Role Of Compaction Research Articles

Compaction-induced porosity loss in the Cretaceous Bima Formation around Lakwaime and Dogon Dutsi, Yola Subbasin, Northern Benue Trough, NE Nigeria

The Bima Sandstone is an alluvial fan to braided river sedimentation that represents purely a siliciclastic depositional system. It is the oldest formation and the main reservoir unit in the entire Benue Trough. Porosity loss is an essential component of petroleum reservoirs that needs to be properly investigated for the purpose of hydrocarbon exploitation. Compaction and cementation processes are partly responsible for porosity loss in many known reservoirs around the world. Outcropping units of the formation around Lakwaime and Dogon Dutsi in Yola Sub-basin have been subjected to an integrated approach involving field observations, petrographic analysis and porosity measurements in order to understand the contribution of each of the processes. Modal composition of the samples shows that they are mostly lithic arkose to feldspathic litharenite, with quartz as the most common detrital mineral grain. Grain fracturing has been attributed to mechanical compaction, whereas grain contacts like sutured and concavo-convex are products of chemical compaction. The average values of compactional-porosity loss (COPL), cementational-porosity loss (CEPL), and compaction index (ICOMPACT) in the studied samples stand at 19.51%, 4.18% and 0.82 respectively. The study indicates that the role of compaction in porosity loss is greater than that of cementation as shown by the COPL-CEPL diagram and, as such considered to be generally responsible for the porosity loss in Bima Sandstone.

On the role of compaction in disputes over the quality of the supplied concrete

This paper evaluates the effect of poor compaction on the compressive strength, sorptivity, gas permeability and accelerated carbonation resistance of bulk concrete in structures, framed in the scenario of disputes over the quality of the supplied concrete. For that purpose, several real-scale elements (beams, columns and slabs) were cast with concrete incorporating Portland-limestone cement and fly ash addition, covering a wide range of slumps (35–123 mm) and compressive strengths (25–65 MPa). The elements were then subjected to different compaction conditions (standard vibration and no vibration), and later cored for concrete testing. A new compaction indicator that overcomes the main practical limitations associated with the determination of the excess voidage of concrete is proposed, as well as new factors for correcting the effects of on-site compaction in the estimation of the potential carbonation resistance and the compressive strength of concrete. It is also shown that vibration no longer improves the quality of bulk concrete in structures for slumps above ~ 140 mm, which suggests that, in cases of dispute where greater slumps are specified, no correction for compaction should be needed in the estimation of the potential properties of concrete.

Depositional and diagenetic controls on sandstone compactional fabrics in an Andean broken foreland basin, the Miocene Vinchina formation, northwestern Argentina

