Water Hammering Evaluation in Perforation Efficiency for Variable Perforation Designs in Unconventional Horizontal Wells

Abstract The main scope of this paper is to expand the existing efforts exerted in the field of water hammering through the reprocessing of existing post-treatment data in the estimation of perforation efficiency and subsequent fracture geometry. The paper focuses on special applications when perforation designs were varied across subject wells that underwent stimulation through multi-stage hydraulic fracturing. The paper deeply investigates fluctuating pressure behavior noticed immediately after a single hydraulic fracturing stage is pumped, commonly referred to as water hammering. The objective of this paper is to showcase the results of examining water hammering signatures across different perforation designs and linking these variances to perforation efficiency, by zooming into the variability of the water hammer amplitude magnitude, and its incremental difference from one perforation design to the next, or from one well to the other. Two application examples are highlighted in the paper: the first evaluated a horizontal well with three different perforation designs, while the second compared a standalone well to an offset well with identical drilling and completion designs. For the first application, there was an inverse relationship between perforation efficiency and the amplitude of the water hammer; where higher perforation efficiency was consistently matched with a lower amplitude magnitude resulting from lowering the total number of perforations per stage, and vice versa. For the second application, two offset wells with similar geo-mechanical, drilling, and completion properties were analyzed. The first well had lower perforation efficiency compared to the second, which corresponded to a larger water hammer amplitude confirming the repeatability of the inverse relationship between the two parameters. For both examples, estimating the incremental reduction in the water hammer amplitude corresponded to the same percentage of improvement in perforation efficiency. That variability was the sole focus of this paper at which it was investigated in details and compared to perforation efficiency estimated using other methodologies such as the step-down test. The novelty of this approach is that it capitalized on existing data that is usually overlooked, in detailing the understanding of perforation performance and efficiency in variable perforation designs implemented, or in performing multiple well comparison.