1. Features
For the existing problems in cementing and completion for the horizontal wells, a selective completion technology is created for complicated and unconventional  wells. It has been successfully applied.
    The selective completion, in contrast to the non-selective completion, uses various BHAs to divide the formation into several zones (sections), so as to stimulate to or produce from different zones later. The selective completions for horizontal well include: cemented casing combined with screen, external casing packer combined with screen, external casing packer, sliding sleeve combined with casing, and fully cemented & perforated completion.

Cemented casing combined with screen.
Liner hanger is used and composite liner string is composed of casing and screen. Upper casing part will be cemented up to the liner hanger. The casing is tied-back to the top of liner hanger, and upper cement returns to surface. The screen is used at the front of the horizontal section. The cementing interval is dependable on reservoir properties.
Combination of screen and external casing packer.
The set-up is used in the horizontal section. The structure depends on oil, gas and water conditions in the horizontal section. The design gives out selectivity: the, screen can take advantage of horizontal section to enhance the productivity and the external casing packer and casing section can seal off the unnecessary zones and realize multzone stimulations. This technique is applicable to the wells with high production rates and heterogeneous interval in the horizontal section, easy collapse formation or near bottom or edge water interval.
Combination of sliding sleeve and external casing packer.
Liner hanger is used and composite liner string is composed of casing and screen. Upper casing part will be cemented up from deviation point to the liner hanger. Combination of sliding sleeve, external casing packer and sliding sleeve is used for the horizontal section. The quantity and positions of sliding sleeves depend on geology and reservoir, gas and water distribution and gas volume in the produced fluids in the horizontal section.

2. Application.
The technique has been used in Jilin, Daqing Sichuan, Tarim and Karamay oilfields.

3. Selective cementing and completion services for horizontal well.
It involves the following steps:
■ Collection and analysis of formation data; completion programs design..
■ Selection and optimized design of cementing completion service in a horizontal well.
Providing completion programs and recommending structure design of completion strings..
Adjustment of products in response to the design and actual formation conditions to realize the desired results and maximum productivity..
Optimization of associated completion tools..
■ Available associated products and tools..
■ Site completion operating technical service.