Evaluation on effect of temporary plugging and diverting in operation of shale gas well fracturing based on ultrasonic imaging logging and suggestion on optimization of technological measures

Abstract

With the application of multi-stage hydraulic fracturing technology in horizontal wells of shale gas, the number of perforating clusters in each section has gradually increased. How to use temporary plugging and diverting technology to improve the opening efficiency of each perforation cluster is crucial to fracturing effect. This paper analyzes the temporary plugging and diverting effect in multi-cluster fracturing by combination of geological characteristics of shallow shale gas in Taiyang structure and perforation hole size inversion from ultrasonic imaging logging data. The analysis result shows that low formation stress is conducive to opening efficiency of perforation cluster. If the density of the temporary plugging balls is large, it is easy to appear unstable plug and sometime fall off the perforation holes. And it is more inclined to plug the holes at the lower perforating section. This aggravates the appearance of non-uniform fracturing and "super hole". The four-parameter method of treating pressure increase, overlaying positive pressure difference, fracture indication (or pressure drop from abrasion) and stop pump pressure increase is proposed. It can provide a more comprehensive and accurate basis for the analysis and evaluation of temporary plugging effect. It is suggested that "variable density temporary plugging balls + temporary plugging agent" or line-connected temporary plugging balls could further improve the temporary plugging effect. This paper have guiding significance for optimization of multi-cluster temporary plugging fracturing scheme in horizontal wells.