Michigan Field Experiences, Focus on the Niagaran

Based on a PTTC Midwest Region workshop, March 19, 2004 in Mt. Pleasant, Michigan

BOTTOM LINE

Independents that are now the operators in the mature Michigan Basin are profitably employing technologies such as horizontal wells, 3-D seismic, other 3-D visualization tools, production logging, CO₂ flooding, and underbalanced drilling to name a few. Sharing and learning from each other in workshops having a case study focus has proven extremely effective, as has leveraging effort with SPE Northern Michigan.

PROBLEM ADDRESSED

The northern Michigan reef play is a very mature producing area, remaining reef targets are smaller than early targets, and major oil companies (and sometimes the service sector) have left the region. It is up to the remaining independents active in the region to get the knowledge and technology they need to conduct profitable exploration and production programs. 

KEY WORDS:

Gas storage, Horizontal well, Niagaran Reef, Production logging, Underbalanced drilling, 3-D seismic

SPEAKERS

History of Horizontal Drilling in the Michigan Niagaran (Guelph Formation),
Bill Harrison, PTTC, Western Michigan University

Imaging of Niagaran Pinnacle Reef Fields Using Well Log Tomography and 3-D Visualization,
A.S. "Buddy" Wylie, James R. Wood, Michigan Technological University

Economic Risk Assessments Impacting Exploration & Development Drilling Decisions,
Mike Barratt, Barratt Consulting LLC

Renewal of A Historic North American Complex, Six-Lakes Field,
Fredrick Metzger and Edward Dereniewski, Michigan Consolidated Gas Company

Production Logging in the Niagaran,
Douglas Elenbaas, El Paso Pipeline Group

Dover 33 and Dover 36 Fields, A Review of Michigan's CO2 Floods, Otsego County,
MI, Tim Brock, Brock Engineering

An Attempted Redevelopment of a Northern Michigan Niagaran Reef Utilizing 3-D Seismic and Lateral Drilling,
John Fowler and Stephen Schaefer, Polaris Energy

Michigan Underbalanced Drilling Cases,
Alejandro Coy, Weatherford Underbalanced Systems

Niagaran Pinnacle Reef Development and Distribution, Mason and Oceana Counties, Michigan,
Wayne Goodman, Northern Lights Energy and Timothy Maness, Maness Petroleum Corporation

Niagaran Reef Seismic, It's More Complicated Than You Think,
Allen Modroo, Modroo Geophysical
 

TECHNOLOGY OVERVIEW

Michigan's Niagaran reef play covers about 10,000 square miles, including the Northern and Southern reef belts. There are nearly 1,200 fields with about two-thirds being in the Northern reef. Cumulative Niagaran production through 2001 is 325 million barrels and 1.9 TCF. Productive reefs are about 50-400 acres in size and have relief ranging from 150 to 700 ft. Interest has been increasing on locating reefs on the western edge in Oceana and Mason counties. Although mature, numerous Niagaran opportunities still exist for Michigan's enterprising independents. Major operators with historically significant technical experience no longer have a presence in the Midwest, but as one speaker noted, "The Big Dogs may have gone, but the rest of the Pack still knows how to hunt." Working together PTTC and SPE Northern Michigan section assembled a critical mass of 160 excited hunters to share experiences and refine their hunting techniques.

Reefs occur in clusters with frequency of about one reef per every two square miles in maturely explored areas. Despite the maturity of production, horizontal wells to control fluid production or access reserves in undrained compartments have been contributing significantly since the mid 1990s. There are more than 270 horizontal legs in Michigan wells. Current horizontal activity was spawned by early success with the Tow Dundee well (www.wmich.edu/geology/corelab/success_crystal.html) in a DOE-supported project. Nothing like good results in an early project to maintain interest as the regional learning curve developed.

Reefs are extremely complex structures. A.S. "Buddy" Wylie and Jim Wood of Michigan Tech University showed how well log tomography provides 3-D visualization of porosity-permeability relationships and distributions. Knowing storage capacity (best porosity) and deliverability (best permeability) locations, well trajectories can be better targeted to achieve their objectives. This technique uses nearly the full information content of log curves, enabling visualization on a local reservoir-scale and broader basin-scale with a precision unmatched by either seismic or conventional formation top-type matching.

