«TYPE OF REPORT: FINAL REPORTING PERIOD START DATE: OCTOBER 1, 1998 REPORTING PERIOD END DATE: SEPTEMBER 30, 2002 PRINCIPAL AUTHORS: JAMES R. WOOD, ...»
ADVANCED CHARACTERIZATION OF
FRACTURED RESERVOIRS IN
CARBONATE ROCKS: THE MICHIGAN
TYPE OF REPORT: FINAL
REPORTING PERIOD START DATE: OCTOBER 1, 1998
REPORTING PERIOD END DATE: SEPTEMBER 30, 2002
JAMES R. WOOD, MICHIGAN TECHNOLOGICAL UNIVERSITY,HOUGHTON, MI
WILLIAM B. HARRISON, WESTERN MICHIGAN UNIVERSITY,KALAMAZOO, MI.
DATE REPORT WAS ISSUED: DECEMBER 2002 DOE AWARD NUMBER: DE-AC26-98BC15100
NAME AND ADDRESS OF SUBMITTING ORGANIZATION:
MICHIGAN TECHNOLOGICAL UNIVERSITY1400 TOWNSEND DRIVE HOUGHTON, MI 49931 FINAL REPORT DE-AC26-98BC15100 1 of 63 Michigan Technological University
FINAL REPORT DE-AC26-98BC15100 2 of 63 Michigan Technological University
ABSTRACTThe purpose of the study was to collect and analyze existing data on the Michigan Basin for fracture patterns on scales ranging form thin section to basin. The data acquisition phase has been successfully concluded with the compilation of several large digital databases containing nearly all the existing information on formation tops, lithology and hydrocarbon production over the entire Michigan Basin. These databases represent the cumulative result of over 80 years of drilling and exploration. Plotting and examination of these data show that contrary to most depictions, the Michigan Basin is in fact extensively faulted and fractured, particularly in the central portion of the basin. This is in contrast to most of the existing work on the Michigan Basin, which tends to show relatively simple structure with few or minor faults. It also appears that these fractures and faults control the Paleozoic sediment deposition, the subsequent hydrocarbon traps and very likely the regional dolomitization patterns.
Recent work has revealed that a detailed fracture pattern exists in the interior of the Central Michigan Basin, which is related to the mid-continent gravity high. The inference is that early Precambrian, (~1 Ga) rifting events presumed by many to account for the gravity anomaly subsequently controlled Paleozoic sedimentation and later hydrocarbon accumulation. There is a systematic relationship between the faults and a number of gas and oil reservoirs: major hydrocarbon accumulations consistently occur in small anticlines on the upthrown side of the faults.
The main tools used in this study to map the fault/fracture patterns are detailed, closeinterval (CI = 10 feet) contouring of the formation top picks accompanied by a new way of visualizing the data using a special color spectrum to bring out the third dimension. In addition, recent improvements in visualization and contouring software were instrumental in the study.
Dolomitization is common in the Michigan Basin, and it is crucial in developing reservoir quality rocks in some fields. Data on the occurrence of dolomite was extracted from driller’s reports for all reported occurrences in Michigan, nearly 50 fields and over 500 wells. A digital database was developed containing the geographic location of all these wells (latitude-longitude) as well as the elevation of the first encounter of dolomite in the field/reservoir. Analysis shows that these dolomite occurrences are largely confined to the center of the basin, but with some exceptions, such as N. Adams Field. Further, some of the dolomite occurrences show a definite relationship to the fracture pattern described above, suggesting a genetic relationship that needs further work. Other accomplishments of this past reporting period include obtaining a complete land grid for the State of Michigan and further processing of the high and medium resolution DEM files. We also have measured new fluid inclusion data on dolomites from several fields that suggest that the dolomitization occurred at temperatures between 100 and 150 C. Finally, we have FINAL REPORT DE-AC26-98BC15100 3 of 63 Michigan Technological University extracted the lithologic data for about 5000 wells and are in the process of integrating this data into the overall model for the Michigan Basin.
FINAL REPORT DE-AC26-98BC15100 4 of 63 Michigan Technological University
TABLE OF CONTENTSDISCLAIMER
TABLE OF CONTENTS
LIST OF GRAPHICAL MATERIALS
1.0 Executive Summary
1.2 Basic Geology of the Michigan Basin
1.3 The “Central Michigan Basin”
2.0 Data Acquisition
2.2 ATLAS Program
3.0 Faults & Deformation Bands
3.2 Previous History of Faults in the Michigan Basin
3.3 History of Fault Interpretation and Identification in the Michigan Basin.36
3.4 Techniques for Mapping Large-Scale Faults
3.5 Relation to Hydrocarbons
5.2 “Top Porosity” / Late-stage Dolomite
Stratigraphic column for Michigan Basin.
Generalized geological map of Michigan Basin.
Map of basement in Michigan Basin showing different provinces and mid-continent gravity high.
3D-surface map of Howell Anticline in SE Michigan. Contoured on top of Dundee Formation. View is looking northwest.
Location map of Central Michigan Basin as defined by the -2900 foot subsea contour on the top of the Dundee Formation structure.
Project Information Screen for setting project paths and parameters.
Main ATLAS screen displays oil and gas well locations.
ATLAS Edit Screen for updating records and viewing Scout Tickets and Driller Reports.
