压裂液对松北致密油典型区块储层伤害评价影响研究

Evaluation and research on the influence of fracturing fluid on reservoir damage in typical block of Songbei tight oil

随着大庆油田致密油储层大规模体积压裂用液规模逐渐扩大,排液周期逐渐延长,压裂液在储层内滞留时间长,因此对典型区块取心并开展不同类型压裂液对储层伤害影响研究。采用CT扫描的方式分析样品的孔隙直径、喉道直径、连通孔隙比等参数,再使用破胶压裂液进行驱替实验,通过对比驱替前后的CT扫描数据,分析压裂液对孔隙直径、喉道直径、连通孔隙比的影响,从而确定不同类型压裂液对储层孔喉的伤害程度。实验结果显示,压裂液侵入储层后大孔喉变少、小孔喉变多;瓜尔胶压裂液伤害引起的参数变化为表面活性剂压裂液的1.75倍;瓜尔胶压裂液主要伤害中等孔喉,表面活性剂压裂液主要伤害小孔喉;因此对于孔喉特征较好的储层可选用瓜尔胶压裂液,但对于孔喉特征较差的储层建议使用表面活性剂压裂液。该研究为产能提高奠定了基础。

With the increasing application of large-scale volume fracturing fluid in tight oil reservoir of Daqing Oilfield,the fluid drainage period is gradually extended;the remain time of fracturing fluid in reservoir becomes longer.Therefore,the coring and studying the influence of different fracturing fluid on reservoir damage in typical blocks have been conducted.The parameters such as pore diameter,throat diameter and connected pore ratio of the samples were analyzed by the CT scanning,and then the gel-breaking fracturing fluid was applied for displacement experiment.Through the comparison of CT scanning data before and after displacement,the influence of fracturing fluid on pore diameter,throat diameter and connected pore ratio has been analyzed,so as to determine the damage level of different types of fracturing fluid on reservoir pore throat.The test results show that the larger pore throat becomes less,and the small pore throat becomes more after the fracturing fluid squeezes into the reservoir,and the parameter of reservoir damage caused by Guar gum fracturing fluid is 1.75 times of that by surfactant fracturing fluid.Guar gum fracturing fluid mainly damages the medium-size pore throat,while surfactant fracturing fluid plugs the small-size pore throat.Therefore,Guar gum fracturing fluid can be used for reservoirs with good pore-throat characteristics,and surfactant fracturing fluid is recommended for reservoirs with poor pore-throat characteristics.The research has laid the basis for improving the oil production.