Appalachian Basin Low-Permeability

81 Pages·2011·1.81 MB·English

Report Number: 94CC-R91-003
APPALACHIAN BASIN
LOW-PERMEABIUTY SANDSTONE RESERVOIR CHARACTERIZATIONS
Final Contractor's Repoit
By
Ray Boswell
Susan Pool
Skip Pratt
David Matchen
April 1993
Wovk Performed Under Contract No. DE-AC21-90MC26328
For:
U.S. Department of Energy
Moiguntown Energy Technology Center
Motgantown, West Virginia 26505
By:
EG&G Washington Analytical Services Center, Inc.
Motgantown Energy Technology Center
Morgantown, West Virginia 26505
DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither
the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or
implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any
information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned
rights. Reference herein to any specific commercial product, process, or service by trade name, trademark,
manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring
by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not
necessarily state or reflect those of the United States Government or any agency thereof.
EXECUTIVE SUMMARY
A preliminary assessment of Appalachian basin natural gas reservoirs designated as
"tight sands" by the Federal Energy Regulatory Commission (FERC) suggests that greater
than 90% of the "tight sand" resource occurs within two groups of genetically-related units; 1)
the Lower Silurian Medina interval, and 2) the Upper Devonian-Lower Mississippian Acadian
clastic wedge. These intervals were targeted for detailed study with the goal of producing
geologic reservoir characterization data sets compatible with the Tight Gas Analysis System
(TGAS: ICF Resources, Inc.) reservoir simulator. The first phase of the study, completed in
September, 1991, addressed the Medina reservoirs. The second phase, concerned with the
Acadian clastic wedge, was completed in October, 1992. This report is a combined and
updated version of the reports submitted in association with those efforts.
The Medina interval consists of numerous interfingering fluvial/deltaic sandstones that
produce oil and natural gas along an arcuate belt that stretches from eastern Kentucky to
western New Yoik. Geophysical well logs from 433 wells were examined in order to
determine the geologic characteristics of six sepaiate reservoir-bearing intervals. The Acadian
clastic wedge is a thick, highly-lenticular package of interfingering fluvial-deltaic sandstones,
siltstones, and shales. Geologic analyses of more than 800 wells resulted in a
geologic/engineering characterization of seven separate stratigraphic intervals.
For both study areas, well log and other data were analyzed to determine regional
reservoir' distribution, reservoir thickness, lithology, porosity, water saturation, pressure and
temperature. These data were mapped, evaluated, and compiled into various TGAS data sets
that reflect estimates of original gas-in-place. remaining reserves, and "tight" reserves. The
maps and data produced represent the fust basin-wide geologic characterization for either
interval. This report outlines the methods and assumptions used in creating the TGAS data
input, and provides basic geologic perspective on the gas-bearing sandstones of the Medina
interval and the Acadian clastic wedge.
TABLE OF CONTENTS
Acknowledgments 1
Introduction 2
PART ONE: The Medina interval 4
I. Regional geology of the Medina interval 5
Stratigraphic terminology 5
Geologic history 5
Oil and gas production 9
II. Geologic investigation 13
Data acquisition 13
Correlation 13
Mapping 13
Medina interval sandstone distribution pattems 15
III. Reservoir characterization 19
Delineation of reservoir extent 19
Log analysis 21
Medina interval reservoir characteristics 24
Compilation of TGAS data sets 24
The TGAS data sets 32
IV. Discussion of data quality 34
Input data 34
Data manipulation 35
PART TWO: The Acadian clastic wedge 36
I. Regional geology of the Acadian clastic wedge 37
Geologic setting 37
Petroleum occurrence 37
Stratigraphic framework 41
II. Geologic investigation 42
Data acquisition 42
Correlation 44
Mapping 44
Deposystem interpretations 45
ii
III. Reservoir characterization 55
Log analysis 55
Weighted averaging of reservoir properties 56
Mapping and extrapolation of reservoir properties 57
Summary of reservoir characteristics 57
IV. Data quality 58
Input data 58
Data manipulation 59
The TGAS data sets 62
Discussion of formation "tightness" 65
Summary 67
References 69
Appendix 1: Results of preliminary ranking of Appalachian Basin
"tight gas" reservoirs 74
Appendix 2: Relevance of FERC criteria to the recognition of tight fonnations
in the Appalachian Basin 76
Appendix 3: Archived data 78
Appendix 4: Pressuje-transient test results from FERC filings compared with
results of this study 79
iii
LIST OF FIGURES
Figure 1-1: Stratigraphic correlation chart of Lower Silurian strata in
the northern and western Appalachian Basin 6
Figure 1-2: West-east stratigraphic cross-section through the Medina interval,
southern Ohio 7
Figure 1-3: North-south stratigraphic cross-section through the Medina
interval, New York and Pennsylvania 8
Figure 1-4: Paleogeography of the "Medina 5" Sandstone 10
Figure 1-5: Regional occurrence of the Medina stratigraphic trap superimposed
on a sub-sea structure map on the top of the Grimsby interval 11
Figure i-6: Distribution of well-log data 14
Figure 1-7: Net sandstone isolith map of the Whirlpool Sandstone 16
Figure 1-8: Net sandstone isolith map of the Grimsby interval 17
Figure 1-9: Net sandstone isolith map of the "Medina 4" interval 18
Figure 1-10: Productive and prospective areas of the Medina interval 20
Figure 1-11: Map of average porosity within pay zones of the Grunsby interval 25
