roberts - terrebonne growth faulting

8/9/2019 Roberts - Terrebonne Growth Faulting

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2001,AAPG/DEG, 1075-9565/01/$15.00/0Environmental Geosciences, Volume 8, Number 2, 2001 7794

K U E C H E R E T A L . : E V I D E N C E F O R A C T I V E G R O W T H F A U L T I N G 77

Evidence for Active Growth Faulting in theTerrebonne Delta Plain, South Louisiana:

Implications for Wetland Loss and theVertical Migration of PetroleumG. J. KUECHER,* H. H. ROBERTS, M. D. THOMPSON,

and I. MATTHEWS*

*Baker Atlas Geoscience, Houston, TX 77073

Louisiana State University, Coastal Studies Institute, Baton Rouge, LA 70803

Argonne National Laboratory, Argonne, IL 60439

ABSTRACT

Two regional growth faults, the Golden Meadow Fault and the

Lake Hatch Fault, were mapped in Terrebonne and Lafourche

Parishes, Louisiana, utilizing over 3000 line kilometers of seis-

mic data. The subcropping location of these faults identify major

vegetation biozonations, new areas of wetland loss, and the po-

sition of transgressive lakes. The proposed mechanism govern-

ing these fault-related manifestations of subsidence involves the

venting of fluid (and gas) from geopressured shales vertically up

fault planes. Saline fluids and gases exiting a basin via growth

faults provide accommodation space at depth, resulting in ac-

tive

, fault-induced subsidence in the down-thrown block. By

contrast, areas along the fault trend where no fluids or gases

were migrating would not result in an increase of accommoda-

tion space and would be considered inactive

regarding fault-induced subsidence. The model that emerges is a growth fault

trace that does not act in concert but more closely resembles a

key-stepping system with sections alternating between active

and inactive. These findings are relevant to the role of growth

faults in subsidence-related coastal land loss and the vertical mi-

gration of hydrocarbons.

Key Words:

wetland loss, oil migration, Louisiana, growth faults.

INTRODUCTION

Growth faults are a variety of normal listric faults associ-

ated with drifting downslope sequences on passive margins

(Bally et al., 1981; Shelton, 1984). Movement along growth

faults is contemporaneous with active deposition (Xiao and

Suppe, 1989; Bally et al., 1981; Shelton, 1984) and prefer-

ential thickening, or growth, can be documented on the

down-thrown sides of these faults (Dula, 1991; Galloway,

1986; Ocamb, 1961). It is believed that growth faults propa-

gate upward through thin sedimentary cover as a series of

minor, en echelon, faults that constitute a single mapped

fault (Crans et al., 1980; Durham, 1971; Roland et al.,

1981). The en echelon pattern explains the large number of

upward-branching horsetails that have been mapped in

high-resolution seismic profiling over shallow sedimentary

sections (Roux, 1979; Shelton, 1984).

Growth faults in south Louisiana originate locally as a

basal dcollement at the top of geopressured diapiric ridges

or ductile folds (Bruce, 1973; Riggs et al., 1991; Xiao and

Suppe, 1989; Bally et al., 1981; Shelton, 1984; Nelson,

1991). The association of growth faults to subsurface con-

trols, specifically geopressure, is direct (Hart et al., 1995;

Hunt et al., 1994; Hunt, 1990; Bruce, 1973), and it is not

surprising that fluids and gases are expelled from such

zones (Sassen et al., 1993; Freed and Peacor, 1989).A substantial body of data collected in recent years docu-

ments the importance of fault zones as conduits of vertical

fluid migration into ancient

sediments (Losh et al., 1999;

Mozley and Goodwin, 1995; Anderson et al., 1994; Bil-

leaud et al. 1994; Echols et al. 1994; Zimmerman 1994; Mc-

Manus and Hanor, 1993; Esch and Hanor, 1995; Galloway,

1986; and others), and the frequency of fluid expulsion up

these faults appears to be episodic (Cartwright et al., 1998;

Wang and Xie, 1998; Lin and Nunn, 1997). Subsurface flu-

ids can also migrate vertically into modern

sediments via

faults (Kuecher and Roberts, 2000; Kuecher, 1995a, 1995b;Mitchell-Tapping, 1995; Verberne, 1992; Morgan, 1951).

