Depositional Heterogeneities and Brittleness of Mudstone Lithofacies in the Marcellus Subgroup, Appalachian Basin, New York, U.S.A.

Organic-rich rocks of the Marcellus subgroup in the study area consist of a diverse suite of mudstone lithofacies that were deposited in distinct facies belts. Lithofacies in the succession range in composition from argillaceous to siliceous, calcareous, and carbonaceous mudstone. Heterogeneities in the succession occurs in the form of varying mineralogical composition, slightly bioturbated to highly bioturbated chaotic matrix, organic-rich and organic-lean laminae, scattered fossil shells in the matrix, and fossils acting as lamination planes. Lithofacies were deposited in three facies belts from the proximal to the distal zone of the depositional system. Bedded siliceous mudstone (BSM) facies occur in the proximal facies belt and consists of a high quartz content in addition to clay minerals and pyrite. In the medial part of the facies belt lies the laminated argillaceous mudstone (LAM), bedded calcareous mudstone (BCaM), and bedded carbonaceous mudstone (BCM). The size of detrital mineral grains in the lithofacies of the medial facies belt is larger than bedded argillaceous mudstone (BAM) of the distal facies belt, characterized by clay-rich matrix with occasional fossil shells and horizontally aligned fossils. Two types of horizontal traces and one type of fecal string characterize the proximal mud-stone facies, whereas only single horizontal trace fossil is found in the mudstones of the medial and distal facies belt. Parallel alignment of fossil shells and fossil lags in lithofacies indicate that bed-load transport was active periodically from the proximal source of the depositional system. Bioturbation has heavily affected all of the lithofacies and presence of mottled burrows as well as Devonian fauna indicate that oxic to dysoxic conditions prevailed during deposition. The deposition of this organic-rich mudstone succession through dynamic processes in an overall oxic to dysoxic environment is different from conventional anoxic depositional models interpreted for most of the organic rich black shales worldwide. Total organic content (TOC) varies from top to bottom in the succession and is highest in BCM facies. The brittleness index, calculated on the basis of mineralogy, allowed classification of the lithofacies into three distinct zones, i.e., a brittle zone, a less brittle zone, and a ductile zone with a general proximal to distal decrease in the brittle behavior due to a decrease in the size of the sediments.

Melt in the Greenland EastGRIP ice core reveals Holocene warming events

We present a record of melt events obtained from the EastGRIP ice core, in central north eastern Greenland, covering the largest part of the Holocene. The data were acquired visually using an optical dark-field line scanner. We detect and describe bubble free layers and -lenses throughout the ice above the bubble-clathrate transition, located at 1100 m in the EastGRIP ice core, corresponding to an age of 9720 years b2k. We distinguish between melt layers (bubble free layers continuous over the width of the core), melt lenses (discontinuous), crusts (thin and sharp bubble free layers) and attribute three levels of confidence to each of these, depending on how clearly they are identified. Our record of melt events shows a large, distinct peak around 1014 years b2k (986 CE) and a broad peak around 7000 years b2k corresponding to the Holocene Climatic Optimum. We analyze melt layer thicknesses and correct for ice thinning, we account for missing layers due to core breaks, and ignore layers thinner than 1.5 mm. We define the brittle zone in the EastGRIP ice core from 650 m to 950 m depth, where we count on average more than three core breaks per meter. In total we can identify approximately 831 mm of melt (corrected for thinning) over the past 10,000 years. We compare our melt layer record to the GISP2 and Renland melt layer records. Our climatic interpretation matches well with the Little Ice Age, the Medieval and Roman Warm Periods, the Holocene Climatic Optimum, and the 8.2 kyr event. We also compare the most recent 2500 years to a tree ring composite and find an overlap between melt events and tree ring anomalies indicating warm summers. We open the discussion for sloping bubble free layers (tilt angle off horizontal > 10°) being the effect of rheology and not climate. We also discuss our melt layers in connection to a coffee experiment (coffee as a colored substitute for melt infiltration into the snow pack) and the real time observations of the 2012 CE rain event at NEEM. We find that the melt event from 986 CE is most likely a large rain event, similar to 2012 CE, and that these two events are unprecedented throughout the Holocene. Furthermore, we suggest that the warm summer of 986 CE, with the exceptional melt event, was the trigger for the first Viking voyages to sail from Iceland to Greenland.

