Unconventional resources are defined to include coal-bed methane (CBM), tight gas and source rock- (often shale) based reservoirs. Tight gas and CBM have not been "unconventional" in the United States and Canada for more than a decade and are being developed in many countries as more or less conventional plays. Source rock-based plays (shale oil, shale gas) in North America have become widely commercialized and contribute substantially to both gas and hydrocarbon liquid production. Vast quantities of shale resources outside of the United States and Canada have been identified but generally remain at early stages of development. Although large numbers of horizontal, multi-stage hydraulically fractured shale wells have been drilled commercially, such plays remain unconventional for a variety of reasons.
Shale plays differ from tight gas, CBM and historically conventional plays for the same reasons. Unlike the other plays whose characteristics that result in success are well known, shale plays only have indicators pointing to success. The reasons for variability in individual well performance for shale plays are poorly known. Methodologies to "derisk" potential plays vary. Mathematical models to predict performance for shale plays are less rigorous and operators often rely on overly simplified approaches.
Highly competitive North American markets with scores of well-funded competitors and relatively easy access to land and technology have resulted in rapid evaluation of many shale plays at the cost of a substantial number of underperforming wells. In the study, several plays are presented, showing how quickly derisking occurs, what factors contribute to them and how they impact long-term efficiency.
A consistent method for gathering data (seismic, test wells, cores, logs, geomechanical information) is proposed to minimize excess costs and maximize NPV. The approaches to optimize development are applied to shale plays with synthetic properties established on observed heterogeneities but reservoir characteristics for some international shale prospects. The economics are tested with various strategies to illustrate the differences in value obtained.
