实际地层温度压力条件下的渗吸实验研究

Experimental Study on Imbibition under Actual Reservior's Temperature and Pressure Conditions

采用低渗透砂岩岩心进行实际地层温度压力条件下的渗吸实验,分析低渗透砂岩注水吞吐过程中的渗吸规律,并与常温常压渗吸实验进行了对比。实验表明,常温常压渗吸效率为18%~24%,平均为21%;前6 h岩心渗吸速率最快,为0.8~1.7%/h。实际地层温度压力条件渗吸效率为24%~31%,平均为27%;第1轮次渗吸速率最快,为2.6~3.6%/h。与常温常压渗吸相比,实际地层温度压力条件下能提升渗吸效率5%~7%,渗吸速率也明显高于常温常压渗吸,分析认为实际地层温度压力条件下可增加渗吸动力、减小渗吸阻力,更有利于发生油水置换。建立了渗吸深度理论计算模型,得出岩心渗吸波及的深度为0.25~0.63 cm,认为前期快速渗吸阶段进入的深度属于厘米级范围,渗吸深度随渗吸效率的增加而增加。综合研究认为,提高地层压力和进行大面积压裂可有效提高渗吸效率。

The permeability and absorption experiments of low permeability sandstone core under the actual formation temperature and pressure were carried out,which were used to analyze the waterflooding huff‐puff's oil recovery law of imbibition and compared with imbibition experiments of normal temperature‐pressure.The experiments show that the imbibition efficiency of normal temperature‐pressure is 18%~24%,with an average of 21%.The permeability rate of core in the first six hours is the fastest,which is 0.8~1.7%/h.The imbibition efficiency of actual reservior's temperature and pressure conditions is 24%~31%,with an average of 27%;Imbibition rate is the fastest in the first round,which is 2.6~3.6%/h.Compared with imbibition of normal temperature‐pressure,the imbibition of actual reservior's temperature and pressure conditions can promote the imbibition efficiency by 5%to 7%,and the imbibition rate is also significantly higher than the imbibition of normal temperature‐pressure.The analysis believes that imbibition of actual reservior's temperature and pressure conditions can increase the imbibition's power and reduce the imbibition's resistance,which is more conducive to oil‐water displacement.Furthermore,the theoretical calculation model of the imbibition depth is established,and the cores'imbibition depth is about 0.25~0.63 cm.It is considered that the depth of the early rapid imbibition stage is in the centimeter range,and the imbibition depth increases with the imbibition efficiency.According to the comprehensive research,increasing the reservior's pressure and large‐area fracturing can effectively improve the imbibition efficiency.