Uncharted Waters: What Can We Learn From Waters Produced From Horizontal Wells in the Permian Basin?

Abstract

use total ion chemistry and isotope geochemistry to differentiate waters from different hydrocarbon bearing zones as one direct indicator of the zones accessed by induced fractures in horizontal wells. Additionally, using these chemical data, we can distinguish water injected during fracture stimulation (frac water) from subsurface waters in the production flow stream. Because frac water is easily distinguished from formation water, we are able to determine that water produced immediately on flowback is dominantly formation water. Frac water returns to the surface as periodic or episodic slugs of mixed formation and frac water, with the frac water contribution typically about 50% or less of the produced water load. Accordingly, the industry practice of monitoring frac water load produced at the surface is relevant only in terms of volume, not water composition, since most of the water produced initially during well flowback is formation water. In another example, two horizontal wells, A and B, were producing significant volumes of water relative to surrounding horizontal wells in the Wolfcamp formation in the Permian Basin. Utilizing microseismic data, we were able to identify a transcurrent fault system with sub-seismic splays that we believed could be affecting water production in the two wells. Water samples were taken from Wells A and B and four additional horizontal wells nearby, which targeted the same producing formations in wells A and B, as well as the underlying formation. Utilizing ion and isotope chemistry data, we were able to show that waters produced from wells A and B were dissimilar to water produced from nearby wells in the same formations, as well as water produced from the immediately underlying formation. We conclude that water in wells A and B were being produced from the fault system and associated sub-seismic splay, and not from the host formation. Microseismic data and production logs showed that the fault splay intersected our horizontal well, providing insight for specific remediation that can be performed to cement off and isolate the majority of the water productive interval.