压裂液冻胶在储层微裂缝中的滤失评价

Evaluation of Fracturing Fluid Gel Filtration in the Reservoir Microcracks

压裂液冻胶作为高黏非反应性液体,一直广泛用于低渗透气藏水力压裂作业的造缝和携砂,对于孔隙型储层具有较好的降滤失性能。通过评价实验,考察了压裂液冻胶在低渗透气藏微裂缝储层中的降滤失性能。实验内容为:考察注液压差、压裂液黏度和微裂缝宽度对压裂液冻胶滤失速率的影响;在恒定微裂缝宽度和注液压差的条件下,通过考察压裂液冻胶滤失速率随时间的变化来评价压裂液冻胶在微裂缝中的造壁性能。实验结果表明:对于微裂缝发育的储层,压裂液冻胶有一定的降滤失性能;滤失速率变化与注液压差、微裂缝宽度成正比关系,与压裂液黏度成反比关系;随着实验时间的延长,压裂液滤失速率变化不大,压裂液冻胶在微裂缝壁面的造壁性能基本失效。建议:对于微裂缝宽度大于0.1mm的储层实施水力压裂作业时,在采用压裂液冻胶辅助降滤的同时,可使用粉砂、纤维等固相降滤剂实施综合降滤;在实施水力压裂作业前,建议通过小型测试压裂来判定地层微裂缝的发育特征。

Fracturing fluid gels with high viscosity and non-reactive behavior have hydraulic fracturing treatments for fracture initiation and proppant carrying in the low been widely used in permeability gas reservoir.The gel has a preferable fluid loss reducing capacity for the porous reservoirs.The fluid loss reducing capacity of the gel was investigated in the microcrack reservoirs of the low permeability gas reservoir through evaluation tests.The influence of fluid pumping pressure difference,filtrate viscosity and microcrack width on filtration rate was studied.Under the conditions of constant microcrack width and the pressure difference,wall building properties of fracturing fluid gel in the microcracks were evaluated after the change of the filtration rate with time was studied.The results show that the gel still has a great fluid loss in the microcracks of microfracture developed reservoirs.The filtration rate is proportional to the pressure difference and microcrack width,and it reversely proportional to the fracturing fluid viscosity.The rate has few changes and the gel almost loses the wall building properties at the wall of microcracks along with the time of the experiment.It suggests that fluid loss additive of silt and fiber and the fracturing fluid gel may be applied for reducing fluid loss together in the hydraulic fracturing of the microfracture reservoirs with microcrack width greater than 0.1mm.Before the hydraulic fracturing,mini testing fracturing should be made to judge the developing property of the microcrack in the reservoirs.