Research On Pressure Sealing Technology Of Fractured Reservoir In

Development of Keshen block’s fracture-type reservoir, the stratum’s pressure capacity is not high, the drilling fluid density window is very narrow.The density window of drilling fluid is narrow.Leakage and overflow easily occurs during drilling process. This paper mainly studies how to improve the stratum’s pressure capacity of Keshen block’s fracture-type reservoir.By means of Keshen block geological background and the distribution of stratum lithology,imaging logging technology as the foundation,clear that the compacted sandstone of the Cretaceous Bashijiqike formation is the typical natural fracture-type reservoir and the majority cracks are large dip angle and half filled.From the statistics of drilled well in Keshen block.the natural cracks’s width are mostly less than2mm.With the increasing of wellbore pressure,the cracks’s width and the shape will change.Through the analysis of Keshen block’s dip logging data,the direction of the maximum principal stress is about from north to South and the minimum principal stress is the east to the west.According to the leakage of drilled well in Keshen block,we find the pressure window is very narrow and sensitive to the density of drilling fluid which lead to leakage.By comparing two kinds of pressure sealing method,the casing naked hole plugging is more suitable for Keshen block.Leakage causes are natural leakage and artificial leakage.According to the size of the leakages,the leakages fall into micro leakage,small leakage,middle leakage,large leakage and serious leakage.According to features of the leakages,the leakages fall into natural leakage,fracturing leakage and extending leakage.You can easily distinguish different leakage from mechanism and the image of imaging logging.Researchers put forward different models of the relationship between stress and crack’s leakage rate.They find that it’s necessary to study on the crack width of0.4mm or more plugging.Finally, a single ideal crack as the object,we can get the relationship between the crack width and the leakage loss.I propose the plugging mechanism among different lost circulation material in the plugging process.Analysis the using of composite plugging plugging material,and the stratum’s pressure capacity vastly improved.Through the mechanical analysising of single particle bridging on the crack’s surface,double particle bridging in the crack and double particle bridging on the crack’s surface,we can conclude the range of grain selections.Through the indoor pressure sealing test,we can add up the leakage of rigid sealing material (walnut shell),elastic sealing material(SQD-98) and Fiber sealing material(sawdust) which test omposite among1-5mm crack.Finally we find out the best solution of comprehensive pressure sealing among1-5mm crack is6%walnut shell(30middle+70%tiny),5%SQD-98and more than3%sawdust. Finally I analysis the fracture-type reservoir application examples of the Keshen2-2-5well.The result is that the stratum’s pressure capacity achieve to4.75MPa.