顺北油气田低压易漏层泡沫水泥浆固井技术

Foamed Cement Slurry Cementing Technology for Low-Pressure and Leakage-ProneLayers of the Shunbei Oil & Gas Field

  • 摘要: 顺北油气田二叠系裂缝发育,地层承压能力低,固井漏失风险大。针对该问题,优选了抗高温抗盐的蛋白质发泡剂和高聚物稳泡剂,二者加量分别为2%~4%和0.4%~0.8%时,泡沫可在120 ℃下保持稳定;研制了密度1.10~1.30 kg/L可调的防漏泡沫水泥浆体系,其流动性好,120 ℃下API滤失量小于50 mL,泡沫水泥石密度差小于0.03 kg/L,密度1.10 kg/L泡沫水泥浆形成的水泥石在低温常压下养护72 h的抗压强度可达7.2 MPa,泡沫水泥浆综合性能优良;研究形成了基于井深、温度和压力的环空分段充气设计方法,充气量根据井深、水泥浆密度和注水泥浆排量实时调整,以保证环空泡沫水泥浆密度上下均匀。基于上述研究成果,形成了顺北油气田低压易漏层泡沫水泥浆固井技术,并在该油气田2口井封固存在低压易漏层的二叠系时进行了应用,泡沫水泥浆均成功返至地面,固井质量优良。该技术为顺北油气田低压易漏层安全高质量固井提供了技术途径,也可为其他区块裂缝性地层防漏固井提供了借鉴。

     

    Abstract: Permian strata in Shunbei Oil & Gas Field display a high level of fracture development, low bearing capacity, and a high risk of cementing leakage. In order to solve these problems, a protein foam agent and a polymer foam stabilizer with high temperature and salinity resistance were selected. Their dosages were optimized to be 2%–4% and 0.4%–0.8%, respectively, which could make the foam stable at 120 °C. In addition, an anti-leakage foamed cement slurry was developed with adjustable density ranging from 1.10–1.30 kg/L. The slurry has good fluidity, with API filtration of less than 50 mL at 120 °C. The density difference of foamed cement rocks was less than 0.03 kg/L, and the compressive strength of rocks with foamed cement slurry with density of 1.10 kg/L can reach 7.2 MPa after 72 h under low temperature and atmospheric pressure, which showed that the comprehensive performance of foamed cement slurry was excellent. Based on the well depth, temperature and pressure, the annular segmented aeration method was designed, and the aeration volume was adjusted on the fly according to the well depth, cement slurry density, and slurry displacement, which ensures uniform cement slurry density. According to the above results, the foamed cement slurry cementing technology for the low-pressure and leakage-prone layers of the Shunbei Oil & Gas Field was developed and applied in two wells, and the foamed cement slurry was back to the ground successfully, with good cementing quality. This technology supplies a way for the safe and high-quality cementing of low-pressure and leakage-prone formations of the Shunbei Oil & Gas Field and provides a reference for anti-leakage cementing of fractured formations in other blocks.

     

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