Conglomerate Layers Research Articles

Application of Integrated Geological and Geophysical Surveys on the Exploration of Chalcedony Deposits: A Case Study on Nanhong Agate in Liangshan, China

Nanhong agate, esteemed for its vivid color and natural shine, is experiencing a scarcity in supply despite its high demand. The primary deposits of agate, typically found near the surface, have not been extensively explored due to the predominance of traditional manual excavation methods. This research examined the Nanhong agate deposits in the Zhaojue–Meigu region of Liangshan, China, employing the integration of geological and geophysical surveys. Field geological surveys allowed us to outline the general areas where agate is found. Following this, using magnetic surveys, vertical electrical sounding, and controlled-source audio magnetotellurics, agate deposits were located within the conglomerate layer of the second member of the Feixianguan Formation from the Lower Triassic period at depths of less than 100 m. Our results identify mineralized layers, Xuanwei Formation mudstone, and the underlying bedrock, thus supporting the creation of a mineral prediction map. This research provides essential insights and guidance for agate exploration and the development of associated mineral resources.

Reevaluating soil amplification using multi-spectral HVSR technique in La Chana Neighborhood, Granada, Spain

This work presents a thorough reevaluation of soil amplification in the La Chana neighborhood of Granada through a pioneering application of the horizontal-to-vertical spectral ratio technique on seismic noise data using various spectral approaches. The research recycles old seismic noise data recorded at 34 stations with 2 Hz instruments in the year 2010, supplemented with additional measurements recorded with broadband seismometers at nearby locations in the years 2013 and 2017. Initial traditional processing identifies a narrowband dominant frequency around 1.5 Hz, attributed to artificial or anthropogenic sources. To address this, the Maximum Entropy Algorithm was implemented to smooth the spectral response below 1 Hz, and filter out frequency peaks with very narrow spectral bands, while preserving the narrowband frequency around 1.5 Hz in some records. The Thomson Multitaper method further refined the spectral ratio, emphasizing the detection and suppression of narrow frequency bands that may be related to industrial activity. The results demonstrated the reappearance of the 1.5 Hz frequency, but this time without narrow bandwidths, indicating its possible correlation with the natural ground movement. Fundamental periods, ranging from 0.45 s to 0.88 s, suggest a diverse lithological composition, indicating the presence of layers of sands, clays, conglomerates, and carbonates over a basement that represents the main impedance contrast in the area. The multispectral approach surpasses conventional methods in precision and reliability, providing valuable insights for earthquake risk assessment, urban planning, and engineering decisions in seismically active regions.

Geoelectric Interpretation of Wenner-Schlumberger Configuration Using Res2Dinv Software: A Case Study of 2D Mapping of Seawater Intrusion in a Landslide Potential Area, North Halmahera District, Indonesia

Research has been carried out on landslides in Saluta-Pelita Village, North Galela District, North Halmahera Regency, Indonesia using the Wenner-Schlumberger method using a Geoelectric Resistivity tool - Naunira NRD 300 HF. This research aims to determine the structure of the subsurface layer in the potential landslide area of Saluta-Pelita Village. In addition, this research aims to determine the slip plane (boundary layer) of sea water intrusion in the research area. The measurement results are processed using Res2Dinv software for 2D resistivity which describes the subsurface layer shown in color. The measurement results on track 1 show a clay layer with a resistivity value of 3.1 ohm -27 ohm at a distance of 1-80 meters (blue and green), a silt layer of 44.3 ohm - 184.1 ohm at a depth of 1-20 meters (Yellow) which is a slip plane (boundary layer) of sea water intrusion with a path length of 40 meters, conglomerate 210 ohm (red) at a depth of more than 7.50 meters. In track 2 there is a layer of clay with a resistivity of 1.4 ohm - 39 ohm at a depth of 1-24 meters (blue and green), silt 43.1 m-185.6 m (yellow) is the slip plane (layer boundary) of sea water intrusion with a 95 meter long track, a conglomerate layer with a resistivity of 203.4 ohm - 407.8 ohm (red) at a depth of more than 12.8 meters. On track 3 there is a layer of clay with a resistivity of 0.186 ohm - 31.4 ohm (blue and green) at a depth of up to 24 meters with a length of more than 120 meters, silt with a resistivity value of 44.4 ohm - 189 ohm (yellow) which is a slip plane (boundary layer) sea water intrusion with a path of 65 meters at a depth of 2.50 meters-24.9 meters.

