Reservoir Characterization Research Laboratory

for Carbonate Studies

Research Plans for 2008

Outcrop and Subsurface Characterization of Carbonate

Reservoirs for Improved Recovery

of Remaining Hydrocarbons

Charles Kerans and F. Jerry Lucia,

Co-Principal Investigators

Bureau of Economic Geology – Scott W. Tinker, Director

Department of Geological Sciences

John A. and Katherine G. Jackson School of Geosciences

The University of Texas at Austin

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Research Plans for 2008

Reservoir Characterization Research Laboratory

Outcrop and Subsurface

Characterization of Carbonate Reservoirs for

Improved Recovery of Remaining Hydrocarbons

EXECUTIVE SUMMARY

The Reservoir Characterization Research Laboratory (RCRL) for carbonate studies is an

industrial research consortium run by the Bureau of Economic Geology (BEG) and the

Department of Geological Sciences of the John A. and Katherine G. Jackson School of

Geosciences, The University of Texas at Austin (UT). RCRL’s mission is to use outcrop and

subsurface geologic and petrophysical data from carbonate reservoir strata as the basis for

developing new and integrated methodologies to better understand and describe the 3-D reservoir

environment.

Funding

With this proposal, we invite you to participate in the continuation of the RCRL Carbonate

Reservoirs Research Program. A list of sponsors during 2007 can be found at the end of this

proposal. In 2008 the annual RCRL Industrial Associates contribution to the program will

continue to be $45,000 per year.

RCRL Program

The RCRL program has run continuously since 1987 and has produced more than 45 external

publications, as well as BEG publications, on carbonate reservoir characterization, sequence

stratigraphy, petrophysics, geostatistics, and petroleum engineering. RCRL has maintained a

membership of between 13 and 20 companies per year (see list of 2007 sponsors at end of

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proposal). The sponsorship currently is interested in a range of domestic and international

carbonate reservoirs ranging in age from Ordovician to Cretaceous. This enrollment,

supplemented by other grants, supports between three and six professional staff members and

varying numbers of graduate student research assistants, as well as strong computer, editing, and

graphics services.

Principal Staff

Dr. Charles Kerans, Geology Professor, Principal Investigator

Mr. F. Jerry Lucia, Geological Engineer, Principal Investigator

Dr. Xavier Janson, Geologist

Dr. Christopher Zahm, Geologist

Mr. Jerome A. Bellian, Geologist

Associate Staff

Dr. Fred Wang, Reservoir Engineer

Dr. Hongliu Zeng, Geophysicist

All staff members have extensive industry experience or have worked closely with industry and

are well aware of the challenges and questions facing development geoscientists and engineers.

We are also proud of our graduate student staff, which has included several award-winning

students, many of whom are now working in industry.

If you have any questions on any aspect of the RCRL Carbonate Reservoirs Research Program,

please contact Charlie Kerans (512 471 4282 or ckerans@mail.utexas.edu) or Jerry Lucia (512

471 7367 or jerry.lucia@beg.utexas.edu).

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RESEARCH DIRECTIONS FOR 2008

Areas of Research

Each year we combine industry input with our own ongoing research plans to develop a set of

key geological and engineering research topics. Plans for 2008 focus on the following areas:

1. Geologic Characterization and Fluid Flow in Fractures and Nonmatrix Pore Systems

2. Outcrop Studies of Carbonate Heterogeneity Style—Platform, Slope, and Basin

3. Subsurface Reservoir Models and Modeling Methods

4. Seismic Imaging of Carbonate Heterogeneities

5. Rock Fabric, Petrophysical, and Predictive Diagenesis Studies

6. Databases

Information Transfer

General

Our industrial sponsors will continue to receive research results at annual review meetings, in

short courses, during mentoring activities, in publications and CD’s, and on our new developing,

members-only RCRL database (http://begdb1.beg.utexas.edu/rcrl/login.aspx). We have also

released to all sponsors TexSim Version 2.0 hard drives, which contain outcrop-interpreted

photopanels, geological models, field guides and papers (in PDF format), lidar models, measured

sections, photomicrographs, geologic maps, and synthetic seismic lines contained in a

geographically correct spatial/visual database. This technology transfer tool was developed by

Statoil, KongsbergSim, and BEG for all study areas within Texas and New Mexico to aid in

technology transfer from current, past, and future field projects.

