Strong Cementation Research Articles

Microfractures in the middle Carboniferous carbonate rocks and their control on reservoir quality in the Zanaral Oilfield

Fractures are considered an important controlling factor for hydrocarbon accumulation in the pre-salt carbonate reservoirs of the Zanaral Oilfield. They are also a precondition for the high and stable production of oil and gas. Based on core observations and descriptions, systematic sampling analysis, including rock mineral composition analysis, petrographic thin sections, stained thin sections, porosity and permeability, the study about the characteristics and major controlling factors of microfractures and their influence on the reservoir seepage capacity was performed on Wells 2399A and 2092. The results suggest that although there are few macrofractures, microfractures are common in the study area. There are several types of microfractures, principally including micro-tectonic fractures, grain breakage fractures, microstylolites and micro-corrosion fractures. The micro-tectonic fractures, especially those with relatively large apertures are mostly completely filled with calcite. The formation of micro-tectonic fractures is related to calcite-filled macrofractures, but unrelated to bitumen-filled fractures. The distribution of grain breakage fractures, microstylolites and micro-corrosion fractures differs substantially among the various wells and layers. Most of the grain breakage fractures are partially filled with calcite or barren, and the major corrosion fractures are partially filled with calcite. The non-tectonic factors controlling the distribution of microfractures are complicated and variable, and include facies and differential diagenesis. Micro-tectonic fractures formation is promoted by the local enrichment of brittle minerals, small grain size and strong cementation. Grain breakage fractures are dominant in pure limestones with coarse grains and abundant intergranular pores. Microstylolites mainly distribute in tight limestones with more impurities, and fine-grained micro-corrosion fractures are associated to porosity, density, dolomite and acid-insoluble residues contents of the limestones intermediate between those of grain breakage fractures and microstylolites. Dolomite and acid-insoluble residues were probably concentrated by the formation of stylolites. By contrast, low acid-insoluble residue content facilitates the formation of corrosion fractures. Fractures could significantly enhance the seepage capacity of the reservoirs in the study area. The contribution of microfractures to reservoir seepage is given by stylolites, tectonic fractures, corrosion fractures and grain breakage fractures in this order. High degrees of filling of the tectonic fractures greatly affect their seepage capacity.

Controlling factor analysis and prediction of the quality of tight sandstone reservoirs: A case study of the He8 Member in the eastern Sulige Gas Field, Ordos Basin, China

The He8 Member is the main producing zone in the Permian rocks of the eastern Sulige Gas Field in the Ordos Basin. It is characterized by low(10%≤Φ<15%) to ultralow(<10%) porosity and ultralow permeability(K < 1mD). To realize efficient exploration and development in this gas field, it is necessary to study the genesis of tight sandstone reservoirs and clarify the factors controlling reservoir development, in order to establish effective methods for reservoir quality prediction. The composition, pore structure, diagenetic type and strength of sandstone reservoirs, as well as their authigenic mineral contents and types, were analyzed. The techniques including casting thin sections, SEM, X-ray diffraction, high-pressure mercury intrusion, porosity-permeability tests and fluid inclusion homogenization temperature tests were used, in order to reconstruct the diagenetic and pore evolution history of the sandstone reservoirs. The effects of 12 sedimentary and diagenetic factors on porosity and permeability were analyzed using the stepwise multiple linear regression method, and a prediction model of reservoir quality (including both porosity and permeability) was constructed. The results show that the reservoir rock is dominated by litharenite, which accounts for 69.76%, followed by sublitharenite, which accounts for 26.15%. The reservoirs are characterized by low to ultralow porosity (porosity ranges from 0.29 to 16.6%, with an average of 7.51%), ultralow permeability (horizontal permeability ranges from 0.0065 mD to 5.21 mD, with most values being less than 0.4 mD). Displacement pressure is high (which ranges from 0.48 to 4.2 MPa, with an average of 1.48 MPa). Sandstone reservoirs are reformed by moderate compaction, moderate to strong cementation and weak dissolution. Cementation mainly occurs as quartz overgrowths, authigenic quartz, ferrocalcite, nonferrous calcite and clay minerals. Clay minerals are dominated by grain-coating chlorite, kaolinite and illite. Dissolution has little influence on reservoir quality. Reservoir porosity is mainly controlled by the contents of kaolinite, siliceous cement, illite, chlorite, and feldspar, as well as the degree of compaction. On the other hand, reservoir permeability is mainly controlled by the amount of siliceous cement, quartz, illite, and kaolinite, as well as the degree of compaction. The porosity and permeability were predicted using the equation established by multiple linear stepwise regression analysis, and good results were achieved. In this paper, the factors that influence the quality of the sandstone reservoir of the He8 Member in the eastern Sulige Gas Field were clarified, and a corresponding prediction model of reservoir quality was constructed. This model provides a new concept and method for quantitatively predicting the quality of tight sandstone reservoirs in other areas.