The very thick (up to 6000 m thick) Miocene Vinchina Formation was deposited between 16 and 8 Ma ago and later covered by more than 2500 m of Pliocene-Pleistocene sediments in a broken foreland basin. The very thick sedimentary pile accumulated in a medium to low-gradient basin must have suffered intense mechanical compaction during burial.Seventy thin sections of unaltered sandstones collected in three sections along the depositional strike of the Vinchina Formation at the Sierra de Los Colorados, La Rioja Province, northwestern Argentina, were analyzed under the microscope for determining compactional paths and controls.The role of compaction in sandstone diagenesis was firstly assessed using the change in intergranular volume (IGV), which is the sum of all cement and remaining primary porosity. It is clear from the IGV analysis that most of the studied sandstones lose more porosity by compaction (COPL) than by cementation (CEPL). In general compaction increased from the upper to the lower member of the Vinchina Formation (i.e with depth) and there is a clear trend of the compaction index ICOMPACT increase from the northern, shorter Los Pozuelos to the central, thicker La Troya sections. Surprisingly, the thickest southern El Yeso section shows anomalous results possibly due to the extensive development of cements as indicated by the highest CEPL values. Cements are related to the depositional environment (gypsum, calcite) and clast composition (zeolites). Early cements may have prevented further compaction while late cements may have produced open fabrics by dissolution of matrix and framework clasts. Both cases show that diagenetic processes are not homogeneous basin-wide and that the diagenetic pathways are not only controlled by the increase in burial depth but also by characteristics associated with depositional environments and framework clast composition.We also attempted to relate compaction to burial depth based on the nature (point, long, concave-convex and sutured contacts) and the number (contact and packing indexes) of grain-to-grain contacts in the studied sandstones. The sandstones present predominance of concave-convex grain-to-grain contacts and IC indexes mostly between 3 and 4. Sutured contacts are uncommon, and stylolites were not observed at all. Persistence of open fabrics, floating textures and point grain-to-grain contacts at different depths are the result of dissolution-cementation processes. A clear trend of increasing mechanical compaction with depth is only seen along the northern coarser-grained but thinner Los Pozuelos section. Although compaction seems to have increased with depth and also from north to south, the thickest but overall finer-grained El Yeso (southern) section do not show a clear pattern of change with depth. This behavior seems to be the result of at least four main factors: 1) mean sandstone grain-size, 2) thickness of muddy intervals, 3) development of early diagenetic cements, and 4) depth of burial.Comparison with comparable examples suggests that similar compactional characteristics are achieved between 3.5 and 6 km of maximum burial depths. However, cumulative thickness of the Vinchina basin-fill indicate that the base of the Vinchina Formation may have been buried at 8.5 km deep but preliminary backstripping models suggest that by 5 Ma this surface may have reached up to 10 km depth. Alternatively, recorded repetitive episodes of deformation, uplift, and erosion (progressive unconformities) in the Vinchina basin may have prevented the sedimentary pile to be deeply buried and therefore allow to reconcile the observed compactional textures with depth of burial.The results obtained in this work show that the analysis of mechanical compaction in sandstones constitutes a complex task and in occasions there is not a linear relationship between the contact indexes and depth of burial. Sandstone compaction is controlled not only by the depth of burial but also by other factors such as, time, geothermal flow, matrix content, the development of early cements, the ratio between ductile and rigid lithic fragments and, in tectonically active basins the development of progressive unconformities. Therefore, in most cases, it is very speculative to extend diagenetic conditions to basin-wide scales. In particular, the porosity-depth relationship must be based on primary porosity only.

Compaction of a Polymeric Membrane in Ultra-Low-Pressure Water Filtration.

Applications of ultra-low-pressure filtration systems are increasing as they offer enhanced sustainability due to lower energy input, almost no use of chemicals, and minimum operational expenditure. In many cases, they operate as a decentralized system using a gravity-driven membrane (GDM) filtration process. These applications are relatively new; hence, the fundamental knowledge of the process is still limited. In this study, we investigated the phenomenon of polymeric membrane compaction under an ultra-low-pressure system. The compaction phenomenon is well-recognized in the traditional pressure-driven system operating at high transmembrane pressures (ΔPs > 200 kPa), but it is less documented in ultra-low-pressure systems (ΔP < 10 kPa). A simple GDM filtration setup operated under a constant-pressure system was employed to investigate the compaction phenomena in a polymeric hollow fiber membrane for clean water filtration. Firstly, a short-term pressure stepping test was performed to investigate the occurrence of instantaneous compaction in the ΔP range of 1–10 kPa. The slow compaction was later investigated. Finally, the compaction dynamic was assessed under alternating high and low ΔP and relaxation in between the filtrations. The findings demonstrated the prominence of membrane compaction, as shown by the decreasing trend in clean water permeability at higher ΔPs (i.e., 3240 and 2401 L m−2 h−1 bar−1 at ΔPs of 1 and 10 kPa, respectively). We also found that the intrinsic permeability of the applied polymeric membrane was significantly higher than the apparent one (4351 vs. 2401 L m−2 h−1 bar−1), demonstrating >50% loss due to compaction. The compaction was mainly instantaneous, which occurred when the ΔP was changed, whereas only minor changes in permeability occurred over time when operating at a constant ΔP. The compaction was highly reversible and could be restored (i.e., decompaction) through relaxation by temporarily stopping the filtration. A small fraction of irreversible compaction could be detected by operating alternating filtrations under ΔPs of 1 and 10 kPa. The overall findings are essential to support emerging GDM filtration applications, in which membrane compaction has been ignored and confounded with membrane fouling. The role of compaction is more prominent for high-flux GDM filtration systems treating less-fouling-prone feed (i.e., rainwater, river water) and involving membrane cleaning (i.e., relaxation) in which both reversible and irreversible compaction occurred simultaneously.

