Figure 1. TVD vs MD plot of the heel of the well, where several stages were landed below the target zone
Completing unconventional wells requires the successful, tandem execution of many complex operations, from design to execution of landing zones, stimulation and cluster/stage design. Any single sub-optimal element in design or execution may result is a poorly producing well. Chief among the steps necessary for
When the lateral of an unconventional well crosses multiple zones, diagnostics are critical in evaluating and comparing the relative productivity of each layer, allowing future wells to land in better rock for improved
In this case an operator landed a few of the heel stages in a lower layer than initially desired (Figure 1). They suspected these stages may not be contributing as much or as uniformly to production as the stages landed in-zone. Since they were unable to determine productive clusters by surface production rates alone, they elected to collect enhanced diagnostics to determine where production was coming from across the lateral to correlate production with landing zone.
Because they were interested in cluster level diagnostics and anticipated the out-of-zone clusters may be producing at rates below the threshold of an array spinner, they opted to deploy Z-System® carbon rod – a dip-in fiber optic well intervention system - to acquire distributed acoustic (DAS) and temperature data (DTS) across the lateral for
The Z-System® was dispatched to the well site, rigged up and the spool of carbon-fiber rod was injected into the well while it was producing. Since the 0.6” OD rod does not choke flow, even in
The distributed acoustic data is analyzed and a qualitative allocation of production from each cluster is determined, based on the proportional relationship between the flow rate from a cluster and the noise produced. Then, a temperature model, based on the DTS data and constrained by the acoustic analysis, allocates and quantifies production per cluster.
Figure 2. Clusters in stages landed out of zone (upper) indicate poor uniformity and lower productivity compared to clusters landed in the target zone (middle and lower), where more uniform and productive clusters are observed.
Comparative analysis of cluster performance in upper (target) and lower (out-of-target) landing zones across the lateral confirmed the customer’s suspicion of reduced performance in the lower layer, where 30% less production is observed in the lower zone.
Newly drilled wells are now targeting this ideal zone revealed through Z-System® deployable fiber optic diagnostics.