Deep ice-core drilling to 800 m at Dome A in East Antarctica

A deep ice core was drilled at Dome A, Antarctic Plateau, East Antarctica, which started with the installation of a casing in January 2012 and reached 800.8 m in January 2017. To date, a total of 337 successful ice-core drilling runs have been conducted, including 118 runs to drill the pilot hole. The total drilling time was 52 days, of which eight days were required for drilling down and reaming the pilot hole, and 44 days for deep ice coring. The average penetration depths of individual runs were 1 and 3.1 m for the pilot hole drilling and deep ice coring, respectively. The quality of the ice cores was imperfect in the brittle zone (650−800 m). Some of the troubles encountered are discussed for reference, such as armoured cable knotting, screws falling into the hole bottom, and damaged parts, among others.

Characterization of organic content, brittleness index and geomechanical properties of the Eocene Cambay Shales – Insights from the Ankleshwar oil field in Western India

Shale resource assessment involves a detailed characterization of organic and geomechanical parameters for better insights on the reservoir properties and classifying areas of economic yield. In order to assess the Eocene Younger Cambay Shale (YCS) Group of the Ankleshwar field, western India for feasible shale resource play, we have applied a multistage screening methodology that combines estimation of organic richness, brittleness index, and geomechanical analyses. The estimated thermal maturity (Ro) and average total organic carbon (TOC) contents are within the range of 0.8-1.0 and 1.8 wt%, respectively. These estimates are comparable to the reported core-based measurements. Brittleness index (BI) based on the mineralogical composition reveals that the YCS intervals of marine origin fall into the ‘less ductile’ to ‘brittle’ zone, whereas the elastic property based estimated BI falls into the ‘less brittle’ to ‘high brittle’ zone. We established a field relationship between BI and shale volume and also deciphered the effect of TOC content on the rock elastic properties. Pore pressure in the shales is slightly above the hydrostatic gradient (10.5-11.5 MPa/km). The estimated average fracture pressure of 18.5 MPa/km, together with the BI of moderately ductile to less brittle behavior suggests that the studied shales are capable of withstanding substantial strain while hydrofracturing for effective production. We demonstrate an expedient example to characterize a potential shale unit within a producing hydrocarbon field utilizing the drilled wells with limited or no core data.

Tracking local brittle zone in the heat affected zone of girth-welded API 5L x46 pipe

In this study, microhardness variation as well as macro and micro structural examination of the heat affected zone (HAZ) of a girth welded API 5L X46 pipeline material were conducted as a means of tracking local brittle zone (LBZ) in the HAZ region. The weldment analysed were built from heat input range of 695 J/mm – 2567 J/mm. Analysis of the results revealed that the HAZ profile changes with variation in the heat input and becomes shallow but wider as the heat input increases. Defects free welds were achieved under the heat input range of 1650 J/mm – 2017 J/mm welding condition. Localized high hardness values were obtained at certain locations within the HAZ of intermediate heat input welds produced at 1467 J/mm due to thermal stresses induced strains at this heat input in the resolidified weld. Other than this, non-equilibrium rapid heating/cooling that is common during welding as well as the magnitude of mechanical strain generated on cooling vary with heat input and was attributed to the development of high hardness value at localized region within the HAZ of the welds in low heat input welding condition. The macrographic profile at these locations, contrasted against that of a failed pipeline material of similar specification obtained from typical oil and gas infrastructure, established that crack initiation and propagation followed the trend of microhardness variations in the girth welded pipe. The crack initiates at specific location in the HAZ with very high hardness in the range 186-216 Hv within a radius of about 3-5 mm from the edge of the fusion zone. Keywords: API 5L X46; Girth welding; Heat input; Heat affected zone; Local brittle zones

