Influences of reservoir properties on the gas well killing effects by the bullheading method

As one of the effective unconventional well control technologies, bullheading killing can reduce and avoid surface and platform risks in the case of overflow, blowout and other accidents. At present, the researches on the calculation of bullheading process only focus on the flow inside the well, without considering the influences of reservoir properties, so they cannot meet the on-site actual demands completely. In order to research the influences of reservoirs properties on the bullheading process, the research firstly established the well gas-liquid two-phase flow model. Then, the flow laws of the killing fluid after being squeezed back into the reservoir were studied by considering the influences of mud cake, reservoir contamination belt, reservoir permeability, porosity and saturation comprehensively, and the change laws of the well pressure in the process of bullheading were analyzed. Finally, the influences of different factors on bullheading reservoir efficiency were quantitatively determined. It is indicated that well killing is influenced less by reservoir gas saturation and mud cake permeability, but more by reservoir thickness and porosity. The bullheading killing which considers the influences of different reservoir properties comprehensively can provide the technical guarantee for the safe drilling of gas wells.