Distribution features of cuttings bed and sensitivity analysis of major drilling parameters for cuttings transport in gas drilling horizontal wells

In the current engineering methods for the gas horizontal drilling, the distribution features of cuttings bed remain an issue to be cleared, and the gas horizontal drilling is still in early stages of development. For on-site drilling, a 3-D transient model is established in this paper to simulate the distribution features and the transport mechanism of the cuttings bed, based on the gas-solid two-phase flow theory. The effects of major drilling parameters, such as the gas velocity, the drill pipe rotation, the cutting size and the eccentricity, on the cuttings transport efficiency are analyzed. The major findings of this study include that the cuttings begin to settle down and build up a fixed cuttings bed, in the most evident regions in front and behind the connector, the dominant parameter of the wellbore cleaning is the gas velocity, and, as the cutting size is increased, the thickness of the cuttings bed developed in the wellbore increases significantly. In addition, the eccentricity has some influence on the cuttings transport, and the drill pipe rotation has little effect on the cuttings transport.