Properties of Conglomerates from the Middle Ordovician Dongchong Formation and Its Response to the Yunan Orogeny in the Yunkai Area, South China

The strata in the Shita Mountain, Yunkai region, are predominantly composed of clastic rocks with intercalated limestones. However, the precise stratigraphic age remains uncertain due to the scarcity of fossils. Previously, conglomerate layers in this region were considered indicative of the Yunan Orogeny during the Cambrian–Ordovician transition. However, through the identification of 12 lithofacies types and 5 lithofacies combinations in the conglomerate layers of the Shita Mountain section, it has been confirmed that these layers represent a fan delta depositional environment characterized by debris flow, traction flow, torrent, and rock flow. Based on the presence of brachiopod fossils dating to the Early–Middle Ordovician, we propose a novel two-episode model for the Yunan Orogeny. The first episode corresponds to submarine fan deposition, while the second episode involves tectonic uplift and a short-term sedimentary hiatus. Further analysis of the detrital zircon provenance reveals a strong affinity among the Yunkai area, India, Antarctica, the Lhasa, the Himalayas, Southern Qiangtang, and Western Australia during the Early–Middle Ordovician transition under the Gondwana assemblage background.

Late Paleozoic and Early Mesozoic radiolarians from chert conglomerates embedded in the Kaeng Raboet Formation (Upper Mesozoic continental red-bed), Kanchanaburi Province, western Thailand

Continental clastic red-beds including red and fine- to medium-grained sandstone, pebbly sandstone, and conglomerates are distributed in the Sai Yok area of western Thailand. This rock sequence is known as the Jurassic Kaeng Raboet Formation by Thai geologists. A similar clastic rock succession, approximately 150 m thick, outcropping at Wat Phu Toey, near Ban Tha Sao, was investigated for paleontological analysis. The lithostratigraphy of the sequence in this section consists of Units 1-3 in ascending order. Unit 1 is characterized by pebble-sized chert conglomerates, Unit 2 by medium-grained massive sandstone, and Unit 3 by fine-grained red sandstone and shale with ripple marks and cross-laminations. Several thin layers of chert conglomerate are intercalated in the lower parts of Units 2 and 3. We collected six chert conglomerate samples from this section and distinguished Tournaisian (Lower Carboniferous) to middle Norian (Upper Triassic) radiolarian-bearing chert clasts that have not been not separated as single clasts but treated as one sample. Although the preservation of radiolarians is generally poor, we identified 40 species belonging to 26 genera with one radiolarian gen. et sp. indet. The exact age of the Kaeng Raboet Formation is still equivocal; however, we assigned the age of the red-bed to the Late Jurassic to Early Cretaceous based on the presence of Middle Jurassic foraminifer-bearing limestone clasts in the limestone conglomerate embedded in equivalent formations. The present chert conglomerate, including radiolarian-bearing chert clasts is interpreted to have been derived from the grained siliceous rock bodies of the Mae Sariang Zone and deposited in an alluvial depositional basin and braided river system during the Late Jurassic to Early Cretaceous.

