08123-12

Goal
The project has three goals. The first is to evaluate the degree of control that primary depositional facies have on current reservoir variability in hydrothermal dolomite reservoirs in the Ordovician Trenton/Black River trend of the Michigan Basin. This involves determining how these primary facies and their position within a sequence stratigraphic framework control reservoir quality units that developed laterally away from the major fault zones. The second goal is to correlate laboratory measured sonic velocity data from various Ordovician Trenton/Black River reservoir and non-reservoir facies to actual sonic logs and 3-D seismic signatures. A third goal is to produce 3-D stratigraphic and reservoir models using Schlumberger’s 3-D Petrel modeling software, that will be tested with data obtained from recently drilled wells.

Performer
Michigan Geological Repository for Research and Education at Western Michigan University (WMU), Kalamazoo, MI 49008-5200

Background
The Ordovician Trenton/Black River trend is a fractured, dolomitized reservoir that has produced 135 MMBO and 260 BCFG in the Michigan Basin. Recent interest by several operators associated with the extension of the Albion-Scipio trend indicated the continuing viability of Ordovician Trenton/Black River production in southern Michigan and suggested that a re-evaluation of the trend utilizing modern geological techniques and approaches would help to accelerate and optimize new exploration and production programs. These benefits may accrue not only in the Michigan Basin but also in similar plays in the Appalachian Basin and other regions of the United States.

Historically, geoscientists have interpreted reservoir quality and distribution in fractured, hydrothermal dolomite (HTD) formations as controlled primarily by the structural processes of faulting and fracturing associated with regional wrench tectonics. As a result, exploration and production strategies focus on identifying fault trends and associated seismic sags. A problem that small operators often face is that of trying to understand the presence of lateral variability in reservoir quality away from the major fault zones, which often results in close step-out dry holes. Preliminary work by WMU in the Albion-Scipio trend, has shown that lateral variability of reservoir quality HTDs away from the major fault zones appears to be related to both the primary depositional facies and the sequence stratigraphic framework. Further testing of such a relationship should lead to better predictability of laterally persistent reservoir zones in these systems and provide a means to enhance reservoir modeling at both the exploration and production scales. This testing must be combined with quantification of pore architecture and permeability values, correlation of pore architecture and permeability to laboratory measured sonic velocity values, and 3-D reservoir modeling.

This project focuses on the giant Albion-Scipio trend of southern Michigan because of the availability of extensive well, core, and production data. Results will help small operators in the Michigan Basin and should be exportable to other HTD plays in the United States. Albion-Scipio field was discovered in 1957, but as with many mature carbonate plays in the U.S., the field has not been extensively studied using a state of the art reservoir characterization approach (i.e., one that incorporates depositional environment interpretation, diagenesis, and reservoir potential into a robust sequence stratigraphic framework that would allow for enhanced predictability of the distribution of reservoir facies at exploration and production scales). Details from such a study, when coupled with the tie between reservoir and non-reservoir facies to sonic velocity signatures, should allow for enhanced prediction of reservoir facies and flow units away from the borehole in 3-D seismic datasets using amplitude time slicing and other techniques. This will enhance the value of modern 3-D seismic data and limit the problem of close step-out dry holes.

Potential Impacts
The correlation of sonic velocity related to pore architecture and reservoir permeability will provide an immediate means to high-grade target zones from sonic log data and may provide enhanced exploration capability when combined with 3-D seismic interpretation. New methodologies resulting from the application of this project will extend the life of similar mature fields and increase the ultimate recovery of hydrocarbons through enhanced understanding of the reservoir distribution away from the major fault zones, which will high-grade the placement of vertical and horizontal wells.

Increasing the current total recovery in Albion-Scipio by only 1 percent would add 1,380,000 BO and 2.6 BCF to the production total from the Michigan Basin. Best practices and approaches identified in this study would likely have similar impact in other regions with HTD reservoirs. It is reasonable to expect that a comprehensive, basin-wide examination of the Trenton-Black River Formation resulting in the development of additional exploration models and methods could ultimately produce a 10 percent increase in recoverable reserves (13.5 MMBO and 26 BCF). The 2004 U.S. Geological Survey’s National Oil and Gas Assessment Fact Sheet of undiscovered resources in the Michigan Basin estimates a mean of 824 MMBO and 1.4 TCF of gas to be technically recoverable from the Ordovician Trenton-Black River basinwide. The application of technology developed through this project could result in the production of hundreds of millions of additional barrels of oil equivalent in Michigan and the eastern U.S.

