Leonard Rice Engineers, Inc. (”LRE”) managed the evaluation and development of the groundwater resources and wells on the 28,000 acre Roark Ranch in west-central Winkler County, Texas for Winkler Services, LLC (Winkler). The well field was constructed with the primary objective of providing completion water for nearby oil and gas clients located in the eastern part of the Delaware Basin of west Texas, and it was completed in multiple phases.
In the first phase, we performed a desktop aquifer sustainability study to determine that there is over 700,000 acre-feet of recoverable water within the Pecos Valley Alluvium (PVA) underlying the Roark Ranch. This analysis confirmed that the Roark Ranch is situated over the Cenozoic Monument Draw Trough, a deep paleo channel feature with an anomalously thick section (700 to 900 feet) of productive PVA aquifer material.
In Phase 2, LRE evaluated the groundwater hydrology to better characterize the PVA. LRE oversaw surface geophysical surveys (CSMAT) to assist in locating water wells in the interpreted PVA “sweet spots” on the ranch. The survey’s goal was to discern coarse grained sands and gravels from fine grained silts and clays and then locate production wells where there is a higher percentage of coarse grained materials. Guided by the surface study results, LRE further refined the subsurface geology interpretation by overseeing installation of 20+ borings with borehole geophysics logs.
In the third phase, LRE prepared a 3D geologic model interpretation of the PVA using the surface geophysical surveys and borehole geophysical logs to identify areas on the ranch that would encounter the thickest section of saturated, coarse grained PVA material in the subsurface. Results of the 3D geologic model assisted in selecting the locations of the LRE recommended production wells.
A well field was developed that consists of six groundwater wells located in the northern part of the ranch that produce from both the PVA and underlying Santa Rosa Sandstone aquifer. Conservative well production, with 10-year constant pumping, ranges from 650 gallons per minute (gpm) to over 1,500 gpm with a total production from the six wells of ~5,600gpm (192,000 Bbls/day) of 2,000 to 3,000 TDS water quality and limited drawdown. In addition, 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; and well commissioning.
Finally, LRE completed detailed groundwater modeling analyses 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 and to evaluate the long-term sustainability of the well field. A 3D groundwater flow model of the ranch and surrounding areas was constructed using MODFLOW 2000 to predict transient drawdown over a long term pumping period, evaluate the sustainability of the aquifer, and 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.