Diagenesis and its impact on reservoir quality for the Chang 8 oil group tight sandstone of the Yanchang Formation (upper Triassic) in southwestern Ordos basin, China

Based on the applications of thin section, cathode luminescence, scanning electron microscope and X-ray diffraction, this paper studies the reservoir characteristics, diagenesis features and their influences on the development of reservoir pores for the Chang 8 oil group of Yanchang Formation in southwestern Ordos Basin. Results show that the reservoir is characterized by low composition maturity, low structure maturity, low porosity/ultra-low porosity and ultra-low permeability which belong to tight reservoir. The reservoirs develop medium intensity of compaction, moderate to strong cementation, relatively strong dissolution, suggesting that it is in stage B of the middle diagenetic evolution. The main diagenetic types include mechanical compaction, cementation by carbonates, quartz and clay minerals, and dissolution which have directly influenced the reservoir quality. In the early diagenetic period, the rapid compaction and cementation of carbonate had rapidly destroyed the reservoir quality, while the particles lining of chlorites had protected the reservoir space. In the middle diagenetic stage A, secondary dissolution pores were formed as soluble clastic grains were dissolved by the acidic fluid with organic matters maturation. The dissolution has played a constructive role for the pore generation and preservation. In the middle diagenetic stage B, the later compaction and cementation further reduced the reservoir quality. The analysis of pore evolution demonstrates that the initial reservoir porosity is about 30.59%. 16.925% overall porosity is lost through compaction, 11.65% porosity loss is due to cementation, and 6.36% porosity was created by dissolution. Finally, the reservoir is holding 8.375% porosity in present.

Petrological features of selected components of the Cergowa sandstones (Outer Carpathians) recorded by scanning electron microscopy – preliminary study

The scanning electron microscope analysis of the Cergowa sandstones brings new data on their petrological features and chemical composition. Previous work in standard petrographic examination, e.g. polarising (PL) or cathodoluminescence (CL) microscopy, displayed limited information on grain surface topography and only assumptions to their geochemistry. Both identification and characterisation of minerals are fundamental in the progress of mining and minerals processing systems. Detrital grains of the Cergowa sandstones are bound by calcite and dolomitic cement and commonly corroded by diagenetic fluids, however, in varying degrees, which is illustrated here by feldspar, quartz and dolomite minerals. Dissolution processes of marginal parts of these mineral grains resulted in corrosion, which increased the contact surface between the grains and the cement. The difference in resistance to these processes was observed not only among distinct groups of minerals, but also within the group of feldspars: between K–feldspars and minerals of plagioclase. That combination resulted in exceptionally strong cementation of the Cergowa sandstones, which is expressed by their high hardness and resistance to abrasion, freezing, and thawing. Inherent parameters of sandstones are characterised by their petrographical properties.

Corrosion resistance of sulfated cements in carbonate and in carbonate-sulfate mediums

Corrosion resistance of sulfated cements in carbonate and in carbonate-sulfate mediums has been studied. The samples have been placed in carbonate and carbonate-sulfate mediums for investigation stability of sulfated cements. The same researches were done with sulfate resistant portland cement to compare stability of samples. High corrosive resistant of sulfated cements is conditioned by forming dense and strong cement stone. The obtaining of corrosion resistant cements is possible with usage of the ordinary portland cement clinker with inclusion to them sulfoferrite and sulfoalumoferrite clinkers. Sulfated cements have the higher corrosion stability in contrast to ordinary sulfate resistant cement.

