Multi Mini-Frac for In-Situ Stress Evaluation Using Real-Time Intelligent Coiled Tubing and Inflatable Straddle Packer a Field Case Study

Abstract In subsurface environments with limited data availability, accurate in-situ stress characterization is crucial for optimizing future reservoir development, particularly in appraisal wells where formation properties remain unknown. This case study presents a methodology for conducting multi mini-frac tests to determine the horizontal stress of the formation in a newly drilled appraisal well. The approach leverages a custom-engineered inflatable straddle assembly, deployed via Intelligent Coiled Tubing Technology (ICTT) to ensure precise depth placement and enhanced operational control, both critical for the safe and efficient execution of the procedure. A 140-meter-long tubing-conveyed perforation (TCP) was executed using ICTT, enabling controlled perforation within the target interval and real-time operational monitoring. Given the necessity of conducting multiple mini-frac stages across such an extensive perforated section, a four-stage custom-designed inflatable straddle assembly was implemented, incorporating: Inflation/Deflation Control, Displacement or Circulation, Pressure Shut-in (Formation/Inflation Monitoring), Test Zone Exposure to the Work String for real-time pressure bleed-off assessment. The straddle assembly, equipped with reinforced rubber elements, was set in the perforated interval, an area inherently prone to mechanical deformation and damage to rubber elements due to liner conditions post-perforation. To capture critical formation response parameters, a dual-gauge carrier was integrated between the packer elements, embedding memory gauges with a 96-hour operational lifespan to sustain extended test durations. Additionally, check valves were removed from the ICTT motorhead assembly, enabling direct formation response measurement and precise control of post-frac leak-off dynamics. A low-viscosity, non-crosslinked product was selected to accurately determine the true horizontal stress of the formation, ensuring fracture sustainability without premature closure. The absence of proppant or solid particulates was mandatory due to the intrinsic operational constraints of the straddle packer, which cannot accommodate solid-laden fluids. However, the use of a low-viscosity fluid system also introduced operational risks, particularly with fluids utilised in the process of inflating the packers. This necessitated the integration of a contingent deflation mechanism, and precise fluid control strategies to mitigate risks and ensure the reliable operability of the inflatable straddle assembly The multi mini-frac tests provided clear formation data, enabling a determination of in-situ horizontal stress. The use of real-time ICTT facilitated continuous monitoring and precise operational control, enhancing data acquisition reliability throughout the process. Despite the operational constraints of using a solid-free, the low-viscosity fluid successfully initiated and sustained the fracture while gradually dissolving over time, preventing premature closure. The additional deflation mechanism remained a contingency measure, ensuring operational safety and packer retrieval efficiency in case of unexpected situation.