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New Progress in Sand Retention Media Plugging

Author:Admin  Time:2013-9-14 7:35:43

The plugging of sand retention media in sand control screen can result in decline of production rate or even production operation shutdown. Therefore, it is necessary to understand the mechanism of such plugging. In this paper, two mechanisms of screen sand retention media plugging are put forward, which concern bridge plugging in well bottom hole unpacked areas and bridge plugging inside the sand retention media. Then, four valuation indexes are proposed to evaluate the media plugging severity. Using micro-displacement testing device, the plugging process was experimentally simulated to verify the above plugging mechanism and determine the factors affecting sand retention media plugging process and severity. The test results show that the plug influencing factors mainly include flow or production time, sand production rate, silt content, shale content, and crude oil viscosity, etc. The tests also demonstrate both qualitatively and quantitatively the relationship between the plugging severity and various factors, the quantitative model of which is evolved based on the testing data fitting. Finally, a software package was programmed to evaluate and predict the sand retention media plugging dynamics. Along with the plugging mechanism, an integrated model and technology for plugging evaluation is formed, which can provide an effective means for optimizing parameters for the corresponding plug-removing design and implementation.

The rotary water jet is one of the most important techniques for horizontal well cleanup. The jet flow is used to remove plugging particles from sand control screens to recover their permeability. Currently, the operation optimization of this technique depends mainly on experience due to absence of applicable evaluation and design models for removing plugging materials. This paper presents an experimental setup to simulate the cleanup process of plugged screens by rotary water jetting on the surface and to evaluate the performance of a jetting tool. Using real plugged screens pulled from damaged wells, a series of tests were performed, and the qualitative relationships between the cleanup efficiency and various operational parameters, such as the type of fluids used, flow rate, mode of tool movement, etc., were obtained. The tests results indicated that the cleanup performance was much better when the rotary jetting tool moved and stopped periodically for a certain time than that when it reciprocated at constant speed. To be exact, it was desirable for the rotary jetting tool to move for 1.5-2 m and stop for 2-4 minutes, which was called the “move-stop-move” mode. Good cleanup performance could be obtained at high flow rates, and the flow rate was recommended to be no lower than 550-600 L/min. The tests results also indicated that complex mud acid was better than clean water in terms of cleanup performance. Good cleanup efficiency and high screen permeability recovery could be achieved for severely plugged screens. Rotary jetting is preferred for the cleanup of horizontal wells with severely plugged screens, and the screen permeability recovery ratio may reach 20% if optimized operation parameters were used.

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Department of Production, School of Petroleum Engineering, China University of Petroleum·66#, Changjiang Xi Road, Huangdao, Qingdao, Shandong, PR China(266580)