allowed meteoric water to reach the Louann Salt causing dissolution initiating the development of salt basin structure. Early diagenetic events in the Smackover involving fabric selective dissolution and dolomitization also began with the water incursion. Convergent movement along the strike of the fault created basement rock structure. Pre-existing basement structures were truncated and offset. However complex, there is still predictability in the system, the structures will occur along the trace of the fault. Although a strike-slip fault interpretation is a new concept in this region, the option has economic importance, and as more complete subsurface data becomes available, the concept can be tested.

Ghadames basin, southern Tunisia: A reappraisal of Triassic reservoirs and future prospectivity (E &amp;amp; P Notes)

Recent discoveries of oil and gas in Triassic reservoirs of the Ghadames basin, eastern Algeria, suggest that similar potential exists to the east, in the southern Tunisian part of the province. For decades, southern Tunisia has remained an underexplored part of the basin, in large part owing to older geological interpretations that focus on Paleozoic reservoirs and to limitations in seismic data quality, resulting from statics problems, that have rendered trap identification inaccurate or tenuous. New analyses of previously and recently acquired geological and geochemical data, as well as improvements in seismic data acquisition and processing, have begun to reverse older notions regarding limited hydrocarbon presence in southern Tunisia. Log correlations indicate that productive, sand-rich intervals of the major Triassic reservoir in the region, the Trias Argilo Greseux Inferieur (TAGI), can be correlated over large distances, suggesting significant continuity into lightly drilled and undrilled areas. Analyses of geochemical data reveal a more complex, multistage history of hydrocarbon maturation and migration than previously believed. Much greater volumes of petroleum have been generated and a larger variety of traps have been created than can be accounted for by older interpretations. Where added to the use of new field and processing parameters for seismic surveys, these factors have together led to important, upgraded evaluations of basin potential in southern Tunisia.

Mine failure associated with a pressurized brine horizon; Retsof salt mine, western New York

Abstract The eventual loss of the Retsof Salt Mine from flooding was initiated on March 12, 1994 with a magnitude 3.6 earthquake, the collapse of a small-pillar panel, an initial inrush of brine and gas to the mine and a sustained inflow of fresh water. An examination of closure data for two mine panels involved in the inflow suggested an anomalous buildup of fluid pressure above the panels in the period leading up to their collapse. The initial brine and gas inflow immediately following the collapse coincided with the apparent relief of the excess pressure. The potential existence of a pre-collapse, pressurized, brine and gas pool above the panels was investigated through an analysis of nineteenth century solution mining data, a review of recent salt mine data, and an interpretation of geologic and geophysical data from post-collapse investigations. Published reports from the nineteenth century reveal that natural brine and gas pools existed in the region prior to mining. Correlation of gamma ray logs with geologic logs from contemporary drill holes and core holes provided a mechanism for interpreting the distribution of those natural brine pools. Our investigation indicated that natural gas and brine pools existed within Unit D of the Syracuse Formation approximately 160 ft above the mining horizon. Such brine accumulation apparently formed from the circulation of meteoric water through vertical discontinuities that were connected to overlying fresh water aquifers long before mining began in the valley in the late nineteenth century.

Free volume model and tradeoff relations of gas permeability and selectivity in glassy polymers

A simple free volume model for permeability ( P) and diffusivity ( D) of polymers has been used to obtain various linear correlations of the type log P i versus log P j or log D i versus log D j for gas pairs M i and M j . These correlations are proven for several hundred glassy polymers and various gas pairs. An important implication of this result is that it predicts the well-known tradeoff relation between permeability P i and permselectivity P i / P j considered by many authors. Possible ways for improving the combination of these two parameters of membrane polymeric materials are discussed. In particular, the role of sorption selectivity and its enthalpic and entropic contributions are emphasized.

Abstract: Refining well log correlation in the Greater Enchilada Area, Mexican Buffet Region,"NE Garden Banks, Gulf of Mexico, using high resolution nannoplankton biostratigraphy"

Abstract: Refining well log correlation in the Greater Enchilada Area, Mexican Buffet Region,"NE Garden Banks, Gulf of Mexico, using high resolution nannoplankton biostratigraphy"

ABSTRACT: A Re-Evaluation of the Hackberry--New Life for a Comatose Trend

Abstract The Oligocene Hackberry trend of southeast Texas and southwest Louisiana has posed one of the Gulf Coast's most perplexing targets for petroleum exploration. Thick, high-quality pays and moderate drilling depths have lured many explorationists to try to unlock its potential. However, reservoir extent has, in the past, been unpredictable. The play was all but abandoned during the late 1980s and early 1990s. A regional re-evaluation of the geologic model arose from the assimilation of well log correlations, dipmeter use and evaluation, interpretation of paleontological reports, and the combination of quality 2-D seismic data. From this work it became very apparent that the majority of the trend should be interpreted as a sub-unconformity/slump block play and not a deep-marine, basin-floor/turbidite sequence. The new model predicted reservoir extent and thickness concisely and logically. The history of the trend is one of prograding shallow-marine deposition from the lower Frio Formation through the Nodosaria blanpiedi and Nonion struma zones, followed by thick shallow-water deposition of up to 500 feet of strand plain sands in the upper Frio Formation. Basin collapse, resulting from regional salt withdrawal and development of salt domes, caused over-steepening of the sea floor. The result was slumping of the soft sediments from the underlying Vicksburg Formation through the early Upper Frio strand plain deposits. Wave-base erosion removed most of the youngest sand section. The erosion was followed by marine shale deposition containing the diagnostic Hackberry faunal assemblage. As subsidence ceased and the basin finally filled with shale, shallow-marine strand plain deposition continued through deposition of the upper Frio section. Armed with this geologic model, a group of industry partners partook to gather regional 3-D seismic coverage in order to take advantage of more than 500 undrilled square miles that still existed in the trend. Eventually the effort resulted in 25 successful wells out of 30 attempts. End_of_Record - Last_Page 281-------