Who’s Right? Imaging of Fractures Often Delivers Conflicting Measures

Abstract

There are two ways to measure how much entry holes grow due to erosion during fracturing, and the results they offer are often different. This matters because these competing technologies, one using cameras and the other ultrasound, have become an essential tool for measuring fracturing performance. When oil companies run side-by-side tests, there are enough differences in the hole size measurements to raise the question: Which one is right? While the averages and trend lines for the data sets look close enough for engineers used to noisy downhole data, differences in the measures of specific entry holes can be disconcerting for those trying to evaluate performance at the cluster level. “There is quite a bit of disagreement in them, with gaps of up to 100%, and many gaps of 25% or more,” said Tobben Tymons, visual analytics director for EV, the company that pioneered visual imaging. He made that observation when he described the result of a two-well test where EV partnered with Archer to measure entry holes using both camera and ultrasound methods (SPE 212322). The paper presented at the 2023 SPE Hydraulic Fracturing Technology Conference and Exhibition (HFTC) included Fig. 1 comparing the measurements using photos and ultrasound as pairs of colored dots within a stage in a side-by-side well test. The red dots were based on a camera image of the entry holes in the casing; the yellow were based on ultrasound. They show that these tools can deliver significantly different measures for some of the holes. Fig. 1 shows multiple instances where only one method can provide a usable measure. The paper offered explanations for the differences with something engineers often ask for and rarely get—a study offering a detailed look at the pros and cons of competing diagnostic methods. The conflicting numbers shown in the EV-Archer paper were in line with the results of a previous side-by-side test by Chevron which showed similar measurement differences (SPE 209122). At the conference, Hess and ConocoPhillips also offered papers on measurement differences. It’s a hot topic because bad data could lead an operator to invest a lot of money and time on changes that don’t deliver the production expected based on the entry-hole measures in test wells. There is agreement that the accuracy of these data matters. But on the question of which method is delivering accurate numbers, the advice varied widely. The paper by Hess offered this advice: “The technology of perforation imaging has come a long way and drastically improved in recent years; however, there are differences in the detail of the images. The trends are very similar between the compared technologies. The learning is to use one technology and consistently benchmark against it.” When asked about picking one method and sticking with it, Tymons said he “strongly disagrees with the approach.” Using one method avoids seeing the inconsistencies between the two technologies, but no matter which method is used, “there are instances where it is simply wrong,” he said.