Leonard Rice Engineers, Inc. (“LRE”) evaluated and developed groundwater resources and wells on the 28,000 acre Roark Ranch in west-central Wink County, Texas. The well field provides completion water for nearby oil and gas clients who are located in the eastern part of the Delaware Basin of west Texas. This project was completed in multiple phases.
Phase 1 – Well Desktop Study
LRE performed a desktop aquifer sustainability study which determined that there is over 700,000 acre-feet of recoverable water within the Pecos Valley Alluvium (PVA) underlying the Ranch. The study also confirmed that the Roark Ranch is situated over the Cenozoic Monument Draw Trough. This trough is a deep paleo channel feature with a 700-900 foot section of productive aquifer material.
Phase 2 – Hydrology Evaluation
LRE evaluated the groundwater hydrology to better characterize the PVA. LRE oversaw surface geophysical surveys (CSMAT) to assist in locating water wells in the Ranch’s “sweet spots”. The survey differentiated coarse-grained sands and gravels from fine-grained silts and clays. The coarse-grained materials are preferred for well location. Guided by the surface study results, LRE oversaw installation of 20+ borings to further refine the subsurface geology interpretation.
Phase 3 – Geologic Model
LRE used surface geophysical surveys and borehole geophysical logs to prepare a 3D geologic model interpretation of the PVA. The model helped identify areas on the ranch that would encounter the thickest section of saturated, coarse-grained PVA material in the subsurface. Based on the results of the 3D geologic model, LRE recommended the production well locations.
Phase 4 – Well Field Development
LRE developed a well field that consists of six groundwater wells located in the northern part of the ranch. This field produces water from both the PVA and underlying Santa Rosa Sandstone aquifer. Conservative well production estimates (with 10-year constant pumping) range from 650 gallons per minute (gpm) to over 1,500 gpm. Total production from the six wells is estimated at ~5,600gpm (192,000 Bbls/day) of 2,000 to 3,000 TDS water quality and limited drawdown. In addition to the well field development, LRE oversaw all aspects of:
- Well design and construction
- Aquifer testing
- Coordination of surface facilities installation (VFDs, SCADA, lightening protection, and fencing)
- Permanent electrical power
- Well commissioning.
Phase 5 – Groundwater Production Analysis
LRE analyzed detailed groundwater modeling of the well field, based on the interpretation of the aquifer testing results to:
- Better characterize the PVA aquifer
- Develop a predictive tool for assisting in future well placement/performance rate
- Evaluate the long-term sustainability of the well field
LRE constructed a 3D groundwater flow model of the ranch and surrounding areas, using MODFLOW 2000, to:
- Predict transient drawdown over a long term pumping period
- Evaluate the sustainability of the aquifer
- Provide a tool for future well siting
Results of a 10-year transient simulation of constant pumping from the initial four wells in the field indicated that there would be several hundred feet of saturated thickness remaining for future pumping.