Workshop and Field Course

In 2007 we conducted one reservoir modeling workshop and a field course for our sponsoring

companies. We will design a new modeling workshop that is tentatively planned for spring 2008.

We will send a more detailed program of the workshop early in 2008.

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The scale and lateral variability that outcrop exposures provide the development geoscientist

cannot be underestimated. The challenge in effective characterization of reservoirs lies in

understanding the scales and complexities of depositional and structural heterogeneity. RCRL is

therefore continuing to develop and improve upon its field-based characterization short course

for sponsor companies. The 2008 course will be similar to that presented in 07, except that we

will conduct the course in a chronological/tectonostratigraphic context, beginning with the

cyclicity and karst development of the Lower Ordovician (greenhouse) passive margin and

continue up through the lower Carboniferous transitional deeper ramp/buildup complexes of the

precollisional Oro Grande Basin, the upper Carboniferous icehouse cyclic mounds of the

syntectonic Oro Grande Basin, and the transitional ramps and rimmed margins of the Permian

Basin in the Guadalupe Mountains. This course will illustrate both exploration and reservoir-

scale stratal architecture and methodologies for interpreting these geometries from contained

facies. Data examined will include outcrops, cores, and subsurface analog data. The course will

also consist of field lectures and hands-on field exercises, such as mapping of lateral facies

variations describing vertical and lateral cycle architecture and seismic-scale stratal geometries

and methods for capturing fracture data, combined with evening discussions/lectures on methods

of constructing 3D reservoir models using both outcrop and subsurface data.

Mentoring Program

RCRL has historically conducted short-term projects with specific companies to help transfer its

research results into an industrial work flow. In 2007 we initiated such a project with Kinder

Morgan on the Cisco Formation in an area of the Sacroc Northern Platform. Apache has also

provided data from the Adair Wolfcamp Unit that is being studied by A. Wilson under the

direction of Charlie Kerans. In 2008 we plan to assist Husky and Shell with their effort to

characterize the large tar accumulation found in the Grosmont and Ireton (Devonian) Formations

in Alberta, Canada.

Sponsors are encouraged to contact us with projects that could be mutually beneficial.

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RESEARCH PROGRAM FOR 2008

Characterization of Fractures and Nonmatrix Pore Systems

Mechanical Stratigraphy within Cretaceous Carbonates

When present as a connected network, open fractures commonly dominate fluid flow in

reservoirs and dictate the success or failure of secondary and tertiary development programs.

Fracture development can be facies specific or confined within composite sequences that

comprise mechanical units. Furthermore, fractures exhibit different attributes (e.g., orientation,

intensity, and style) depending on the mechanical properties of the sedimentary facies within

which they occur. Facies-bound fracture systems are problematic in the subsurface because they

typically occur below seismic resolution and may be detected only in core and image logs. Their

vertical extent, geometry, and genetic relationship to sedimentary facies must be understood to

improve subsurface prediction and modeling. Field work will be done in several Lower

Cretaceous outcrops in Texas to collect samples and map fracture distribution and

characteristics, including mechanical properties of facies within a robust stratigraphic

framework.

Fractures Associated with Stratigraphic Discontinuities, Sacramento and Franklin Mountains

Stratigraphic features such as carbonate mounds or karst breccias are associated with an

apparent increase in fracture development, which in turn can be a productive element in

subsurface reservoirs. Better characterization of fractures that develop in association with these

features is required to assess their spatial distribution, frequency, timing, and fluid flow potential

and to address challenges that they may pose for enhanced hydrocarbon recovery. Mississippian

mounds that crop out in the Sacramento Mountains and collapse karst bodies that crop out in the

Franklin Mountains represent two types of discontinuities that have an associated increase in

fracture intensity. In 2008, fracture in these two areas will be characterized to quantify the

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intensity, orientation, and fracture style observed in these outcrops. Through this

characterization, we hope to highlight relationships between fracture intensity and other geologic

phenomena such as differential compaction, facies type, discontinuity shape, and distribution.

