Scope of Application

This technology is applicable for horizontal wells with completed open hole, casing cementation and screen completion. For fracturing improvement for oil sheet and horizon modification near water layer, and transformation of wells with ineffective packer due to broken casing, this technology has obvious technological advantages.

Technical Principle

This technology consists of conventional string drag type hydraulic sand blasting fracturing technology and immovable string type hydraulic sand blasting fracturing technology.

(1)Conventional string drag type hydraulic sand blasting fracturing technology

Tool string with blasting gun is put down by tubing or coiled tubing to complete one stage hydraulic sand blasting fracturing. After choking and killing, the string is dragged into the next well section for further construction. Maximum 5 sections can be constructed at one time.

(2)Immovable string type hydraulic sand blasting fracturing technology

Hydraulic sand blasting fracturing tools with sliding sleeve are put down into the well at once. After the completion of the first stage construction and fracture closure, a ball is thrown into the well through the wellhead plug valve. After the setting of the ball on ball seat, the casing gate is open and the second staged fracturing is carried out. Well sections are fractured successively.

Construction Tools

(1)Compositions of conventional string drag type hydraulic sand blasting tool

(From bottom to top) guiding shoe + screen + lower centralizer + blasting gun + upper centralizer + N80 external upset tubing + deeper pup joint+ N80 external upset tubing + hanger. Steels with N80 grade and above shall be adopted for cross-over. The temperature and pressure resistance of the technique strings are 149 ℃ and 70 MPa respectively.

Structure Diagram of Drag Type Hydraulic Jetting Tool 

(2)Composition of immovable string type hydraulic sand blasting tool

Guide head + perforated pipe + non-return valve(ball diameter Φ22mm) + centralizer + unclosed blasting gun + centralizer +27/8 ″upset tubing + centralizer + sliding sleeve type blasting gun + centralizer + 27/8 ″ upset tubing + 27/8 ″ external upset safety joint + 27/8″ upset tubing + tubing hanger Immovable string can be divided into 5 fracturing stages. The temperature and pressure resistance of the technique strings are 149 ℃ and 70 MPa respectively.

(3)Composition: The sand blasting gun consists of an unclosed blasting gun assembly at the bottom and a sliding sleeve type blasting gun on the top. The outer diameter of the blasting gun body is 108 mm and that of the centralizer is 116 mm. Every blasting gun is equipped with a 6×φ6.0mm nozzle assembly and the nozzle is arranged spirally in 120 ° . Nozzle is made by materials like diamond, super rigid alloy and ceramics, etc..

Structure Diagram of Immovable String Type Hydraulic Sand Blasting Tool 

Technical Features

⑴ Conventional string drag type hydraulic sand blasting fracturing technology

① Tools used in downhole are simple and short in length.

② The outer diameter of the tools are small.

③ Backwashing channels are available.

④ The possibility of string stuck in sand is low.

⑵ Immovable String Type Hydraulic Sand Blasting Fracturing Technology

① No string moving is required during fracturing construction.

② The outer diameter of the tools are small.

③ Backwashing channels are available.

④ Construction is limited by high wellhead pressure and well depth.

Service Ability and Performance

At present, hydraulic jet sand fracturing technology has become one of the most important fracturing and production stimulation methods. Currently the company has carried out field construction on 15 wells at each major oil field in China with a success rate of 100%. The average stimulation amount for a single well is 625t and the yield increases significantly.