Successful Application of Integrated Fiber-Optics with Coiled Tubing Operations Enhances Acid Stimulation Treatment

Abstract Matrix-stimulation methods are often applied in Carbonate reservoirs to ensure uniform distribution of treating fluids / acid and successful stimulation in the hydrocarbon-producing wellbore. The treating fluids typically take the path of least resistance (or high permeability zones), thereby requiring the use of diverters for effective stimulation of low permeability and/or damaged zones. However, under downhole conditions, it is challenging to directly determine, measure, or simulate the effect of a specific acid / diverter operation. As a possible solution, distributed temperature sensing methods can be used to understand the complex downhole dynamics, effects of treating fluids on the formation (through transient temperature response) and most importantly, qualify and quantify the success of a stimulation operation. Of interest to this study is a horizontal, open-hole producer well in the prolific Carbonate formation in one of the major fields. As part of the objectives to effectively optimize acid and diverter placement, an integrated fiber-optics enabled coiled tubing intervention operation was planned for this study. The technology involved deploying a 2.375-in. coiled tubing string with a 0.125-in. tube wire housing a triple fiber-optic cable. Distributed temperature sensing (DTS) measurements were taken at several stages of pre-and-post stimulation that involved visualization and interpretation of temperature traces to identify fluid distribution and optimize acid-diverter strategy. In a systematic process, DTS surveys at depth for two scenarios: well base-line conditions followed by pre-stimulation solvent treatment were first conducted. The DTS analysis included heat maps and transient temperature curves along the entire wellbore. Comparisons between the baseline and pre-stimulation flush conditions provided qualitative insight into areas of the well that took a greater proportion of the pre-treatment fluid. This information was then used to revisit the original acid-treatment plan and update the stimulation plan to optimize the acid-diverter placement in target zones. As part of the optimized strategy, 45% of the open hole was treated with a proprietary acid-diverter system and the remaining 55% with 20% HCl acid. This unique approach of fiber-optics enabled coiled tubing operation and analysis resulted in an optimized acid program reducing the total acid volume by over 30%, thereby saving the operator around 20% from the allocated budget on this well. In summary, the data presented here demonstrates that the distributed nature of fiber-optics monitoring in conjunction with intelligent coiled tubing and pumping strategies can be effectively used to improve and optimize future acid-stimulation jobs.