A variable density pre-packed screen and its use

Abstract

The present invention relates to a variable density pre-filled screen and its use method. The variable density pre-filled screen includes a base pipe, a plurality of first flow holes are arranged on the side wall of the base pipe, and a protective cover is provided on the outer side of the base pipe. Structure, the protective sleeve structure is equipped with an axially penetrating filling annulus, which can be tightly filled with ultra-low density proppant, the two ends of the filling annulus are open, and the base pipe is located at the two ends of the protective sleeve structure respectively The sleeve is provided with unlocking structures, each unlocking structure can close and fill the annular space from both ends, and each unlocking structure can move away from the protective sleeve structure under the action of the pressure of the blocked annular space. In the present invention, the unlocking structures at both ends of the protective sleeve structure can move away from the protective sleeve structure under the action of the clogged annulus clogging pressure, which can realize the high-density filling on the ground of the pre-filled screen and the low-density filling in the downhole. Effective control of sand control can also effectively reduce screen clogging, thereby effectively solving the contradiction between sand production and sand control.

Description

technical field [0001] The invention relates to the technical field of petroleum exploitation, in particular to a variable-density pre-packed screen pipe and a method for using the same. Background technique [0002] In my country, unconsolidated sandstone reservoirs occupy an important position. For example, there are a large number of such reservoirs in Shengli Oilfield, Liaohe Oilfield, Dagang Oilfield, Bohai Oilfield, and Jidong Oilfield in the Bohai Rim region. This type of reservoir has some common features: shallow burial, relatively weak cementation, and easy sand production during mining. [0003] As an important sand control method, mechanical screen sand control mainly includes: slotted screen, high-quality screen and pre-packed screen, etc. Among them: high-quality screens are suitable for homogeneous reservoirs and reservoirs with low shale content. The disadvantage is that the sand retaining medium is prone to erosion damage, resulting in sand control failure;...

AI Technical Summary

Problems solved by technology

Among them: high-quality screens are suitable for homogeneous reservoirs and reservoirs with low shale content. The disadvantage is that the sand retaining medium is prone to erosion damage, resulting in sand control failure; slotted screens are simple to process and low in cost, but they are prone to occurrence Due to the restriction of the processing technology, the sand control accuracy is limited, and it is only suitable for reservoirs with relatively coarse sand particle size; the pre-packed screen has the characteristics of partial gravel filling sand control mode, simple processing, convenient installation, suitable for In long horizontal wells, ultra-long horizontal wells and high-inclination wells, which are difficult to carry out gravel packing operations or have high operating costs, it has been found from field application that pre-packed screens are prone to clogging, resulting in a significant reduction in oil well productivity

This is mainly because the pre-packed screen gravel layer is too densely filled with gravel, which reduces the flow accuracy of the pre-packed screen, and the gravel layer where muddy particles are easy to stay leads to blockage of the screen

If the packing is loose, it is difficult to ensure the filling state of the gravel during the screen pipe transportation and screen pipe descending process, which will easily lead to local shortage and sand control failure

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