Computation Of Flow Parameters For Gas Drilling

It can reduce drilling time and drilling cost using gas drilling. Gas drilling is an effective drilling method considering economic factor. Computation of flow parameters is academic gist for gas drilling. It is important to make sure that every parameter of gas drilling to apply the technique. Air is low density medium. Optimized outcome and great economic benefit lie on some factors. Especially in dry circumstances or without reservoir fluid, air drilling has distinguished effect. In air drilling, the shape, size and density of solid phase in the annular are different. So, each particle has single falling velocity. Under turbulent flow in the annular, cuttings are separated and bruised. Then, annular are filled with different size particles. In this paper, the methods of calculating the borehole pressure are introduced and computation models of multiphase flow in annulus are established. By calculating the relative parameters about the multiphase flow, calculating all kinds of variables by trial and error and sufficiently considering the compressibility of the gas, the calculation accuracy of the bottom pressure is enhanced. At the same time, the paper analyzes flow parameters in air drilling using air state equation and first law of thermodynamics. Discussing stress the questions such as flow rate when reservoir fluid inrush, injection pressure in the pipe and bit nozzle pressure. Calculation formula was proposed in detail. The method supplied necessary theory foundation for air drilling. The paper compiled application software based on established modeling and modified modeling considering field practices. It offers reference in air drilling in Daqing.