Evaluation of hydrogeologic properties of the Barbados accretionary prism: a synthesis of Leg 156 results

Zwart, Gretchen; Brückmann, Warner; Moran, K.; MacKillop, A. K.; Maltman, Alex; Bolton, A. J.; Vrolijk, Peter; Miller, Terry A.; Gooch, M J; Fisher, A. T.

doi:10.2973/odp.proc.sr.156.036.1997

Cited by 17 publications

(22 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The underthrust sediments remain relatively underconsolidated [ Saffer and Bekins , 2002] and the porosity of this unit was set to a value higher than the average porosity of the prism sediments. Underthrust sediment permeability was constrained by laboratory testing [ Zwart et al , 1997] and is simulation specific (Table 2). The permeability assigned to the underthrust sediments is lower for simulations in which there is no fluid flow in this layer, to represent an end‐member case where nearly all the fluid flow occurs along the décollement.…”

Section: Steady State Velocity and Flow Patternsmentioning

confidence: 99%

Three‐dimensional numerical simulation of fluid flow and heat transport within the Barbados Ridge accretionary complex

Cutillo

Screaton

2003

J. Geophys. Res.

View full text Add to dashboard Cite

[1] The thickness of the Barbados accretionary prism varies along strike. The increased thickness of the prism to the south is believed to affect the transport of heat by fluids, resulting in anomalously high heat flow at the deformation front. We utilized a coupled three-dimensional numerical fluid flow and heat transport model to investigate the effect of variable accretionary prism thickness on fluid flow patterns and heat transport in the décollement zone. The variation in sediment thickness produced along-strike fluid flow in the more permeable décollement. Although surface heat flow is higher for simulations where flow occurs along both the décollement and underthrust sediments, the resultant advective heat transport was not sufficient to appreciably raise steady state surface heat flow at the latitude of the Ocean Drilling Program transect. Simulated temperatures in the décollement were consequently much lower than in situ borehole measurements, suggesting an additional source of warmer fluid. We then investigated the transient hydrologic and thermal response of the system to enhanced fault permeability. Model results provide insight into the degree to which episodic faulting may drive fluid flow and heat transport within subduction complexes. A transient scenario in which décollement permeability was increased two orders of magnitude with fluid flow along both the décollement and underthrust sediments caused the temperature gradient at the location of the drill sites to increase by a factor of two within 7100 years. The results of the threedimensional numerical simulations indicate that while both along-strike advective heat transport and transient fluid flow events should be considered in the heat flow distribution of the northern Barbados accretionary complex, the effects of episodic fluid flow are more significant.

show abstract

Section: Steady State Velocity and Flow Patternsmentioning

confidence: 99%

Three‐dimensional numerical simulation of fluid flow and heat transport within the Barbados Ridge accretionary complex

Cutillo

Screaton

2003

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…1997), drilling disturbance around the borehole (Screaton et al. 1997), and varying test methods which sample a range of formation volumes (Zwart et al. 1997; Screaton et al.…”

Section: Introductionmentioning

confidence: 99%

“…1997); (iii) cross‐hole test (Screaton et al. 2000); (iv) lab tests of two décollement samples (Zwart et al. 1997); and (v) model results (Screaton et al.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reanalysis ofin situpermeability measurements in the Barbados décollement

Bekins¹,

Matmon²,

Screaton³

et al. 2010

Geofluids

View full text Add to dashboard Cite

A cased and sealed borehole in the Northern Barbados accretionary complex was the site of the first attempts to measure permeability in situ along a plate boundary dé collement. Three separate efforts at Hole 949C yielded permeability estimates for the dé collement spanning four orders of magnitude. An analysis of problems encountered during installation of the casing and seals provides insights into how the borehole conditions may have led to the wide range of results. During the installation, sediments from the surrounding formation repeatedly intruded into the borehole and casing. Stress analysis shows that the weak sediments were deforming plastically and the radial and tangential stresses around the borehole were significantly lower than lithostatic. This perturbed stress state may explain why the test pressure records showed indications of hydrofracture at pressures below lithostatic, and permeabilities rose rapidly as the estimated effective stress dropped below 0.8 MPa. Even after the borehole was sealed, the plastic deformation of the formation and relatively large gap of the wire wrapped screen allowed sediment to flow into the casing. Force equilibrium calculations predict sediment would have filled the borehole to 10 cm above the top of the screen by the time slug tests were conducted 1.5 years after the borehole was sealed. Reanalysis of the slug test results with these conditions yields several orders of magnitude higher permeability estimates than the original analysis which assumed an open casing. Overall the results based on only the tests with no sign of hydrofracture yield a permeability range of 10 )14 -10 )15 m 2 and a rate of increase in permeability with decreasing effective stress consistent with laboratory tests on samples from the dé collement zone.

show abstract

“…Models simulating this fluid expulsion from the prism suggest that the flow is transient (Bekins et al, 1995). The faults are characterized by suprahydrostatic, and locally nearly lithostatic, fluid pressures Labaume et al, 1997;Screaton et al, 1997;Zwart et al, 1997).…”

Section: Tectonic Setting Of the Northern Barbados Accretionary Prismmentioning

confidence: 99%

Introduction to Logging-While-Drilling Investigations of Faulting, Fluid Flow, and Seismic Images of the Northern Barbados Subduction Zone

Moore¹,

Klaus²

1998

Proceedings of the Ocean Drilling Program

View full text Add to dashboard Cite

Deformation and fluid flow in sedimentary sequences alter physical properties. In situ measurements of physical properties evaluate diagenetic and structural processes (consolidation, cementation, and dilation) operating during deformation, fluid flow, and faulting. Because seismic images are affected by changes in physical properties, the measurement of physical properties allows the calibration of seismic data as a tool for remotely sensing evidence of deformation and fluid flow. Logging while drilling (LWD) can evaluate physical processes in situ, including transient borehole conditions. During Ocean Drilling Program Leg 171A, a series of LWD holes was drilled to measure physical properties through the Barbados accretionary prism. Extensive previous coring and a three-dimensional seismic survey provide a rich framework for log interpretation, seismic calibration, and evaluation of active diagenetic and structural processes. The results will assist interpretation of similar but less active systems in sedimentary basins elsewhere, contributing to the analysis of groundwater flow, hydrocarbon migration, and earthquake processes.

show abstract

Evaluation of hydrogeologic properties of the Barbados accretionary prism: a synthesis of Leg 156 results

Cited by 17 publications

References 19 publications

Three‐dimensional numerical simulation of fluid flow and heat transport within the Barbados Ridge accretionary complex

Three‐dimensional numerical simulation of fluid flow and heat transport within the Barbados Ridge accretionary complex

Reanalysis ofin situpermeability measurements in the Barbados décollement

Introduction to Logging-While-Drilling Investigations of Faulting, Fluid Flow, and Seismic Images of the Northern Barbados Subduction Zone

Contact Info

Product

Resources

About