Sample Scout Ticket Display.
Sample Driller Report Display.
ATLAS Export Selection Screen.
Sample data from table exported from ATLAS.
ATLAS display of wells within an approximate 1 mile radius of Permit 01754.
The permit number is posted to the upper right of each well spot, and the subsea Dundee top depth is posted to the lower right of each well spot.
ATLAS selection screen for selecting counties and map features for enhancing the ATLAS display map.
ATLAS map display showing lakes, rivers, roads, section lines, and township lines.
ATLAS map display of Michigan fault lines.
ATLAS map display of major oil fields in Michigan with fault lines.
Location map showing trends of major basin-scale faults in Michigan Basin.
FINAL REPORT DE-AC26-98BC15100 6 of 63 Michigan Technological University Figure 3.2. Map of United States showing major faults mapped by USGS. Note absence of any faults in Michigan.
Structural trends in the Michigan Basin from Ells (1969).
Structural trends in the Michigan Basin from Catacosinos (1991).
Anticlinal and probable and possible faults in the Michigan Basin (Ells, 1962).
Figure 3.6 Regional Trenton structure of the Michigan Basin illustrating major fault lineations (Buthman, 1995).
Structure map of top of the Dundee Formation in Michigan that suggests the presence of a basin-wide system of subparallel faults/lineations.
High resolution structure contour map on top of the Dundee Formation in the Central Michigan Basin showing the presence of the large-scale faults.
Terrain aspect map of the Central Michigan Basin delineating the large-scale faults.
Map showing the relationship between the large-scale fault system and major gas and oil fields in Michigan.
Structure map of the Top of the Dundee Formation at Vernon-Rosebush fields showing the relationship between these fields and the fault.
Plot of the Devonian age rocks for the Eastern United States showing progressive deformation from west (least deformed) to east (most deformed).
(Tow 1-3-1) Photograph of slabbed core from Tow 1-3 HD showing coarse white saddle dolomite-filled fractures in Dundee limestone. Note cavities filled with euhedral dolomite. 3195 ft.
(Rieman 1-1) Medium-grained euhedral dolomite (2 types) filling vugs. 3749 ft.
(Lee 1-1) Coarse, white saddle dolomite in abundant fracture in Dundee Limestone. 3466.5 ft.
(Shuttle 1-5) Photo of core segment 1-10-2 showing fracture and vug-filling saddle dolomite in Dundee Limestone.
Map showing location of dolomitized Dundee Fields. The large faults reported elsewhere in this report are superimposed on the dolomite occurrences.
1.1 Introduction The main results of this study can be summarized under three topics: (1) data acquisition, (2) faults, (3) fractures and (4) diagenesis. Accordingly this report is organized into four main chapters under these headings (Chapters 2-5). All of this refers to the Michigan Basin and it is therefore appropriate to preface the discussion with a brief discussion of the Michigan Basin and it petroleum history.
1.2 Basic Geology of the Michigan Basin The Michigan Basin is one of several intercratonic basins of N. America. Others include the Illinois, Williston and Hudson Bay basins (Figure 1.1). These basins are all characterized by large volumes of sedimentary fill, both clastic and carbonate, and relatively mild deformation. The Michigan Basin is characterized by Cambrian and Ordovician basal clastics followed by a large volume of Silurian and Devonian chemical sediments, carbonates and evaporites, and a general absence of Mesozoic and Cenozoic rocks, except for a scattering of Jurassic rocks in the center of the Basin (Figure 1.2). The basin itself is often characterized as a gently dipping circular or slightly elliptical bowl (Figure 1.3) with little structural character and generally conformable sedimentary relationships.
The basement rocks below the sedimentary fill in the Michigan Basin is known to be fairly complex, with at least 3 structurally different provinces characterized by rocks of different compositions and ages split by the extension of the mid-continent gravity high (Figure 1.4), which is considered to be mainly Keweenaw-type basalts.
This simple picture is complicated by the presence of a significant geologic structure in the SE corner of the basin, the Howell Anticline and the associated Monroe-Lucas Anticlinal structures (Figure 1.4). The Howell Anticline is thought to represent basement uplift and is often interpreted as a normal fault with 800+ feet of throw and undisclosed (negligible?) lateral offset. This structure is often the only fault shown on a geologic map of Michigan, and even then is often omitted, although the evidence is persuasive if not compelling.
The Monroe-Lucas structures are likewise almost certainly faults, with a more complex history and a definite but ambiguous relationship to the Howell structure.
1.3 The “Central Michigan Basin” The Central Michigan Basin is that part of the Michigan Basin that occupies the very center of the basin and appear to be bounded in almost all directions by a break in slope as evidenced by structural contours on a number of different formations, including the Dundee Formation. On the Dundee Structure map, the Central Michigan Basin can be defined as the -2900 foot subsea contour, a closed contour that encompasses most of what we refer to as the Central Michigan Basin (Figure 1.5). It appears that tectonic events that occurred in the basin were most intense here and that most of the structural deformation (excepting the Howell-Monroe-Lucas Anticlines) occurred here. Much of the gas and oil FINAL REPORT DE-AC26-98BC15100 8 of 63 Michigan Technological University in the basin are also located here, with the exception of Albion Scipio, West Branch and Deep River fields.