Operators typically must choose from several opportunities when making drilling decisions. Mike Barratt, Barratt Consulting LLC, drove home the point that a structured risk analysis process helps operators make better decisions. Learning from disappointments as well as successes is part of managing risk.

Niagaran Reef Seismic
Silurian pinnacle reefs, which are vertically tall yet horizontally small, manifest themselves seismically as a loss of data. 2-D seismic data are full of acquisition, processing and interpretation problems. 3-D seismic can have some of the same problems, but Allen Modroo of Modroo Geophysical indicates that well-designed surveys do approach an 80% success rate for reef development. One must never forget that the target reefs can be small, just 30 or 40 acres. 3-D survey designs must recognize that small bin size and high shallow fold is a must even though costs are higher. 3-D interpretations from seismic must also tie with geological data.

Polaris Energy did share a case study of an unsuccessful horizontal well redevelopment that was based on 3-D seismic data. In this instance, both sample cuttings and Thermal Decay Time log data indicated substantial matrix porosity in dolomitized reef rock, but it was salt-filled. This is an area where current technology lacks, adding another element of risk when exploiting areas prone to salt plugging.

Underbalanced Drilling in Horizontals
Weatherford shared the benefits of drilling underbalanced in horizontals, citing a Michigan gas storage example. Former overbalanced wells drilled with brine or clear water would lose lots of water to the formation, taking up to a couple years to clean up. A horizontal well drilled underbalanced with air-water was drilled without problem, and initial tests over MMCFD confirmed the reservoir was not damaged. Another example, in the Brown dolomite in Hugoton Field, Texas, documented that an underbalanced horizontal, compared to vertical: (1) increased net present value by 400%, (2) increased productivity and reserves, and (3) extended well life by seven years. Several other positive benefits were noted.

Production Logging (Storage Examples)
Production logging can be used to identify high flow rate zones in the wellbore, in both injectors and producers and in verticals and horizontals. They are also helpful in identifying tubing or casing collar leaks. Several types of production logs exist: Spinner logs; Temperature logs; Bottom hole pressure surveys; Noise or sound logs, including channeling behind casing; and Flowing neutron logs that will identify liquid levels and gas saturation changes in the wellbore. Acquisition options include real-time recording on electric line, real-time recording on fiber optic cable, and memory recording conveyed by coiled tubing or electric line.

CO₂ Flooding Pinnacle Reefs
Tim Brock, Brock Engineering, presented CO₂ flood results in two Niagaran reefs. CO₂ from an Antrim Shale gas processing plant is being transported a few miles. In the Dover 36 field, developed for IOR with a vertical producer and a vertical injector, there was good rate acceleration and incremental recovery. In the Dover 33 field, which for IOR used one vertical injector and two horizontal producers, rate acceleration was much better, termed excellent, but there was only limited incremental recovery. Ultimate recovery in both fields will be about 43% of original oil-in-place. Brock considers many Niagaran reefs to be attractive CO₂ flooding candidates.

Horizontals in Gas Storage Operations
Michigan Consolidated Gas Company (MichCon) operates the Six Lakes gas storage field (not a Niagaran reef). As with many storage operations, deliverability declines, averaging 5.6% per year from 1968 to 1993, are a problem at Six Lakes. Single and multi-lateral horizontals have been the most effective approach for combating continuing declines. Single laterals have been drilled with an openhole length of 3,000 ft, and multi-laterals have openhole lengths exceeding 5,000 ft. Currently, one horizontal well replaces eight vertical wells. Less water is produced with horizontals completed in the upper pay section, and with high flow capacities, the liquids that are present are more easily lifted out. Grouping of horizontals within "pads" takes less space, reducing environmental impact, and surface facilities cost less. For example, required length of the gathering system with pods is 65% less than with vertical well development.

