ABSTRACT:

The transient solids production (TSP) is the first stage of massive solids production, different from the massive quasi-steady-state solid production, which has been considered in the past (see reference in the text). Transient solid production can be strongly pronounced during the well start-up as well as during the drilling if it triggers blowout. We develop an analytical model of transient solids production which allows us to formulate the dimensionless control parameters of TSP, and to compute the rate and cumulative volume of solid production vs. time as a function of such input parameters as far-field stress, pore pressure, uniaxial compressive strength, and hydraulic diffusivity. The transient solid production proceeds by growth of the vanguard zone of influence (ZI) which followed by growing plastic zone, or a cavity which is not empty but is filled by flowing dilated sand. The transient behavior of pore pressure inside the zone of influence is described by conventional hydraulic diffusion equation but with the moving vanguard and rearguard boundaries. Solution of this problem is obtained by the method of integral relationships, which we generalized for the case when not only the vanguard front of ZI but the rearguard boundary of ZI is moving outward from the borehole inside the reservoir. The rearguard of ZI, at the same time, is the front boundary of the growing plastic zone. The dilation of the fabric at the moving boundary between zone of influence and the plastic zone leads to solids production to the borehole. The model is also applicable to the description of transient sand production from perforation cavities.

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