The Austin Chalk Formation has re-emerged in the oil and gas industry over the past few years, accounting for some of the most prolific wells in the L48. However, Austin Chalk success appears to be somewhat localized as wells offsetting strong producers often show much lower production.
The Giddings Field in East Texas is one of the largest historic Austin Chalk fields (Figure 1). With step-change improvements in resource extraction technology, E&Ps have continuously modified their approach to the Austin Chalk. This play was drilled conventionally from 1970 to 1990 with vertical wells targeting localized fracture zones (Figure 2). Later, these extensive fracture zones were targeted horizontally until the mid-2010s. These earlier designs were either unfrac’ed or stimulated with acid treatments. Within the last four years, horizontal wells within the field shifted from conventional, structural targets to a “hybrid” play with contiguous matrix porosity and hydrocarbon saturation trends, employing multi-stage frac’ing to induce permeability. Despite relying on different reservoir parameters than those historically targeted, the formation has supported increased activity and delivered success in some previously uncommercial or untested areas.
But why do we see mixed success in this play? Carbonate reservoirs, like the Austin Chalk, are geologically complex and have less predictable reservoir properties, making them a challenge to develop. The variability is influenced by depositional environment, burial conditions, diagenesis (chemical or mechanical alteration of the rock) and active faulting. The best operators will have a robust understanding of this structural and stratigraphic complexity using seismic data and cored wells to delineate the Austin Chalk landing zone and faults. Operators are consistently challenged by repeatability, drilling accuracy and geological risks (such as drilling through unforeseen faults or water-bearing upper Austin Chalk intervals).
The long production history, high well control and varied well configurations in the Giddings field can be leveraged as an exploitation analogue to the emerging Louisiana Austin Chalk.
FIGURE 1 | Giddings Field Austin Chalk Wells
FIGURE 2 | Schematic of Historical Production Uplift in the Giddings Field