Facies to Flow Characterization of the Pipe Creek Analog

Geometry and distribution of intact rudist mounds and their associated debris facies are

poorly characterized. In addition, fluid flow through large, connected pores common within these

facies is difficult to quantify using standard simulation techniques. Since 2003, RCRL has been

using the Pipe Creek outcrop as an analog for detailed mapping of spatial and vertical

relationships of the mound core and debris and will continue characterization of this mound

complex in 2008. The goal of this year’s work is to build a 3D outcrop model that adequately

captures observed facies heterogeneity. This work will be supported by acquisition of ground-

penetrating radar and field mapping of facies using differential GPS. In conjunction with

ongoing work supported by NSF, we will drill additional wells for tracer test studies. With these

new wells we intend to collect down-hole GPR while performing cross-hole tomographic studies

and circular VSP surveys for a better understanding of the challenges of geophysical

characterization within large pore systems.

Franklin Mountain Karst Study

Strontium isotope ratios (87Sr / 86Sr) for host rock and breccias in the Southern Franklin

Mountains will be examined for correlation along the lower Paleozoic 87Sr / 86Sr isotope curve.

These data, in conjunction with biostratigraphic ages from conodonts extracted from breccia

matrix, will be used to look for patterns within the breccia bodies. Stratigraphic modeling will

continue utilizing existing measured sections, samples, and airborne lidar for the 20-km2 field

area.

Outcrop Studies of Carbonate Heterogeneity Styles—Platform, Slope, and Basin

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Channelization, Erosion, and Collapse of Reef-Rimmed Platform Margins

At what scale do large platform-margin collapse scars or reentrants influence slope and

basin accumulation of reservoir-quality carbonate fan-channel complexes? What large-scale

structures control the character of platform-margin and slope accumulations, their fracture

patterns, and their compaction-driven geometries?

The various Permian shelf-to-slope systems as exposed in Guadalupe Mountain National

Park are ideal for addressing issues related to large-scale stratal architectures of carbonate

platforms and their relation to margin erosion and downslope export of sediment. In 2008 we

will expand our earlier Wolfcampian and Leonardian studies to younger Guadalupian margins.

Our goal is to use the range of Permian stratigraphic architecture to better understand the timing,

mechanism, and architecture of these collapses and their influence on the nature, morphology,

and distribution of deep-water, redeposited carbonate sediments.

We will continue our modeling in Shumard Canyon, where a wide range of slide scars,

slumps, and bedrock submarine canyons can be mapped in 3D. Younger Permian margins also

show erosion, reentrant, and margin collapse. In 2008, we will characterize and model these

large-scale collapse features in 3D on the basis of outcrop along the Western Escarpment,

Slaughter Canyon, Walnut Canyon, and Dark Canyon, while conducting reconnaissance in

intervening canyons. These study areas will be integrated in a robust regional stratigraphic model

built on DEM and airborne lidar data (see below).

Airborne Lidar Model of the Southern Guadalupe Mountains

3D analysis and reconstructions of the Capitan shelf-to-slope system as exposed in

Guadalupe Mountain National Park is ideal for addressing structural and stratigraphic issues

related to large-scale stratal architectures of carbonate platforms. An airborne lidar survey will be

carried out with a helicopter-mounted unit shooting at a low or oblique angle, allowing effective

capture of cliff faces and flatter surfaces. Airborne data collected in this way from the Guadalupe

Mountains will allow us to work in digital 3D structure and stratigraphy at the platform scale,

rather than at the flow-unit to local platform-margin scale associated with most of our models

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constructed using ground-based lidar?. We are still in the process of designing a regional survey

and will soon take bids over a range of coverage areas of varying size during the winter and

finalize the funding strategy by spring 2008.

Forced Regressive Depositional Patterns and the Origin of Sheetlike Grainstone Reservoir

Facies in the Jurassic-Cretaceous

Many of the major Cretaceous and Jurassic carbonate-ramp reservoir units, such as the

Arab D, Shuaiba and Thamama, contain widespread carbonate grainstones that appear to exceed

dimensions predicted by study of any of our modern analogs. The origin of similar dip-

continuous shore-parallel sand bodies in greenhouse systems like the Cretaceous Western

Interior Seaway has been for a decade the subject of discussion in clastic literature. Laterally

extensive carbonate grainstone bodies of the superbly exposed and tectonically quiescent

Comanche Shelf provide an opportunity to document the architecture and petrophysical

characteristics of these compound, laterally diachronous grainstone bodies. A combination of

detailed facies and petrophysical characterization and digital mapping technology will be applied

to improve our understanding of these grainstone systems and evaluate the relevancy of the

forced regressive model for such deposits.