The photo shown in Figure 1 serves as a model for this fluid

migration story.

Notice the boils that occur when gases and fluids es-

cape via faults from overpressured sediments trapped

within centimeters of the land surface. This shallow exam-

ple, the authors suggest, serves as an analog for expulsion of

fluids and gases from deep systems into shallow reservoirs

and even onto the surface. In fact, formation brines, crude

oil, and gas hydrates have been observed issuing from or

frozen in the vicinity of scarps, assumed to be faults, in the

deep Gulf of Mexico (Roberts and Carney, 1997).


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E N V I R O N M E N T A L G E O S C I E N C E S

FIGURE 1. Minor stress (as with afootstep) applied to fine-grained sed-iments in the lower delta plain mayproduce arcuate faults that serve asvertical conduits for waters and gasestrapped below.

FIGURE 2. Model proposed by Loshet al. (1999) of vertical transport offluids and gases into reservoirs alongthe trace of a fault.

RELATED STUDIES

Deep-seated fault-bound compartments episodically rup-

ture due to the buildup of geopressure, releasing large quan-

tities of water, gas, and oil vertically into shallower aquifersvia fault planes (Losh et al., 1999; Alexander and Hand-

schy, 1998; Cartwright et al., 1998; Lin and Nunn, 1997;


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Waples, 1991). The model presented in Figure 2 summa-

rizes recent thought on the dynamics of this system.

This study proposes that regional growth faults respond to

the basinal buildup of fluid and gas volumes in the following

feedback fashion: (a) geopressured fluid and gas from deep

shale masses exceeds the strength of the faults sealing

gouge, (b) fluids enter the fault zone and migrate verticallyuntil reservoirs adjacent to the fault or the surface or both are

encountered, (c) volume decreases at depth in the geopres-

sured shale mass in response to the volume of expelled fluids

and hydrocarbons, (d) excess pore pressures are attenuated in

the deep shale mass, (e) the down-thrown block subsides, and

(f) the fault gouge reseals. Periods of active fluid venting, it

follows, are followed closely by active

subsidence (Hart et

al., 1995). Along any regional growth fault, nonsealing or

leaky characteristics may correlate with presently active seg-

ments, juxtaposition of permeable facies, or both. In contrast,

sealing characteristics may represent either presently inactive

segments of regional growth faults, juxtaposition of imper-

meable facies, or both. The movement along growth faults,

consequently, is not uniform or in concert along the entire

length of a fault. Instead, growth faults must move downslope

in a key-stepping fashion, alternating between periods of ac-

tivity and nonactivity.

INTRODUCTION TO PROBLEM

A linkage between active

sections along growth faults

and concomitant neotectonic settlement (expressed in the

Louisiana lower delta plain as wetland loss) is proposed. If

the relationship is direct, active faults may be expressed on

the coastal plain as arcuate and sharply defined boundaries

between new marsh or open water on the faults down-

thrown side to higher and drier ground on the faults up-

thrown side.

Searching the Mississippi Rivers lower delta plain for ex-

amples of fault-related subsidence, a few candidates emerge

FIGURE 3. GIS wetland loss map,Empire Quadrangle, Louisiana, thatincludes trace of suspected growthfault and orientation of AA seis-mic section.


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for further investigation. One prospective area has been

identified approximately 45 miles southeast of New Orleans

in the in the vicinity of Adams and Bastian Bays, Empire

Quadrangle, Louisiana (Figure 3). The dark color in this

presentation represents new areas of wetland loss and ter-

ranes that only recently converted from brackish marsh to

saline open waters. More importantly for this discussion,the northern limit of the dark color was suspected as the

subcropping location of a major growth fault.

Seismic dip section AA

(Figure 4) was provided by

Seismic Exchange, Inc. (SEI) as a courtesy of this research.

As per agreement between SEI and researchers, no shot

points or identifying information are allowed in referencing

this section. The location of this subcropping fault trace pre-

cisely defines the northern limit of dark-colored new marsh

areas as mapped in Figure 3, section AA

. This fault must

be currently active to produce a down-thrown block that is

perennially wet (saline marsh/incipient bay) and the mar-

gins of which are closely coincident with the fault trace.

