Temperature Delta Diagnostics During Coiled Tubing Drillout for Evaluating Post-Fracture Formation Communication

Abstract

The objective of this paper is to demonstrate the use of downhole temperature delta measurements recorded during coiled tubing drillout operations to evaluate formation communication and stimulation effectiveness. The scope focuses on post-fracture plug drillout in horizontal wells, where conventional surface indicators provide limited insight into which perforation clusters are contributing flow during early completion activities. The paper evaluates a self-contained downhole memory sub (recording tool) equipped with high-frequency pressure and temperature sensors positioned near the bit within the drillout bottomhole assembly (BHA). The tool autonomously records time-based temperature and pressure data throughout the operation without requiring surface telemetry or real-time intervention. Post-run data retrieval enables temperature-delta analysis across depth and time. Temperature changes observed while drilling out composite plugs are correlated to plug depth, stimulated interval location, and surface operating conditions to identify relative thermal responses associated with formation fluid movement into the wellbore. Field observations from multiple coiled tubing drillout operations indicate that temperature-delta trends provide meaningful insight into formation communication immediately following stimulation. Zones exhibiting measurable temperature increases during drillout are interpreted as intervals with active fluid inflow, while zones showing minimal or negative temperature deviation suggest limited communication. Comparisons across wells within the same development area demonstrate consistent temperature-delta behavior, increasing confidence in trend interpretation. Pressure-delta data recorded concurrently shows strong correspondence with temperature trends, supporting the validity of observed thermal responses. Placement of the sensor near the bit minimizes uncertainty associated with depth offset and thermal lag. The results indicate that downhole temperature-delta logging during routine drillout operations can provide early, cost-effective insight into stimulation effectiveness without requiring additional logging runs. The conclusions support the use of memory-based thermal diagnostics as a practical supplement to traditional completion evaluation methods. This paper adds to existing completion diagnostics by documenting the use of downhole, memory-based temperature-delta measurements acquired during drillout operations to assess formation communication. The approach leverages routine intervention activity to generate subsurface insight, expanding the state of knowledge around post-fracture evaluation without additional operational complexity.