Fiber Optic DAS and DTS in Multicluster, Multistage Horizontal Well Fracturing: Interpreting Hydraulic Fracture Initiation and Propagation Through Diagnostics

Abstract

The application of high-resolution fiber optic distributed acoustic sensing (DAS) and distributed temperature sensing (DTS) during multistage hydraulic fracturing has increased in recent years. However, fiber optic has been used for communication networks, surveillance, and monitoring and diagnosing wellbore integrity for quite some time. The technology has also been used to diagnose reservoir and well performance, e.g., production and injection profiling. Optical fibers were placed in a small stainless steel tube, which was clamped to the casing while running in the hole in a horizontal unconventional gas well. The casing was then cemented in place, and fracturing treatments were completed by limited-entry techniques using the "plug & perf" process, resulting in multicluster (each stage), multistage fractures. Perforations were placed on the topside of the casing, oriented to avoid damaging the optical fiber (zero degree phasing, at 5 shots per foot, one foot per cluster). This paper shares images and results from DAS and DTS data that allow for interpretation of fracturing treatments in multicluster, multistage horizontal wells. The images illustrate the dynamic nature of the spatial and temporal fluid distribution pertaining to initiation, propagation and arrest of hydraulic fractures during simultaneous stimulation of multiple clusters. First, fracture initiation appears not only during early time, as expected, but also late time initiation events may develop in previously dormant clusters. Second, propagation of multiple fractures can occur randomly within a cluster array, and these multiple fractures are sometimes in close proximity to one another. Third, dominant clusters are often observed during stimulation. Further, during the treatment cycle, the position of dominant cluster(s), within a given stage, may actually change. We leverage these observations with various other data sources in a modeling exercise to demonstrate the implications of unequal fracturing fluid distributions on propped fracture performance.

Experimental Study on the Initiation and Propagation of Multi-Cluster Hydraulic Fractures within One Stage in Horizontal Wells

“…For instance, the production logs show that one-third of the perforation clusters in some basins contribute two-thirds of the production, while almost one-third of the clusters in all basins do not contribute to the production [6]. Other scholars [7][8][9][10] have reached similar conclusions.…”

Spatial distribution of production in a Marcellus Shale well: Evidence for hydraulic fracture stress interaction

“…However, because there is no means of directly controlling the partitioning of the fluid, uniform partitioning of the fluid is probably seldom attained even in an approximate sense. For example, recently-published Distributed Acoustic Sensing (DAS) data shows dominant clusters within 9-10 cluster stages take around 30% and around 70% of the fluid (and proppant) in the two examples given, respectively (Sookprasong et al, 2014).…”

Four critical issues for successful hydraulic fracturing applications

“…For example, distributed acoustic sensing (DAS) using fiber optic sensors along a horizontal well in a shale reservoir shows good initiation from all 9-10 clusters in each stage of this study. However, as the treatment goes on, one cluster dominates, taking in total 30%-70% of the fluid and proppant that is injected (Sookprasong et al, 2014). Similarly, growth from multiple perforation clusters but with dominance of one cluster can be inferred from microseismic data from the Barnett Shale (Daniels et al, 2007).…”