High-Temperature Mechanical Properties of 4.5%Al δ-TRIP Steel

The high-temperature mechanical properties of a 4.5% Al-containing δ-transformation-induced plasticity (TRIP) steel were studied by using the Gleeble 3500 thermomechanical simulator. The zero ductility temperature (ZDT) and the zero strength temperature (ZST) were measured, and the brittle zones were divided. The phase transformation zone was determined by differential scanning calorimetry (DSC). The temperature of the phase transformation and the proportion of the phase were calculated by the Thermo-Calc software. The ZDT and the ZST of the 4.5% Al-containing δ-TRIP steel are 1355 and 1405 °C, respectively. The first brittle zone and the third brittle zone of the steel are 1300–1350 °C and 800–975 °C, respectively. The reason for the embrittlement of the third brittle zone of the 4.5% Al-containing δ-TRIP steel is that the α-ferrite formed at the austenite grain boundary causes the sample to crack along the grain boundary under stress. The ductility of the 4.5% Al-containing δ-TRIP steel decreases first and then increases with the increase of the α-ferrite. When the proportion of the α-ferrite reaches 37%, the reduction of area (RA) of the 4.5% Al-containing δ-TRIP steel is reduced to 44%. The 4.5% Al-containing δ-TRIP steel has good resistance to the high-temperature cracking.

Hot Ductility Behavior of 9SiCr Alloy Tool Steel by Thin Slab Casting

In order to evaluate the feasibility of 9SiCr alloy tool steel produced by thin slab casting, the high temperature mechanical properties of 9SiCr alloy tool steel were investigated by Gleeb-1500 thermal simulator. The morphologies of the tensile fracture at different temperatures were observed by scanning electron microscope (SEM), together with analysis of fracture mechanisms in different regions. The results showed that there were two brittle zones in the temperature range from 600 °C to 1200 °C. A melting fracture was characterized in the high temperature brittle zone of above 1170 °C, whereas a typical cleavage fracture was exhibited in the low temperature brittle zone from 820 °C to 600 °C, Meanwhile, a good hot ductility behavior characterized by typical dimple fracture was demonstrate at the temperature range from 1170 °C to 820 °C.Thus, the 9SiCr alloy tool steel with the final gauge of 1.5mm was produced by CSP, based on the optimal process parameters.

An Investigation on Microstructural Evolution of X70 Steel Pipe During Hot Induction Bending

It is generally accepted that hot induction bending (HIB) results in a decrease in strength and an increase in fracture toughness in bend area, heat affected zone (HAZ) and weld metal (WM). As the result, Post bend heat treatment (PBHT) is not considered to be a requirement and could be waived for saving money and time. This research work raises the concern that factual verification of proper microstructure and no localized brittle zone is vitally necessary prior to waving PBHT. Evaluation of the steel microstructure and mechanical properties as the result of various pipe chemistries during pipe bending has been verified in this experimental work. It is emphasized that knowledge and control of prior steel pipe chemistry, control of temperature, cooling rate and bending speed assures the reliability and repeatability of induction bends, especially in critical environments such as low temperature application. In the present work, qualitative and quantitative microstructural analysis, hardness and impact test performed and evaluated on samples from X70 line pipe with 3 different steel chemistries. The samples prepared from different locations on body, weld and HAZ in the as received and as bent condition. It was found that the final microstructure and mechanical properties in the as bent condition is dependent on the chemistry, steel cleanliness and microstructural uniformity. It was observed that small localized brittle zone with traces of upper Bainite and Martensite islands could be transformed in the microstructure with rich chemistry containing non-homogenous central segregation. It is concluded that factual verification of proper microstructure with no localized hard zone is required prior to waving PBHT.