Comanche Shelf

Two locations along the west and south margins of the Comanche Shelf provide excellent

study areas for this analysis. Geological characterization of the Albian ramp in the Fort Stockton

Embayment that was presented during the 07 field excursion will be a primary area of analysis in

2008. Initial work has shown that the upper Albian succession along and proximal to I-10

between Ozona and Bakersfield provides an almost continuous section from the landward side of

the ramp crest to the intrashelf basinal area, especially for the latest cycles of the Albian 21

composite sequence.

This year’s goals are to complete the regional stratigraphic architecture along this 80-km

transect. We will focus on evidence of a diachronous origin of the capping grainstone complex

and emphasize tools that might assist in subsurface analysis of such low-angle prograding

systems. Investigations will include diagenetic changes along the profile that predictably affect

reservoir quality. Because of the similarities between stratigraphic architecture and facies in this

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Albian Comanche Shelf system and the Aptian Shuaiba Formation reservoirs of the Middle East,

we are planning to characterize petrophysical changes along the depositional profile in selected

facies tracts.

The second area that will be part of this study is the Pecos River transect from Pandale to

the Rio Grande. In this section, basic stratigraphic framework is already in hand, but the lateral

continuity of the sequence-capping (possibly combined highstand/falling stage) grainstones is

not well understood. Detailed evaluation of updip to downdip changes in the Albian 19 and 20

grainstones will complement studies along I-10.

Jurassic Outcrop Analog Reconnaissance

Several of the world’s largest hydrocarbon reservoirs are contained within prograding

Jurassic foreshore-shoreface systems, namely the Arab-D and Smackover. The subsurface of

these reservoirs has been described, and a clear need for a better understanding of these facies

associations has been identified. Potential outcrop study areas will be evaluated in 08 and

presented for group evaluation during the October meeting.

Subsurface Reservoir Models and Modeling Methods

SACROC Northern Platform Cisco Study

In 2007 we began a reservoir study of part of the Northern Platform (NP) of SACROC

(Pennsylvanian) field in the Permian Basin. The NP reservoir is divided into Canyon and Cisco

strata, this study focusing on the complex stratigraphy of the Cisco. Integration of seismic and

well log data showed a complex system of carbonate buildups on the west side of the NP and a

more layered system on the east side. Analysis of extensive porosity and permeability data

indicates that most of the facies have similar permeability, albeit slightly different porosity

values. In 2008 we plan to integrate recent production data into the model and use flow

simulation to test the similarity between simulated performance and actual production data.

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South Texas Reservoir Study

In 2008 we will initiate a study of Cretaceous fractured and burial enhanced carbonate

reservoirs in South Texas as part of our ongoing investigation into touching-vug reservoirs and

the impact of burial dissolution on porosity and permeability development. This study is

contingent on obtaining core, production, and seismic data from operating companies.

Modeling Carbonate Systems Using Multipoint Statistics

In collaboration with Dr. Sanjay Srinivasan of the U.T. Center for Petroleum and

Geosystems Engineering, we have started a 3-yr research program to investigate how to apply

multipoint statistic modeling methods to carbonate systems and reservoirs. The strength of

multipoint statistics is that it is based on pattern recognition rather than a pixel-based variogram

approach. We are hoping to integrate more a priori geological knowledge into this geostatistical

technique by constructing both statistically and geologically meaningful training images for a

range of carbonate stratigraphic architecture. Ultimately our goal is to develop algorithms and

workflows that combine geostatistic and deterministic approaches to better guide our ability to

model carbonate systems in subsurface. The initial focus will be on remodeling phylloid algal

mound architecture in the Dry Canyon outcrop by building a training image that integrates the

conceptual growth model of the mounds developed on the outcrop.

Seismic Imaging of Carbonate Systems

Lateral and Vertical Distribution of Seismic Properties in Carbonate Rocks

Using a new outcrop velocity device based on surface wave measurement, we will

investigate vertical and lateral seismic velocity heterogeneity in carbonate rocks. Our plan is to

investigate first the grainstone cycle in Lawyer Canyon, where RCRL has already collected

detailed porosity and permeability and extensively analyzed the scale of petrophysical

heterogeneities in the past. We will follow a similar acquisition and processing workflow so that

we can compare scale and style of heterogeneity between these two rock properties that are

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difficult to relate. The goal of this study is not only to examine the potential covariance between

seismic velocity and other petrophysical characteristics, but also to investigate the amount of

small-scale heterogeneity that needs to be modeled in our synthetic experiment to render natural

properties variation adequately.