Middle Pleistocene glaciation, alluvial fan development and sea-level changes in the Bay of Kotor, Montenegro

Abstract A coarse-grained alluvial fan at Lipci in the Bay of Kotor, western Montenegro, was deposited in the Middle Pleistocene by a high-energy, steep gradient proglacial stream draining an outlet glacier on the Orjen massif. The fan apex is currently about 50 m above sea-level, but the majority ( c. 60%) of this landform now lies offshore. Field mapping, sedimentological analysis and uranium-series dating were combined with a marine bathymetric survey and seismic profiling to explore the morphology and history of the entire fan complex. The Lipci fan was deposited on the margin of a large polje downstream of moraines that formed during the Middle Pleistocene (Marine Isotope Stage 12). The sea-level may have been more than 120 m lower than present during the glacial stages of the Middle Pleistocene. The sediments on the terrestrial portion of the fan are strongly cemented by secondary calcite and the oldest uranium-series ages show that the fan was deposited before 320 ka. These ages are consistent with a larger uranium-series dataset ( n =39) from other glacial and glacio-fluvial formations surrounding Mount Orjen. Seismic profiling of the submerged portion of the fan in the Bay of Kotor shows well-preserved palaeochannels with inset terraces. The Lipci fan is unusual because even its distal segments are well preserved after exposure to multiple post-Marine Isotope Stage 12 regression–transgression cycles. This is probably due to the strong cementation of the fan sediments and its sheltered location in the Bay of Kotor.

Relining effects on the push-out shear bond strength of glass fiber posts

Abstract Introduction The correct use of glass fiber posts in endodontically treated teeth is essential for the clinical success of restorative treatment. Objective This study evaluated the push-out shear bond strength of relined (R) or non-relined (NR) glass fiber posts, cemented with self-adhesive resin cement [RelyXTM U100 (U100)] and conventional resin cement [RelyXTM ARC (ARC)]. Material and method Sixty human single-rooted teeth were endodontically treated and divided into ARC-NR; U100-NR; ARC-R; U100-R groups. The teeth were sectioned into cervical, middle and apical thirds, and subjected to the push-out test. Bond strength was analyzed by the Friedman test; cement and post types were compared by the Mann Whitney test. The pattern of failures was evaluated with digital camera through images at 200x magnification, and was classified as adhesive (at the cement/dentin or cement/post interface), cohesive (cement or post), and mixed failures. Result In ARC-NR, bond strength values were higher in the cervical third; in U100-NR and ARC-R they were similar between the thirds. In U100-R, in the cervical and middle thirds the bond strength values were similar, and there was lower value in the apical third. For non-relined glass fiber posts, the highest mean bond strength values were observed with self-adhesive resin cement. Whereas, relined posts cemented with conventional resin cement had stronger cement layer in comparison with non-relined fiber posts. Conclusion The post relining technique was efficient in ARC-R. ARC-NR and U100-R showed improved bond strength in the cervical region of canal walls. The main failures were adhesive at the cement-post interface.

鄂尔多斯盆地吴起地区长8油层组成藏地质条件分析

吴起地区三叠系长8油层组是鄂尔多斯盆地勘探的重要层位，该油层组具有砂体厚度较大，横向连片性好，但砂岩粒度细、填隙物含量较高、胶结作用强、储层物性差的地质特征。通过对生、储、盖特征的研究表明，区内长7油层组烃源岩较为发育，具有丰富的油源条件；在低渗透背景下局部发育相对高孔、高渗的优质储层，能够为石油聚集提供场所；生、储、盖组合配置关系良好，具备发育大规模岩性油藏的石油地质条件。 Chang8 Reservoir in Yanchang Formation of Wuqi Area was an important stratum for exploration in Ordos Basin. It was characterized by thicker sand body, good lateral connection, fine granularity of sandstone, high content of packing material, strong cementation and poor physical property. The analysis of oil source, reservoir and caprock indicates that there exists rich oil source condition. Under the low permeability condition, a good reservoir with relatively high permeability and porosity is developed, by which position is provided for oil accumulation with good source, reservoir and caprock relation; it provides oil geological condition for the development of large-scale lithological reservoirs.

