Damage Mechanism And Evaluation Of Fractured Reservoir Of Daqing

The joint, designed and processed in this paper, can satisfy the request of samples made with natural sandstone, tuff, and esite, basalt matrix; the artificial crack formation can simulate the crack surface morphology of natural fractures. The results showed that the stress sensitivity of fractured reservoir at east of daqing changyuan is strong. The permeability and width of crack dicrease with the increasing of the effective pressure; the larger is the initial crack width, the more serious is the stress sensitivity. The results of comprehensive experimental show that the major damage is the liquid-phase damage caused by the invasion of filtrate for the fractured reservoir in 1.8 ~ 2.60μm; while the major damage way is solid-phase damage for fractured reservoirs in16.5 ~ 19μm and 50 ~ 70μm. It need not consider drilling process of reservoir protection problems when the width of crack is less than 50μm.Considering the crack surface characteristics and the inner flow characteristics of crack, and adopting hydromechanics, percolation mechanics and the fractal dimension of crack, the mathematical model of the effective width of crack is established, wihich is more suitable for studying the damage assessment of the drilling liquid through linking the permeability of fracture core. Grain size analyses and temporary plugging experiments have proved that the effective flow width is practical and accuracy. The results of the simulation experiment by using the bridge theory with 1/2 ~ 2/3 times of crack width showed that: for the fractured core in 70-110μm crack width, when 5.0% rigid bridge particles with D50 value was added into the common amphiphilic drilling liquid D50 value, it can meet the needs of the rapid forming bridge and the reduction of the wall drilling depth by the solid-phase invasion. The theory is applicable for the temporary plugging of the gas reservoir. The fractured gas reservoir can not be damaged by the drilling in the underbalance drilling process. Under the considerable condition, the fractured gas reservoir can be opened by the underbalanced drilling technology, which can effectively protect the fractured gas reservoir under pressure for all the width of the fractured reservoirs, and the method is the optimal way for protecting the fractured gas reservoir.