GPR Study of Albian Cretaceous Rudist Mounds

In 2008, we will expand and compress our 2D GPR grid over Georgetown Lake spillway

to map distribution and morphologies of the rudist mounds. In addition, a 3D GPR dataset will

be acquired over one of the best-developed buildups to investigate the 3D architecture of these

small (a few meters high and a few tens of meters wide) buildups. Additional 2D GPR surveys

will be acquired in Pipe Creek and potentially in the Pecos River and Waco area mounds that

will allow comparison of a range of rudist mounds in terms of rudist type, size, morphology,

distribution, and architecture.

Seismic Imaging of Karst

In 2007, we began investigating the seismic response of various karst morphologies on

the basis of modern karst features and various velocity models for the karstified zone. In 2008,

we will continue this study by investigating and modeling in more detail velocity distribution in

the karstified area. We will investigate the amount and style of seismic velocity heterogeneities

in the paleokarst breccia in the Franklin Mountains. In addition, we will continue building 3D

synthetic seismograms using modern karst features and combinations of modern karst features,

as well as various velocity distribution scenarios.

Rock Fabric, Petrophysical, and Predictive Diagenetic Studies

Origin and Petrophysics of Limestone Rock Fabrics

In 2006 we initiated a detailed study of the diagenesis and petrophysics of limestones,

which included investigations into intragrain microporosity and complex grain-dominated

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fabrics. The study concluded that most of the complex limestone fabrics can be attributed to

conversion of aragonite grains and crystals to LMC and subsequent grain crushing due to

overburden pressure. In addition, we now have data showing that modern carbonate grains (ooids

and Halimeda) have 17 to 21% porosity, suggesting that the porosity within ooids and other

skeletal grains is inherited and not formed by burial dissolution. In 2007 this study was

broadened to include the concept of increase in porosity through burial dissolution. In 2008 we

will continue to investigate the impact of burial dissolution on the porosity and permeability of

limestones and to measure the porosity of modern skeletal fragments.

Capillary Pressure Models

In the past we have been unable to develop a general capillary pressure model that

integrates rock fabric information owing to the lack of sufficient capillary pressure data with

fabric information. However, we have acquired considerable new information over the past few

years and think that renewed effort is warranted. In 2008, therefore, we plan to construct a

general capillary pressure model using the concept of “rock-fabric number” instead of the

“k/phi” term used in the Leverett J model. The advantage of the rock-fabric number is that it

provides a closer link to the geologic model than does the k/phi term.

Diagenetic Studies: Outcrop-Based Numerical Modeling

For the past several years RCRL has supported student research on modeling

dolomitization by hypersaline reflux. Current research focuses on modeling dolomitization of the

extensive San Andres (Permian) outcrop located on the Algerita Escarpment, Guadalupe

Mountains, New Mexico. The outcrop, 1,500 ft high and over 50 miles long, has an equivalent

subsurface section some 50 miles downdip and along depositional strike. In 2007 the initial flow

model was completed on the basis of facies-derived petrophysical parameters. The model has a

series of time steps that are based on a sequence stratigraphic model. Results are encouraging,

and in 2008 we plan to construct a more detailed petrophysical model and focus on reactive

transport modeling.

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Databases

Currently RCRL has two databases, both of which contain georeferenced information. One is

more global in reach and has online query capability (http://begdb1.beg.utexas.edu/rcrl/login.aspx).

The second, more of a visual/spatial database restricted to Texas and New Mexico, was

distributed on a USB removable hard drive to each company at the annual meeting. Updates to

both of these databases are planned biannually. These are in addition to our Industrial Associates

webpage (http://www.beg.utexas.edu/indassoc/rcrl/index.htm), which contains web-accessible

copies of annual meeting summaries and annotated PowerPoint® talks.

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List of 2007 Sponsors

• Anadarko

• Apache

• Aramco

• BP

• BPC

• Chevron

• ConocoPhillips

• ENI

• ExxonMobil

• Hess

• Husky Energy

• Kinder Morgan

• Marathon

• Norsk Hydro

• Oxy Permian

• PDO

• Pioneer

• Repsol YPF

• Shell

• Statoil