Exploration and Production Technologies
Analysis of Critical Permeability, Capillary and Electrical Properties for Mesaverde Tight Gas Sandstones from Western U.S. Basins

DE-FC26-05NT42660

Goal: 
The goal of this project is to provide petrophysical formation evaluation tools related to relative permeability, capillary pressure, electrical properties, and algorithm tools for wireline log analysis of Mesaverde Group tight gas sandstones in Rocky Mountain basins.

Performer
University of Kansas Center for Research, Lawrence, KS

Background
Understanding the minimum gas saturation necessary for gas flow is fundamental to defining the tight gas sandstone resource. The objective of this study is to investigate the relationships among critical gas saturation, capillary pressure, electrical and basic porosity, permeability, and lithologic properties in the tight gas sandstones of the Mesaverde Group. Of key importance is the impact of these variations on natural gas drainage. A detailed and accurate moveable gas-in-place resource assessment is most critical in marginal gas plays, and there is a need for quantitative tools that can accurately define the limits on gas producibility.

This project will collect published advanced rock property data and at least 300 rock samples and digital wireline logs from four or five wells in each of the five major Rocky Mountain tight gas sandstone basins (Washakie, Uinta, Piceance, Upper Greater Green River, and Wind River). Basic properties will be measured on these core samples, and based on these properties, samples will be selected that represent the range of porosity, permeability, and lithofacies in the wells and basins. Additional measurements on the selected samples will include critical gas saturation; routine and in-situ mercury intrusion capillary pressure analysis; cementation and saturation exponents and cation exchange capacity; core description such as thin-section microscopy, including diagenetic and point-count analysis; and standard wireline log analysis. The compiled published data and data measured in the study will be input to a relational database. Web-based access to the data will be provided to allow the construction of rock catalog-format output sheets based on user-input search criteria. In addition, core and wireline log-calculated properties will be compared and algorithms developed for improved calculation of reservoir properties from log response. The scale dependence of critical gas saturation will be evaluated through bedform-scale reservoir simulations that parametrically analyze how critical gas saturation and relative permeability scale with size and bedding architecture.

Impact
Tight gas sandstones represent 72 percent (342 trillion cubic feet, or Tcf) of the projected unconventional resource (474 Tcf) for the United States. Rocky Mountain tight gas sandstones represent 70 percent of the total tight gas sand resource base, and Mesaverde Group sandstones are a principal productive unit in Rocky Mountain basins. Industry and government assessments of the regional gas resource, projections of future gas supply, and successful exploration and development operations depend on an accurate understanding of the tight gas sandstone reservoir properties and accurate tools for formation evaluation of drilled wells. The improvement in formation evaluation accuracy that will result from this project will help to more accurately quantify limits on gas producibility, leading to more cost effective development of tight gas sand resources. An active and aggressive web-based, publication, and short-course technology transfer program will make the results of this research available to the widest possible audience of potential users, maximizing its impact.

Accomplishments
The University of Kansas Center for Research has completed its study on the Mesaverde Sandstones in six basins in the Western United States. The goal of this study was to provide petrophysical formation evaluation tools related to relative permeability, capillary pressure, electrical properties and algorithms for wire line log analysis. Detailed and accurate moveable gas-in-place resource assessment is most critical in marginal gas plays and there is need for quantitative tools for definition of limits on gas producibility due to technology and rock physics and for defining water saturation. The Mesaverde Sandstones represent a principal gas productive tight sandstone unit, which begs the fundamental questions concerning: 1) gas storage; 2) gas flow; 3) capillary pressure; 4) electrical properties; 5) facies and upscaling issues; 6) wire line log interpretation algorithms; and 7) providing a web-accessible database of advanced rock properties. Over 9 gigabytes of data are available for download from the Project Website (http://www.kgs.ku.edu/mesaverde/ [external site]) comprising 1) Excel workbooks containing tables of data from previous studies; 2) Excel workbooks containing data for all petrophysical measurements performed in this study including: 2,102 helium porosity, 2,075 routine air permeability, 2,062 in situ Klinkenberg permeability, 2,101 grain density measurements, 907 electrical resistivity measurements, 301 mercury intrusion capillary pressure analyses, 150 air-brine critical gas saturation measurements, 113 pore volume compressibility analyses, 310 air-brine in situ porosity measurements; 550 core slab images representing the range of lithofacies exhibited by the Mesaverde in the six basins studied; 750 thin-section photomicrographs from 41 wells; 6,447 feet (2,054 m) of digital core descriptions presented both in Excel workbook format and in graphical core descriptions for 42 wells from 6 basins; graphical core descriptions of core from 42 wells; 21 standard wire line log analyses; 21 advanced wire line log analyses. The Final Technical Report can be found on the NETL website (/File Library/Research/Oil-Gas/Natural Gas/NT42660_FinalReport.pdf)

Current Status (January 2010)
All work on this project is complete and the final report is available below under "Additional Information".

Start Date: September 28, 2005
End Date: June 30, 2008

Anticipated DOE Cost: $411,030
Performer Cost: $102,804 (20% of total)

Contact Information:
NETL – Virgiina Weyland (Virgiina.Weyland@netl.doe.gov or 281-494-2517)
University of Kansas Center for Research – Alan Byrnes (apbyrnes@cox.net or 785-864-3965)

Additional Information:

Final Project Report [PDF-13.0MB]

Publications
Byrnes, A.P., (2007, in press), “Issues with gas and water relative permeability in low-permeability sandstones,” in S. Cummella, K. Shanley, W. Camp (eds.), Proceedings of the American Association of Petroleum Geologists Hedberg Conference on Understanding, Exploring, and Developing Tight Gas Sands, Vail, CO, April 24-28, 2005, 30 pgs.


Crossplot of Klinkenberg proportionality constant, b, versus in-situ Klinkenberg permeability measured at 4,000 psi net effective stress using nitrogen gas. Reduced major axis analysis indicates the correlation can be expressed as b(atm) = 0.851 kik-0.341, n = 1264.


In-situ Klinkenberg permeability versus calculated in-situ porosity by basin. Range of porosity and permeability of Mesaverde sandstones is generally exhibited by all basins.

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