Abstract

Exploration of the Haynesville and Bossier shale play in east Texas and western Louisiana provides an opportunity for many onshore-focused, U.S. geoscientists to reacquaint themselves with biostratigraphy. Using both vintage and new biostratigraphic data, this study showcases the integration of multiple biostratigraphic disciplines for (1) identification of unique correlation surfaces within the basin; (2) increased resolution and confidence in the age assignments for surfaces defined by logs and seismic; and (3) the recognition of distinct biofacies, which aid in the prediction of preferred intervals and geographic areas for hydrocarbon accumulation within shales.

This study incorporates interpretations from five wells using nannofossils, foraminifera, ammonites, and radiolarians. The strengths and weaknesses of each fossil discipline are discussed in the context of a multidisciplinary stratigraphic evaluation. Rock materials for the study were collected from both cuttings and core from stratigraphic intervals interpreted as Haynesville Shale, Bossier Shale, Taylor Sands, and Cotton Valley Group siliciclastics. Biostratigraphic interpretations, which range from lower Kimmeridgian to lower Berriasian, establish more accurate and reliable timelines than have previously been published from a Jurassic basin in North America. Complementing the age interpretations, four key biofacies are recognized and mapped. Some of the biofacies are interpreted to be associated with significant dysoxic to anoxic bottom conditions and potentially areas of corresponding elevated surface productivity, whereas others likely represent changes in sediment supply into the basin from nearby terrigenous clastic and/or detrital carbonate sources.