An Overview of theWilliams Fork Formation

Reservoir Characterization at Mamm Creek Field,

Piceance Basin, Colorado

Matthew J. Pranter, Alicia Hewlett, Sait Baytok, Rachel Shaak

University of Colorado at Boulder

Outline

I. Research Objectives

II. Study Area

III. 3-D Reservoir Characterization and Modeling of Matrix Properties

IV. Seismic Interpretation, Fracture Analysis, and Fracture Modeling

V. Conclusions

Research Objectives

• Within the southeastern Piceance Basin and Mamm Creek Field, how does the lower Williams Fork Formation vary in terms of stratigraphic architecture, shoreline stacking patterns, and lithology?

• For the Williams Fork Formation at Mamm Creek Field, what is the stratigraphic variability of sandstone-body type and distribution, matrix reservoir quality, and static connectivity?

• For the Williams Fork Formation at Mamm Creek Field, what are the main fault types and their distribution and how does fracture distribution vary with faulting, lithology, architectural elements and other parameters?

N

Discrete fracturenetwork modeling

Fracture intensity and seismic attributes

3-D seismic analysis of fault and fracture distribution

3-D reservoir modeling of tight-gas sandstones

Regional distribution of coastal plain and marine deposits

Study Area and Focus

• data from 1,400 wells• 3-D seismic survey• 8 cores • 12 borehole image logs• outcrop sandstone-body statistics• measured section

Image Logs

Cores

SeismicSurvey

ReservoirModelArea

MeasuredSection

Study Area and Focus

Reservoir Characterization and Modeling

2 mi2

91 wells irregular 10-acre density

Coastal /Alluvial Plain

Shoreface/DeltaicMarsh, Mire, Swamp, and Estuarine

Marine Shelf/Ramp

Modified from Carroll and others (2004); Cole and Pranter (2008)

Stratigraphic Intervalfor Reservoir Modeling

StratigraphicInterval

forReservoirModeling(~2200 ft)

Model Framework

• 91 wells• 15 zones• 40’ x 40’ x 1’• 89.4 million cells

V.E. = 4X

CameoMiddle Ss.

Upper Ss.

Middle WilliamsFork Formation

Upper Williams Fork Formation

Paonia Sh. Mbr.

Lower Williams Fork Formation

Rollins

V.E. = 1X

Model Inputs and ConstraintsCalculated Lithology logs Interpreted Architectural Element Logs

Variography Outcrop dimensional statistics and object shapes

MD

1:143

0.00 190.00GR_NRM 0.30 -0.05DPHI_NRM

0.30 -0.05NPHI_NRM

Floodplain

Floodplain

Point bar

Point bar

Floodplain

Crevasse splay Floodplain

Point bar

Point bar

Floodplain

Ar chit ect ur al_Elem ent _Log

05045168680000 [MD]

point bar

crevasse splay

MD

1:143

0.00 190.00GR_NRM 0.30 -0.05DPHI_NRM

0.30 -0.05NPHI_NRM

Mudrock

Mudrock

Sandstone

Mudrock

Sandstone

Mudrock

Sandstone

Mudrock

Lithology_log

Mudrock

Mudrock

Shaley sand

Clean sand

Clean sand

Mudrock

Shaley sand

Mudrock

Shaley sand

Clean sand

Mudrock

Lit hology_log_updat ed

05045168680000 [MD]

0.00 190.00GR_NRM 0.30 -0.05DPHI_NRM

0.30 -0.05NPHI_NRM

Sandstone

Lithology_log Lit hology_log_updat ed

05045168680000 [MD]

sandstone/clean sandstone

shaleysandstone

Azimuth: 39˚

Variogram Map

Experimental Variogram

Architectural Element Object Shapes

Channel Bar / Point Bar Crevasse Splay

Refined Lithology

0 0.2 0.4 0.6 0.8 1

Upper Williams Fork

Middle Williams Fork

Lower Williams Fork (Paonia)

Upper sandstone

Middle sandstoneCameo-Wheeler

Top Rollins

Basic Lithology

0 0.2 0.4 0.6 0.8 1

Architectural elements

0 0.2 0.4 0.6 0.8 1

Vertical Constraint:Vertical Proportion Curves

3-D Spatial Constraint: Seismic Probability Volume

Provided by iReservoir.com

Middle Williams Fork

Middle Sandstone

3-D Lithology Modeling and3-D Architectural-Element Modeling

Sequential-indicator simulation (SIS) of basic lithology• Sandstone, mudstone, coal modeled• With 3-D seismic-based spatial probability constraint

Sequential-indicator simulation (SIS) of refined lithology• Clean sandstone, shaley sandstone, mudstone, and coal

modeled

Object-based simulation constrained to lithology • Constrained to outcrop dimensional statistics for fluvial

architectural elements (Pranter et al., 2009)

Object-based simulation constrained to architectural elements• Constrained to outcrop dimensional statistics for fluvial

architectural elements (Pranter et al., 2009)

Basic Lithologyw/ 3-D seismic constraintBasic Lithology

Refined LithologyBasic Lithology Architectural Elements

Refined Lithology

Modeling Examples

Future Modeling work

• Petrophysical modeling– Porosity– Permeability (conventional core data)

• Channel cluster analysis

• Static sandstone-body connectivity

3-D Seismic Interpretation

verticalslices

throughseismic data(amplitude)

Depth slice through

ant tracking volumewithout

interpretation

Depth slice through

ant tracking volumewith

interpreted faults

Noise on survey edge

Uninterpreted Interpreted

3-D Seismic Interpretation

NN Deep Faults

Uninterpreted Interpreted

Middle Sandstone

• Fault interpretation based on seismic amplitude, ant-tracking results, and curvature attributes

• Two near-vertical fault sets (shallow faults strike N60W; deep faults strike N45E)

3-D Seismic Interpretation

• Fault interpretation based on seismic amplitude, ant-tracking results, and curvature attributes

• Two near-vertical fault sets (shallow faults strike N60W; deep faults strike N45E)

N NShallow Faults

Uninterpreted Interpreted

Top Mesaverde Group

Fracture / Seismic Attribute Analysis

Relationship between ant tracked seismic attribute and fracture intensity in fractured zones

Fra

ctu

red

Zo

ne

Upscaled Fracture Intensity

An

t-tr

acki

ng

Att

rib

ute Correlation coefficient: 0.73

Fracture Analysis and DFN Modeling

Fracture Intensityand Lithology

+

Fracture Dip Angle and Dip Azimuth

DFN (discrete fracture network) model

Scale up fracture properties

Ki

Kj

Kk