超深裂缝性碳酸盐岩伤害及解堵酸化模拟

ULREA-DEEP FRACTURED CARBONATE FORMATION DAMAGE AND ACIDIZING SIMULATION

川东灯影组储层埋藏深(大于7500 m),天然裂缝发育,钻井过程中钻井液对储层伤害严重,解堵酸化是实现超深气井建产、增产的重要技术手段。因缺乏灯影组储层钻井液伤害机理及解堵酸化效果实验,使得酸化工艺的选择和注酸参数优选缺乏针对性。以川东灯影组岩样为实验样品,模拟储层条件下天然裂缝宽度在10~250μm范围的钻井液伤害和酸化过程,并研究了注酸参数对酸化效果影响。结果表明,当缝宽小于80μm时,钻井液伤害主要集中在裂缝入口端;当缝宽大于80μm时,钻井液可伤害整个裂缝壁面;随着裂缝宽度的增加,钻井液伤害程度先增加后减小,当缝宽为200μm时钻井液伤害最严重,渗透率伤害率为96.53%。当缝宽小于10μm时,酸液难以突破岩样,解堵效果较差,建议在限压条件下,尽可能提升注酸排量增加缝宽,提高酸化效果;当裂缝宽度为80μm时,解堵效果非常好,渗透率恢复率至507%;当缝宽大于200μm时,受裂缝面钻井液滤饼影响,胶凝酸解堵效果一般,建议采用复合解堵酸化工艺,解除裂缝面滤饼伤害。当注酸排量为4 m^3/min,注酸时间为60 min时可以获得较好的酸化效果。实验结果可为超深裂缝性碳酸盐岩解堵酸化工艺及注酸参数优选提供实验依据。

The reservoirs in the Dengying formation of the eastern Sichuan basin are deeply buried with buried depth greater than 7500 m,and natural fractures are well developed.The reservoir is seriously damaged by the mud during drilling process.Plugging removal and acidizing is an important technical means to realize the production and increase production of ultra-deep gas wells.However,lacking of experiments of mud contamination and plugging removal,which makes the selection of the acidizing process and the acid injection parameters are not targeted in Dengying formation.The outcrop of the Dengying formation were used as experimental samples to simulate the mud pollution and acidizing process with natural fracture widths ranging from 10 to 250μm under reservoir conditions,and the effect of injecting parameters on acidizing was studied.The results are as following:when the width is narrower than 80μm,the mud contaminates mainly cumulates at the fracture entrance,while the width excess 80μm,it contaminates all fracture surface,and the contamination increases first and then decreases as the width increasing.When the width is 200μm,the mud contamination is the most serious with a damage rate to permeability of 96.53%.When the width is less than 10μm,the acid is difficult to break through the rock sample,and the plugging removal effect is poor.It is recommended to increase the acid injection displacement to increase the width of fracture and improve the acidizing effect under the pressure limiting condition.When the width is 80μm,the plugging removal and acidizing effect is very good,the permeability recovery rate is up to 507%.When the width is greater than 200μm,it is affected by the fracture mud filter cake,and the gelledacid is generally blocked.It is recommended to use the compound plugging removal acidizing process to remove the fracture face mud cake damage.When the acid injection displacement is 4m^3/min,the acidizing effect can be obtained when the acid injection time is 60min.The experimental results can provide experimental basis for the plugging removal and acidizing process and acid injection parameters of ultra-deep fractured carbonate formation.