Geochemistry, Lu–Hf garnet ages, and P–T conditions of blueschists from the Meliatic and Fatric nappes, Western Carpathians: Indicators of Neotethyan subduction

Basaltic rocks from ophiolitic mélanges provide information on geodynamic setting, origin, and later tectonometamorphic conditions. This paper resolves the P–T conditions and timing of high-pressure metamorphism in an accretionary wedge that formed during the Late Jurassic closure of the Neotethyan Meliata Basin. Blueschist-facies metabasites of the Meliatic Bôrka Nappe and the Albian conglomerate pebbles of the Fatric Klape Nappe contain rare assemblages of garnet in association with glaucophane, phengite, rutile, and epidote (±albite). Here, we compare a Lu–Hf garnet age from the Meliatic Bôrka Nappe in the southern margin of the Inner Western Carpathians (IWC) with a garnet age from inferred Meliatic blueschists of the Klape Nappe overlying the IWC northern margin. The Hačava type locality of the Bôrka Nappe hosts calc-alkaline type metabasite (∼VAB-C; εNd(245) = +0.9) embedded within Middle to Upper Triassic marbles of the Neotethyan Meliata Basin northern continental margin. The investigated Klape Nappe island arc tholeiite (∼VAB-T; εNd(240) = +5.9) blueschist pebble, and associated deepwater metasedimentary rock pebbles were found in a conglomerate layer of unmetamorphosed Albian flysch. The garnet ages of 153.95±0.69 Ma and 152.1±1.5 Ma correspond to closure of the Meliata Basin during southward intraoceanic and continental margin subduction. This was followed by the exhumation of HP blocks in serpentinite mélange and the formation of an accretionary wedge with included anchimetamorphosed Jurassic flysch. The P–T conditions of the blueschists were constrained by Perple_X modelling to be 520°C and 1.55 GPa for the Bôrka Nappe, and 490–510°C and 1.68–1.72 GPa for a pebble from the Klape Nappe conglomerate. The similarity of garnet dates and metamorphic conditions between the two samples suggest that the blueschists formed during the Late Jurassic Meliatic subduction. The north-vergent Meliatic nappes are the inferred source of the Albian flysch conglomerates deposited in the foreland Fatric Basin. This material was subsequently transported by the Fatric Klape Nappe to the IWC orogenic front during the Turonian, following the closure of the Fatric Basin.

The Characteristics and Geological Significances of Tectonic Regime Changes in Chepaizi Uplift, Junggar Basin, Western China

Tectonic regime change refers to the process in which the two periods of tectonic movement changes and produce corresponding tectonic regime change surfaces (unconformity surfaces) and other geological responses in the process of basin development and evolution. The change of tectonic movement is the root cause of tectonic regime change. Tectonic regime changes produce different geological responses, which can be used as the signs to identify tectonic regime changes. In order to study the characteristics of tectonic regime changes of Chepaizi Uplift in Junggar Basin and the control on oil and gas migration and accumulation, four stages of tectonic regime changes were identified by using the techniques of the rock acoustic emission (AE) technology, tectonic subsidence analysis, and tectonic stratigraphic sequence analysis, which occurred at the end of Early Permian, the end of Late Triassic, the end of Jurassic, and the end of Paleogene, respectively. The main stratigraphic product of tectonic regime change is the unconformity structure. The unconformity structure has obvious stratification, including the bottom conglomerate layer, the weathered clay layer, and the semiweathered rock layer, and plays an important role in controlling oil and gas migration and accumulation. The weathered clay layer and the hydrolysis layer have a sealing and shielding effect on oil and gas; the leaching layer can become the effective reservoir; at the same time, the leaching layer can provide a channel for the lateral transportation of oil and gas.

Prediction and Analysis of PDC Bit Wear in Conglomerate Layer with Machine Learning and Finite-Element Method

