Vugular Loss Simulating Vug Tester for Screening and Evaluation of LCM Products

Abstract

An apparatus to simulate fluid loss through vugs in formations includes a housing defining an inner volume, and having a first end and a second end. The inner volume represents an inner region of a wellbore formed in a formation containing a vugular loss zone. The housing can receive wellbore fluid within the inner volume. A first cover late, which sealingly covers the first end, represents a first volumetric boundary of the inner region of the wellbore. A second cover plate, which sealingly covers the second end, represents a second volumetric boundary of the inner region of the wellbore. An outlet in the second cover plate can be switched between open and closed states. The outlet in the open state represents a vug in the inner wall of the wellbore. The apparatus includes a pressure port configured to transmit fluidic pressure in a direction of gravity within the inner volume and to apply the fluidic pressure to the wellbore fluid within the inner volume.

1 . A method of simulating loss of wellbore fluid in a vugular loss zone, the method comprising:
 filling a housing defining an inner volume with wellbore fluid, the inner volume representing an inner region of a wellbore at least partially formed in a loss triggering subsurface formation;   sealing a first end and a second end of the housing with a first cover plate and a second cover plate, respectively, the second cover plate comprising an outlet switchable between an open state and a closed state, the outlet in the open state representing a vug in the inner wall of the wellbore;   with the outlet in the closed state, applying fluidic pressure in a direction of gravity from the first end of the housing toward the second end;   with the outlet in the open state, applying the fluidic pressure in the direction of gravity from the first end of the housing toward the second end; and   evaluating sealing and blocking properties of the wellbore fluid to flow through the vug in the inner wall of the wellbore based on a comparison of results of applying the fluidic pressure in the closed state and applying the fluidic pressure in the open state.   
     
     
         2 . The method of  claim 1 , wherein the wellbore fluid with which the inner volume is filled is a first wellbore fluid, wherein evaluating the properties of the wellbore fluid comprises:
 mixing an additive to a second wellbore fluid having a volume equal to that of the first wellbore fluid, the additive configured to alter the properties of the wellbore fluid;   filling the housing with a mixture of the second wellbore fluid and the additive;   sealing the first end and the second end of the housing with the first cover plate and the second cover plate;   with the outlet in the closed state, applying the fluidic pressure in the direction of gravity from the first end of the housing toward the second end;   with the outlet in the open state, applying the fluidic pressure in the direction of gravity from the first end of the housing toward the second end; and   evaluating the sealing and blocking properties of the wellbore fluid to flow through the vug in the inner wall of the wellbore based on a comparison of results of flow of the first wellbore fluid and the second wellbore fluid through the outlet in the open state.   
     
     
         3 . The method of  claim 1 , wherein the housing is transparent, wherein the method further comprises visually evaluating the properties of the wellbore fluid based on visual inspection of an effect of applying the fluidic pressures on the wellbore fluid in the inner volume with the outlet in the closed state and with the outlet in the open state. 
     
     
         4 . The method of  claim 1 , further comprising:
 coupling a flexible hose to the outlet, the flexible hose representing a flow pathway through the vug within a formation starting at the inner wall of the wellbore; and   visually observing flow through the flexible hose with the outlet in the open state.