Accomplishments
Work on this project began in October 2009. The Project Management Plan, with a work breakdown structure that concisely addresses the objectives and approach for each task with all major milestones and decision points, and the Technology Status Assessment, describing the state-of-the-art of the proposed technology, have both been completed.

Significant progress has been made on the PETRA database. For the two fields of primary interest, Albion-Scipio and Stoney Point, formation tops, perf zones, and production histories are being compiled for comparison and analysis. Select paper copies of wireline logs throughout the fields of interest are being digitized for cross sections and mapping. Initial key facies types were identified, and initial samples for thin sections were sent out for laboratory analysis.

The initial set of core plugs was drilled from the reservoir and seal facies for sonic velocity and computerized tomography (CT) scans. Cores will continue to be described, and petrophysical facies will be further defined through integration of core analyses and wireline logs in order to determine sampling horizons for laboratory sonic velocity measurements.

Current Status (January 2011)
The key tasks to be undertaken are outlined below.

Construction of Sequence Stratigraphic Framework – The reason for establishing a regional sequence stratigraphic framework is to enhance the predictability of reservoir facies and bounding flow unit barriers on a regional (i.e., seismic) scale. A well-constrained sequence stratigraphic framework will serve as a guide to understanding and predicting the distribution of reservoir flow units in the subsurface. The research team will establish a geologic and sequence stratigraphic framework in the following manner. First, the team will identify lithofacies and interpret depositional environments from core analysis. Second, the team will tie these lithofacies and depositional environments to non-cored wells utilizing data from wireline logs. Third, the team will define gross geometries of sedimentary bodies based upon interpreted depositional facies through the application of various analogs. Finally, the researchers will divide strata into genetically related units separated by unconformities.

In order to describe and quantify depositional and diagenetic history, porosity, and permeability variations, and other factors affecting reservoir heterogeneity, it is necessary to first develop a qualitative and quantitative database of lithologic, petrographic, and petrophysical data. The sequence stratigraphic framework will thus be constructed utilizing cores from the Albion-Scipio area currently at the Michigan Geological Repository for Research and Education facility by analyzing and grouping genetically related depositional units (i.e. sequences and cycles), then extrapolating to wells without core throughout the field.

High-Resolution Reservoir Characterization Tied to Cyclostratigraphy – Previous research has shown that in other carbonate units similar to the Trenton and Black River, depositional cycles on the meter to tens of meters scale represent the fundamental unit at which variations in rock-fabrics occur and that therefore control the distribution of reservoir flow units. To establish the scale of lateral and vertical heterogeneity of reservoir flow units, which are created by the complex interplay between depositional facies and diagenesis, the research team will examine the stratigraphic framework of the system to the level of individual cycles (i.e. meter-scale). The team will do this by utilizing core as a foundation and extrapolating out with wireline log data in wells that do not have associated core materials.

Sonic Velocity and Permeability Tied to Pore Architecture for Enhanced Prediction of Reservoir Facies in 3-D Seismic Data – Establishing a predictable connection between pore type and pore architecture to laboratory measured sonic velocity values will help operators more fully recognize, and ultimately predict with increased confidence, reservoir type and quality in the subsurface. Because pore geometry is a crucial factor in controlling acoustic properties in carbonates, detailed characterization of pore types and pore architecture through petrographic and image analysis and refined analysis and interpretation of sonic log borehole data, should help operators predict the pore architecture and therefore the permeability of reservoir rocks, more effectively. Detailed characterization of porosity and permeability trends should also provide enhanced predictability of the regional distribution of reservoir facies in 3-D seismic data sets through the application of techniques such as amplitude time slicing and correlation back to depositional and sequence stratigraphic models. In this task, the research team will establish these connections and test their applicability in predicting the regional distribution of reservoir facies.

Technology Transfer – This task will include workshops held by the Michigan Petroleum Technology Transfer Council (PTTC). The team will present results from this research project at these workshops and at regional and national American Association of Petroleum Geologists (AAPG) meetings and will maintain a website for research data and results. The primary deliverable for this project will be a summary report and the development of a series of “best practices” that can be utilized within the budgetary and technical limitations faced by small operators.

Project Start: October 14, 2009
Project End: October 13, 2011

DOE Contribution: $393,369
Performer Contribution: $745,496

Contact Information:
RPSEA – Martha Cather (martha@prrc.nmt.edu or 575-835-5685)
NETL – Chandra Nautiyal (chandra.nautiyal@netl.doe.gov or 918-699-2021)
Western Michigan University – Dr. G. Michael Grammer (michael.grammer@wmich.edu or 269-387-8679)