Role of compaction in melt extraction and accumulation at a slow spreading center: Microstructures of olivine gabbros from the Atlantis Bank (IODP Hole U1473A, SWIR)

The exposure of gabbroic sequences at Oceanic Core Complexes (OCC) along ultraslow- to slow-spreading ridges permits the study of the processes forming the lower oceanic crust. On top of the Atlantis Bank OCC along the ultraslow-spreading Southwest Indian Ridge, IODP Expedition 360 drilled Hole U1473A, mainly composed of primitive olivine gabbros interspersed with more evolved Ti-Fe oxide-bearing gabbros and minor felsic veins. These rocks record a complex history of protracted magmatism during continuous uplift and deformation of the gabbroic sequence. Extensive crystal-plastic deformation is dominantly recorded in the shallower sections of the drillhole, whereas the deeper sections better preserve primary magmatic features. We focus on microstructures, including intra-crystalline deformation of rock-forming minerals, and plagioclase crystallographic preferred orientations of olivine gabbros lacking evidence for exhumation-related crystal plastic deformation, to gain insights on the relationship between compaction, melt migration and melt accumulation during the early magmatic history of this section of lower oceanic crust. Olivine gabbros are characterized by ubiquitous grain-size variations, from coarse- to fine-grained intervals. Minerals in coarse-grained intervals show intra-crystalline deformation, while fine-grained crystals lack internal strain. Bent coarse-grained plagioclase associated with weak magmatic foliation and lack of lineation suggest that the coarse-grained intervals were deformed under weak compaction. On the other hand, crystallographic preferred orientations of undeformed fine-grained plagioclase show weak lineations, likely indicative of non-coaxial strain. We thereby infer that the coarse-grained intervals underwent ongoing weak compaction from the stage of olivine + plagioclase ± clinopyroxene crystal mush to the melt-poor stage, and that this process likely aided melt extraction and accumulation in discrete melt-rich zones where crystals orientated in the direction of magmatic flow. Crystallization of melts in the melt-rich zones ultimately formed the fine-grained intervals at different depths in Hole U1473A. This indicates that processes of compaction can lead to local chemical and grain-size heterogeneities in a lower crustal section, while had a minor role in the melt movement at larger scales (e.g., the whole crystal mush) within the oceanic crust.

Role of compaction and drying-wetting cycles on the capability of precompression stress to indicate load history of heavily disturbed soils

Wetting and drying are common processes in agricultural soils, which change particle rearrangement, cementation and related properties. Some recent studies have noted that soil precompression stress (σp) – the soil capacity to support stress – can be affected by wetting and drying cycles and should be seen as state variable instead of a soil mechanical characteristic. In this study, we investigated how wetting and drying cycles change the σp of remolded samples, i.e. soil without distinct loading history. Soil material from three highly weathered soils with different textures (62, 35 and 15% of clay) of the most common soil classes of Brazil were used. The soils were milled and then used to create two set of samples with different compactness. In one set, named not compacted (NC), the milled material was just poured (loose material) into the cylinders, while in the other set the milled material inside the cylinders was compacted (COMP). In the NC samples, zero and three drying (under 33 kPa matric suction) and wetting (saturation) cycles (0D-S and 3D-S) were applied. The COMP samples were subjected to 0, 2, 4, and 6 D-S cycles. In the NC samples, the σp (35–49 kPa) in 0D-S was similar to the matric stress soil samples had experienced prior to the compression test (33 kPa), but σp increased to 60–92 kPa after 3D-S. In the COMP samples, σp increases ranged between 65 and 53 kPa from 0 D-S to 2 D-S and then decreased to a value similar to that of 0 D-S again after 6 D-S. Changes of σp tended to be more remarkable in the soils with 62 and 35% of clay, but only a weak association between σp and texture was noticed. These results indicate that internal forces a soil experiences during shrinkage and swelling are key drivers of the σp parameter of the topsoil of agricultural areas. Thus, one σp value cannot characterize a site over time as it might be altered thoroughly during the year and thus fail in reflecting documented load history by means of traffic.