The authors propose a linkage between active growth

faults and wetland loss. Granted, there are numerous con-

trols on wetland loss that are not fault-related, but we be-

lieve the controlling mechanism for wetland loss has been

positively identified in this case. Similar studies on the roleof faults in wetland loss have been conducted in The Neth-

erlands, and leveling surveys there reveal the role of active

faults in subsidence and localized flooding (Groenewoud et

al., 1991).

APPLICATION OFELECTROMAGNETICS

Electromagnetics (EM) provides an easy-to-use method

that can rapidly measure the conductivity of sedimentary

sections to depths of 60 meters or more without ground cou-

FIGURE 4: Uninterpreted seismicsection AAacross Empire surfaceanomaly revealing fault.


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It was hypothesized, in these initial studies, that line

sources of conductive saline pore waters in these fresh to in-

termediate marsh terranes were derived from deep overpres-

sured shale beds and that growth faults were the conduit by

which fluids migrated vertically from deep into shallow

aquifers. The Argonne studies were attempting to document

active migration of saline fluids by faults into modern sedi-ments. The pilot study of this technique occurred at the Ba-

ton Rouge Fault, and this will be the focus of the following

discussion.

THE BATON ROUGE FAULT

Rollo (1969) performed hydrologic studies on shallow

aquifers adjoining the mapped position of the Baton Rouge

Fault and published on salt-water encroachment into these

aquifers.

Kazmann (1970) found differences in chloride concentra-

tion between aquifers north and south of the Baton Rouge

Fault, suggesting that faults in fact do transport basinal sa-

line fluids vertically from deep aquifers into shallow aqui-

fers and, furthermore, compartmentalize hydrologic ter-

ranes into blocks. It is important to note that saline chemical

data and its relationship with active growth faulting wasfirst documented in south Louisiana at the Baton Rouge

Fault. These boundary conditions, the authors suggest, are

not unique to growth fault terranes in south Louisiana.

In a 1992 article, the Baton Rouge Advocate

newspaper

called attention to a narrow zone of saltwater intrusion that

is becoming increasingly saline on the north side of the

USGS position of the Baton Rouge Fault trace (Figure 6).

The northern limit of this saltwater intrusion zone along Aca-

dian Thruway was reported to be largely south of Govern-

ment Street. The Baton Rouge Water Company responded

FIGURE 6. Saline groundwaters mapped in near-surface sediments in the vicinity of the Baton Rouge Fault (after Verberne, 1992).


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with a plan to isolate this zone of saline influx via strategic

well drawdowns.

Argonne National Laboratory proposed and conducted a

pilot study to determine the response of an EM instrument

in traverse across the Baton Rouge Fault and its attendant

salinity anomaly. This fault has been mapped at the surface

in Baton Rouge by examination of geomorphic expression

(McCulloh, 1991; Roland et al., 1981). Argonnes Baton

Rouge Fault EM profile is shown in Figure 7. A sharply de-

fined, positive conductivity anomaly is revealed in the vi-

FIGURE 7. EM traverse across theBaton Rouge Fault, Baton Rouge,LA.


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cinity of Station 2, indicating this type of fault is a leaky,

active

fault. It is interesting to note that McCulloh (1991)

maps the trace of the Baton Rouge Fault immediately south

of Station 5. These data suggest a fault zone, bounded by

Stations 4 and 5.

The Baton Rouge Fault case study conclusively proves

the worth of EM investigations in detecting salinity anoma-lies in south Louisiana. The Baton Rouge Fault was de-

tected because saline groundwaters associated with the fault

produced the predicted EM response. Environmental scien-

tists, the authors believe, can now step away from the Baton

Rouge Fault with confidence and remotely identify actively

leaking, actively subsiding terranes along growth faults and

do so in real time with the EM tool.

Growth faults and their attendant surface manifestations

have long been recognized in the lower coastal plain of

Texas (Collins et al., 1980; Kreitler and McKalips, 1978)

but evidences from similar terranes in Louisiana are not

well documented. The role of faulting in the localized sub-

sidence of Terrebonne Parish, Louisiana will be the focus of

the ensuing discussion.

