压裂裂缝长期导流能力衰退规律实验研究

Experimental study on long term conductivity decline of hydraulic fracturing fracture

裂缝导流能力是计算压裂增产效果和有效期的重要参数。受地层应力影响,裂缝导流能力随时间不断下降,而下降规律受应力大小、岩石性质、铺设厚度等多种因素影响。为研究裂缝长期导流能力变化规律,该研究以岩板性质、驱替液类型、铺设浓度及闭合压力为研究因素,共开展6组对比试验。结果显示破胶液和岩板组合时,裂缝导流能力下降幅度大且较快;清水和无岩板组合时,裂缝导流能力下降相对平稳。破胶液、岩板及低铺设浓度下,裂缝导流能力衰退最严重,闭合54 h后下降幅度为90.15%;清水、无岩板及低铺设浓度下,裂缝导流能力衰退最弱,闭合54 h后下降幅度为23.12%。该实验研究阐述了支撑裂缝长期导流能力随时间的衰退规律,可为评价压后产能、压裂有效期及压裂工艺优化提供依据。

Fracture conductivity is an important parameter for calculating fracturing stimulation effect and validity period.Affected by formation stress,fracture conductivity decreases with time,and the decline law is affected by many factors such as stress,rock properties,laying thickness and so on.In order to study the change law of long-term conductivity of fractures,six groups of comparative tests were carried out with rock plate properties,displacement fluid type,laying concentration and closure pressure as research factors.The results show that:When the gel breaker and rock plate are combined,the fracture conductivity decreases greatly and rapidly;When the combination of clear water and no rock plate,the decline of fracture conductivity is relatively stable.Under the conditions of gel breaker,rock slab and low laying concentration,the decline of fracture conductivity is the most serious,and the decline range is 90.15%after 54 hours of closure.When there is clear water,no rock slab and low laying concentration,the decline of fracture conductivity is the weakest,and the decline range is 23.12%after 54 hours of closure.This experiment study expounded the decline law of long-term conductivity of supporting fracture,which provided a basis for evaluating post-fracturing productivity,fracture validity period and fracturing process optimization.