Study on multi pulse fracturing technique of coalbed methane in shallow depth and calculation model of power utilization rate

In order to study an effective technology suitable to develop a high- energy gas fracturing of the shallow depth coalbed methane, based on the principle and study on the high energy gas fracturing, in combination with different lithology features of the seam and oil reservoir, with a series of the experiments and the study on the technical design and experiment, a technology and process of the multi pulse fracturing development for the shallow coalbed methane seam were successfully d eveloped. The results showed that the multi pulse fracturing device designed for the shallow depth coalbed methane increased the total charge quantity ( total power) a nd expanded the time of the pulse pressure role. The design on the fracturing process of the full sealed wellhead had increased the power uilization rate to the seam.W ith the study on the theoretical analysis and the calculation method of the power loss during the multi pulse fracturing process, a power uilization calculation model of t he full sealing multi pulse fracturing was established. In combination with the site Z2- 033 well test, the calculation results showed that the power utilization rate affecte d on the coal seam was about 70%. In comparison with the open wellhead fracturing with similar well performances, the full sealed wellhead fracturing could improve th e power utilization rate about0. 6 ~ 1. 3 times.After the site experiment, the well gauge tool and well logging results would not be affected to the casing.