Permeability and frictional properties of halite-clay-quartz faults in marine-sediment: The role of compaction and shear

Faults in marine-sediment basins often dictate fluid flow and act as petroleum traps or seals. Permeability contrasts between these zones and the surrounding country rock can be large, depending on fault composition, stress, and strain history. Despite the importance of such faults, our understanding of their frictional properties and permeability is relatively poor. Here we report on a suite of laboratory experiments to assess the roles of fault composition, stress, and shear strain for dictating poromechanical properties of fault. Experiments were conducted at room temperature on synthetic fault gouge composed of quartz, halite, and clay (illite shale or Ca-montmorillonite). We sheared layers that were 5–7 mm thick and measured fault permeability at effective normal stresses from 2 to 6 MPa for hydrostatic conditions and after shear strains from 2 to 10. We find that fault permeability is highly sensitive to clay content, with permeabilities spanning 2–4 orders of magnitude under otherwise identical conditions. Permeability decreased up to 2 orders of magnitude with imposed shear strain >1 and ∼1 order of magnitude with increasing normal stress from 2 to 6 MPa. During shear, halite deformed via both ductile flow and brittle failure, while quartz and clay particles formed force chains that spanned the layers and defined shear localization fabrics. Samples with higher halite content exhibited greater permeability reduction, perhaps by plastic flow and pressure solution. Our results suggest that the permeability of faults in marine sediment is dictated by clay content, and that the most dramatic permeability changes occur with relatively small fault throw (shear strain from 2 to 5). This highlights the importance of understanding minor faults and fault sets when estimating subsurface fluid flow and potential reservoir compartmentalization.

Production of high porosity Zn foams by powder metallurgy method

Open-cell Zn foams with 74–92% porosity were fabricated by space holder technique, including compacting spherical carbamide granules coated with Zn powders followed by leaching the space holder and sintering. The role of compaction and sintering parameters on pore structure, cell wall integrity and compressive properties of foams was investigated. The results show that compressive yield strength and modulus of elasticity decrease with porosity and a good compatibility with Gibson–Ashby model of cellular solids is discovered. The optimum structure and mechanical properties of Zn foams are achieved by compaction at 300 MPa and sintering for 2 h at 410°C.

Porosity trends in the Skagerrak Formation, Central Graben, United Kingdom Continental Shelf: The role of compaction and pore pressure history

This paper describes reservoir properties in the Triassic Skagerrak Formation in the Central North Sea. This prolific sandstone reservoir often possesses anomalously high porosity for its depth of burial. Simple statistical analysis of wire-line-log-derived porosity data is used to derive empirical trends as a function of both depth and vertical effective stress that show variations between neighboring hydrocarbon fields and between different parts of the basin. Porosity data from the Josephine (J) Ridge (Quadrant 30 of the United Kingdom Continental Shelf [UKCS]) show a marked degradation with depth, but the porosities are significantly higher than in similarly deeply buried areas such as the Puffin high to the west (Quadrant 29) or the Forties–Montrose high to the north (Quadrant 22). To understand the porosity patterns better the data have been analyzed by plotting against vertical effective stress. This allows a better comparison to be made between fields and wells within the high-pressure–high-temperature (HPHT) realm. High pressure here refers to fluid pressures above 10,000 psi (), whereas high temperatures are above 300°F (149°C). Results show that porosity and fractional effective reservoir (the proportion of net sandstone with a porosity greater than a predetermined cutoff) decrease systematically with increasing vertical effective stress. Data from the different J Ridge fields fall on a common compaction trend even though they are derived from structures with marked variations in present-day depth of burial and static formation overpressure. Trends from the other areas of the Central Graben (the Puffin and Forties–Montrose highs) indicate more indurate reservoir states. The observed porosity trends are independent of fluid type within the reservoir and the absolute magnitude of overpressure. The main observed hydrocarbon effect is the result of buoyancy forces. The analysis supports the contention that, after accounting for facies-related grain-size variations, compaction controls average reservoir properties. Differences in compaction state between areas are postulated to relate primarily to structurally controlled timing of overpressure development relative to burial, and how these affect the resultant vertical effective stress history. Both the Puffin and Forties–Montrose highs are directly attached to the basin margins across stepped faults. These marginal terraces were open to lateral fluid flow for longer probably because across-fault seals were only established late in the burial history when higher temperatures promoted cementation and the destruction of permeability within fault cores. As a result, they developed overpressures in the last 5–10 m.y. or so and are largely normally compacted. The J Ridge horst block is hydrologically more isolated within the basin center by across-fault juxtaposition seals. Here, overpressure development appears to have started earlier, possibly between 50 and 60 Ma, retarding compaction and allowing preservation of higher porosities. Compaction continues to present day driven by the large static vertical effective stress gradients in these deeply buried reservoirs. The observed empirical trends offer a means of predicting average reservoir properties in deep untested exploration targets.