Genesis and Classification of Soils Containing Carbonate on the Apodi Plateau, Brazil

Information is scarce on the genesis and classification of soils derived from calcareous rocks in the Northeastern region of Brazil. This study describes the morphological, physical, chemical, mineralogical, and micromorphological properties of four soil profiles (P1-P4) located in the Apodi Plateau. A pedogenesis hypothesis and soil classification, according to the Brazilian System of Soil Classification (SiBCS), are proposed for these profiles. The interactions between parent material, surface topography and climate affected the pedogenesis processes and soil properties, although the calcareous nature of the parent material most affected the soil morphology and chemical properties. The sand fraction contained mainly quartz and calcite, and a smaller amount of mica. Smectite and interstratified illite-smectite occurred in the clay fraction of profile P1 and in some horizons of P2 (Ccmќ and Ccrќ) and P3 (2Ccrќ). Kaolinite predominated in profiles P2, P3, and P4; where as illite and vermiculite were present in the Bicќ, Bcќ, Bcmќ horizons of P2, in Bt2c of P3, and in C of P4. The mineralogy showed illite, hematite, and goethite, and anatase in a number of horizons. Micromorphological analysis of P2 indicated a strong cementation of Bcmќ and Ccmќ by calcium carbonate, and other properties indicate the formation of a petrocalcic horizon, but this horizon lacked lateral continuity in the profile. Therefore, the parapetrocalcic term is proposed for classifying P2 in the fourth level of the SiBCS. The 3Biќ-P1 horizon exhibited calcite coating and iron coating or quasi-coating, indicating distinct pedogenesis processes occurring under different environmental conditions. Likewise, the occurrence of petroplinthite in P2 indicates that climatic conditions during its formation differed from present conditions, and both situations are interpreted as evidence that the soils were formed by polygenetic processes. In the SiBCS classification, the soils are classified as Cambissolo Haplico Carbonatico vertissolico (P1), Cambissolo Haplico Carbonatico concrecionario (P2), Luvissolo Cromico Palico petroplintico (P3), and Neossolo Litolico Carbonatico tipico (P4); and a new class (parapetrocalcico concrecionario) is proposed for P2 in the fourth level.

Dolomitization Associated with Sea Level and Ocean Current Circulation in the Southern Marion Platform, Offshore Ne Australia

On the Southern Marion carbonate platform, dolomitization is triggered by the circulation of normal or slightly modified seawater and is related to changes in sedimentation rate and sea level change. Dolomitization further modifies formation permeability and fluid flow patterns. Dolostone/calcareous dolostone with large vuggy or moldic porosity is formed by fabric-preserving dissolution and recrystallization, which increases the pore space and facilitates the fluid flow effectively, with permeability ranging from 1[Formula: see text]mD to 10,000[Formula: see text]mD. The frame flexibility factor ([Formula: see text]) is a rock physics parameter which is a proxy of pore structure. We find that at given porosity dolostone with larger pores, higher permeability and higher sonic velocity usually has lower values of frame flexibility factor than limestone. After strong compaction and cementation, the limestone frame occludes fluid flow, prevents dolomitization and has permeability as low as 0.02[Formula: see text]mD. Acoustic impedance inversion confirms that the asymmetric geometry of the Southern Marion platform is shaped by the oceanographic currents, which are caused by the southward-flowing East Australian Current. Three layers of dolostone with large pores in the upper platform reveal strong fluid flow within the carbonate platform, leading to dolomitization and dissolution. These three strongly dolomitized zones follow the platform topography, indicating that the diagenetic fluid flow is driven by oceanographic currents. Three large-pore-formation dolomitization events match well with three highstands of sea level events, illustrating that the highstand of sea level induces the formation of dolomitization zones with large pores. This study demonstrates the positive feedback loop of dolomitization and ocean current circulation, as well as the relationship between dolomitization and sea level change, which could be applicable for better understanding subsurface fluid-rock interactions and dolomitization pore systems in other carbonate environments.

An analytical solution to simulate the effect of cement/formation stiffness on well integrity evaluation in carbon sequestration projects

Cement Sheath integrity has been gain more attention due to the increase of carbon sequestration activities in the recent years. Sealing ability of cement sheath can be lost because mechanical disruption in the CO2 injection wells. Cement sheath mechanical failure can occur in the CO2 injection wells. This paper proposes an analytical solution to address this issue. Cement sheath and formation rock stiffness are considered in the proposed model to simulate the cement sheath sealing ability on different depth of the formation. Both mechanical properties of cement and formations are evaluated and analyzed. Real field example is also provided. Young's modulus of cement sheath is identified as a major factor that affects the sealing ability of cement sheath. The sealing ability of cement sheath in shale formation is better than that in sandstone formation. Weak cement has better sealing ability than strong cement. The critical failure point lies at the top of sandstone formation. This model can also be used to design and optimize the cement system of new CO2 injection wells in carbon sequestration projects.

