Variations of Porosity in Calcareous Sediments from the Ontong Java Plateau

Bassinot, Franck; Marsters, Janice C.; Mayer, Larry A.; Wilkens, Roy H

doi:10.2973/odp.proc.sr.130.058.1993

Cited by 11 publications

(8 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Leg 130 examined five sites, 803 to 807, and shipboard porosity versus depth data were reported from 14 holes. There is evidence to suggest that Site 804 shows sediment disturbance due to slumping (Bassinot et al, 1993), which may explain why the porosity data from Site 804 shows wider scatter than the data from the four other sites. For this reason, Site 804 was not included in this study.…”

Section: ) and V=so M Ma-' (High End-member Value) One Obtainsmentioning

confidence: 99%

Modelling of porosity evolution and mechanical compaction of calcareous sediments

Audet

1995

Sedimentology

View full text Add to dashboard Cite

A continuum mechanics model for the gravitational compaction of sediments is derived by assuming that the sediments are normally pressured and in a one‐dimensional state of stress. Sediment strength is characterized in terms of effective stress laws adopted from soil mechanics. The model is a relatively simple mathematical formula that gives the porosity as a function of burial depth. The shape of the porosity profile is controlled by two mechanical parameters, the compression index and the void ratio at an effective stress of 100 kPa. The model was verified by analysing the porosity—depth data of oozes and chalk from the Ontong Java Plateau, gathered during Leg 130 of the Ocean Drilling Program. The mechanical parameters of the sediments were estimated using a least‐squares method to fit the theoretical profile to the porosity data. The theoretical profile described accurately the ooze porosity data over depth ranges of 100 m or more. However, over smaller length‐scales of 10–50 m there were systematic deviations between the theoretical porosity values and the ooze porosity data. The porosity deviations correlated with variations in the mean grain size of the sediments, due in part to changes in the foraminifera abundance. In the case of the oozes, the estimated mechanical parameters were consistent with published values obtained from one‐dimensional compression tests. In contrast, the estimated mechanical properties for the chalks differed from published values. The chalk porosities were lower than could be explained by mechanical compaction. This explanation is supported by the compressional (P‐wave) velocity data. In the chalk sections, the P‐wave velocity increases more rapidly with burial depth than it does in the ooze sections, suggesting that sediment elastic properties are increasing due to interparticle binding.

show abstract

Section: ) and V=so M Ma-' (High End-member Value) One Obtainsmentioning

confidence: 99%

Modelling of porosity evolution and mechanical compaction of calcareous sediments

Audet

1995

Sedimentology

View full text Add to dashboard Cite

show abstract

“…Early carbonate diagenetic processes include dissolution of aragonite and magnesian calcite, precipitation of low-Mg calcite, as well as dolomitization (Meyers and Hill, 1983;Scholle and Halley, 1985). These processes can both add and remove large volumes of material, such that subsequent mechanical compaction during the first several hundred meters of burial depends strongly on the early diagenetic history (Hamilton, 1976;Scholle and Halley, 1985;Bassinot et al, 1993;Wallace et al, 2002). Although initial porosities of carbonate sediments are very high ranging around 50-60% (Enos and Sawatsky, 1981;Kroenke et al, 1991), porosities of subsurface carbonate reservoirs are generally much lower than in sandstones and commonly show trends of regular decrease as burial increases (Schmoker, 1984;Brown, 1997;Ehrenberg and Nadeau, 2005).…”

Section: Introductionmentioning

confidence: 96%

Petrophysical properties of bioclastic platform carbonates: implications for porosity controls during burial

