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Basic Knowledge
7.7 Horizontal well cementing slurry system
  • Detailed description
The enhance of the well drilling and well logging technology accelerate the success rate of horizontal well and decrease the drilling cost. And the success of the horizontal well drilling, has make the oil and gas productive of single well three to five times larger than vertical wells, and sometimes even 10-20 times. Practice has proved, the horizontal well can not only successfully used in low permeability reservoirs mining, fractured reservoir and thin reservoir, and make oil and gas production sharply increased, and also can do the second exploration and development in maturing field, and mine the remaining oil which cant be mined in the past at the max.
The horizontal cementing slurry system performance requirements
The function of horizontal cementing is 1. Seal the cement injection interval.2. Support and protect the casing. 3. The intermediate media of perforation. 4. Confirm not strong sand layer. 5. Control stratum pressure. Succeeded in horizontal well cementing project, it must consider all the cement comprehensive performance to ensure that has good replacement effect. At the same time, it necessary to keep every permeable formation sealed, and some performances in the horizontal cementing are more important than these in small angle well. The two cement performances which should be considered mainly are stability and the volume of fluid loss. The free fluid of horizontal well cementing slurry required is 0, and the slurry should be stable. The density difference between higher, middle, lower should be small than 0.05g/cm3 (vertical height is higher than 20m). at the same time, the volume of horizontal well cementing fluid loss should less than 50ml, and control the fluid loss should not affect the other performances of the slurry.
Horizontal well cementing slurry’s performance testing method
For succeeded in horizontal well cementing project, all slurry properties must be considered, including free liquid content, dispersion stability. This two indexes performance is more important than them in ordinary well. The testing method of free fluid already has industry standard. But the phenomenon shows that this test method is not suit to this kind special well cementing slurry. This is because the slurry is completely different when it flows by the horizontal well section and vertical well section. So the testing method is different.
The evaluation method for free fluid should be in accordance with chapter 7 of SY/T5546. But the measuring cylinder should be inclined 45°(the volume under this angle is the biggest). Put it into water both and the temperature is the testing temperature.
The evaluation method for dispersion stability. The slurry prepared according to the chapter 4 of SY/T5546 should be pure into the consistometer. Stir it for 20min at the test temperature. And then pour the slurry into the settlement stability test mold which is clean and dry. When the slurry is up to half scale line, stir it 25 times with stir stick. Then fill stir it 25 times. When the mold is fall with slurry, scrape the excess slurry with scraper, put the mode in high temperature and high pressure curing container, when achieve different curing age, put the mode out, cure for 5h in room temperature water, and then cut cement pillars into five pieces from top to bottom, weight each small stone the weight and volume, calculate each density, the settlement ability is represented by the density.
The cement slurry performance requirements of fluid loss property, rheological property, settlement stability and free fluid content exists contradiction, so the choice to the horizontal well cementing cement additives is very strict, its various performance should meet the horizontal cementing technical requirements.