Study On Cement Slurry System For Long Wells With Large Temperature Difference

As the oil and gas fields are being further explored and developed, more and more deep wells and ultra deep wells are drilled. The complex factors such as deeply oil&gas reservior and higher temperature in bottom hole often results to larger temperature differenc between the top and bottom of long isolation section. This put forwards higher requirement on cement slurry performance to ensure the cemet slurry can be safely pumped in high temperature condition and the early strength of lead slurry can quickly develop. This also results to more challenges on the cement slurry design. To solve the above mentioned problems, we should study the cement slurry system on the cement strengthen material and cement additives.This paper aims to at solve the ultra retarding problems existed in the top of long isolation section through the combination of theoretical research and experimental research. New cement strengthen material and cement retarder, fluid loss additive are developed, the cement slurry system matched with deep well and ultra deep well is optimized.Firstly, the new cement strength material GWB-1S is developed, it can adapt to the temperature of 90 ~170 ℃ and assure the strength of slurry can reach 10 MPa in 24 hours. Its dosage is 13~ ~ 20 % of dry cement content.Secondly, new fluid loss additive GWF-200 L is developed. It can adapt to the temperature of 60~170℃, and has the properties of anti-salt. It is easy to adjust the slurry thickening time and rapid to develop the strength of slurry when GWF-200 L is used in the slurry.Thirdly, the new cement retaeder such as GWR-100L(60~120℃) and GWR-200L(120 ~170℃) are developed, which have the properties of little dosage and no effect on the cement strength.Fourthly, the slurry system is devided into three temperature sections, that are 90~105℃, 105~135℃ and 135~145℃. The slurry under the corresponding temperature section is optimized. This can decrease the quantity of cementing equipment, simplize the cementing operation technology and lower the operation cost.Fifthly, newly developed cement slurry recipe adapting to the temperature of 90~170℃ is optimized with the new cement strength material, new cement retatder and new fluid loss additive. The indoor tests show that the performance of the new slurry system is good.All the field application further prove that the optimized slurry system are good, reliable. And all the cementing quality operated in Liaohe oilfield are excellent. It is worth popularization and massive application in deep well and ultra deep wells.