Multi-layer fracturing technology is challenging because of the risk of packer failure and high cost in the deep thick formation. It depends largely on the effectiveness of packer tools. However, a new degradable fiber ball could be successfully used to temporarily block the open perforations, and then the layer with higher fracturing pressure is broken down. This paper presents a new tool-less layered fracturing technique and its pilot test results with this special material.

A series of laboratory experiments were conducted to evaluate the feasibility of this new technique. Degradable fiber balls were applied to perforated pipes under simulated reservoir conditions. The ball carried by the fluid first sealed the perforation holes and then increased the pressure in the pipe to simulate the resistance to pressure. In addition, the fluid was heated up to 140°C to simulate the degradation rate of fiber balls. Throughout these processes, the flow rate, temperature and pressure were continuously monitored for subsequent analysis.

Experimental and application results showed that: (1) fiber balls could be thoroughly degraded at 140°C temperature after six hours; (2) at a pressure difference of 50-70MPa, its deformation rate was less than 1.5%, which indicated its higher compression capability; (3) it could effectively block the perforation holes at 90°C and a pressure difference of 20MPa; (4) The blockage of perforations by the fiber ball could significantly enlarge the net pressure in the wellbore. This technique was applied for 35 wells in a deep and thick oil reservoir, which had achieved a great success and the post-treatment oil production was enhanced by 50-60% compared with conventional stimulation techniques.

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