FAULT STUDY IN TERREBONNEPARISH, LOUISIANA

Kuecher (1994) mapped the approximate subcropping lo-

cation of growth faults in eastern Terrebonne and western

Lafourche Parishes, Louisiana, utilizing over 3000 line kilo-

meters of seismic data provided courtesy of Seismic Ex-

change, Incorporated (Figure 8). Fault nomenclature was

borrowed from existing Pennwell Publishing Company

maps, and as per agreement with Seismic Exchange, Inc.,

neither processing parameters nor shot-point locations are

to be discussed in referencing the forthcoming sections. A

FIGURE 8. Mapped distribution of growth faults in the Terrebonne Parish study area (Kuecher, 1994, 1995a; Kuecher and Roberts, 2000). Transects AAand BB

refer tolocations of seismic sections provided in this report.


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FIGURE 11. Louisiana GeologicalSurvey subsidence measurementsalong Bayou Lafourche, in cm/hr forthe period 19651982 (Penland etal., 1988). The mapped positions ofthe Baton Rouge and the Lake HatchFaults are shown.

FIGURE 9. Interpreted seismic line segment AAtraversing the Golden MeadowFault. Two-way time (TWT) is expressed in seconds.

FIGURE 10. Interpreted seismic section BBacross the Lake Hatch Fault. Two-way time (TWT) is expressed in seconds. Note the well-developed anticline of thedown-thrown block.


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location map indicating the seismic traverses included in

this study is provided in Figure 8.

Two regional EW trending growth faults, the Golden

Meadow and the Lake Hatch Faults, as well as a number of

minor faults, were mapped in this exercise. These faults are

seismically quiet because they are not directly tied to base-

ment movements. Occasionally, however, earthquakes withRichter magnitudes of 3.0 or less are associated with south

Louisiana fault movements (Lopez, 1991).

THE GOLDEN MEADOW FAULT

The Golden Meadow Fault (see Figures 8 and 9) is an

EW trending, down to the basin, regional growth fault that

appears to join the Lake Hatch Fault on the northeast side of

Lake Decade. This fault proceeds in a southeasterly direc-

tion toward Dulac, Louisiana, then turns to the east and ex-

its the study area near Golden Meadow, Louisiana, along

Bayou Lafourche. Minor faults, both mapped and un-

mapped, are associated with the Golden Meadow Fault.

The Golden Meadow Fault forms a curvilinear trace sub-

cropping the surface. Vertical displacement generally in-

creases with depth, as required of growth fault systems, and

reflection discontinuities identify the fault. Vertical offset is

mappable below the 0.6 second reflector datum but not

mappable above due to near-surface statics problems.

THE LAKE HATCH FAULT

The Lake Hatch Fault (refer to Figures 8 and 10) is a

SWNE trending, slightly oblique to the basin, regional

growth fault that joins the Golden Meadow Fault on the

north side of Lake Decade and appears to be through-going.

This fault is presently mapped with a conspicuous bend to-

ward the north in the area immediately southeast of Houma,

Louisiana. The fault then turns to the eastnortheast and the

end of our mapping is in the vicinity of Valentine, Louisi-

ana, along Bayou Lafourche. Minor faults, both mapped and

unmapped, are associated with the Lake Hatch Fault.

Three reflector horizons are interpreted to provide the

reader with the sense of increasing displacement with depth,

FIGURE 12. SPOT-1 image (1989) of the northern portion of the study area with mapped faults superimposed on the image. This image was acquired in near-infrared wavelength.

Blues and greens represent winter vegetation (December 14 image capture) atop terrain slightly higher than the water table. Yellow and orange colors represent warm sediment-laden open water lakes.


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a requirement of growth fault systems. The reader should

also note the rollover anticline that has developed on this

faults down-thrown block and the statics problem that

characterizes the near-surface.

Now that these growth faults have been mapped at the

surface, the obvious question is whether these are currently

active, as reported in Texas (Zlotnik, 2000; Norman, 1994;Etter, 1981; Collins et al., 1980) and in Louisiana near Ba-

ton Rouge (McCulloh, 1991). Surface subsidence measure-

ments by the Louisiana Geological Survey (Figure 11)

along Bayou Lafourche indicates greater subsidence values

on the down-thrown sides of these mapped faults than their

respective up-thrown sides (Kuecher, 1995a, 1994; Kuecher

and Roberts, 2000).

