Coalbed Methane in the Upper Cretaceous Fruitland Formation, San Juan Basin, New Mexico and Colorado

RI0218. (Copublished with Colorado Geological Survey). Coalbed Methane in the Upper Cretaceous Fruitland Formation, San Juan Basin, New Mexico and Colorado. W. B. Ayers, Jr. and W. R. Kaiser, eds. 216 p., 168 figs., 14 tables, 1994. Print.


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From the Preface
Coalbed methane is playing an increasingly important role in meeting the energy needs of the United States. According to one estimate, this unconventional gas may supply 4-5% of the domestic natural gas in 1994. In the San Juan Basin, Fruitland Formation coal beds contain an estimated 43 to 49 trillion cubic feet (Tcf) of methane. This basin is the most active area of coalbed methane development and production in the United States. The San Juan Basin led the nation in coalbed methane production in 1992, when nearly 2,100 Fruitland coalbed wells produced approximately 447 billion cubic feet (Bcf) of coalbed methane-81% of the total U.S. coalbed methane production of approximately 553 Bcf.

From August 1987 through July 1990, the Bureau of Economic Geology (BEG) at The University of Texas at Austin evaluated geologic and hydrologic controls on the occurrence and producibility of coalbed methane in the Fruitland Formation for the Gas Research Institute (GRI). The Colorado Geological Survey and the New Mexico Bureau of Mines and Mineral Resources participated in the research through subcontracts with BEG. Results from the first two years of research were summarized in annual reports to GRI (GRI-8810322.1 and GRI-9010014.1, respectively). A topical report submitted to GRI in 1991 (GRI-9110072) superseded those annual reports, integrating their contents with research results from the final year of the study. This publication includes all except two papers from that topical report. Themes of the omitted papers were generic; therefore, those papers were omitted to focus this publication on the San Juan Basin.

The unpublished GRI contract reports had limited distribution. Their goal was the timely transfer of technology to industry. Because requests for the topical report exceeded the number of copies printed and because many of the topics covered in this research appeal to a broad audience of geoscientists and engineers, this publication was issued to increase the availability of the research results. This report discusses five areas that relate to controls on the occurrence or producibility of coalbed methane.

The first topic, the tectonic setting of the San Juan Basin, reviews regional tectonic controls on depositional systems and coalbed attitude. Among the most important geologic factors affecting the occurrence and producibility of coalbed methane is the depositional setting, which is covered in the second part of this report; a chapter on the regional depositional setting of Fruitland coalbed methane is followed by two chapters describing local studies. Fracture patterns in Fruitland coal beds and adjacent strata are addressed in three chapters that discuss regional cleat trends and lineament analysis. Studies of hydrology, thermal maturity, and gas composition, are essential to understanding and predicting regional hydrodynamics and coalbed gas content and composition; these considerations are the subject of two chapters. Finally, the last topic is the integration of geologic and hydrologic studies. In this section we summarize gas and water production from Fruitland coal beds, and on the basis of the relations between production, geologic setting, and hydrodynamics, we divide the San Juan Basin into regions in which Fruitland coal beds have similar reservoir characteristics.


Keywords: coalbed methane, Fruitland Formation, San Juan Basin, Colorado, New Mexico, hydrology, tectonics
 

CONTENTS

Preface

Acknowledgments

TECTONIC SETTING

1. Tectonic setting of the San Juan Basin
S. E. Laubach and C. M. Tremain

Abstract

Location and structure of the basin

Evolution of the basin

Minor structures and stress regime

Acknowledgments

DEPOSITIONAL SETTING

2. Coalbed methane in the Fruitland Formation, San Juan Basin-depositional and structural controls on occurrence and resources
W. B. Ayers, Jr.. W. A. Ambrose, and J. S. Yeh

Abstract

Introduction

Regional geologic setting and stratigraphy

Previous studies

Objectives

Methods

Structural evolution of the San Juan Basin
Structure of Huerfanito Bentonite Bed

Elevation of Pictured Cliffs Sandstone

Depositional framework of the Pictured Cliffs Sandstone and the Fruitland Formation

Huerfanito Bentonite Bed to top of upper Pictured Cliffs tongues (markers 20 to 58)

Upper Pictured Cliffs tongues (markers 50 to 58)

Isopach

Lithofacies

Fruitland Formation isopach (markers 50 to 64)

Huerfanito Bentonite Bed to base of Ojo Alamo Sandstone (markers 20 to 80)

Fruitland coal

Coal identification

Coal stratigraphy

Coal overburden

Coal distribution

Net coal thickness

Maximum coal thickness

Number of coal seams

Average coal thickness

Geologic controls on occurrence of coal seams

Previous studies

Relations between depositional systems and coal occurrence

Geologic controls on producibility of coalbed methane

Coal and coalbed methane resources

Conclusions

Acknowledgments

3. Geologic controls on coalbed methane occurrence and production in the Fruitland Formation, Cedar Hill field and the COAL site
W. A. Ambrose and W. B. Ayers, Jr.