Polycrystalline diamond compact (PDC) bits experience a serious wear problem in drilling tight gravel layers. To achieve efficient drilling and prolong the bit service life, a simplified model of a PDC bit with double cutting teeth was established by using finite-element numerical simulation technology, and the rock-breaking process of PDC bit cutting teeth was simulated using the Archard wear principle. The numerical simulation results of the wear loss of the PDC bit cutting teeth, such as the caster angle, temperature, linear velocity, and bit pressure, as well as previous experimental research results, were combined into a training dataset. Then, machine learning methods for equal-probability gene expression programming (EP-GEP) were used. Based on the accuracy of the training set, the effectiveness of this method in predicting the wear of PDC bits was demonstrated by verifying the dataset. Finally, a prediction dataset was established by a Latin hypercube experiment and finite-element numerical simulation. Through comparison with the EP-GEP prediction results, it was verified that the prediction accuracy of this method meets actual engineering needs. The results of the sensitivity analysis method for the gray correlation degree show that the degree of influence of bit wear is in the order of temperature, back dip angle of the PDC cutter, linear speed, and bit pressure. These results demonstrate that when an actual PDC bit is drilling hard strata such as a conglomerate layer, after the local high temperature is generated in the formation cut by the bit, appropriate cooling measures should be taken to increase the bit pressure and reduce the rotating speed appropriately. Doing so can effectively reduce the wear of the bit and prolong its service life. This study provides guidance for predicting the wear of a PDC bit when drilling in conglomerate, adjusting drilling parameters reasonably, and prolonging the service life of the bit.

The unconformity caused by the Huaiyuan movement and the deep natural gas exploration field in the Ordos Basin, China

In order to clarify the hydrocarbon accumulation significance and exploration prospect of the unconformity caused by the Huaiyuan movement in the Ordos Basin, this paper studies the spatial distribution and structural plane characteristics of this unconformity and its relationships with hydrocarbon accumulation by observing field outcrops and cores and analyzing logging data, based on the previous research results and the interpretation results of 2D and new 3D seismic data. And the following research results are obtained. First, the unconformity was mainly formed in the Floian Age of Early Ordovician and widely occurs at the bottom of the Jiawang Formation and the top of the Sanshanzi Formation and the related tectonism lasts 30 Myr. Second, basal conglomerate and sandstone less than 1 m in thickness are developed above the unconformity at the edge of the basin, while thin mudstone, argillaceous dolomite (limestone) and marl are developed above the unconformity in the central part of the basin. Third, the unconformity structurally consists of three layers, including a basal conglomerate layer, a paleosoil layer and a fully–semi weathered carbonate layer from top to bottom, among which, the last one is 20–90 m in thickness with developed dissolution fractures and pores to form a quality reservoir. Fourth, the unconformity results in the development of a series of large valleys landforms, which incise the Lower Ordovician–Upper Cambrian. Fifth, the unconformity can act as a good channel for hydrocarbon migration, and it connects with the unconformity caused by the Caledonian movement within the paleo-uplift of the Ordos Basin, which is favorable for the the hydrocarbon of different sources in the west side of the basin eastwards to migrate, accumulate and form a gas reservoir. In conclusion, the deep Lower Paleozoic related to the Huaiyuan unconformity is expected to be an important natural gas exploration field in the Ordos Basin.

Characteristic and paleoenvironment significance of microbially induced sedimentary structures (MISS) in terrestrial facies across P-T boundary in Western Henan Province, North China

AbstractWe report varied microbially induced sedimentary structures (MISS), and other sedimentary surface textures, from the Induan (Early Triassic) Sunjiagou Formation and Liujiagou Formation in the Xingyang, Dengfeng, Jiyuan and Yiyang areas, western Henan Province, North China. Microanalysis shows that these MISS are characterized by a U-shaped structure, thin clayey laminae, and discontinuous mica sheet that are arranged parallel to the bedding plane, as well as directionally oriented quartz grains floating in lamina, which are indicative of a biogenic origin. The MISS of the studied area were probably affected by four main factors, including the end-Permian mass extinction, the megamonsoon, the adapted sedimentary environment, and the sediment supply, and they possess significant stratigraphic correlation. Abundant microbial-related sedimentary structures from the study area indicate that continental ecosystems were severely devastated in the aftermath of the Permian-Triassic biocrisis. These sedimentary structure assemblages, including MISS, red beds, conglomerate layers, and calcareous concretions in the western Henan Province, show a specific, post-extinction continental ecosystem that was characterized by microflora dominance, monotonous and rare fossils, extreme hot climate, soil ecosystem devastation, and poor vegetation.

