Teasing Meaning Out of a Tangle of Fracturing Data

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The snarled red lines on the chart look more like a plate of spaghetti than a source of fracturing insights. It looks like a meaningless mess, which is generally how the ups and downs of difficult stages are viewed. To Adam Hoffman, a completion engineer for Chesapeake Energy, those 47-stages-worth of data look like a valuable opportunity. “We see so many stages with so many odd spikes and drops or chatter. We chop it off and say that was an odd stage. In my mind when we are looking at all those stages, we should wonder, ‘what was that pressure spike telling us,’” he said. That curiosity became a research project after Chesapeake encountered a spate of blockages in recently fractured Eagle Ford wells. The investigation into the cause of the casing damage led to a collaboration with Well Data Labs to look for connections between pressure changes and what is happening in the wells. Based on hundreds of stages of data from 19 wells fractured in the Eagle Ford, and later in the Powder River Basin, they reported finding a distinctive pressure signature that provides a reliable, but not foolproof, guide to when casing damage is likely. Well Data Labs has automated the search for those signatures as it looks for the meaning of the terabytes of fracturing data in this overwhelming number of seemingly random, squiggly lines. The oilfield data and software company is working on ways to monitor changes in the fracturing-fluid chemistry, the proppant intake into perforations, and an explanation for the pressure spikes seen before the pressure falls, said Jessica Iriarte, research manager at Well Data Labs. The troubleshooting and pressure analysis were covered in paper SPE 201484 presented at the 2020 SPE Annual Technical Conference and Exhibition (ATCE). It described how engineering trouble-shooting revealed that geological stresses were the likely source of problems in one case, and faulty pipe in the other. It followed up with data analysis, which used machine learning to identify distinctive patterns that provide an early warning of what is happening in the well faster and more objectively than a completion engineer studying the chart. Based on the troubleshooting, Chesapeake made changes that largely eliminated those costly problems. But it was also a costly learning process. In the Eagle Ford, they identified the underlying problem by investigating why multiple coiled-tubing runs were blocked while they were trying to drill out plugs after fracturing. When that happens, Hoffman said, “it can mean a week lost working past it.” Failure to drill out a plug can block access to the productive rock further down the lateral. A reliable automated treating-pressure analysis in the daily report could alert the completion team to problems while fracturing is in progress. They could then make adjustments on later stages and create a plan to limit the time lost when drilling out plugs on stages where they are likely to encounter tight sections.