Comments: New Fracturing Rules

Editor's column For US operators, new regulations from the federal government regarding hydraulic fracturing practices could not have come at a worse time. Already battling the economic fallout from sharply lower oil prices, the rules seem especially ill-timed for smaller operators that fear the requirements could have a long-lasting impact on how they do business. The new regulations proposed by the US Department of the Interior are designed especially to address public concerns about the safety of drinking water. The rules Require companies to disclose the chemicals they use in hydraulic fracturing operations. The chemical additives are to be listed on the FracFocus website, which many states already use for disclosure requirements. Set standards for the integrity of oil and gas wells, including using strong cement barriers between the wellbore and water zones. Elsewhere in this issue, hydraulic fracturing expert George King of Apache discusses well construction in a Beyond the Headlines column. Force companies that are operating on federal lands to store waste water in surface tanks instead of lined pits. Require pre- and post-drilling inspections and additional reporting requirements. The Interior Department estimates that the regulations will add approximately USD 45 million annually to operations costs on federal lands. But for oil and gas companies, the big concern is the precedent it could set for operations outside of federal lands, opening the door to additional regulation. The Independent Petroleum Association of America (IPAA) and the Western Energy Alliance, both trade associations representing oil and gas producers, have sued the federal government over the rules, claiming that they interfere with individual state’s rights to govern their land. Some states have also responded negatively, including Wyoming and North Dakota, indicating they may join the lawsuit. The interior secretary has said she hopes the rules will serve as guidelines for states desiring to regulate oil and gas activity. The lawsuit states the federal government standards were “a reaction to unsubstantiated concerns” and claims that “there is no factual, scientific, or engineering evidence necessary to sustain” the rules. “At a time when the oil and natural gas industry faces incredible cost uncertainties, these so-called baseline standards will threaten America’s economic upturn while further deterring energy development on federal lands,” said IPAA President and Chief Executive Officer Barry Russell. To the trade associations, the regulations represent a more aggressive stance on hydraulic fracturing from the federal government, which up to now has largely left that oversight to the states. Some local governments have banned outright or put limits on hydraulic fracturing. The Interior Department maintains that it tried to strike a balance among the concerns of the industry, those of environmentalists, many of whom would like to see further restrictions or an outright ban on fracturing, and the public. The new standards can be found on the Interior Department’s website at www.doi.gov. JPT

Development of ultra-lightweight cement composites with low thermal conductivity and high specific strength for energy efficient buildings

Energy efficient building is defined as achieving satisfactory internal environment and service with minimum energy consumption. One of the most important parameters that affect the heat transfer through the building envelope is thermal conductivity. The thermal conductivity of lightweight concrete is generally lower than that of normal-weight concrete due to the lower thermal conductivity of air. Although introducing voids in concrete reduces its thermal conductivity and increases its insulation capacity, the mechanical properties are generally compromised.This study focuses on the development of ultra-lightweight cement composites (ULCCs) with low thermal conductivity but high specific strength so that they can be used for structural applications. The lightweight is achieved by incorporating hollow cenospheres from fly ash generated in thermal power plants. The ULCCs had 1-day densities ranged from 1154 to 1471kg/m3 and 28-day compressive strengths ranged from 33.0 to 69.4MPa. The properties of the ULCCs were compared with those of cement pastes with comparable water/binder and those of a concrete with 28-day compressive strength of 67.6MPa.Results indicate that the compressive strength, flexural tensile strength, and elastic modulus of the ULCCs were reduced with the decrease in density. However, compressive and flexural tensile strength of 69.4 and 7.3MPa were achieved for the ULCC, respectively, similar to the cement paste with w/b of 0.35 and concrete. With similar 28-day compressive strength, the thermal conductivity of the ULCC was 54% and 80% lower than that of the cement paste and concrete, respectively. The low thermal conductivity of the ULCC is due to the incorporation of hollow cenospheres as micro-aggregate which effectively introduce voids and decrease density of the ULCC. The high specific strength of the ULCC may be attributed to (1) the presence of hard and stiff shell in the cenospheres, (2) the “control” of void sizes in the cenospheres, and (3) the creation of strong cement paste matrices that provide “three dimensional” confinement to the cenospheres.

