Geologic Architecture of the High Plains Aquifer, Northeastern Texas Panhandle: Implications for Implementation of Surface and Airborne Monitoring Techniques

Abstract

Surface and airborne gas monitoring programs are becoming an important part of environmental protection in areas favorable for subsurface storage of carbon dioxide. Understanding structural architecture and its effects on the flux of fluids is helping design and implement next generation monitoring technologies, including unmanned aerial vehicles (UAVs). An important aspect of this research is using subsurface fracture data to inform the design of flight pathways for UAVs in the Farnsworth Oil Unit of the Anadarko Basin. The High Plains Aquifer of the northeastern Texas Panhandle disconformably overlies Permian and Triassic redbeds and is dominated by weakly to moderately indurated sandstone in the Ogallala Formation (Miocene-Pliocene). Ogallala strata are overlain by Quaternary strata that include a siliceous caprock west of the Farnsworth Oil unit and a thick (∼25 m) section of caliche east of the oil unit. The target zone for CO₂ storage and enhanced oil recovery in the Farnsworth Oil Unit is in upper Morrow sandstone (Lower Pennsylvanian) at subsurface depths greater than 2,000 m. Field study reveals that indurated sandstone and a chert caprock strata contain numerous joints that provide crucial insight into aquifer architecture and subsurface flow pathways. Length, orientation, spacing, and cross-cutting relationships of more than 1,700 joints were measured in the field and in high-resolution satellite imagery. The joint networks consist of well-developed systematic joints and cross-joints. In vertical section, the joints are typically curvilinear and strata-bound, cutting indurated strata and terminating within friable sandstone. Two distinctive joint systems forming a conjugate pair were identified in the study area. Joint spacing follows a log-normal statistical scaling rule. These fractures appear to be the product of regional tectonic stress and may have a significant effect on flow in the High Plains Aquifer system, as well as near-surface gas flux. Based on the results of this research, design of UAV flight paths should be oblique to fractures in a way that maximizes the likelihood of CO₂ and CH4 flux from of systematic joints and cross joints.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016