Croizé

Ehrenberg

Bjørlykke

et al. 2010

Marine and Petroleum Geology

View full text Add to dashboard Cite

International audienceThis study is based on rock mechanical tests of samples from platform carbonate strata to document their petrophysical properties and determine their potential for porosity loss by mechanical compaction. Sixteen core-plug samples, including eleven limestones and five dolostones, from Miocene carbonate platforms on the Marion Plateau, offshore northeast Australia, were tested at vertical effective stress, View the MathML source, of 0–70 MPa, as lateral strain was kept equal to zero. The samples were deposited as bioclastic facies in platform-top settings having paleo-water depths of <10–90 m. They were variably cemented with low-Mg calcite and five of the samples were dolomitized before burial to present depths of 39–635 m below sea floor with porosities of 8–46%. Ten samples tested under dry conditions had up to 0.22% strain at View the MathML source, whereas six samples tested saturated with brine, under drained conditions, had up to 0.33% strain. The yield strength was reached in five of the plugs. The measured strains show an overall positive correlation with porosity. Vp ranges from 3640 to 5660 m/s and Vs from 1840 to 3530 m/s. Poisson coefficient is 0.20–0.33 and Young's modulus at 30 MPa ranged between 5 and 40 GPa. Water saturated samples had lower shear moduli and slightly higher P- to S-wave velocity ratios. Creep at constant stress was observed only in samples affected by pore collapse, indicating propagation of microcracks. Although deposited as loose carbonate sand and mud, the studied carbonates acquired reef-like petrophysical properties by early calcite and dolomite cementation. The small strains observed experimentally at 50 MPa indicate that little mechanical compaction would occur at deeper burial. However, as these rocks are unlikely to preserve their present high porosities to 4–5 km depth, further porosity loss would proceed mainly by chemical compaction and cementation

show abstract

“…In clay-rich marine sediments, positive transverse anisotropy will vary from 0% near the surface (complete isotropy) to >12% at depths of several hundred meters. In the interpretation of seismic reflection and refraction data, velocity anisotropy has to be taken in consideration because it will determine the mode of wave propagation in the sediment (Bassinot et al, 1993;Carlson and Christensen, 1977;Bachman, 1979;Milholland et al, 1980). Compactional anisotropy, parallel alignment of pores and particles parallel to bedding because of gravitational compaction under increasing overburden, is commonly assumed to be the most important single source for the downhole increase in acoustic anisotropy in fine-grained, clay-rich sediments (Hamilton, 1970;Kim et al, 1983Kim et al, , 1985O'Brien, 1990).…”

Section: Acoustic Anisotropymentioning

confidence: 99%

Directional properties of P-wave velocities and acoustic anisotropy in different structural domains of the northern Barbados Ridge accretionary complex

Brückmann¹,

Moran²,

Housen³

1997

Proceedings of the Ocean Drilling Program, 156 Scientific Results

View full text Add to dashboard Cite

Ocean Drilling Program (ODP) Leg 156 revisited the northern Barbados Ridge, where the previous Deep Sea Drilling Program Leg 78A and ODP Leg 110 studied the frontal part of this accretionary prism. Drilling and logging-while-drilling at Sites 947, 948, and 949 successfully identified major thrust faults and the décollement, which was the target of several downhole experiments. Two of the eight holes drilled were equipped with borehole observatories that will monitor temperature, pressure, and fluid flow over the next years. Coring at Hole 948C recovered 180 m of sediment, centered around the décollement, which was positively identified based on structural information. The aim of this study is the evaluation of the possible correlation of preferred orientation of acoustic properties and the direction of maximum compressive strain in the frontal part of the accretionary prism. For this purpose, shipboard P-wave velocities from Holes 948C and 949B were reoriented. This information was then used to compare the directional properties of accreted and subducted sediments. In Hole 948C, lowest transverse velocities (T min ) were observed to be consistently oriented perpendicular to the maximum horizontal compressive stress, believed to be parallel to the convergence vector. In the underthrust domain of Hole 948C, several preferred orientations for T min were detected, but no correlation with the geotectonic reference frame could be identified. Acoustic anisotropy does not show a comparable pattern in Hole 948C. It is concluded that the observed directional dependence of P-wave velocity in the accreted sediment domain in Hole 948B is the result of moderate to steeply inclined bedding, although this conclusion can not adequately be tested due to the lack of corrected structural data.

show abstract

Variations of Porosity in Calcareous Sediments from the Ontong Java Plateau

Cited by 11 publications

References 22 publications

Modelling of porosity evolution and mechanical compaction of calcareous sediments

Modelling of porosity evolution and mechanical compaction of calcareous sediments

Petrophysical properties of bioclastic platform carbonates: implications for porosity controls during burial

Directional properties of P-wave velocities and acoustic anisotropy in different structural domains of the northern Barbados Ridge accretionary complex

Contact Info

Product

Resources

About