Improves oil well production of high-water content sandstone reservoirs based on fracturing and water shutoff with ultrafine cement
Solved the problem of difficulty in achieving effective placement of plugging and adjusting fluids in deep areas and long-term regulation of high permeability zones using existing deep profile control and deep fluid flow diversion technologies.By using ultrafine cement as the plugging material and employing a fusion plugging process based on fracturing and water shutoff,the ultrafine cement slurry is placed deep to regulate the high permeability bands in the deep effectively,expand the water flow volume of the injection water,and effectively utilize the remaining oil,which can improve the recovery rate in a low-cost and efficient manner.Based on the geological understanding of controlling the dominant direction of water flow through micro cracks,and the experimental understanding of a 30%decrease in the mechanical strength of water-immersed rocks,a high displacement and high-pressure injection method was adopted to construct a deep penetration fluid flow turning and plugging process if ultrafine cement combined with hydraulic fracturing and water blocking.Optimize the supporting ultrafine cement formula system,with an optimized formula of 50%G-grade cement+50%ultrafine cement+0.9%retarder+1%drag reducer,and a water-cement ratio of 1∶0.8.The mechanism of penetration and migration of ultrafine cement slurry was confirmed by the concrete model of two sets of 2 m long sandstone cores under different injection rates and pressure.Furthermore,a technical system suitable for this process was developed for high permeability zones in medium-high permeability reservoirs,and on-site tests have been carried out.After optimizing the performance of the ultrafine cement slurry,the thickening time was 8.5 hours,the water loss was 75ml,the water separation rate was 1%,and the fluidity was 30 cm,indicating that the optimized sealing system has sufficient construction time.The slurry can meet the requirements of deep migration with good fluidity,low water separation rate,and insignificant filtration loss in the reservoir.The results of the physical model experiment show that when injected at a low flow rate of 5 L/h,the cement slurry only seeps into 40 cm through seepage.Injecting at a high flow rate of 16 L/h,the cement slurry compresses the rock core to form cracks,which can achieve a penetration depth of more than 2 m and extend the effective distance by 4 times.The on-site test results of the A36 block in the medium-high permeability reservoir show that the actual construction pressure is consistent with expectations,and the measures have no effect on water absorption near the well.The effectiveness of the well group reflects the technology can achieve deep fluid flow diversion,with an effective period of more than 12 months and cumulative oil increase of 781 tons.Through the injection process of large injection rate and high pressure,high-density and high-dose cement slurry plugging agents can be used to effectively block deep high permeability bands and achieve deep fluid flow diversion.
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维普
