SUCTION FLOW CONTROL DEVICE

INTRODUCTION

It has been discovered that changing the pump energy distribution to a well can change the hydraulic flow characteristics observed for both the well and the surrounding aquifer. As early as 1898, it was recognized that Darcy's Law (linear flow) did not properly describe the hydraulic flow field around a well bore. In large capacity wells, the pump energy forces the entry of water to occur in or near turbulent flow opposite the end of the suction pipe or point of energy release by the casing to the screen or formation below.

Sand control to a well can be achieved by reducing the velocity at the critical points opposite the pump suction or the entry of energy to the formation or well screen and reduce flow to laminar conditions. In laminar flow there would be no inertial forces to physically move the sand particles thus they would remain in place in the formation. For a device like Aquastream, a type of suction flow control device (S.F.C.D.) to work, it must shift the energy distribution of the pump to distribute the flow over a larger column height of well bore or screen thus decreasing the overall velocity of flow to transitional or laminar conditions.

THEORY OF OPERATION

To develop the basic theory of operation of suction flow control devices, one first must refer to the law of conservation stated by Darcy that the flow rate through the aquifer is the product of the formation permeability times the cross sectional flow area times the hydraulic gradient.

Q = K A I
[Equation 1]

	Q	=	Flow of water in gallons per day,
	K	=	Formation permeability gpd/ft2 (Meinzer units)
	A	=	Cross Section area
	I	=	Hydraulic gradient in feet/foot

Formation permeability is the velocity at unity hydraulic gradient through porous material which is the approximate limit of laminar flow through the formation for the existing temperature and fluid viscosity present. For a given area of flow, the velocity then decreases linearly in proportion to the driving force or hydraulic gradient.

When the velocity is no longer directly proportional to the driving head, it becomes turbulent in which the square of the velocity is proportional to the driving force. There is a transition between laminar and turbulent flow in which neither condition is mathematically defined called transitional flow.