Abstract

The Second Sand Member of the Bone Spring Formation is a submarine fan complex of Leonardarian (Permian) age in the Delaware Basin of southeast New Mexico. Along the slope, channel and levee/overbank facies within the Second Sand are locally of reservoir quality with average porosities of 9-10% and permeabilities ranging from less than 1 md up to 6 md. A 3-D seismic survey collected over an established oil field in Lea County, New Mexico was integrated with available well logs and cores to determine the stratigraphy and reservoir characteristics of the Second Bone Spring Sand. In this area, the dominant control on the distribution of the Second Sand is the structure of the underlying units. Faulting and flexures associated with Mississippian to Early Permian tectonics created a small sub-basin bounded by a series of N-S trending faults that acted as a local depocenter during Second Sand deposition. The depositional history of the Second Sand in the study area can be divided into three periods based on seismic reflection configuration, well and core data: 1) an early period characterized by sediment bypassing the upper slope and being deposited in a series of discrete submarine fan lobes prograding to the southeast, 2) a middle period when sediment briefly onlapped the upper slope, and 3) a final period marked by a gradual lowering of sea level, progressive slope bypassing, and southward progradation of the submarine fan.

A combination of crossplot porosities from well logs and seismic attributes were used to determine a predictive relationship between seismic attributes and thickness of net pay within the most productive reservoir interval of the Second Sand. The highest values of net pay occur in an elongate, N-S trending zone just below a major re-entrant in the upper slope and are believed to correspond to the channel facies. In contrast, the distribution of the lowest quality reservoir rocks appears to be controlled by faults and fractures indicating that these features may serve as barriers to fluid flow.