Discussion on Safe Drilling Technologies for the Asphalt Layer in the YD Oilfield

During drilling through asphalt layer in the Yada Oilfield, asphalt invasion posed a lot of down-hole issues such as mud contamination, well kick and mud loss coexistence, bringing tremendous challenges in operation. In order to solve those problems, studies were conducted on safe drilling technologies for the asphalt layer in the YD Oilfield. Depending on asphalt invasion characteristics, induced down-hole issues and major techniques and measures taken, the wells were divided into 4 classes. The techniques and measures applied in drilling through asphalt layer in the YD Oilfield were summarized. For each of the 4 classes of wells, it is proposed to employ specific drilling techniques and measures depending on the characteristics and extent of asphalt invasion. The drilling practices in the YD Oilfield demonstrated that specified drilling techniques and measures should be implemented depending on types of asphalt invasion in order to effectively ensure the safe drilling through asphalt layer in the YD Oilfield.