Plugs have been widely used for staged fracturing in horizontal wells. But in wells with long lateral or low reservoir pressure, plug milling are far more complex due to debris accumulation and fluid loss.

This study proposed a new multistage fracturing solution for horizontal wells using one kind of ball seat. Researchers have designed mechanical model of the seat. Metal material with great flexibility has been selected out and processed into seats according to the model. The key tools such as elastic seat, large-diameter soluble ball and the matching tools such as cylinder and launching tool were developed. The results of indoor tests and large-scale simulation tests of real parameters have shown that the seat has the capability of repeated rebounding and the capacity of pressure bearing and packing reaches 70MPa. Field tests of 12 horizontal wells, containing totally 115 stages, have been carried out and achieved the technological goals of infinitely large-scale staged fracturing, no milling, and nearly full-bore access. The fracturing cycle has been shortened by more than 30% and the operation cost of single well has been reduced by more than 15%.

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