According to the geological characteristics of oil and gas reservoirs and the technical requirements of development and exploitation, the process of establishing a reasonable communication channel or way between the oil and gas reservoirs and the wellbore at the bottom of the well is called well completion(Well Completion).
1. Completion Technology Completion requirements
- 1). The optimal connectivity conditions should be maintained between the oil and gas reservoirs and the wellbore to minimize the damage to the oil and gas reservoirs;
- 2). The seepage area between the oil and gas layer and the wellbore should be as large as possible to minimize the resistance of oil and gas entering the well;
- 3). It should be able to effectively seal oil, gas and water layers, prevent gas channeling or water channeling, and prevent mutual interference between layers;
- 4). Sand production should be effectively controlled to prevent wall collapse and ensure long-term production of oil Wells;
- 5) Stratified treatment measures such as stratified water injection, gas injection, stratified fracturing and acidification should be available to facilitate artificial lifting and downhole operation;
- 6). For heavy oil reservoirs, heavy oil production can meet the requirements of thermal recovery (mainly steam huff and puff and steam flooding);
- 7). The conditions of sidetracking directional Wells and horizontal Wells are available in the later stage of oilfield development;
- 8). The process is as simple as possible and the cost is as low as possible;
2. Completion method
- 1). Perforating completions are divided into casing perforating and liner perforating;
- 2). Open-hole completion (open-hole);
- 3). Slotted Liner completions;
- 4) Gravel packing completion methods are divided into open hole Gravel packing, casing Gravel packing and pre-packed Gravel screen;
3. Wellhead installation for completion
A well is composed of three parts from top to bottom: wellhead device, completion string and bottom hole structure.
Wellhead device mainly includes casing head, tubing head and oil production (gas) tree. The main function of wellhead device is to hang downhole tubing string and casing string, seal the annular space between tubing, casing and two layers of casing to control the production of oil and gas Wells. The key equipment for reinjection (steam injection, gas injection, water injection, acidification, fracturing and chemical injection, etc.) and safe production.
Completion string mainly includes tubing, casing and downhole tools combined with certain functions. Running a completion string to get the production or injection well up and running is the final step in a completion. The type of well (production well, gas well, injection well, steam injection well, gas injection well) is different, and the completion string is also different. Even if it is a production well, the production method is different, and the completion string is different. At present, the main oil production methods include self-injection and artificial lift (rod pump, hydraulic piston pump, submersible electric pump, gas lift).
The bottom hole structure is an organic assembly of tools and strings that match the completion method and are connected to the bottom of the completion string.
4. Completion technology Main steps of completion
- 1). Place ground equipment according to design requirements
- 2). Vertical drill pipe or string
- 3). Install BOP/function/pressure test
- 4). Pipe scraping and well cleaning
- 5). Perforation depth correction
- 6). Fire the stick
- 7). Backsurge/washout
- 8). Scrape the pipe and clean the well again
- 9). Lower packer
- 10). Run sand control string
- 12). Run production string
- 13). Remove the blowout preventer
- 14). Wellhead tree installation
- 15). The unloading
- 16). Acceptance of well crossing