Differential sticking test fixture

Abstract

A test fixture includes a cylindrical main body extending in a longitudinal direction that receives a test piece. The main body includes a cylindrical screen filter with a mesh surface that extends in along a longitudinal axis coincident with an axis of the main body. The mesh surface generates a filter cake when particle-entrained fluid is supplied through the mesh surface and the particulate is retained on the mesh surface. The main body also includes an offset shaft that extends in the longitudinal direction along an offset axis that is offset from the axis of the main body, and the test piece extends through the offset shaft and the interior of the screen filter. The main body further includes a bearing that decouples rotational motion of the offset shaft from the end cap. Additionally, the test fixture includes an actuator that dislodges the test piece from the filter cake, a computer that determines the dislodging force, and a reservoir pump that pumps the particle-entrained fluid into the screen filter. When the alignment wheel is actuated, the offset shaft forces the test piece to move from a first position where a longitudinal axis of the test piece is coincident to the longitudinal axis of the screen filter to a second position in which the axes are offset.