Sintering of Ti(C,N)-Based Cermets: The Role of Compaction

Abstract Different compaction processes were employed in studying the effect of green state on the sintering of TiC-TiN-Ni-Mo2C and Ti(C0.3N0.)-Ni-Mo2C cermets. Specimens were uniaxially pressed and some being subsequently compacted by cold isostatic pressing. Liquid and solid phase sintering was carried out in nitrogen atmosphere. Green state porosity, pore size distributions, as sintered morphologies, micro-hardness and microstructural development were characterized. Mercury porosimetry measurements indicate that with increasing compacting pressure, large pores are eliminated and the pore size distribution curves shift towards smaller pores. Higher compaction load also leads to decrease in average pore size and a wider pore size distribution. It was found that the Ti(CN)-based cermets are superior than the (TiC-TiN)-based cermet. Cermets with carbowax additives are better sintered than those without the wax. The two-stage consolidation (diepressing + CIP) results in better sintering properties than die-...

The Role of Compaction in Agglomeration in Liquid and Formulation of Scale-up Equation.

The effects of agitation intensity and amount of bridging liquid on agglomerate formation in agglomeration in liquid were experimentally investigated. An increase in agitation intensity advanced the compaction of agglomerates, reduced the porosity and changed the saturation degree which is the ratio by volume of the bridging liquid to the pores of an agglomerate. It was observed that the process of agglomerate growth depended on the changes in porosity. Based on this observation, the effects of agitation intensity on the process of compaction and changes in porosity were quantitatively elucidated and a scale-up equation was formulated. In addition, model agglomerates of the zirconia powder were cold isostatically pressed to investigate the influence of green agglomerate porosity on the density of sintered agglomerates. The results showed that the agglomerates produced by agglomeration in liquid must have porosities less than 0.51 in order to achieve high density and strength after sintering. To achieve this objective, the formulated scale-up equation was utilized to design a batch-type horizontal agglomerator that can provide the agitation energy required to produce agglomerates with porosities below 0.51. The newly designed agglomerator was successfully tested in the production of highly dense microspherical agglomerates of zirconia.

Role of Compaction in Determining Sandstone Porosity: ABSTRACT

Role of Compaction in Determining Sandstone Porosity: ABSTRACT

Role of Compaction in Listric Shape of Growth Normal Faults

Growth normal faults propagate syndepositionally at the depositional surface and their dips flatten with depth as the surrounding sediments compact, as described by the equation tan ^Thgr tan ^Thgr0 = (1-^phgr0) (1-^phgr) , where ^phgr0 and ^phgr are the initial and final porosities of the surrounding sediments and ^Thgr0 and ^Thgr are the initial and final fault dips after compaction. This equation is tested on several southern Louisiana growth normal faults whose shapes are known from well penetrations and whose porosity/depth relationships for sand and shale are derived from well logging. The initial surface fault dip ^Thgr0 = 67° and the initial sand and shale porosities ^phgr0ss = 39.3% and ^phgr0sh = 68%, respectively, were determined by an inversion technique on an extensive data set from one fault. Once these initial conditions were determined, the shapes of other faults were computed accurately based on knowledge o the sand-shale stratigraphy from single well logs. The compaction equation allows accurate determination of the proportion of fault flattening caused by compaction and other processes. For example, one fault flattens from an initial dip of 67° to a dip of 38° at 5 km depth; 23° of the flattening is caused by compaction and 6° is caused by footwall folding. Finally, in pure shale the compaction-induced flattening of a growth fault is as much as 19° in the first 500 m of burial and reduces to about 1°/km below this depth; in pure sand the flattening is approximately 1°/km throughout.

