玛湖致密砂砾岩油藏纳米排驱滑溜水体系

Development of Nanofluid Slickwater System for Stimulating Mahu Tight Glutenite Reservoirs

玛湖油田致密砂砾岩油藏压裂液减阻剂为阴离子聚合物,易于与高矿化度配制水和压裂液添加剂中的有机或者无机阳离子发生反应而形成沉淀,堵塞致密砂砾岩孔隙,造成近井地带压力异常升高,不利于压裂裂缝的进一步延伸。为了实现储层保护、促进裂缝扩展,研究提出了一套具有原位驱油功能的纳米排驱滑溜水体系,结合室内环路摩阻测试和表界面张力测试实验,确定了该体系中各个组成部分的添加比例,并依据玛湖油田现场实验数据和实验材料,对整个纳米排驱剂体系的持续抗剪切能力、耐盐能力、溶解能力和洗油能力进行评价。结果表明,所研发的纳米排驱滑溜水体系在1.2×104 s-1剪切速率下,减阻率为78.92%,且在该剪切速率下,利用玛湖油田不同矿化度配制水所配制的纳米排驱滑溜水体系剪切20 min减阻率依旧保持在73%以上,同时通过使用索氏提取装置测定纳米排驱滑溜水体系对玛湖油田油砂的洗油能力为93.3%。初步筛选出一套适用于玛湖油田砂砾岩油藏的纳米排驱滑溜水体系。

The drag reducer of fracturing fluid in the tight glutenite reservoir of the Mahu Oilfield is a kind of anionic polymer,which is easily precipitated by the reaction with organic or inorganic positive ions in fracturing additives.The precipitations can easily block the pores of tight glutenite,and cause an abnormal pressure increase in the near-wellbore.It will be not conducive to the further extension of the fracture.In order to realize reservoir protection and promote crack propagation,a nanofluid slick water system with in-situ oil displacement ability was developed.Loop test and surface tension test were used to determine the optimal doses of each components in this system.Based on the field data and materials of Mahu oilfield,continuous shearing resistance,salt tolerance,solvency and wash oil ability of the nanofluid system were evaluated.The results show that,under the shearing rate of 1.2×10^4 s^-1,the drag reduction efficiency of the fluid is 78.92%.In addition,the nanofluid system can work well at the different salinity of the formation water of Mahu oilfield.At the same shearing rate,the drag reduction efficiency after 20 min shearing is still above 73%.What’s more,the wash oil efficiency of the system is determined to be 93.3%by the Soxhlet extraction system with Mahu oil sand.