In this paper, the hydraulic jet volume fracturing technology was developed for thin interbedded formation with thin oil layers and close to water layers. Not only can it precisely control the location of fractures initiation, but also can achieve simultaneous initiation of adjacent thin reservoirs, communicate fractures in the interbedded formation, and accomplish volumetric fracturing. Based on the mechanism of hydrodynamic sealing and stress interference between cracks, a corresponding hydraulic jet fracturing tool was developed. Meanwhile, the design and optimization of nozzles, displacement of pumps and the prediction methods of pump pressure were given. The combination of sliding sleeve and pitching ball can flexibly realize the simultaneous fracturing of multilayer-section. The results of field tests indicate that this technology can effectively minimize the pump pressure and greatly decrease the amount of fracturing fluid. As a result, the construction costs and operating risks can be effectively reduced. Production data manifests that the technology can activate "dead wells", improve reservoir permeability, and increase reservoir productivity.

1. Introduction

When the oilfields enter the late stage of production, the water cut of oil wells increased significantly. Some wells would even completely lost their production capacity. Besides, with the increasing development of tight reservoirs, hydraulic fracturing has become the key technology to improve formation permeability and oil-gas production (An et al., 2020; Dontsov, 2021; Huang et al., 2020; Li et al., 2012; Xiao et al., 2021; Zhong et al., 2021). However, conventional hydraulic fracturing technology has a high construction cost. Moreover, it is also not suitable for well sections with screen completion or poor quality of cementing (Zhang and Hascakir, 2021; Mou et al., 2021).

The development of thin interbedded oil layers requires the precise control of the fracturing position. It is necessary to open up the reservoir while protecting the environment and avoiding contamination of adjacent reservoirs. Based on this, the technology of hydraulic jet fracturing was developed (Surjaatmadja et al., 1998). This technology integrates hydraulic sandblasting and fracturing, achieving the purpose of fracturing multiple sections of the string in one trip without packers (Love et al. 1998). The fracturing process can effectively save the fracturing fluid, reduce construction costs and the risk of sand stuck pipe strings, and has achieved good results in major oilfields all over the world (McDaniel et al., 2002).

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