Sweet-spotting the Niobrara LTO Play, NW CO, USA: Three Key Learnings for Emerging Plays

Abstract

The Niobrara is an emerging LTO play in NW Colorado, U.S. Despite proved production since the 1920's, exploiting the Niobrara as an LTO bore several subsurface and operational challenges that together with NTR restrictions, impacted the execution plans, drilling schedule, and commerciality. A key exploration step was sweet-spotting the play given its multiple maturity windows and development concepts. Traditionally, sweet-spotting a play assesses the quality of each play element (source, reservoir, and seal/trap) resulting in a number of play segments ranked by potential. The outcome is manifest in an appraisal strategy/drilling sequence seeking to validate the potential of each segment and prove/disprove commerciality. Unlike conventional oil & gas systems, however, self-sourced systems are more complex where katagenic processes and local migration occur within the system as intricate, inter-dependant elements. Well results suggest that evaluating the interaction between matrix, fractures, and maturity as a dynamic system, rather than static, is a critical step towards properly characterizing the play elements, and sweet spotting. The results also impact estimates of well drainage areas, EUR and eventually development plans. Our learning is that static sweet-spotting may not be enough, understanding the dynamic systems is key to a successful appraisal. As a consequence of this dynamic interaction, finding the right play analogs could be tricky. In this Niobrara case, quickly drawing on DJ basin as play analog showed key differences despite that both plays belong to the same basin and are a geological extension of each other. We share some results from 28 wells drilled in NW CO and highlight three subsurface themes that can positively impact the delivery and commerciality of other emerging LTO plays, namely: utilize dynamic sweet-spotting, beware of analogs, and drill at a slower pace. We recommend that it is best to first assume a play is unique, then adopt the right analogs (if any), with more weight on the data, and not the analogs. In this way, repeatability of success can be tested independently, and a robust POS can be evaluated for the proper risk segment and the subsequent drilling and development plans.

AAPG Datapages/Search and Discovery Article #90194 © 2014 International Conference & Exhibition, Istanbul, Turkey, September 14-17, 2014