SPE 124388 modeling analysis of sand-screen collapse resistance under geotectonic load
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The manufacturer's specifications of sand screen usually provide information such as base pipe collapse pressure, maximum tensile load, and bending strength. However, the problem is that a very heavy base pipe is thus required to satisfy such specifications if the pipe collapse pressure indicated by manufacturer is used for field application. The reason is that the screen collapse tests are conducted under hydrostatic loading for screens wrapped with rubber jacket by screen manufacturers. Observation of these tests shows that screen collapse occurs immediately after the base pipe starts yielding. However this is not the case if screens are installed in the wellbore under geotectonic load. A series of laboratory tests are conducted using either straight pipes without screen or pipes with screen installed in a drilled borehole of some large rock sample. Since the base pipe failure is the dominant factor for screen failure, half of the experiments shown in this paper used straight pipe without including screen or shroud. These tests show that tubular strings may initiate yielding earlier than the specified yielding data provided by screen manufacturers. However, after the initial yielding the base pipe deforms gradually and it never collapses even after exceeding the ordinary base pipe yielding (0.2-0.4% deformational strain) by more than 10 times. Based on these laboratory tests, a numerical model is constructed for screen design along with gravel pack or standalone screen in openhole completions. The numerical model first simulates hydrostatic screen collapse tests conducted by manufacturers to confirm the design specifications as measured. Then, it is extended to simulate screen behavior after it is installed downhole. It assumes that a screen is placed in the borehole, and then gravel-pack covers the screen, followed by reservoir depletion and drawdown in production mode. This paper sheds light on the sand screen collapse resistance under three typical loading types: hydrostatic, geotechtonic load without void around sand screen and geotectonic load with void for openhole standalone screen applications. Distinctly different failure scriteria are proposed for these three types of loadings. Empirical data undedr such high stress levels are rarely found in the literatures. Copyright 2009, Society of Petroleum Engineers.
