Sandstones of the Bone Spring formation (Leonardian) with significant potential in the northern portion of the Delaware basin include the Avalon sandstone and third Bone Spring sandstone intervals. The Avalon sandstone is a very fine to fine-grained submarine-fan deposit, 10-18 m thick, distributed across parts of southern Eddy and southwestern Lea counties, New Mexico. The Avalon consists of a series of individual sandstone zones separated by carbonaceous and shaly siltstones. The sandstone zones display moderate porosities (7-17%) and low permeabilities (0.5-7.2 md) and require artificial stimulation to produce. Net pay is commonly 4-8 m. Reserves per well seldom exceed 100,000 bbl, and the Avalon interval is considered a secondary reservoir.

The third Bone Spring sandstone is widely distributed across the northern Delaware basin and is especially prospective within the deeper basinal area to the east. In contrast to the Avalon sandstone, which was sourced from the north and northwest, submarine-fan systems of the third Bone Spring sandstone were supplied from the northeast and east, with detritus derived from the Central Basin platform (CBP). Productive sandstone zones are very fine grained channel and levee/overbank facies, with porosities of 7-18% and permeabilities of 2.0 md or

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I thank the following companies and individuals who helped make this paper possible: Larry Brooks, Parker and Parsley, for data and expertise related to all aspects of the study; Mike Hayes, Yates Petroleum; Ralph Worthington; and Floyd Bardsley for artwork.

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k = thousand, M = million, G = billion.