Optimization of Stimulation Treatments in Naturally Fractured Carbonate Formations Through Effective Diversion and Real-Time Analysis

摘要

Long horizontal open holes and naturally fractured reservoirs have always presented a challenge to the industry for successful matrix treatment operations. This is particularly true in western Canada where the reservoirs are competent carbonate formations completed open hole over a length of 2,000 m with a bottomhole static temperature of 110°C. These naturally fractured formations exhibit substantial and unpredictable permeability variations over the length of the interval. During treatment, all or part of the acid may thief to a high-permeability interval leaving the rest of the wellbore poorly stimulated. The industry has developed a range of products and techniques to divert the stimulation treatments from these thief zones in an attempt to improve wellbore coverage and reservoir drainage. However, the placement of these diverting techniques and the evaluation in situ and in real time of their effectiveness were yet to be accomplished. An innovative technique, developed in Western Canada, combines state of the art viscoelastic acid diversion with fiber optic technology for accurate downhole fluid placement and optimum diversion effectiveness. This is a unique system consisting of live downhole temperature and pressure measurements transmitted to surface through fiber optic telemetry installed in the coiled tubing (CT). Real-time analysis of distributed temperature survey (DTS) and single-point downhole measurement of temperature and pressure, along with petrophysical data, provide an in-situ visualization of the dominant thief zones. The analysis of this information allows for on-the-fly adjustment to the diversion placement schedule matching current downhole conditions. This technique provides a unique way to ensure the entire pay zone is fully and homogeneously stimulated, optimizing the reservoir contact and delivering the full well potential. The technique was systematically applied to all newly drilled wells in the Suncor Panther field in the western Canadian Rocky Mountain foothills. The comparison of gas production over the entire field for 16 new wells illustrates that results have substantially improved since the introduction of this innovative technique.