Research On The Safe Unsetting Multi-stage Fracturing String

Since shale and tight sandstone reservoir has the characteristic of longitudinal span, multiple oil layer and the large thickness, it is required to use the multi-stage fracturing techniques to satisfy the high efficiency development. However, it is difficult and need more time to install and unsetting the complex multi-stage fracturing string with the easier sand blocking problem. The higher risk of downhole accidents will cause schedule delay, the reservoir stimulation failing, and the abandon of the whole well.Therefore, the unsetting safety of multi-stage fracturing string is studied in this thesis, which includes: safety factor analysis of the multi-stage fracturing process, technology of safety unsetting multi-stage fracturing string, the improvement of the safety unsetting fracturing tools, safety installment process design and the indoor and field safety performance test. Two sets of multi-stage safety reopened fracturing strings and the matched easier unsetting fracturing packer with other security unstuck tools are developed. With the help of the safety installment process, the unsetting can satisfy the safety, high efficiency and economy of the construction of the multi-stage fracturing string.