Structural architecture of the Farnsworth oil unit: Implications for geologic storage of carbon dioxide

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, specifically CO 2 and CH 4 , in the shallow subsurface and atmosphere is helping with designing and implementing 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 target zone for CO 2 storage and enhanced oil recovery in the Farnsworth oil unit is in the upper Morrow sandstone at subsurface depths greater than 2000 m (6562 ft). Field study reveals that sandstone and chert in the High Plains Aquifer contain numerous joints that provide crucial insight into aquifer architecture and subsurface flow pathways. Properties of more than 1700 joints were measured in the field and in high-resolution satellite images. Two distinctive joint systems interpreted as a conjugate pair were identified in the study area. Joint spacing follows a lognormal statistical scaling rule. These fractures appear to be the product of an east–northeast regional compressive stress and may have a significant effect on flow in the High Plains Aquifer system. 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 CO 2 and CH 4 flux of systematic joints and cross joints.