变黏滑溜水性能评价及吉木萨尔页岩油藏矿场应用

Laboratory evaluation of viscous slickwater and its field application in Jimsar shale oil reservoirs

非常规油气储层需要大规模压裂改造形成复杂裂缝网络从而实现经济开发的目的。滑溜水是该领域应用最为广泛的压裂液体系,但其黏度低,携砂性能差,砂堵风险高。变黏滑溜水可有效解决以上问题,该体系通过浓度的变化,即可实现低黏和高黏的转换,在简化施工工艺与降低降阻剂用量的同时,能够有效降低管路摩阻损失,增加压裂液携砂效率与压裂液体效率。通过流变性能评价、室内降阻性能测试及室内悬砂等一系列性能评价实验,以常规滑溜水作对比分析,对变黏滑溜水的降阻及携砂性能进行了评价。室内实验表明:通过控制降阻剂的浓度,可实现大范围连续变黏的效果。0.6wt%及以上浓度的变黏滑溜水在高剪切状态下仍可保持50 mPa·s以上黏度,而在0.1wt%浓度下的变黏滑溜水与常规滑溜水区别较小,均低于5 mPa·s。0.1wt%的变黏滑溜水管内流速达到11 m/s以上,降阻率可达到77.5%,与常规滑溜水表现相近。0.6wt%的变黏滑溜水管内流速达到10 m/s以上,降阻率可达到60%以上。相比同浓度常规滑溜水,其室内悬砂实验没有明显的砂堤形成且砂粒较为均匀的填充至整个裂缝,携砂能力显著提升。吉木萨尔页岩油储层应用效果显示,使用变黏滑溜水体系的压裂试验井降阻率最高可达81%,改造后增产效果显著,最高日产油接近90 t/d,80天累产油高达4000 t,最高为常规压裂液体系施工井产量的4倍,应用效果良好。

Unconventional oil and gas reservoirs require a large-scaled fracturing to form dense and effective fracture network,so as to achieve the economic development.Slickwater(i.e.,water with the friction reducer)has been widely applied in this field.However,it has low viscosity and poor sand-carrying performance,which increases the risk of sand plugging during fracturing.As for friction reducers,although increasing its concentration in water can slightly increase the viscosity of the slickwater,but this can dramatically decrease the friction reduction rate of the slickwater,which turns out to be detrimental to the stimulationnew.New viscous slickwater(i.e.,water with the viscous friction reducer)was developed that can solve the above problems.It can meet the requirements of different viscosity by changing the concentration of the friction reducer(from 0.1wt%to 0.8wt%).With a simple operation process and lower friction reducer,it can effectively maintain a high friction reduction rate,and increase the efficiency of proppant carrying and fracturing fluid.In this study,through a series of laboratory experiments(including the rheological performance tests,friction reduction rate tests and sand-carrying tests),the friction reduction and sand-carrying performance of one chosen viscous slickwater were evaluated,and further compared with the conventional slickwater was conducted.Experimental results showed that a continuous viscosity change in a wide range could be achieved by controlling the concentration of the new viscous friction reducer.The viscous slick water with a concentration above 0.6 wt%could maintain the viscosity more than 50 mPa·s even with a high shear.While there was less different between the conventional slick water and the viscous slick water with the concentration of 0.1wt%,the viscosity of both was lower than 5 mPa·s.The friction reduction rate of the 0.1wt%slickwater could up to 77.5%with the flow rate in a pipe of 11 m/s.In the sand-carrying tests,no sand-settlement was observed.This allows sands to transport further into the hydraulic fractures and be uniformly distributed.The further tests were carried out in two horizontal wells in Jimsar shale oil reservoirs.Field data showed that the friction reduction rate was 81%in the fracturing,and the maximum daily oil production rate was 90 t/d,and the cumulative oil production was up to 4000 t/d in 80 days,which is 4 times of the production with the conventional fracturing fluid.