The idea of using hydrocarbons to coax more hydrocarbons from tight rock is showing additional real-world promise, as demonstrated by recent field tests in Texas.
In one of the latest examples, private shale producer BlackBrush Oil & Gas said it achieved two notable outcomes in a remote section on the southwestern edge of the Eagle Ford Shale.
The first involves enhanced oil recovery (EOR) using unfractionated natural gas liquids (NGLs), also known as Y-grade, to see a 50-fold production boost from a mature shale well. The second phase of BlackBrush’s strategy involves replacing water with condensate to hydraulically fracture horizontal wells.
Kevin DeLapp, vice president of reservoir engineering for BlackBrush, said the pilot well on flowback in June was “dramatically outpacing our water fracs” after it delivered a 60-day total 15,000 bbl above that of nearby slickwater wells.
“That is native oil, so after we’ve extracted the condensate, which is a nice improvement,” he added.
Apart from using condensate, DeLapp described the 7,500-ft lateral section as receiving an otherwise contemporary completion design of about 2,500 lb/ft of sand across 10 stages.
San Antonio, Texas-based BlackBrush operates in the Chittim Ranch area of south Texas which is well out of the Eagle Ford’s fairway to the northwest. Due to a complex geologic history, the formation there produces a low-API-gravity crude and lacks the reservoir energy needed to move large volumes of fluids naturally—making it a strong candidate for EOR.
Results published earlier this year in SPE 224381 showed how after three huff-and-puff cycles using Y-grade, a struggling 7-year-old well that was producing 18 B/D was able to turn out more than 1,000 B/D over a 5-day period.
Put another way, in less than a week, the well recovered about 75% of what it was expected to produce over an entire year. The same well also had a 1-day peak of just 760 B/D when it came online in 2017.
To get these kinds of numbers, BlackBrush first committed to a 3-year effort to model and plan for the project.