If elevation differences do exist across the Golden

Meadow and Lake Hatch Faults, then the authors of this

study suggest these faults may be presently active

(Groene-

woud et al., 1991). Satellite photos of this area support the

active nature of these mapped faults (Figure 12). In the im-

age provided, the up-dip limit of new marsh largely delimits

the seismically mapped position of each fault. These new

marsh areas subside and become open water transgressive

lakes. The location of such transgressive lakes are first-or-

der approximations for the location of active faults (White

and Morton, 1995; Lopez, 1991). These observations indi-

cate slight elevation differences do exist at the land surfaceacross these growth faults and that they are manifest as

lakes and incipient new wetlands. Surface manifestations of

active fault systems may result when slight elevation differ-

ences exist at the surface between up-thrown and down-

thrown fault blocks (White and Morton, 1995), a condition

that can only be met if the fault system is active.

The area included in this French SPOT-1 image is imme-

diately east of Lake Decade and more or less centered on

Lake Boudreaux (refer to Figure 8 for geographic orienta-

tion). Both the northern fault trace (Lake Hatch Fault) and

the southern fault trace (Golden Meadow Fault) appear to

exert controls on the distribution of lakes, some incipient

FIGURE 13. EM traverses along Bayou du Large (BdL) and Bayou Grand Caillou (BGC) across the Lake Hatch (LHFZ) and Golden Meadow (GMFZ) Fault Zones.


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and some well developed on the respective down-thrown

blocks. As these lakes develop, wetlands are lost. The rela-

tionship between faulting (especially active faulting) and

wetland loss is very compelling.

Electromagnetic profiles were then conducted along two

bayou levee systems, Bayou du Large and Bayou Grand

Caillou, as indicated in Figure 13. EM traverses alongBayou du Large (BdL) and Bayou Grand Caillou (BGC)

across the Lake Hatch and the Golden Meadow Fault Zones.

The first EM traverse was conducted along Bayou Du-

large, or BdL (Figure 14). This profile revealed two strong

conductivity anomalies on the 40 meter coil spacing data.

The northernmost anomaly, represented by Station 4, is cor-

related with the proposed subcropping location of the Lake

Hatch Splinter Fault Zone (LHSFZ). To the south, another

positive conductivity anomaly is evident at Station 6. This

anomaly correlates with the mapped position of the Lake

Hatch Fault Zone (LHFZ). No conductivity anomaly was

measured at Station 15 nor at Station 32, where the Golden

Meadow Fault Zone (GMFZ) intersects this EM line of

transect. These data suggest a correlation between positive

conductivity anomalies and actively leaking (i.e., active)

faults and nonleaking (i.e., inactive) faults. Preliminary evi-

dence indicates both actively leaking (actively subsiding)

and nonleaking (i.e., not presently subsiding) terranes are

encountered along these two mapped growth faults, and the

EM tool provides a methodology to differentiate them.

A profile was also taken at Bayou Grand Caillou, BGC

(Figure 15). This profile reveals no positive conductivity

anomalies along the length of the transect. Markedly differ-ent pore water conductivities are clearly observed on each

side of the GMFZ, however. On the up-thrown block, the

average conductivity value, based on eight field measure-

ments, was 54.0 mS/m. On the down-thrown block (south-

ernmost point excluded), the average conductivity value,

based on four field measurements, was 18.0 mS/m. Appar-

ently, a localized lens of fresh water is hydrodynamically

trapped on the down-thrown block along the Bayou Grand

Caillou transect.

The LHFZ in the Bayou du Large data set appears to be

active

as determined by the presence of conductive fluidsmigrating up the fault zone, while the LHFZ at Batou Grand

Caillou appears an inactive

system. The GMFZ, on the

other hand, is distinctly inactive

and sealing in both data

sets, and the distinctly different bulk conductivities on ei-

ther side indicate disequilibrium. Spatial changes in EM

data are significant, and sealing characteristics of faults can

be surmised by steep conductivity gradients. Growth faults

inhibit lateral fluid movement at very shallow depths, facili-

tating the phenomena that adjacent fault blocks commonly

retain markedly different salinity regimes (Galloway et al.

1991; Kuecher and Roberts, 2000). The EM device has the

potential to not only differentiate active from inactive status

but also sealing from non-sealing characteristics at a recon-

naissance level and in real time. Again the authors empha-

size the importance of calibrating EM to analytical results

and hope to accomplish additional ties in future studies.

