The Characteristic Line Theory For The Study Of The Seepage Of The Double Porous Medium For The Coal Seam

Coal is typical double porous medium, not pure porous medium. To study the fluid flow among coal in the course of water–drive-gas water injection in theory, when water injection is carried out, according to the fact that coal is double porous medium, when water injection is carried out, according to the fact that coal is double porous medium, the differential equations set of water plane radical flow are discussed according to two kinds of condition. One condition is that assuming that the effect of adsorption and seepage is neglected, which is plane radical flow among double porous medium. In this case, the water molecule group can't enter the pore. There is no fluid's flowing among the pores, and the flow is still single seepage among the cracks. The other condition assumes that the effect of adsorption and seepage is existing, in this case, the water enters the cracks driving the gas among them firstly and encloses the pores space of then expends the gas among pores into cracks, so after the water-drive-gas course, the region is divided into parts with different saturation degree, in which the flow is water-gas-two-phase flow. In this thesis ,the closest double porous medium model of the cracks and pores is applied ,then we study the problem of water injection in the coal seam for the first step. we explain the double porous medium model and its equations. According to the base the coal seepage is the double porous medium. we get the differential equations of water plate radical flow, and the equations of water-drive-gas injection. In this thesis , we discuss the steady state of the crack seepage flow, and study the problem of water injection displacement under the steady flow state. At last ,we get the characteristic equations and the characteristic solution of the problem. So the thesis will give the important theory for mining coal gas and numerical calculation.