Figure 1-12: Map of average gas saturation within pay zones of the Grimsby interval 26
Figure 1-13: Net pay isolith of the Grimsby interval 27
Figure 1-14: Net pay isolith of the Whirlpool Sandstone 28
Figure 1-15: Coates penneability map of the Grimsby interval 29
Figure 2-1: Location of major Acadian clastic wedge low-permeability reservoirs 38
Figure 2-2: Generalized cross-section of the Acadian clastic wedge 39
Figure 2-3: Distribution of well-log data used in the reservoir characterization 43
Figure 2-4: Illustration of the 50% gamma-ray base-lining method 46
iv
Figure 2-5: Net sandstone isolith map of the Benson interval 47
Figure 2-6: Net sandstone isolith map of the Bradford interval 49
Figure 2-7: Paleogeography of the Appalacliian basin during four stages of
Acadian clastic wedge deposition 50
Figure 2-8: Net sandstone isolith map of the Venango mterval 51
Figure 2-9: Net sandstone isolith map of the Berea interval 52
Figure 2-10: Net sandstone isolith map of the Weir interval 53
Figure 2-11: Net sandstone isolith map of the Squaw interval 54
Figure 2-12: Correction for previous production, Bradford interval 64
v
LIST OF TABLES
Table 1-1: Preliminary ranking of "tight gas" reservoirs in the Appalacliian Basin 3
Table 2-1: Correlation of TGAS intervals to mapped sub-intervals 41
Table 2-2: Correlation of TGAS intervals to regional stratigraphic terminology 45
Table 2-3: Average reservoir characteristics of the Acadian clastic wedge 57
Table 2-4: Acadian clastic wedge field discoveries in Pennsylvania 61
vi
ACKNOWLEDGMENTS
The authors wish to thank Anthony Zammerilli and the U.S. Department of Energy for
providing the opportunity to investigate the regional geology of the major Appalachian basin
natural gas reservoirs. The project provided the investigators an opportunity to study the
regional geology of major Appalachian basin reservoirs at a level of detail that has not been
reported previously.
During the first phase of the study, invaluable computer assistance was provided by Ed
Robey and Frank Hutchinson of EG&G WASC. Special thanks to Ed Rothman of Columbia
Natural Resources for providing access to copies of all the FERC "tight-gas sands" filings for
the Appalachian basin.
The completion of Part Two is due in large part to the tireless effort of Lori Mayes in
analyzing well logs. Ed Robey's effort in writing software used to organize and compile log
data was gready appreciated. The software used to create and measure irregular grid cells
written by Jim Dean was an invaluable aid when unforeseen manpower shifts threatened to
significantly delay the project. John Piunkett's edits improved the text. Scott Bittinger's help
in copying, recording, and filing data is also appreciated. Once again, we would also like to
thank Ed Rothman for providing access to all of the Kentucky and Virginia well logs
included in this study. Finally, we would like to acknowledge Dr. Alan Donaldson and
Xiangdung Zou of West Virginia University for providuig well logs in several areas where
our data were sparse.
1
INTRODUCTION
In 1978, the Federal Energy Regulatory Commission (FERC) instituted a program of
price supports for natural gas produced from low-permeability reservoirs ("tight fonnations":
see 18 CFR 271.701 and related legislations). FERC's goal was to provide an incentive for
the continued development of reservoirs that were uneconomic producers due to low market
prices, poor flow rates, and the necessity of costly well stimulation procedures.
Tliroughout the early 1980's, Appalachian Basin operators and state geologic surveys
filed successful petitions requesting "tight formation" status for 17 separate reservoirs (or
packages of related reservoirs) in seven states. Efforts to accurately assess the resource base
of these fonnations have been greatly hindered by a lack of modern, accurate, and complete
geologic and production data. Consequently, the most recent estimate of the unconventional
gas resource of the Appalachian basm relied largely on extrapolation of historical finding
rates normalized for changes in the level of industry activity (NPC, 1992). The NPC study
indicated that up to 19 trillion cubic feet of gas (Tcfg) can be recovered from "new plays"
and over 5 Tcfg from "old plays" with advanced teclmologies. The United States Department
of Energy (US DOE) is currently re-assessing the resource potential of FERC-designated
"tight fonnations" in the Appalachian Basin using a quantitative approach based on the direct
collection mid analysis of reservoir data. In support of this effort, EG&G was tasked to
conduct detailed geologic investigations of the most significant Appalachian "tight gas sands"
with the goal of constructing geologic data sets compatible with the Tight Gas Analysis
System (TGAS; ICF Resources, Inc.) reservoir simulator.
In order to identify which reservoirs to study, EG&G conducted a preliminary
assessment of the resource potential of all FERC-designated "tight fonnations" in the
Appalachian basin. These estimates were based on reservoir data gathered from the original
FERC petitions, and suggested that six reservoirs comprise over 90% of the total estimated
"tight gas" resource. The basis and meaning of the rankings is fully described in Appendix 1.
TABLE 1-1: PRELIMINARY RANKING OF FERC-DESIGNATED "TIGHT GAS"
RESERVOIRS IN THE APPALACHIAN BASIN (Estimates are of original, potential
reservoir volume, not gas-in-place)
Rank Reservoir Estimate % of Total
1. Medina interval 154 Tcf 44.9 %
2. "Bradford" sandstones 39 11.2
3. Beiea Sandstone 38 11.0
4. "Injun/Squaw" sandstones 31 8.9
5. "Weir" sandstones 27 7.7
6. "Venango" sandstones 24 6.8
All other Appalachian Basin
"tight gas sandstone" reservoirs: 33 9.5
2