A comparison of the Bayou du Large and the Bayou

Grand Caillou data sets indicates clearly that hydrochemical

regimes are mappable with EM, and these coincide closelywith the mapped position of growth faults. Differences be-

tween the location of the chemical inflection point and the

mapped location of faults may actually indicate where ad-

justments are required in seismic mapping.

ARGONNE NATIONAL LABORATORYELECTRICAL STUDIES

Argonne National Laboratory, under contract for the Gas

Research Institute (GRI), performed shallow earth resistiv-

ity sounding surveys at random stations in Terrebonne Par-

ish, Louisiana. Resistivity values were converted to total

dissolved solids (TDS) salinity as per methodology de-

scribed in McGinnis et al. (1995), and a TDS salinity map

was generated (Figure 16).

A salinity anomaly was identified from this mapping ef-

fort approximately 18 km south of Houma, Louisiana, as

defined by the 5 ppt contour. The northern limit of this

anomaly is steep in gradient and ENE trending. Kuecher

(1994) interpreted this linear anomaly to be fault-related,

but the coarseness of data sampling precluded a determina-

tion of whether this phenomena identified the Golden Meadow

or the Lake Hatch Fault Zone. However, clearly this map

describes a line/point source for saline fluids. Bulls-eye-shaped salinity anomalies within Louisianas fresh to brack-

ish water wetlands, in fact, cannot be explained by tradi-

tional means of saltwater encroachment (McGinnis et al.

1995; Chabreck and Linscombe, 1978). The maximum sa-

linity value measured in this exercise was 21 ppt (intermedi-

ate value between brackish and open marine). A similar re-

sistivity exercise was conducted in Texas by Kreitler and

McKalips (1978).

Values derived from electrical field acquisition represent

the combined (bulk) conductivities of sediment matrix and

interstitial fluids contained therein to the effective data ac-quisition depth of the instrument. Clay soils exhibit a higher

conductance than do sandy soils by an order of magnitude

(Benson, 1982). Thus one could assume the anomaly McGinnis

et al. (1995) mapped in Figure 8 could be due to clay-rich

soils on the down-thrown side of a fault, while sand-rich

soils predominate on the up-thrown block. But a contrast in

sediment matrix alone does not fully explain the magnitude

of the anomaly. Neither is it appropriate to explain the

anomaly solely on the basis of pore fluid salinities. What is

needed in future studies is the analytical confirmation of

salinities encountered in groundwater, as accomplished in

the case of the Baton Rouge Fault.


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FIGURE 14. EM profile alongBayou du Large (BdL) illustratingthe conductivity profile across theLake Hatch Splinter Fault Zone(LHSFZ), the Lake Hatch FaultZone (LHFZ), and the GoldenMeadow Fault Zones (GMFZ).


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FIGURE 15. EM profile alongBayou Grand Caillou across the areaof seismically mapped faults.


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IMPLICATIONS OF VERTICALTRANSPORT UP FAULTS

Leach (1993) concluded the bulk of all oil and gas re-

serves in south Louisiana is concentrated near the top of ab-

normal pressure and added that mapping of temperature hot

spots, sourced from deeper (i.e., hotter) shales, may be a

useful technique for identifying actively charging reservoirs

along a given fault. Recent studies on the industry consor-

tium well, Pathfinder, in Eugene Island Block 330, offshore

Louisiana, provide conclusive support that geopressured

fluids migrate vertically up the planes of active growth

faults (Losh et al., 1999; Alexander and Handschy, 1998;

Losh, 1998; Lin and Nunn, 1997; Billeaud et al., 1994; and

others). These studies have made powerful arguments in fa-

vor of fluid flow out of the basin via faults.

Vertical fluid flow up faults have been a topic of seriousinvestigation over the past few years, especially in the pe-

troleum exploration community. The strongest implication

of vertical fluid flow concerns the source rock-reservoir

rock relationship. Vertical fluid flow demands the source

rock is structurally lower (and generally down-section

from) the reservoir. Matching geochemical signatures of

source material found above to oils found below, this

study suggests, may be like comparing apples to oranges.