Offshore Industry Gets a Fresh Look at Foamed Cement

Foamed Cementing An ongoing research project started nearly 3 years ago by the US Department of Energy’s National Energy Technology Laboratory (NETL) is shedding new light on what really happens to foamed cement as it is pumped deep down offshore wells during completions. The genesis of the research was the 2010 subsea blowout of the Macondo well in the US Gulf of Mexico (GOM) that destroyed the Deepwater Horizon drilling rig and claimed 11 lives. In the aftermath, the industry faced tough questions about the limits of its technology and the US government tapped NETL to improve the safety of offshore development. After 6 months of interviewing experts in the offshore industry, lead researcher and NETL scientist Barbara Kutchko, who served as an objective expert in the federal litigation over the Macondo incident, decided to focus on foamed cement based on the clear need for more information about how the technology performs outside of the laboratory. “I knew there was a big issue with foamed cement,” Kutchko said. “There was not a lot of research behind it. Foamed cements are mixed under atmospheric conditions, yet there was little known about its properties in the wellbore.” Cement specialists who are lending their expertise to the research said initial findings confirm long-held theories about how the 25-year-old technology performs. As the work progresses, they also said it may result in improvements in how foamed cement is made and applied. Among the things that the research has proved thus far is that as the density of the bubbles inside the foamed cement varies, so does its strength. When the bubbles are smaller, the chances of them joining together to form a larger bubble is less likely, resulting in higher quality and stronger cement. Foamed cement was first introduced in the early 1980s as a low-density substitute for conventional cement and can be pumped more easily down deep wells. In the offshore environment, where deck space and weight are always at a premium, lighter-weight foamed cement has also greatly improved the logistics of completing subsea wells.

Cathodoluminescence-revealed diagenesis of carbonates and feldspars in Cergowa sandstones (Oligocene), Outer Carpathians

Streszczenie Piaskowce cergowskie (dolny oligocen) charakteryzują się doskonałymi właściwościami fizyko- mechanicznymi, jednymi z najlepiej ocenianych wśród kruszyw budowlanych eksploatowanych w polskich Karpatach fliszowych. Obrazy katodoluminescencyjne piaskowców cergowskich przed- stawiają przede wszystkim węglany i skalenie, dlatego te dwie grupy minerałów zostały wybrane, aby zaprezentować i lepiej zrozumieć procesy odpowiedzialne za wyjątkowo silną cementację detrytycznych komponentów skały. Katodoluminescencja (CL) z zimną katodą umożliwia obserwację i interpretację cech diagenetycznych węglanów i skaleni, wizualizuje relacje przestrzenne między szkieletem ziarnowym i cementem, a tym samym pozwala na lepsze zrozumienie genezy wysokich wartości parametrów technicznych piaskowców cergowskich. W piaskowcach cergowskich roz- poznano za pomocą katodoluminescencji z zimną katodą trzy generacje cementu węglanowego (kalcytowego) wypełniającego przestrzenie międzyziamowe: kalcyt brązowy, kalcyt pomarańczowy i kalcyt żółty. Generacje te reprezentują spektrum od eo- przez mezo- po telodiagenezę. Skalenie zostały poddane procesom: albityzacji i zastępowania przez węglany. Dodatkowo, rozpuszczanie składników mineralnych wspomagane było ciśnieniem wywołanym kompakcją osadu. Proces roz- puszczania był na tyle słaby, że zniszczone zostały głównie brzeżne partie ziaren (korozja). Pomimo niedużej intensywności, proces ten był bardzo istotny w lityfikacji osadu. Przyczynił się on do zwiększenia powierzchni kontaktu korodowanych ziaren ze spoiwem. Kombinacja wspomnianych procesów spowodowała bardzo silną cementację składników piaskowców cergowskich, co przejawia się ich wysoką twardością i odpornością.

Tensile Behaviour and Durability of Mortar-Based Strengthening Systems with Glass-Aramid Textiles

Mortar-based composite materials are currently receiving great attention for strengthening masonry structures, especially when specific preservation criteria need to be fulfilled. Their mechanical properties and durability, however, still need to be fully investigated. An experimental campaign has been carried out to characterize the tensile behaviour of composite strengthening systems comprising glass-aramid textiles. First, textile specimens comprising either E-glass or AR-glass have been aged in alkaline environment, for different durations up to 1000 hours, and tested under tension to investigate their durability. Then, composite specimens have been manufactured with the AR-glass-aramid mesh and four different mortar matrices, ranging from strong mineral and cement mortars, to weak hydraulic lime mortars. Strength and stiffness, failure mode and response stages under tension have been identified and compared to those of the dry textiles to investigate the contribution provided by the matrix and derive design parameters for various field applications.

