The Key Technologies Of Secondary Stimulation For Coalbed Methane Well In A Block Of Huaibei

Many coalbed methane wells in our country have not achieved commercial production after first stimulation.If abandoned,these wells would be unable to recovery the cost and cause serious waste of resource.So,it is necessary for these CBM wells to be secondary stimulated and achieve commercial production.Therefore,this thesis systematically study the basic theory of network stimulation in CBM well’s secondary stimulation and the stimulation mechanism of triple-prevention fracturing fluid by laboratory experiments,field test and theoretical analysis,and draw the following conclusions:(1)Secondary stimulation is a reservoir stimulation technique which is based on the analysis of the first stimulation failure factors and the reservoir characteristics,and the construction parameter optimization of fracturing position,perforation method,pumping procedure,etc.After analyzing the first stimulation failure factors of two CBM wells in a block of Huaibei,this thesis make a scheme of secondary stimulation based on the technical theory of network stimulation: turning the stimulation object from coal seam to coal measures strata;turning the stimulation process from conventional hydraulic fracturing to network stimulation;turning the pumping procedure to large fluid volume,large displacement,and low sand ratio;turning the perforation method from monolayer perforation to stratified uneven perforation.(2)Put forward a systemetic development method of triple-prevention fracturing fluid which can prevent water sensitivity damage,water blocking damage and velocity sensitivity damage.Reveal the stimulation mechanism of triple-prevention fracturing fluid from water sensitivity damage preventing,water blocking damage preventing,velocity sensitivity damage preventing and friction decreasing.(3)This technology is conducted for two CBM wells,which are named as HN-01 and HN-02 and locate in a block of Huaibei.Good effect have been achieved after stimulation: the reservoir permeability of HN-01 well is lifted from less than 0.339 mD to 1.162 mD,and less than 0.36 mD to 1.227 mD of HN-02 well,which increase more than 3.4 times of these two wells.At present,these two wells are still in the initial stage of drainage.