This hypothesis of short-distance migration is in contrast to

long-distance horizontal transport hypotheses.

SUMMARY

This study was designed to test the utility of point mode

EM technologies to precisely identify subcropping growth

faults in south Louisianas wetlands. Results indicate EM is

an effective method to discriminate active, nonsealing faults

from inactive, sealing faults on the basis of bulk conductiv-

ity contrasts between aquifers and sediment across south

Louisiana growth faults.

The relationship between active growth faults, surface

subsidence, and vertically migrating saline fluids appears to

be direct. Fault-related subsidence is documented and a

feedback mechanism is proposed. This study has important

implications concerning fault-related wetland loss and the

vertical migration of petroleum.

ACKNOWLEDGMENTS

The authors wish to thank John Havens, Jeff Lester, and

Christine Gilmour of Seismic Exchange, Inc. for their will-

ingness to share seismic data with the authors. Also due cred-

its are Lyle McGinnis and Dorland Edgar, formerly of Ar-

gonne National Laboratories near Chicago, for their support

of this project. Credits for editing are due Rick McCulloh of

Louisiana State University and Lee Esch of Exxon-Mobil in

Houston. Computer graphics support was provided by Stacy

Williams of Baker Atlas in Houston. And none of this would

have been possible had it not been for my advisor, Harry Rob-

erts, who has encouraged me throughout my professional ca-

reer. Argonne National Laboratorys involvement with this

project occurred during the senior authors tenure as a post-

doctoral fellow, 19941995.

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FIGURE 16: Argonne National Laboratory total dissolved solids salinity map(1995) of shallow earth horizon in the study area.


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ABOUT THE AUTHORSGerald J. Kuecher

Gerald J. Kuecher is a Sedimentologist

for Baker Atlas GeoScience in Houston

where he serves as Coordinator of Deep-water Reservoir Characterization, Image

Log Analyst, and Field Studies Consultant.

He has 11 years experience in exploration

and production companies, and two years

experience in the service industry. He is an

instructor for Oil and Gas Consultants, Inc., and teaches two course

offerings. He has published on such diverse topics as deep water sed-

iments, deltaic sediments, tidal sediments, subsidence, faulting, fluid

flow, and on the application of high resolution seismic electromag-

netics, and ground-penetrating technologies to sedimentology.

Ingeborg Matthews

Ingeborg Matthews works at Baker At-

las in the capacity of Log Analyst. Her spe-

cialties include software support and data-base management. She is in her final year

of a Computer Science degree at the Uni-

versity of Houston.

Michael D. Thompson

Michael D. Thompson received his B.S.

(1985) in geology from Southern Illinois

University, and an M.S. (1989) and Ph.D.

(1997) in geology from Northern Illinois

University. He is currently employed at Ar-

gonne National Laboratory where his re-

search interests focus on the application of

geophysical techniques to environmental

problems. Particular emphasis is placed on using geophysics in can-

tonment and industrial areas. He is an active member of the Environ-

mental and Engineering Geophysical Society and the American Geo-

physical Union.

Harry H. Roberts

Harry H. Roberts is Director of Coastal

Studies Institute, and a member of the De-

partment of Oceanography and Coastal

Sciences at Louisiana State University. He

is recognized on an international level for

sedimentological and sidimentary process

research in both terrigenous clastic and car-

bonate depositional systems. His experi-

ence in deltaic and associated marine sediments includes studies of

delta plains to submarine fans. He is the author of over 130 scientific

papers related to research conducted in the U.S. as well as Africa,

Australia, Indonesia, South America, Central American, and many

sites in the Caribbean. Most of these studies have incorporated acqui-

sition and interpretation of high-resolution geophysical data in con-junction with sediments, cores, borings, and bottom grabs. He is an

advisory editor for two international journals, and has had over 30

years research experience. During this period, he has been a consult-

ant for most major oil companies that operate in the U.S. Gulf Coast.

He has also taught continuing education courses both in the U.S. and

in several foreign countries, including Australia, Indonesia, Sin-

gapore, and sites in the Caribbean. His current research deals with de-

velopment of an understanding of the surficial geology of northern

Gulf of Mexico continental slope and continuing work on problems

associated with the deltaic coasts of Louisiana.

roberts - terrebonne growth faulting

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