Abstract

Introduction

Objectives

Methods

Stratigraphic and structural setting

Depositional systems

Pictured Cliffs Sandstone

Fruitland Formation

Lower Fruitland subunit

Middle Fruitland subunit

Upper Fruitland subunit

Fruitland coal groups

Coal group A

Coal group C

Lower C coal seams

Middle and upper C coal seams

Coal group D

Depositional controls on coalbed continuity and structural attitude
Controls on coalbed permeability

Formation pressure

Coalbed methane resources

Gas production trends

Water production

Conclusions

Acknowledgments

4. Coalbed methane in the Fruitland Formation, Navajo Lake area-geologic controls on occurrence and

Producibility
W. B. Ayers, Jr., and S. D. Zellers

Abstract
Introduction

Objectives

Methods
Regional geologic setting and stratigraphy

Structural evaluation

Structure of Huerfanito Bentonite Bed

Elevation of Pictured Cliffs Sandstone and top of the Fruitland Formation

Isopachous trends

Huerfanito Bentonite-Pictured Cliffs Sandstone isopach

Fruitland Formation isopach

Sedimentary facies

Pictured Cliffs lithofacies

Pictured Cliffs Sandstone

Upper Pictured Cliffs Sandstones (UP1 and UP2)

Fruitland Formation lithofacies

Coal occurrence

Net coal thickness

Maximum coal thickness

Number of Fruitland coal seams

Depositional controls on coal occurrence, trends, and thickness

Structural controls on depositional systems

Structural controls on producibility of coalbed methane

Coalbed methane activity and reservoir conditions

Summary and conclusions

Acknowledgments

FRACTURE PATTERNS

5. Fracture (cleat) patterns in Upper Cretaceous Fruitland Formation coal seams. San Juan Basin
C. M. Tremain, S. E. Laubach, and N. H. Whitehead, III

Abstract

Introduction

Characteristics of Fruitland Formation cleat

Cleat types and cleat spacing

Causes of variation in cleat spacing

Cleat-filling minerals

Cleat orientation

Basin-scale cleat-strike domains

Faults and associated fractures

Timing and cause of cleat formation

Implications for coalbed methane exploration and development

Acknowledgments

6. Fracture swarms: potential targets for methane exploration in Upper Cretaceous sandstone and coal, northern San Juan Basin, Colorado
S. E. Laubach and C. M. Tremain

Abstract

Introduction

Regional cleats and joints

Fracture-trace maps

Map areas: Fort Lewis mine and Animas-Florida river transect

Fracture swarms

Small-scale fracture swarm: Carbon Junction outcrop

Reservoir-scale fracture swarms: Fort Lewis mine

Surficial (set 11) fractures at Fort Lewis mine

Shape and microstructure of swarm (set I) fractures

Fracture swarm dimensions and orientation

Fracture patterns within swarms

Fracture connectedness

Relation of swarms in sandstone to coal fracture patterns

Regional-scale fracture swarms: Animas-Florida river exposure

Causes of fracture development

Fracture swarms: targets for natural gas exploration

Summary

Acknowledgments

7. Use of lineament attributes to predict coalbed methane production in the northern San Juan Basin

R. W. Baumgardner, Jr.

Abstract

Purpose

Review of lineament and fracture studies in the San Juan Basin

Data sources and procedures

Results

Definition of significant lineament azimuths

Coincidence of lineaments from different studies

Lineament azimuth

Well-lineament distance

Correlation between lineament attributes and production

Distance from well to nearest lineament

Length of nearest lineament

Lineament intersections within a given radius

Number of lineaments within a given radius

Discussion

Stress in the study area

Lineaments and stress

Conclusions

Acknowledgments

HYDROLOGY, THERMAL MATURITY, AND GAS COMPOSITION
Hydrologic framework of the Fruitland Formation, San Juan Basin
8. W. R. Kaiser, T. E. Swartz, and G. J. Hawkins
Abstract

Introduction
Hydrodynamics

Hydraulic head

Equivalent fresh-water head

Potentiometric surface

Potentiometric mounds

Pressure regime

Hydrochemistry

North-central basin

Chemical evolution

Chlorinity

Hydrostratigraphy and regional flow

Abnormal formation pressure

Cross-sectional modeling

Hydrostratigraphy

Computer program

Modeling
Model limitations

Model simulations

Model simulations 1 and 2

Model simulation 3

Recharge and discharge

Conclusions

Acknowledgments

9. Thermal maturity of Fruitland coal and composition of Fruitland Formation and Pictured Cliffs Sandstone gases
A. R. Scott, W. R. Kaiser, and W. B. Ayers, Jr.

Abstract

Introduction

Objectives

Methods

Thermal maturity of Fruitland coal

Composition and distribution of Fruitland and Pictured Cliffs gases

Fruitland Formation gases

Fruitland Sandstone gases

Fruitland coalbed gases

Pictured Cliffs Sandstone gases

Relation of gas composition to thermal maturity and pressure regime

Origins of Fruitland coalbed gases

Conclusions

Acknowledgments

INTEGRATION OF GEOLOGIC AND HYDROLOGIC STUDIES

10. Coalbed methane production, Fruitland Formation, San Juan Basin: geologic and hydrologic controls

W. R. Kaiser and W. B. Ayers, Jr.

Abstract

Introduction

Production

Decline behavior

Production statistics

Maximum annual gas production

Initial gas potential

Water production

Coalbed methane production history and trends

Controls on coalbed methane production

Coal occurrence, trends, and thickness

Coal rank

Reservoir pressure

Tectonic fractures and cleats

Gas composition

Produced water

Regional characterization of Fruitland coalbed reservoirs

Area 1: regionally overpressured area

Meridian 400 area

Cedar Hill field

Allison unit

Area 2: underpressured, regional discharge area

WAW-Gallegos area

Area 3: underpressured, eastern area

Conclusions
Acknowledgments

REFERENCES


Citation
Ayers, W. B., Jr., and Kaiser, W. R., editors, 1994, Coalbed Methane in the Upper Cretaceous Fruitland Formation, San Juan Basin, New Mexico and Colorado: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 218, 216 p.