In unconventional reservoirs, the drivers of reservoir quality and hydrocarbon producibility are mostly evident at the scanning electron microscope (SEM) scale. For field applications, the practical scales of observation have resolutions from few feet to tens of feet. Finding ways of integrating the two scales allows propagation of knowledge, obtained at SEM and core scale, across the field. This is achieved via strong understanding of rock texture and composition, and of the geologic processes that defined them. The objective is to understand the rock, via detailed geologic and petrologic core studies, and define ways to identify core-scale rock texture and composition with well log and seismic measurements.
We define the depositional and diagenetic transformations that occurred in the various facies of the Haynesville and Bossier system using core geologic and petrologic studies. We identify the different textural and compositional properties that define these facies and, by selecting a log suite sensitive to texture and composition, investigate their ability to discriminate these differences. We use a core-log model to predict the distribution of these geologic facies in other regions of the field, and validate these predictions with additional core studies in these regions. The potential and limitation of the log responses to identify subtle changes in rock texture and composition is critical to this effort. Once validated, the log-scale model is filtered to seismic resolution, and used to map geologic units at the seismic scale.
The log-scale measurements detect sequences of the core-scale facies, thus allowing us to map their presence and distribution across the play. The method improves field geologic characterization, defines an efficient selection criterion for additional science wells with core and for selection of additional seismic data.
Core-log integration was successful across a region of 7,185 square miles, and core-log-seismic integration was successful across a region of 200 square miles. The method provided a cost efficient concept for exploration, and for tying the varying geologic processes in the basin to the resulting conditions of reservoir quality and production potential. It also provided information for more effective well placement design.