Shale gas drilling technologies used in Bozhou-Fuyang area of the Southern North China Basin

In order to seek for the breakthrough of oil and gas resource exploration in the northern Anhui of the Southern North China Basin, many exploration wells are deployed in the area of Bozhou and Fuyang. The middle Paleozoic formation in Well Wanbocan 1 is poorly drillable and the coring there is difficult and blocked easily. In view of these difficulties, dual-centralizer coring barrel is adopted, the clearance of core catcher is regulated, the PDC bit is selected and the coring parameters are optimized. As a result, the coring in the 230 m broken formation is completed efficiently with recovery rate of 96.89%. In Well Wantaican 1, complex downhole situations occur in the second long open hole section, e.g. mud loss with no return and pipe sticking. To deal with these complex situations, a variety of mud loss formulas are adopted and a series of process is applied to free the stuck pipe successfully, such as compound shock-sticking point explosion-washover. Through the implementation of several wells, a set of efficient coring technology and complex processing methods suitable for shale gas survey well in Bozhou-Fuyang area have been formed. Drilling practice and experience can provide the reference for the drilling construction of similar wells in this area in the following step.