Experimental Study On The Effect Of The Wetting Property Of Support Agent On The Fracturing Operation

At present, the production of Daqing Oilfield enters the middle and late period of extra-high water-cut development. With the water cut increases gradually, it is urgent to take measure on stabilizing oil production and controlling water cut. In addition to injecting polymer solution and compound system to expand the swept volume and improve displacement efficiency, fracturing oil well to release the remaining oil in the low permeability layer is also an effective technical measure. In recent years, in order to improve the increasing oil and decreasing water effect of oil well fracturing, scientific personnel develop lipophilic sand support agent(selective support agent). And a total of 45 field tests have been tested in the mine fracturing construction. After fracturing, the average oil increment of single well reaches 2.9t/d and water cut decreases by 10.4% at early stage. Although the lipophilic sand support agent achieves a good effect of “increasing oil and decreasing water”, but its effect on the action mechanism is still unclear.In this paper, theory guided by reservoir engineering, polymer materials science and physical chemistry, taking experimental detection, chemical analysis and physical simulation as technological means, taking reservoir geology of Daqing Oilfield and support agent(quartz sand and lipophilic sand) as research object, experimental study was conducted on effect of the wetting property of support agent on the fracturing operation. Results indicate that, compared with quartz sand, the lipophilic sand has hydrophobic and oleophylic characteristics and its resistance function can increase the flow resistance of water phase in the cracks. For the sand-packed model(core) of lipophilic sand filling cracks, with the increase of crack length, the spread effect of injected water on the matrix part is reduced. And the lipophilic sand in the crack can increase the flow resistance and expand the spread effect. Due to the experimental model, the spread effect influence degree of the former is much greater than that of the latter. So the increase of crack length can reduce swept volume and oil recovery. For the core cemented by epoxy resin of lipophilic sand filling cracks, with the increase of crack length, the water flooding recovery rate first increases and then decreases. In conclusion, the effect law of crack length on the water flooding recovery rate of two types of lipophilic sand filled crack cores(sand filled and epoxy resin cemented) is different. The main reason is that there are differences in the injection-production pattern structure of the two types of cores. The sand-packed core is two-dimensional longitudinal heterogeneous core with one injection and one production well. The core cemented by epoxy resin is three-dimensional simulation core with one injection and three production wells. The former only has fluid flow between high and low permeable layers in the same seepage direction. The latter not only has fluid flow between high and low permeable layers, but also has the liquid flow between “corner well” and “side well”. Experimental data shows that, when the lipophilic sand filling fracture length is a third or a quarter of injection-production well spacing, the increasing oil and decreasing water effect of oil well fracturing is better.