New insights on the petroleum migration and accumulation in the basal conglomerate reservoir of Cretaceous Qingshuihe Formation of Yongjin area, Central Junggar Basin

The Junggar Basin is one of the largest and most petroliferous superimposed petroleum basins in China. This study focussed on the characteristics of the unconformity between the Jurassic and Cretaceous (J/K) and its influence on hydrocarbon accumulation in the Yongjin area, Junggar Basin. Based on the seismic reflection characteristics and wireline well logging response, we identified the structure of the unconformity, which consists of three layers: the basal conglomerate layer, weathered clay layer, and semi‐leached layer. Geochemical studies show that the crude oils of the Lower Cretaceous Qingshuihe (K1q) Formation in the Yongjin area are mainly derived from Permian source rocks and partly from Cretaceous source rocks. The abnormally high value of acoustic time and the low value of resistivity of mudstone indicate that the overpressure condition is pervasive in the Yongjin area and may act as the driving force for the vertical migration of hydrocarbon‐containing palaeo‐fluids. The poor sealing ability of the weathered clay layer of the unconformity between the Jurassic and Cretaceous (J/K) and the high abnormal overpressure indicate that the petroleum from Permian source rocks may break through the sealing of the weathered clay layer and migrate upward to the Cretaceous conglomerate to accumulate. In addition, the combination of faults, sheet sand bodies, and unconformities constitutes a three‐dimensional petroleum migration pathway. The evolution of the Che‐Mo palaeo‐uplift also affected the formation of source rocks and petroleum migration. Accordingly, the hydrocarbon accumulation model of the Cretaceous in the Yongjin area indicated that Late Palaeogene is the first accumulation period. Permian source rocks have entered a mature to high‐mature stage, where a large amount of generated oil and gas migrated along faults and unconformities and accumulated in the braided river channel sand bodies of the K1q Formation. The second accumulation period was the Neogene. The basin experienced a regional tilt leading to a south‐inclined stratum. The oil and gas migrated upwards along the Late Hercynian deep reverse fault (Carboniferous–Permian) and then passed through the shallow faults and migrated to the bottom sandstone of Cretaceous reservoirs.

Engineering geology and geotechnical characterization of Tabriz Metro Line 2, Iran

The present study was performed in order to determine the engineering geology and geotechnical details of soils and rocks along Tabriz Metro Line 2(TML2) by using the information and raw data which were acquired by borehole drilling and all field and laboratory tests in the study area. The minimum and maximum depths of the boreholes were 15 and 40 m, respectively. The results of their analysis revealed that geologically, the areas of metro route, mainly formed by alternating layers of claystone, siltstone, marl, and conglomerate, covered mainly by the alluvial deposits and in addition to older, dextral, strike-slip North Tabriz Fault (NTF) which is a major and most important geological structure of Tabriz area, there are also many minor and generally young and seismically active faults. The results of investigation on the groundwater depth in boreholes of TML2 also indicated that the groundwater depth varies between 1.5 and 30 m, along the route of metro. Eventually, based on the standard penetration test values (N-SPT), it was revealed that soils of the western parts of TML2 are in the group of dense to very dense, the central parts are in the group of very dense (Bazaar area) and dense (Fahmideh area), and the eastern parts are very dense. And finally the results achieved from determining groundwater sulfate values according to Concrete Code of Iran (CCI) indicated that the amount of soluble sulfate in the soil is mild to extremely high. Accordingly, the amount of sulfate increases from the western to the eastern parts. So that, this value is between 200 and 26,500 ppm. Based on these studies, the average of sulfate in the western, central and eastern parts is, respectively, 1118, 1275 and 4840 ppm. Thus, the groundwater in the east part is highly aggressive, and deterioration of concrete lining of the tunnel is expected in the near future.

