Abstract

Abstract The global horizontal well fracturing market has grown tremendously in the last decade with the increase of multistage fracturing operations. Many of these wells are cased and cemented and had a sequence of a plug and a series of perforations for each stage of the fracturing process. Intervention optimization became a key element for work efficiency and thus cost reduction. A common approach worldwide is to pump-down the plug combined with a few guns and initiate the firing downhole sequentially using switches. Despite the efficiency of this technique, it requires an overflush after each fracturing stage to clean the wellbore of leftover proppant and allow free passage of the plug and guns to be pumped down. Unfortunately, overflushing hampers the fracture's performance because it allows the fracture to close near the perforations. This effect on productivity is now being realized on these overflushed wells, although these wells were once constructed very efficiently. To move away from overflushing, some operators switched from pump-down to coiled tubing (CT) conveyance of the multiple guns. Conventional CT or CT with electric wireline were used, and each technique has its own advantages and limitations. A newer technology is CT equipped with fiber optics in combination with an optic-based selective perforating system that enables the firing of multiple guns in a single run. This technology combines the advantages of both the conventional CT and the CT equipped with wireline cable. Equipped with gauges, the CT equipped with fiber optics also permits better acquisition of fracture data in horizontal wells. The result is a more efficient operation, better fracture evaluation, and well productivity enhancement by avoiding the damaging effect of overflushing. After an evaluation of current conveyance techniques, an implementation trial of the new technology on multiple fracturing stages was performed in a horizontal well in Oman. The first trial showed successful application of the technique, especially the accurate real-time gamma ray and casing collar locator (GR-CCL) correlation of the multiple short guns. Even more important was the successful placement of the proppant into the formation during the hydraulic fracturing process. The technique was shown to be efficient while mitigating the possible damage to the formation.

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