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John A. Harper, P.G. Pennsylvania Geological Survey

Geology of Pennsylvania’s Shale Gas Plays. John A. Harper, P.G. Pennsylvania Geological Survey. MORE THAN JUST THE MARCELLUS AND UTICA. U.S. SHALE BASINS. Modified from Groundwater Protection Council, 2009. MARCELLUS SHALE. GENERALIZED GEOLOGIC COLUMN FOR WESTERN PA. About 3,500 feet.

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John A. Harper, P.G. Pennsylvania Geological Survey

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  1. Geology of Pennsylvania’s Shale Gas Plays John A. Harper, P.G. Pennsylvania Geological Survey

  2. MORE THAN JUST THE MARCELLUS AND UTICA U.S. SHALE BASINS Modified from Groundwater Protection Council, 2009

  3. MARCELLUS SHALE GENERALIZED GEOLOGIC COLUMN FOR WESTERN PA About 3,500 feet UTICA SHALE

  4. “THREE BELT” DISTRIBUTION OF THICK (>100 FEET) DEVONIAN SHALES IN PENNSYLVANIA GENESEO / BURKET Modified from Piotrowski and Harper, 1979; and Harper and Abel, 1980

  5. WHAT IS SHALE? Shale is rock, made out of mud, that is easily split and fragmented MUD = very fine-grained sediment

  6. ORGANIC-RICH SHALE IS JUST SHALE WITH A LOT OF ORGANIC MATERIAL LOCKED UP IN THE MINERAL MATRIX

  7. CONVENTIONAL RESERVOIR Source rock (organic-rich shale) – generation and expulsion Migration – from source to reservoir Reservoir rock (sandstone or limestone) – holds petroleum in internal pore space Trap (e.g. unconformity or fault) – keeps petroleum in reservoir Seal – impervious rock such as shale or non-porous limestone Overburden – buries reservoir under thousands of feet of rock

  8. SANDSTONE: A TYPICAL CONVENTIONAL RESERVOIR ROCK

  9. THIN SECTION PHOTO OF POROUS SANDSTONE EMBEDDED IN BLUE EPOXY TO SHOW PORE SPACES PORE SAND GRAIN SAND GRAIN SAND GRAIN PORE SCALE:

  10. SHALE (UNCONVENTIONAL) RESERVOIR • Source rock elements (organic compounds) remain in the shale • Reservoir and seal are vastly different than those in conventional systems • Porosity (total pore space) and permeability (interconnected pore space) are extremely limited Modified from Laughrey, 2009

  11. TYPICAL ORGANIC-RICH SHALE

  12. THIN SECTION PHOTO OF ORGANIC-RICH SHALE SHOWING LITTLE OR NO POROSITY ALGAL CYSTS SCALE:

  13. SCANNING ELECTRON MICROSCOPE (SEM) PHOTO OF THE MARCELLUS SHALE PORE PORE PORE PORE PORE SCALE: 40 Microns

  14. EXTENT OF DEVONIAN SHALES IN THE APPALACHIAN BASIN

  15. 9000 10000 8000 3000 11000 4000 5000 7000 THICKNESS AND EXTENT OF THE DEVONIAN SHALE INTERVAL IN THE NORTHERN APPALACHIAN BASIN 1000 6000 2000 Line of thickness (feet) Milici and Swezey, 2006 Extent of shales

  16. DRILLING DEPTH TO THE BASE OF THE MARCELLUS SHALE From Boswell, 1996

  17. APPROXIMATE ORIENTATIONS OF J1 AND J2 JOINT SETS IN THE MARCELLUS SHALE OF PENNSYLVANIA Tectonic fractures Natural hydraulic fractures

  18. WAYS TO DRILL AND FRAC A MARCELLUS WELL Green arrows indicate the orientation of J1 fractures and blue ovals indicate the gas drainage area in a Marcellus well: A – a vertical well will produce a relatively smaller amount of gas because the borehole may or may not intersect a limited number of J1 joints. Even fracing the well will have a limited effect. B – a horizontal well drilled parallel with the J1 joint set will produce a relatively smaller amount of gas for the same reason as in A. C – a horizontal well drilled perpendicular to the J1 joint set will intersect numerous J1 joints, and thus have the ability to drain a much larger area.

  19. MOST OPERATORS IN PENNSYLVANIA ARE DRILLING HORIZONTAL MARCELLUS WELLS ORIENTED PERPENDICULAR TO THE J1 JOINT SET Natural hydraulic fractures

  20. THE MARCELLUS PLAY IN THE APPALACHIAN BASIN Modified from Durham, 2011

  21. MARCELLUS WELLS IN PENNSYLVANIA Permits Issued and Wells Drilled as of November 30, 2011

  22. EXTENT AND DRILLING DEPTH OF THE UTICA SHALE Modified from Geology.com

  23. Utica Shale Very little carbonate TOC 1 – 3% Point Pleasant Formation Interbedded limestone and shale Shale TOC up to 3% Modified from Smith, 2011

  24. Geneseo/Burket Marcellus Utica/ Pt. Pleasant

  25. THIN SECTION PHOTOS OF THE UTICA SHALE FROM OHIO AND THE MARCELLUS SHALE FROM PENNSYLVANIA UTICA MARCELLUS Scale bar = 0.5 mm

  26. SEM PHOTOS OF UTICA SHALE IN NEW YORK AND OHIO MICROPORES IN NEW YORK UTICA ORGANIC-RICH SHALE IN OHIO Organic-rich regions From Daniels and others, 2011

  27. PERMITTED, DRILLED, AND COMPLETED UTICA/POINT PLEASANT WELLS IN PENNSYLVANIA AS OF APRIL 6, 2012

  28. Source rock maturation status based on combined CAI to Ro regression equation (Hulver, 1997; Rowan, 2006) Modified from Patchen and others, 2008

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