低渗砂岩油藏注水井缓速酸深部酸化技术研究

Research on Retarded Acid Deep Acidization Technology for Water Injection Wells in Low-Permeability Sandstone Reservoirs

在低渗砂岩油藏使用原位生成的氢氟酸(HF)进行砂岩酸化,酸性前体(氟化铵NH4F)与氧化剂(溴酸钠NaBrO_(3))发生放热反应。制备新型自生酸混合物与纯石英样品反应,并通过电感耦合等离子体技术分析反应产物以确定硅离子。使用砂岩心进行岩心侵入实验。在处理前后对岩心样品进行划痕测试和核磁共振扫描。结果表明,新型自生酸混合物可以溶解石英样品,并使其质量减少80mg。溶解的硅离子质量浓度超过90 mg·L^(-1),证明了化学混合物生成HF的能力。在流速为2 cm^(3)·min^(-1)的条件下测得初始岩心渗透率为33 mD。在酸预冲洗阶段后,岩心渗透率降至31mD。第一次处理循环后,岩心渗透率立即增加并达到41mD,结果显示砂岩心渗透率提高了近40%。溶液的ICP分析显示螯合的硅离子总量为10.5 mg。除了井口附近产生的高温,由于放热反应产生的氮气导致压力增加,达到约4.14 MPa。划痕测试显示样品的单轴抗压强度增加了约12.4 MPa。动态杨氏模量和泊松比分别增加了约9.83 MPa和0.02。通过应用这种新型自生酸可以实现砂岩储层的深部酸化,最小化井筒腐蚀,并避免处理HF等危险化学品。

Sandstone acidization using in situ generated hydrofluoric acid(HF)in low-permeability sandstone reservoirs was carried out by exothermic reaction of an acidic precursor(ammonium fluoride NH4F)with an oxidant(sodium bromate NaBrO_(3)).Novel authigenic acid mixtures were prepared to react with pure quartz samples,and reaction products were analyzed by inductively coupled plasma techniques to identify Si ions.Core intrusion experiments were performed using sandstone cores.Scratch tests and NMR scans were performed on the core samples before and after treatment.The results showed that the new autogenous acid mixture could dissolve the quartz sample and reduce its mass by 80 mg.The mass concentration of dissolved Si ions exceeded 90 mg·L^(-1),demonstrating the ability of the chemical mixture to generate HF.The initial core permeability was measured to be 33 mD at a flow rate of 2 cm^(3)·min^(-1).After the acid pre-rinse phase,the core permeability decreased to 31 mD.Immediately after the first treatment cycle,the core permeability increased and reached 41 mD,which showed an increase of nearly 40%in the permeability of the sandstone core.ICP analysis of the solution showed a total of 10.5 mg of chelated Si ions.In addition to the high temperatures generated near the wellhead,the nitrogen generated due to the exothermic reaction resulted in an increase in pressure to approximately 4.14 MPa.Scratch tests showed an increase in the uniaxial compressive strength of the samples of approximately 12.4 MPa.The dynamic Young's modulus and Poisson's ratio increased by approximately 9.83 MPa and 0.02,respectively.Through the application of this novel autogenous acid,it was possible to deep acidize sandstone reservoirs,minimize wellbore corrosion,and avoid handling hazardous chemicals such as HF.