seismic imaging of spur and groove structures in the san...

Seismic imaging of spur and groove structures in the San Andres Formation, Midland Basin,

Texas. Gabriel Machado

1, Kurt J. Marfurt

1, Oswaldo Davogustto

1 and Matthew Pranter

2

1 Oklahoma University and

2University of Colorado

Summary

Spur and groves are reef related structures that form in the

windward side of fringing or barrier reefs owing to

different intrinsic and extrinsic mechanisms. The purpose

of this study is to characterize these structures through different seismic attributes and interpret the growth history

of the reefs within the seismic volume.

Geologic Setting

The San Andres Formation is a mainly carbonate

prograding stratigraphic unit of Guadalupian age in the

northern shelf of the Midland Basin, Texas. The lithology

includes dolomite, limestone, salt and some siliciclastics facies like silty sandstones and skeletal wackestones,

among others (Ramondetta, 1982).

The study area is located in the Diamond M field in the Scurry Reef Trend in Scurry County, Texas (Walker et al,

1991) and corresponds to the section above the Horseshoe

Atoll in the same region (see Figure 1)

The studied section corresponds to a fringing reef back

barrier lagoon sequence .Spur and grooves structures form

in the windward side of modern reefs (Wood and

Oppenheimer, 2000) with their long axes normal to the refracted waves, which can make them good

paleohydrodynamic indicators (Sneh and Friedman, 1980).

They range from 8 to 65 m in width, up to 10 m in height

and can form 45 m below sea level. Two processes are taking place in the formation of these reef structures:

organic growth of the reefs and erosion owing to backsurge

of refracted waves (Cloud, 1959).

DOI http://dx.doi.org/10.1190/segam2013-1431.1© 2013 SEGSEG Houston 2013 Annual Meeting 545

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Seismic Imaging of Spur and Groove structures

Data Available

A 33 mi² survey was acquired with an inline and crossline

interval of 75 ft. Since the San Andres formation is one of

the most prolific reservoirs of Texas in the 1980s

(Ramondetta, 1982) many wells were drilled in the region, so that 165 were available with up to 65 well logs in some

of them.

Methodology

We used eight wells with P-wave sonic logs to tie with the

seismic in order to make a seismic inversion and better recognize the carbonate buildup related features, as can be

observed in Figure 2

We recognized from seismic inversion five different stages through time for the fringing reef.

Spur and grooves

Based on the seismic inversion and the known geology,

several spur and groove structures were recognized in the

seismic volume. They are easily differentiated through

different attributes, such as curvature and dip magnitude.

On Figure 3, the spur and groove structures can be seen in

the west part of the survey. The K1 most positive curvature

highlights the spurs and the K2 most negative curvature the grooves. A shorter wavelength allows viewing some of the

heterogeneities in the carbonate structures, with the same

general trend.

On Figure 4 Sobel filter similarity and dip magnitude

attributes are used. In the Sobel filter the spur and groove

structures are not well defined.

DOI http://dx.doi.org/10.1190/segam2013-1431.1© 2013 SEGSEG Houston 2013 Annual Meeting Page 1546

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On the other hand, many of the spur and grooves structures

of different scales can be well observed through the dip magnitude attribute, allowing a better defining of the

steepness they have in their boundaries with each other.

Figure 5 shows the same structures through the reflector convergence attribute showing the preferential refracted

wave orientation and the direction in which these structures

were eroded by them.

Discussions

A very interesting thing happens when the spur and

grooves are observed through the reflector convergence

attribute, as shown in Figure 6. When looking at the change

of this attribute through the San Andres Formation, a very marked difference in the general orientation of the

reflectors can be observed, from southwest-west and north

at 500 ms to northeast-east at 700 ms. The attribute was co-

rendered with most positive principal curvature in black and white so the carbonate structures could be located in

the seismic image.

This change in general convergence orientation could happen in response to changes in the marine conditions

which would have affected the coral reef growth general

orientation, or due to changes in the accommodation space

inside the basin, which would also affect the carbonate structure.

Dunlap and Wood (2010) pointed at the seismic

architecture and morphology of a seismic feature similar in form to the spur and groove structures, but that must not be

mistaken with them. Sediment waves have a similar shape

in seismic time slices, but are usually normal to the basin

slope and have lower acoustic impedance, whereas the spur and groove structures have greater acoustic impedance and

are usually normal to the refracted waves that generate

them.


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Conclusions

Spur and grooves are carbonate structures that form on the

windward side of modern fringing and barrier reefs. They

form as a combination of the coral organic growth and the erosion generated by backsurge of refracted waves that hit

the reef.

Seismic most-positive and most-negative curvature attributes clearly delineate spur and grooves in the San

Andres Formation, while reflector convergence show not

only the orientation of the carbonate but also changes in the

hydrodynamic conditions that affected their growth

Acknowledgments

Thanks to Parallel Petroleum for providing the data used in

this research. Seismic interpretation was done using

Schlumberger’s Petrel and inversion using Hampson Russell’s Strata software. Attributes were generated using

software developed as part of the OU AASPI consortium.

We thank all who helped me in attribute interpretation and

imaging – Alfredo Fernandez, Luis Castillo, Roderick Perez and Rebecca Da Silva, among others.


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http://dx.doi.org/10.1190/segam2013-1431.1 EDITED REFERENCES Note: This reference list is a copy-edited version of the reference list submitted by the author. Reference lists for the 2013 SEG Technical Program Expanded Abstracts have been copy edited so that references provided with the online metadata for each paper will achieve a high degree of linking to cited sources that appear on the Web. REFERENCES

Cloud, P. E. Jr., 1959, Geology of Saipan, Mariana Islands, Part 4—Submarine topography and shallow-water ecology: U.S. Geol. Survey Professional Paper 280-k, 361–445.

Dunlap, D. B., and L. J. Wood, 2010, Seismic architecture and morphology of Mesozoic -Age sediment waves, offshore Morocco, northwest Africa: 2010 GCSSEPM, in Seismic imaging of depositional and geomorphic systems, 30th annual GCSSEPM Foundation Bob F. Perkins Research Conference, L. J. Wood, T. T. Simo and N. C. Rosen, eds., 551–571.

Ramondetta, P. J., 1982, Facies and stratigraphy of the San Andres Formation, northern and northwestern shelves of the Midland Basin, Texas and New Mexico: Bureau of Economic Geology Report of Investigation No. 128.

Sneh, A., and G. M. Friedman, 1980, Spur and groove patterns on the reefs of the northern gulfs of the Red Sea: The Society of Economic Paleontologists and Mineralogists: Journal of Sedimentary Petrology, 50, 981–986.

Walker, D. A., J. Golonka, A. M. Reid, and S. T. Reid, 1991, The effects of late Paleozoic paleolatitude and paleogeography on carbonate sedimentation in the Midland Basin, Texas; Permian Basin plays: Society of Economic Paleontologists and Mineralogists, Permian Basin Chapter, Tomorrow’s Technology Today, 141–162.

Wood, R., and C. Oppenheimer, 2000, Spur and groove morphology from a Late Devonian reef: Sedimentary Geology, 133, no. 3-4, 185–193, http://dx.doi.org/10.1016/S0037-0738(00)00032-4.


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seismic imaging of spur and groove structures in the san...

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