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An Emerging Vaca Muerta Formation Unconventional Development, Sierras Blancas and Cruz de Lorena Blocks, Neuquen Basin, Argentina


In the fall of 2016, Shell Oil Company resumed drilling in Sierras Blancas and Cruz de Lorena Blocks to further assess commerciality of this Vaca Muerta development. The emphasis of the current drilling campaign is on delivering repeatable well performance and reducing well costs. We will have five new wells drilled by early spring of 2017. A measured derisking plan has set us up for success. Shell Argentina has focused on multi-well pad drilling and data gathering during 2015. Our derisking strategy is simply the collection of selected static and dynamic data in a small area early in the appraisal phase; then given good results, expansion of the pad to prove commerciality. The multi-well pad operations took place in three areas Sierras Blancas West, Cruz de Lorena Triangle and Cruz de Lorena West. In addition to horizontal wells, the appraisal program included a vertical well, a slant well, and collection of conventional core, sidewall cores, wireline logs, microseimic, production logs, oil and water tracers and produced oil fingerprinting. Results indicate potential for a two layer development. Porosity in Sequence 1 (Lower Vaca Muerta) averages 11% and in Sequence 2 (Upper Vaca Muerta) averages 7%. This drilling phase delivered three “best in basin” producing wells: SB 1005h, SB 1006d, and CdL 7h. We extended our understanding of the subsurface away from the well pads by employing a Bayesian classification scheme; we created rock types using learnings from our data acquisition program at the core and log scale. This allowed us to understand that TOC, porosity, and Young's modulus are our most important reservoir properties at the log scale. The same rock types are then translated into elastic impedance space where the same type of classification can be performed at the seismic scale with the use of seismic inversion techniques. The resulting integrated rock property model predicts key reservoir properties away from the well bore. These new data and understandings fed a refresh of the play based exploration (PBE) exercise for the blocks. The PBE demonstrated Sequence 1 is more laterally continuous and homogeneous, and therefore, the preferred initial development target. We anticipate a single rig drilling campaign to supply the recently completed early production system. Further de-risking of Sequence 2 will continue as Sequence 1 drilling proceeds.