超深裂缝性致密砂岩储层在我国分布较多,常规压裂改造的效果不明显.缝网压裂的成功实施可以有效沟通天然裂缝,最大限度的增加致密砂岩储层的泄流面积,获得较为长期的高导流能力,进而保证改造效果.本文对缝网压裂改造技术的关键点进行了阐述,并对裂缝性储层缝网的形成进行了力学分析,认为缝网形成的关键在于如何在压裂施工中成功的激发天然裂缝.现场应用结果表明,采用人工裂缝转向技术能够较好的沟通天然裂缝,形成复杂的缝网结构.

针对油藏注水开发中后期常出现的高渗条带或窜流通道难以封堵的问题,用新研制的SAMG-Ⅰ低温调堵剂进行了室内高渗透岩心封堵特性实验研究.SAMG-Ⅰ调堵剂由5%～7%的淀粉,4.5%～7%的丙烯酰胺,0.05%～0.2%的有机交联剂,0.1%～1%的引发荆,0.1%～0.5%的缓聚剂以及吉林油田地层水配制而成,在30℃地层温度下,具有成胶时间可调,凝胶强度大,成胶稳定性好、抗剪切、抗老化能力强等特性.SAMG-Ⅰ调堵剂在高渗透岩心中运移特性好,运移深度可控,与砂岩孔隙骨架粘结强度大,封堵强度高,段塞厚度达10cm时测得突破压力为2.5 MPa,封堵率达99.91%.SAMG-Ⅰ调堵剂具有较好的封堵选择性,适用于低温油藏大孔道、窜流通道的封堵.图2表2参6.

The titled profiling/water plugging agent is composed of 4.1% starch,4.1% AM,0.16% polymerization initiator,and 0.04% crosslinker and prepared in Jilin produced water of TSD=5.15 g/L,it gelates at 30℃ in 17 hrs and the gel formed has strength of 0.85—0.95 MPa,which is measured as the driving pressure for the gel to flow through 2 layer screen of 20 mesh of area 28.3 cm~2.The gelling fluid(GF) prepared in produced waters of other main oil fields with TSD in range 4.47—263 g/L can form qualified gels at the corresponding reservoir temperatures,40—120℃.When the GF being injected into a long tubular sand pack of a 40—60 mesh outcropping oily sand containing ～30% clay minerals to 9.5 m length,the pressure values determined along show a smooth transfer of the GF in the porous medium,its apparent viscosity calculated is decreased from 0.05 Pa·s at the entrance to zero at 8.16 m distance and,when the fluid gelled,the water injection pressure is decreased from 60 MPa at the entrance to zero at 5.50 m distance.≥90% mass of the GF flown out from a 2 m long sand pack of K=9.78 μm~2 at different flowing rate is gellable.On four sand packs of 1 m long and of K in range 0.199—23.7 μm~2 with 0.3 PV of the GF injected and gelled,the breakthrough pressure of injected water(7.8—8.4 MPa/m) and the residual resistance factor(30—2850) and the plugging rate(96.7—99.7%) at 9 PV water injected are increased with increasing the initial permeability of the sand packs.Through 2 sets of high and low permeability sand packs 0.3 m long in parallel,the fractional flow rate ratio of the GF in 0.35 PV is proportional to the permeability variation coefficient and of the injected water is reversed after the GF injected and gelled..

The variation of seepage velocity, resistance coefficient, reservoir permeability and oil recovery in porous media of water-drive reservoir in direct current (DC) electric field are studied in detail. In the positive electric field, the seepage velocity of single-phase fluid, the effective absolute permeability coefficient R_k of the low permeability core and oil recovery remarkably increase with the increase of electric field strength. And the electro-kinetic became the main fluid seepage drive power because the resistance coefficient F_(r+) is far less than 1 and negative even in low velocity. However, contrary variations of seepage flow characteristics in porous media are showed in opposite electric field. Thus, the experimental results show that the fluid flowing behavior in the porous media is greatly influenced by the polarity and strength of the electric field.