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Retrievable Seat Sliding-Sleeve Open-hole Staged Fracturing Technology

Scope of Application

This technology is applicable for 6" open holes.

Technical Principle

This technology can isolate horizontal well into several sections with packer and sliding sleeve according to the need of reservoir development. During fracturing, sliding sleeve is opened through drop-ball ejection and specific construction can be carried out accordingly. Dedicated switch groove is designed for the outer sliding sleeve of the drop-ball double-layered sliding sleeves, so as to match with the size of the outer teeth of the special tool for switch’s outer sliding sleeve. The sliding sleeve inside ball seat is fishable. After fracturing, fishing tools can be lowered into the ball seat to fish all the inner ball seats at once.

Diagram of Outer Sliding Sleeve Switch Tool

Structure Diagram of Double Sliding Sleeves 


Main tools:


Diagram of Retrievable Seat Sliding-Sleeve BHA


① Release/Tie-back mechanism—The release/tie-back tool of the top packer is connected with the drill rod or fracturing string. Turn 90° right for top packer releasing and turn 90° left for seal connection.

② Top packer (hanger assembly)--No other auxiliary tool is required when setting and the setting pressure is 3500psi.

③ Open hole packer—Two layer sealing with adjustable packer setting pressure. Initial setting pressure: 9.9MPa; temperature resistance: 149 ℃ .

④ Drop-ball double-layered sliding sleeves—After fishing the inner sliding sleeve, consistent inner diameter of the tool can be achieved. The outer sliding sleeve can be closed or opened as required, so as to realize a selective secondary fracturing. This technology can realizes fracturing in 18 stages.

⑤ Differential pressure sliding sleeve (constant pressure sliding sleeve)—The pressure of opening the differential pressure sliding sleeve can be adjusted. The shear stress when opening the sliding sleeve is 19.7MPa and the temperature resistance of the sliding sleeve is 149 ℃ .  

Technical Features

⑴ The double-layered design of the drop-ball double-layered sliding sleeve enables a one-time fishing of all the inner ball seats and a full bore realization.


⑵ The outer sliding sleeve can be closed or opened as required, so as to realize water plugging or staged selective water injection of the horizontal well. Service Ability and PerformanceAs of June 2013, the open hole horizontal well fishable ball seat double sliding sleeves staged fracturing technology has been successfully applied for 11 wells in China with a success rate of 100%. For instance, in a horizontal segment of a well in Honghe Oil Field which was divided into 10 fracturing stages, tools were put down and setting was carried out smoothly with 217 cubic meters of sand were filled in. After fracturing, fishing and pushing of ball seats were carried out successfully with less than 3 hours spent for each ball seat fishing . A 4" inner diameter was maintained after ball seat fishing and pushing. No steps were established inside the shaft, so that good condition has been maintained for future intervention, refracturing, water plugging detection and so on.