Results of numerical modeling of the convective burning of particulate explosive systems in the presence of increasing pressure

The authors analyze the results of a numerical simulation of the convective burning of explosive powders in the presence of increasing pressure. The formulation of the problem reproduces a typical experimental technique: a strong closed vessel with a channel uniformly filled with the explosive investigated is fitted with devices for initiating and recording the process of explosion. It is shown that the relation between the propagation velocities of the flame and the compression waves in the powder and the rate of pressure increase in the combustion zone is such that a narrow compaction zone is formed ahead of the ignition front. Another important result is obtained by analyzing the difference between the flame velocity and the gas flow velocity in the ignition front. A model of the process is given. The results of the investigation throw light on such aspects of the convective combustion mechanism and the transition from combustion to detonation as the role of compaction of the explosive in the process of flame propogation and the role of the rate of pressure increase and dissipative heating of the gas phase in the pores ahead of the ignition front.

Geometry and Mechanisms of Folding Related to Growth Faulting in Nordheim Field Area (Wilcox), De Witt County, Texas: ABSTRACT

ABSTRACT The Nordheim area in western De Witt County, Texas has produced over 121 billion cubic ft of gas of which over 53 billion cubic ft has come from the deep lower Wilcox. Consequently, a better understanding of folding in the Nordheim area should aid future exploration efforts, especially in the deeper (greater than 10,000 ft) Wilcox. In order to better understand folding, methods are presented which separate the contribution various folding mechanisms to fold geometry. The folding mechanisms recognized are: mechanical folding, or folding due to faulting; drape compaction; and differential compaction. As a consequence of separating the various folding mechanisms, important geometric aspects of folding were recognized at Nordheim. They include: a) the upward movement of folds relative to regional dip, b) the shift of fold crests along dip and strike at various depths and c) the role of compaction in the final fold geometry. Upfolding is the term used to define the upward movement of folds relative to regional dip. Up folding is recognized where intervals thicken off a fold crest in all direction, and not just in the direction of the growth fault. For example the deepest interval in the lower Wilcox, the Migura, has over 200 ft of isopach relief and about 250 ft of closure. Shallower intervals and horizons show similar relationships between structure and isopach but with less relief. Upfolding is the dominant mechanism of folding in the Nordheim area. Most of the folding not explained by upholding is explained by either drape or differential compaction. Mechanisms of folding related to growth faulting proposed by previous authors have only incorporated two dimensions. Upfolding is a three dimensional concept, and it is believed to be caused by material moving down a concave shaped listric normal fault. The concave shape may cause a volume problem, which is overcome by the upward movement of material. Three specific exploration concepts have been developed as a result of this study.

Role of Compaction in Development of Geometry of Superposed Elongate Sandstone Bodies: ABSTRACT

End_Page 455------------------------------Pennsylvanian and Permian nearshore facies on the eastern shelf of north-central Texas contain channel-fill sandstone bodies, which have been mapped from the outcrop westward down the paleoslope for 50 miles. These elongate sandstone bodies range in width from several yards to 3-4 miles and in a few places are more than 100 feet thick. Where the thickness values of the subsurface dendritic (distributary) sandstone bodies are unusually great, sandstone from subjacent bar-finger deposits probably has been included. Within shallow, poorly developed synclines, which apparently provided primary paleotopographic control of channels, superposed channel systems commonly are offset laterally as a result of (1) interchannel subsidence by differential sandstone (channel)-shale (interchannel) compaction and (2) channel subsidence by compaction of sediments beneath massive channel-fill sandstones. The common offset patterns of superposed channel pairs is mainly a result of dominant interchannel compaction. Stacked or cross-over relations of channel pairs are less common and occur where the lower member is unusually thick. Channel-pair intersect maps illustrate the persistent geographic position of stacking and cross-overs, which may reflect tectonic control of channel location. Because of differential sandstone-shale compaction, axes of sandstone bodies commonly coincide with maximum thicknesses of thin, conformity-bounded sequences which enclose the elongate sandstone body. Axes representing maximum thickness of these enveloping strata, supplemented by high sandstone percentage trends, and synclinal axes, are useful in outlining the general position of channel-fill sandstone systems, but sandstone isopachous maps, paleotopographic maps, and cross sections (necessitating denser well control) are more definitive. End_of_Article - Last_Page 456------------