Lee F. Krystinik¹

(1) Krystinik Litho-Logic, Fort Worth, TX

ABSTRACT: Big Bucks or a Money Disposal Project?... New Perspectives on Basin-Centered Gas from Horizontal Drilling, Deep Frontier Fm., Green River Basin, SW Wyoming

The Greater Green River Basin Production Improvement Project is a DOE/industry partnership to make drilling for deep (>15,000'), ultra-tight (<0.001 md.), fractured gas resources economically viable. This effort culminated in the drilling of a horizontal well, the UPR Rock Island 4-H (RI 4-H). Results include: 1) Drilling cost was reduced to 50% of the industry average; 2) Over 400 open fractures were intersected in a 1750' horizontal leg; 3) The deepest horizontal tight-gas sandstone cores in the world; 4) Economic production >14 MMCF/D; and 5) An ongoing industry drilling effort was initiated.

Important observations from 4 wells drilled since the RI 4-H include: 1) Isolated pressure cells with pressure gradients ranging from 0.5 to 0.85 psi/ft; 2) Matrix sandstone appears regionally gas saturated; 3) Intense fracturing occurs adjacent to shear faults; 4) Productive fractures are opened by shear reactivation; 5) Fractures can be highly productive of gas or water; 6) Water production from fractures is related to structural position (gas above water) in each pressure cell; and 7) Water production, where encountered, does not suggest infinite aquifer support.

Stratigraphic reservoir compartments have undergone different pressure histories due to intermittent movement along shear faults. These shear faults reactivate and open fractures, but also rupture pressure seals and allow water into the fracture system. Finding a balance between adequate open fractures and low water production will be critical to economic success in this play. It may be possible to dewater Frontier fracture systems as with coal bed methane wells.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado