WolfBone Play Evolution, Southern Delaware Basin: Geologic Concept Modifications That Have Enhanced Economic Success.

Bill Fairhurst, Mary Lisbeth Hanson, and Nick Pieracacos
Eagle Oil & Gas, Co., Dallas, Texas

The WolfBone play is an emerging unconventional oil-resource. Exploration and development has been a systematic evolution from geologic concept to drilling, evaluation and revision of targets. Originally, Wolfcamp sandstone reservoirs below and Third Bone Spring sandstone reservoirs above the Wolfcampian shale source section were targeted. Current drilling and production is focused on the 1,000’ thick, oil-rich, unconventional Wolfcamp shale. The Wolfcamp is an ideal heterogenetic resource consisting of quartz, carbonate and kerogen. Exploration and field development will be successful over a large area. However, the geologic and economic sweet spot is limited to the basin floor. In this setting quartz and kerogen accumulated in the quiet deep-basin interrupted by episodic deposition of shelf to basin floor carbonate debris flows that settled basinward of the deceleration boundary. These depositional processes resulted in compositional and grain-size heterogeneities and accumulation of the thick organic-rich targets. During maturation large volumes of oil were sealed in place (108 MMBOIP per Section). Expansion from kerogen to oil in a sealed system resulted in overpressure and abundant fracturing that has resulted in enhanced productivity. Individual wells have flowed 45 MBO from 11,000’ prior to initiating artificial lift which is atypical of Permian Basin reservoirs. Farther into the basin and upslope these conditions do not exist and are outside the economic sweet spot. Basinward, the unit is consistently thick, however, there is more shale and the section is starved of siltstones and carbonates. Upslope, the unit thins and is more gas-prone. In these slope environments the mixture of coarser-grained shelf carbonates and sandstones breached the system providing migration pathways which have limited productivity and lower ultimate economic recoveries. Since 2009, this play has been developed with vertical wells co-mingling the oil-resource with conventional reservoirs. Interpretation of imaging logs has identified the primary fracture orientation and zones with conjugate fractures systems. Integration with production logs has optimized horizontal target identification and horizontal drilling has begun. The Leonardian, Avalon sweet spots occur at similar depositional setting as the Wolfcampian resource and the same geographic position in this portion of the basin. The Avalon is estimated to have 103 MMBOIP per Section.

AAPG Search and Discovery Article #90152©2012 AAPG Southwest Section Meeting, Fort Worth, Texas, 19-22 May 2012