Niagaran Development in Mason and Ocean Counties
Expansion into Mason and Oceana Counties has presented a daunting challenge that has included several periods of technical/land activity and drilling. Analysis of relatively recent activity, which has yielded discoveries of several producing pools as well as non-productive pinnacle reefs, indicates that reefs along the so-called West Shore Area grew under a markedly different depositional setting from those prevalent along the Northern Ramp, resulting in distinct changes in reef distribution, density and diagenetic history. Key findings of a recent study by Northern Lights Energy and Maness Petroleum Corporation are:

• While reef development and distribution in the Northern Fairway is chiefly controlled by factors relating to the sedimentologic setting, the key factor governing distribution in southern Mason and Oceana Counties is recurrent structural movement that produced more local and areally restricted loci for areas most conducive to reef growth. That structural fabric can be defined by the major Salina salt solution trends that postdated pinnacle development.
• While crestal reef heights along the Northern Fairway follow a fairly straightforward and predictable trend toward taller reefs as one moves basinward, there is a clear trend toward a bimodal distribution of reefs by crestal height in the southern Mason-Oceana area.
• Reefs in the study area are located in a basinward position largely akin to the reefs most basinward in the Northern Fairway. Unlike reefs across the broader pinnacle belt, Mason-Oceana reefs show prevalent downdip dolomitization. Much of this early-dolomitized porosity was destroyed by early salt plugging prior to hydrocarbon migration.
• West Shore pinnacle reefs are small, perhaps averaging 40-50 acres, which is less than in the Northern Fairway. Although smaller, they still offer attractive economic targets.

Keys to future exploration success will be using detailed geological work consistent with the above regional model, coupled with high-quality geophysical data.
 

CONNECTIONS:

Mike Barratt
Barratt Consulting LLC
2173 White Owl Way
Okemos, MI 48864
Phone: 517-347-8629
E-mail: mbarrattconsulting@hotmail.com

Tim Brock
Brock Engineering
763 Wolverine
Mason, MI 48854
Phone: 517-676-7023
E-mail: brockengineering@voyager.net

Alejandro Coy
Weatherford Underbalanced Systems
515 Post Oak Boulevard, Suite 600
Houston, TX 77027
Phone: 713-693-4437
E-mail: alejandro.coy@weatherford.com

Ed Dereniewski
Michigan Consolidated Gas Company
500 Griswold Street
Detroit, MI 48226
Phone: 313-235-1115
E-mail: dereniewskie@dteenergy.com

Doug Elenbaas
El Paso Pipeline Group
27725 Stansbury Blvd, Suite 200
Farmington Hills, MI 48334
Phone: 248-994-4046
E-mail: Douglas.elenbaas@elpaso.com

John Fowler
Polaris Energy
P.O. Box 83
Jackson, MI 49204
Phone: 517-787-5533
E-mail: jhenryfowler@yahoo.com

Wayne Goodman
Northern Lights Energy
P.O. Box 218
Gaylord, MI 49734
Ph: 989-939-7510
E-mail: wrgnle@freeway.net

Bill Harrison
Western Michigan University
Geology Department
Kalamazoo, MI 49008-5150
Phone: 269-387-5488
E-mail: william.harrison_iii@wmich.edu

Timothy R. Maness
Maness Petroleum Corporation
P.O. Box 313
Mt. Pleasant, MI 48858
Phone: 989-773-5475
E-mail: tim@manesspetr.com

Frederick Metzger
Michigan Consolidated Gas Company
500 Griswold Street
Detroit, MI 48226
Phone: 313-256-5358
E-mail: metzgerf@dteenergy.com

Allen Modroo
Modroo Geophysical
12935 S. West Bay Shore Dr.
Traverse City, MI 49684
Phone: 231-933-9337
E-mail: modroo@aol.com

Stephen Schaefer
Polaris Energy
P.O. Box 83
Jackson, MI 49204
Phone: 517-787-5533

James R. Wood
Michigan Technological University
Dept. of Geosciences and Engineering
Houghton, MI 49931
Phone: 906-487-2894
E-mail: jrw@mtu.edu

A.S. "Buddy" Wylie
Michigan Technological University
1400 Townsend Drive
Traverse City, MI 46986
Phone: 231-941-0107
E-mail: aswylie@mtu.edu

For information on PTTC’s Midwest Region and its activities contact:
Steve Gustison, Illinois State Geological Survey
615 East Peabody Drive, Champaign, IL 61820
Phone 217-244-9337, Email: gustison@isgs.uiuc.edu

Disclaimer: No specific application of products or services is endorsed by PTTC. Reasonable steps are taken to ensure the reliability of sources for information that PTTC disseminates; individuals and institutions are solely responsible for the consequences of its use.

The not-for-profit Petroleum Technology Transfer Council is funded primarily by the US Department of Energy’s Office of Fossil Energy, with additional funding from universities, state geological surveys, several state governments, and industry donations.

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