Source(s) of Produced Water in the Permian Delaware Basin, West Texas: A Geochemical Analysis

摘要

The Permian Delaware Basin (DB) is one of the most desirable regions for production of unconventional oil in the United States. While extended horizontal wells, stimulated with hydraulic fracturing, can recover economic volumes of oil in the DB, this production is often associated with large volumes of water. Relatively high water-oil ratios (WORs) can erode the value of producing wells. This of course begs the questions: where is the water coming from and why is so much being produced? This study shows that the produced waters (PWs) are primarily in-situ Wolfcamp shale formation water and not water associated with hydraulic fracturing or well completions. This conclusion is based on the observation that the Wolfcamp shale formation water has an oxygen isotopic composition of ~6.5 ± 0.5 ‰ (SMOW) and a salinity of ~23 kppm. These oxygen isotopic data and salinities are consistent with illite-water equilibrium at peak burial conditions.