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A regional look at Morrow Formation gas in light of conflicting resource development in southeast New Mexico

¹ New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, New Mexico 87801; pwalsh{at}gis.nmt.edu

Patrick Walsh received his M.S. degree in 2000 from the University of Texas at Austin and his B.S. degree from Penn State University in 1998. He has worked as an exploration geoscientist for Texaco and a consultant for Landmark Graphics and John Shomaker and Associates. He is currently a subsurface fluids geologist at the New Mexico Bureau of Geology, where his research includes investigating structural controls on hydrogeology as well as mapping oil and gas reservoirs.

ABSTRACT

Several factors have led to reservoir underdevelopment in the Morrow Formation in southeast New Mexico, including conflicting interests with potash development companies, government regulations protecting potash resources, lack of completions within successful wells, and lack of exploration. Over the past 70 yr, the Secretary of the Interior has set aside 777 mi² (2012 km²) of southeastern New Mexico, referred to as the Secretary of the Interior's potash area (SPA), to preserve potash resources. Oil and gas drilling are severely limited within the SPA, where leasing is managed by the Bureau of Land Management. The Morrow Formation reservoirs have significant undiscovered reserves in the SPA. Morrow Formation production-well density is roughly half that of the surrounding area, which may also be underdeveloped. Operators have drilled a few directional wells to target Morrow Formation reservoirs while avoiding potash resources near the boundaries of the protected area, and they used horizontal wells to develop the shallower Brushy Canyon Formation in one area. Older abandoned wells within the SPA may be used in the future for drilling islands, but this practice has not yet begun. The purpose of this article is to provide structural and stratigraphic maps of Morrow Formation reservoir horizons, to present areas with future potential, and to suggest future development scenarios. The article also provides a regional Morrow Formation depositional picture and correlates this regional description to field-scale interpretations.

The Morrow Formation is typically divided into two intervals: the Morrow clastics and the overlying Morrow limestones. The fluvial-deltaic to shallow-marine Morrow clastic interval currently provides more than 40% of the natural gas production within the SPA. Depth to Morrow clastic production ranges from about 11,000 to approximately 14,000 ft (3352 to approximately 4267 m) in the SPA. This study divides the Morrow clastic interval into three informal subunits based on log character and uses flooding surfaces marked by correlatable bounding shales. The resulting net sand maps for these subunits indicate an overall transgression from deltaic to distributary-mouth bar or reworked deltaic to deposition of overlying carbonates and marine shales. Trends of producing wells along depositional axes that are interpreted in this report indicate potential areas for future exploration and development. Future drilling will target depositionally complex reservoirs. The author recommends directional and horizontal drilling, aided by three-dimensional seismic imaging, to explore and develop SPA resources.