A new potentially large uranium district in Russia (Far East)

Research subject. The aim was to justify the prospects of uranium deposits in the Tyrminsk area of the Far East, which were briefly studied over 60 years ago. These deposits are highly similar to those located in the Streltsovsk mega uranium district. Materials and methods. The materials were geological data on uranium deposits in the promising Tyrminsk district and in the largest Streltsovsky district in the Far East. The research method was a comparison of the available information about the geological features of uranium deposits and ore areas as a whole. Results. The uranium ore regions under study are localized in Mesozoic volcanogenic calderas, within Paleozoic granites. Specific uranium deposits are formed at intersections of multidirectional faults, most frequently in the vicinity of volcanic caldera boundaries. The deposits formed within a contrasting geological section are represented by steep vein-like and stock-like bodies, as well as by gently sloping formation-like bodies under the screens of layers of dense sandstones and siltstones. In addition, deposits are found in favourable layers of conglomerates and effusives breccia. The length and thickness of ore bodies comprise 0.2–1 km and 1–80 m, respectively. Uranium ores belong to the fluorine-molybdenum-uranium type; near-ore rocks are represented by mudstones and hydrosludites. Some fields in the Tyrminsk district are opened by wells to a depth of 80– 160 m from the surface, while the fields in the Streltsovsk district are explored by wells and underground mine workings to a depth of 1.5 km from the surface. Conclusion. The extent of uranium deposits in the Tyrminsk district is predicted to reach a depth of 500–700 m, with their resources being estimated as “large” based on the high similarity of localities in the areas under study. As the most promising uranium area in the south Far East, the Tyrminsk district is recommended as a priority exploration site for uranium.

Geophysical characteristics and interpretation methods of the buried hill surface in the west slope of Shulu depression

In the cause of the buried hill and conglomerate layer are carbonate rock type, there is no obvious difference between the wave impedance and the overlying strata. Therefor there is no strong reflection on the surface of the buried hill, and no obvious change in the logging curve. In order to solve this problem, taking west slope of Shulu depression as an example, the logging characteristics of the conglomerate surface and seismic reflection characteristics of the buried hill surface are summarized. The sedimentological characteristics of the buried hill surface are analyzed. The differences between the identification of the buried hill surface and the identification of the conglomerate surface are found. The interpretation method of the buried hill surface is defined. It provides a theoretical basis for better interpretation of buried hill reservoir.

Retrospective analysis of the Pico del Castillo de Vinuesa large historical landslide (Cordillera Iberica, Spain)

The failure mechanism of a large historical landslide that caused the partial destruction of the Pico del Castillo de Vinuesa has been determined and characterized by a multidisciplinary approach. This study combines the application of complementary fields such as geological analyses, field and laboratory tests, geomorphological, geomechanical and hydrogeological characterizations, retrospective mathematical simulations, and absolute dating methods to determine the origin and age of the landslide. The instability event occurred shortly before 1600 BP and mobilized more than 30 million m3 of debris from the competent conglomerate layer that formed the ancient summit. The conglomerate is considered to have slid over a claystone layer dipping 12°, following a translational sliding model. The underlying claystone layer constituted the impervious base of the aquifer formed by the displaced material. The hydrogeological conditions played a key role in the slide by changing the mechanical properties of both the claystone and the conglomerate layers.

The Ordovician iron ore of the Anti-Atlas, Morocco: Environment and dynamics of depositional process

In Morocco, iron deposits of sedimentary origin are mainly developed in the Ordovician where they are interbedded at different levels of the stratigraphic column. A detailed analysis of the sedimentary facies shows that the iron ores are not randomly distributed but are concentrated at omission surfaces of the sequences thus raising the question of their sedimentological significance within the sequences that shelter them. This study determines three morphological types of ore, which provide a possible avenue for economic exploitation. These morphological types are: firstly, from metric to decametric bodies of regional extension (examples are “Caid Rami” and “Tachilla”), consisting of a set of detrital facies organized in two stratigraphic stages that cyclically recur to form genetic sequences. Within each sequence, the maximum mineralization is at the top of the prograding basal stage and is expressed by diagenetic iron cement and at the base of the regressive stage in the form of strata of iron oolites, or in massive beds. Secondly, lenses with a thickness up to 30 m over a kilometer width (example of “Imi n’Tourza” field), corresponding to incisions cut along the ravinement surfaces. The maximum mineralization of this second type is within the median sandstone stage in connection with a large transgressive event. Thirdly, there is a type of reworked material consisting of discontinuous layers of ferruginous conglomerates and bioclastics lining the ravinement surface that separates the higher order sequences. It is this third type that has generated the most economic interest. The iron-bearing mineral phases identified are: magnetite, hematite, iron chlorite, maghemite, iron hydroxides (goethite, lepidocrocite) and siderite. The ultimate source of iron would probably be the large reserves of banded iron formation of the West Africa Craton (Mauritania in particular). Intense tropical weathering would have leached the silica and left a highly enriched iron residuum that was carried as particulate iron to shallow marine shelf environments where Fe3+ was converted to Fe2+ during early diagenesis. This reduced iron was recycled into the water column by tidal currents or storm waves where it precipitated as ferric oxide or ferrous silicate ooliths. This depositional mechanism accounts for the positioning of ironstone beds at times of stasis and reworking.

Uncertainty analysis of key factors affecting fracture height based on box-behnken method

Hydraulic fracturing technology was one of the main technologies to achieve efficient development of unconventional oil and gas resources. Longitudinal propagation of hydraulic fracture was one of the main factors affecting the reservoir stimulation. At present, there was still a lack of qualitative analysis for the problem of hydraulic fracture penetration. Based on the linear elastic fracture mechanics, the fluid-solid coupling mechanical behavior of reservoir was simulated by plane strain three-dimensional model. The longitudinal initiation and extension process of hydraulic fracture was simulated and analyzed. The effect of in-situ stress and physical parameters on fracture height was studied. At the same time, the key parameters for controlling fracture height were screened through hurricane analysis and Box-Behnken test design. Based on the response surface analysis method, a mathematical statistical model with good fit with the actual calculation results was established to predict the statistical significance of the key parameters controlling the fracture height. According to the designed fracture height, the combination of parameters corresponding to the fracture height was calculated by using the mathematical statistical model prediction. The results showed that the stress difference and elastic modulus difference between the mudstone and the conglomerate layer were the key factors to control the fracture height. The overlying mudstone layer with high in-situ stress and low elastic modulus can reduce the fracture height and effectively restrict the fracture penetration. This study had theoretical significance for understanding the mechanism of hydraulic fracturing.

Cutting Mechanism Study of an Innovative Non-Planar Cutter PDC Bit and Its Field Application

Tarim Kuqa tight sandstone reservoir is overlaid with extreme thick conglomerate, which has high compressive strength, strong heterogeneity and poor drill ability, resulting in low drilling ROP and less bit drilling footage. Through research study and analysis of PDC bit failure and wear modes, this paper described the development of an innovative non-planar PDC bit through cutting mechanism study and lab testing verification. When drilling through the strong homogeneity formation, it will still be surface contact between the non-planar cutter and the rock and therefore the rock-breaking mechanism is still the conventional shearing fracturing; When drilling through the heterogeneity formation, the convex ridges will generate the linear contact with the hard rock and the mechanical stress will be accumulated at the conglomerate surface to initially create the cracking and then break the rock with composite cutting mechanism of shearing and crushing to improve the rock breaking efficiency. Experimental results also showed that the non-planar cutter delivers several folds of impact resistance improvement over conventional cutter. The bit was successfully field tested in ultra-thick conglomerate layer in the Kuqa foreland thrust belt of the Tarim basin. The field test tripled bit footage and doubled ROP comparing to same intervals and formation in offset wells. It demonstrated the broader prospect of the non-planar PDC technology in conglomerate and highly heterogeneous applications.

