干热岩超高温防衰退水泥浆体系及应用

Ultra-high Temperature Resistant Cement Slurry and Its Application in Hot Dry Rock

干热岩长期高温导致水泥石强度衰退,易造成套管挤毁或窜流,严重影响钻井的安全。针对200℃以上常规加砂水泥石强度衰退难题,基于硅铝键结合增强效应,通过优化水泥物相组成,开发了超高温增强材料SCKL,可以满足210~300℃下固井要求,不仅抑制了水泥石强度衰退,且促进了水泥石强度长期发育,300℃、48 h的抗压强度为18.2 MPa,30 d抗压强度高达23.2 MPa,探索了超高温增强材料对水泥石微观结构的影响,揭示了超高温水泥石微观作用机制。研选了温度广谱型缓凝剂,开发了大温差防衰退水泥浆体系,可以满足干热岩100℃温差下安全固井需求,并在青海共和盆地成功应用5口井,固井质量均为优质,为干热岩井筒水泥环密封完整性提供了安全保障。

It is easy to cause the strength retrogression of cement sheath,especially at the long-term high temperature condition of dry hot rock.At present,the method of adding sand to strengthen cement is widely used in high temperature cementing operations.However,the strength retrogression of cement still exists when the temperature is above 200℃,resulting in casing collapse and annular flow,which seriously affects the wellbore safety.To solve the problem of cement strength retrogression at the ultra-high temperature,a new high-temperature stabilizer(SCKL)was developed by optimizing the phase composition of cement based on the enhanced effect of silica aluminum bonding.The effect of SCKL on the inhibition of set cement strength retrogression at high temperatures was evaluated.The results showed that the compressive strength of set cement was 18.2 MPa at 48-hour age for 300℃curing temperature.And the strength reached 23.2 MPa after 30 days,which inhibited the strength retrogression of cement under long-term high temperature conditions.The influence of temperature on the microstructure and hydrates of set cement was revealed based on the XRD and SEM tests.Finally,a new durable heat-resistant cement system was developed.The cement slurry had very good settlement stability and could meet the requirement of safe cementing in DHR wells at a temperature difference of 100℃.The durable heat-resistant cement system has been successfully applied in five wells in Gonghe Basin,Qinghai Province.The cementing qualities are very good,which provides a guarantee for the integrity of cement sheath sealing in dry hot rock.