Assessing Failure Envelopes of Soil–Fly Ash–Lime Blends

AbstractThis study aims to establish the influence of curing time and the amount of lime and porosity in the assessment of the Mohr-Coulomb failure envelope of fly ash–lime-treated soils based on unconfined compressive strength (σc) and splitting tensile strength (σt) of such materials. Founded on the concept that the σt/σc relationship is unique for each specific fine-grained soil, fly ash, and lime blends, it is shown that the angle of shearing resistance of a given lime-treated soil is independent of the porosity and the amount of lime of the specimen and that cohesion intercept is a direct function of σc (or σt) of the improved soil, which depends of the porosity and volumetric amount of lime of the soil–fly ash–lime blends. Finally, the concepts are tested with success for a sandy soil treated with fly ash and lime at distinct curing time periods, considering moderate to strong cementation levels.

The Base Material Segregation Control Technology Research of Strong Interlocked Skeleton Dense Graded Aggregate

Compared with the traditional framework dense structure, strong embedded squeeze skeleton dense cement stabilized crushed stone has a stronger embedded squeeze force, the more excellent mechanical properties.This article briefly describes strong embedded squeeze the skeleton dense cement stabilized crushed stone grading design and mechanical properties, and strong embedded squeeze Framework Grading cement stabilized crushed stone in the construction of many materials Segregation. Through the experimental contrast research with traditional construction method, the new method almost eliminate the problems of mixture segregation, which can be used for reference in construction application.

Variation and mechanisms of clastic reservoir quality in the Paleogene Shahejie Formation of the Dongying Sag, Bohai Bay Basin, China

Reservoir quality varies greatly in the Shahejie Formation in the Dongying Sag. It is essential to analyze the variation and mechanisms of reservoir quality for determining the controlling factors based on cores, porosity measurements and fluid inclusion techniques and so on. The sandstones in the fluvial, (fan) delta-front have the best reservoir quality due to the depositional conditions mechanically controlling the petrology configuration and the primary porosity, and chemically influencing the diagenesis and development of secondary pores. The activity of the boundary faults and the sedimentary facies dominate the variation of reservoir quality in different areas and intervals. The reservoir quality varies with the position of sandstone beds in different vertical models of sandstone and mudstone. This mainly arose from the strong cementation or strong dissolution in the sandstone caused by the diagenesis evolution of adjacent mudstone. With higher oil saturation reservoir quality is better because the hydrocarbon charge favors dissolution and restricts cementation. Diagenesis, depositional conditions and tectonic setting are the key controls of reservoir quality in the Shahejie Formation of the Dongying Sag.

A method proposed for the assessment of failure envelopes of cemented sandy soils

This study aims at quantifying the influence of the amount of cement (C), the porosity (η) and the porosity/cement ratio (η/Civ) in the assessment of the Mohr–Coulomb failure envelope of artificially cemented sands centered on splitting tensile strength (σt) and unconfined compressive strength (σc). Based on the concept previously established by Consoli et al. that the σt/σu relationship is unique for each specific sandy soil and cement agent, it is shown that the effective angle of shearing resistance of a given cemented sandy soil (Ø′) is independent of the porosity and the amount of cement of the specimen and that effective cohesion intercept (c′) is a direct function of the unconfined compressive strength (σc) [or splitting tensile strength (σt)] of the improved granular material, which depends on the porosity/cement ratio (η/Civ) of the soil–cement blends. These concepts are tested with success for a uniform fine sand treated with early strength Portland cement and a silty sand treated with ordinary Portland cement, considering weak, moderate and strong cementation levels, as well as for a volcaniclastic formation deposit composed of moderately cemented fine sand and silt-size particles (naturally cemented soil). The methodology developed herein allows estimating c′ and Ø′ for any specific condition comprised inside the range of porosity and amount of cement employed during basic testing, without the necessity of carrying out triaxial testing or any other complex and time consuming tests.