Geological and geophysical investigations to analyse a lateral spreading phenomenon: the case study of Torrioni di Rialba, northern Italy

We combined geological, geomechanical, geophysical and remote sensing investigations, including persistent scatterer interferometry and bathymetry, to study a slope where four conglomerate towers laterally spread over a shale layer. Electrical resistivity tomography surveys confirm a shale layer that underlies the rock towers with an attitude parallel to the slope. Field mapping reveals that the stability of the rock towers is threatened by weakly cemented conglomerate layers, large eroded zones and karstic weathering due to water circulation. We deem that the most probable failure mechanism would be the toppling of the southernmost tower, promoted primarily by the weak conglomerate layer in its lower section. The plastic shale layer underneath the rock cliff is very likely to promote lateral spreading that may have triggered the toppling of an additional former rock pillar, whose rock blocks were found in the lake during a bathymetric survey. Close- and long-range remote sensing of displacements provide no results that could be interpreted with confidence. Seismic noise recording sessions with 3C low-frequency velocimeters suggest that the dynamic conditions of the towers do not show appreciable variations across the recording sessions, especially considering the two rock towers featuring the most interesting spectral characteristics. However, both the resonance frequencies and the preferential oscillation directions estimated from the seismic noise datasets are consistent with the analytical relationships and will support the design of an effective monitoring strategy.

Architectural and facies characterization of the Aptian fluvial Barbalha Formation, Araripe Basin, NE Brazil

Abstract The Aptian Barbalha Formation records the beginning of the post-rift stage of the Araripe Basin. It consists predominantly of sandstones and mudstones interbedded with thin layers of bituminous black shales and conglomerates. The depositional and architectural features of the alluvial succession of the Barbalha Formation were characterized by detailed study and descriptions of the selected outcrops and analysis of well core data. In this study, two main depositional sequences were identified. The lower depositional sequence is more than 100 m thick and comprises a vertical facies succession composed of amalgamated, multistorey, braided fluvial channel sandstone bodies overlain by a widespread lacustrine black shale up to 10 m thick. The lacustrine black shales–carbonate mixed interval is known as the Batateira Beds and constitutes a regionally important stratigraphic correlation marker in the basin. This interval records the establishment of a large lake that experienced severe water-level fluctuations and anoxic events. The upper depositional sequence is 60–95 m thick, and mainly consists of thin, yellowish, medium- to fine-grained sandstones and variegated shales. The upper sequence rests unconformably on the lacustrine black shales of the Batateira Beds. Thin and discontinuous conglomerate beds at the base of the upper sequence laterally grade into coarse-grained sandstones. These coarse-grained sandstones are overlain by interbedded sandstones and mudstones organized in fluvial cycles. The upper and lower sequences of the Barbalha Formation are separated by an erosive unconformity, traceable throughout the study area, formed during a period of stratigraphic base-level lowering. This surface marks a change in the lower sequence from a dominantly fluvial depositional style, with amalgamated multistorey braided fluvial channel sand bodies, to a lacustrine system in the top to an eminently fluvial sedimentation, which in the basal section comprises amalgamated, multistorey, braided fluvial channel sand bodies, and in the superior section the amalgamated fluvial channels are overlain by floodplain and overbank sandstone bodies with fixed fluvial channel deposits, interpreted as a suspended-load-dominated fluvial system in the upper sequence. This change in the depositional style is accompanied by a reduction in grain size and a change in the fluvial regime, suggesting that the drainage system was restructured due to tectonic movements in the basin and climatic variations. In addition to the restructuring of the drainage basin, the characteristics of the discharge of the river system have changed, probably because of the more humid climatic conditions that dominated during the deposition of the upper sequence. The fluvial deposition in the lower sequence is associated with more ephemeral river systems, while the facies architecture of the upper sequence is associated with perennial systems and is suggestive of a suspended-load-dominated fluvial system. This fluvial system is capped by lacustrine deposits of the Crato Formation. The upper sequence grades upwards into the Crato Formation. The boundary between these two units is delineated by the presence of greenish calciferous shales that are covered by lacustrine laminated limestones and shales of Neoaptian age. Palaeocurrent readings from the fluvial deposits of both sequences display a consistent palaeoflow to the SE. Sedimentological and palaeontological evidence indicates a tectonic control on sedimentation and humid to subhumid climate conditions.