Selective segmented well cementing technology of double-target layer coal bed gas well and well structure

Abstract

The invention belongs to the technical field of coal bed gas well cementation, and specifically relates to a selective segmented well cementing technology of a double-target layer coal bed gas well and a well structure. The upper and lower intervals of two target coal beds are sealed and cemented by one-time well cementation; the well structure with target coal beds having set sliding sleeves inside and without cementing the well, and the corresponding process reduce reservoir stratum pollution and improve the permeability. The selective segmented well cementing technology has the advantages that (1). the sliding sleeves are set in coal bed sections without well cementing, so that the pollution of well cementing cement rings to coal beds is reduced, and meanwhile the coal beds can be prevented from collapsing into a shaft; (2). the one-time well cementation realizes the cement well cementation in the non-coal bed section, prevents a water-rich stratum from affecting the subsequent drainage, and meanwhile maintains the original permeability of the coal bed section; (3). the second-section well structure has a simple structure, downhole materials are set at one time, and the operation efficiency is high; (4). compared with the technical scheme with CN104481468B, the selective segmented well cementing technology does not sand filling and sand flushing, does not cause reservoir stratum turbulence and reduces the permeability of near-wellbore areas; and (5). the sliding sleeves are set in the coal bed sections in advance, and the subsequent fracturing construction does not require perforation.

Description

Technical field [0001] The invention belongs to the technical field of coalbed methane cementing, and specifically relates to a selective segmented cementing process and a well structure of a dual-target layered coalbed methane well. Background technique [0002] Establishing communication between the production layer and the borehole through the completion of coalbed methane is the key link between gas production and drilling. Commonly used CBM well completion methods include open hole completion, casing completion, and cave completion. In order to prevent the drilling fluid and cement from damaging the coal seam, the open hole of the coal seam section is not cemented. Although the damage to the reservoir is small, the well needs to be cleaned frequently due to the collapse of the coal seam. The casing completion is cemented for the coal seam section. , Stabilize the structure of the reservoir section, and cooperate with hydraulic fracturing in the later stage. The disadvantage...

AI Technical Summary

Problems solved by technology

However, there are still deficiencies in this scheme: ①The screen pipe in the coal seam section and the casing below it need special running tools to run the casing pipe and screen pipe and recover the upper part; The communication between the formation and the wellbore cannot be blocked. If there is a water-rich formation, it will be difficult to lower the liquid level, which is not conducive to the desorption of coalbed gas. The reservoir pressure surge during the sand washing process has an adverse effect on the permeability of the near-wellbore area. ④It is only applicable to a single coal seam. For the area where multiple target layers are developed at the same time, sand filling and sand washing operations need to be performed many times, and the efficiency is low. ⑤Coal seams The space between the screen and the screen is filled with fracturing sand. There are 16 holes per meter on the screen 7. The diameter of the hole is 10mm, and the contact surface is very small. It is almost impossible to wash all the fracturing sand between the screen and the coal seam. , ⑥If the fracturing sand in the screen section enters the wellbore along the screen pores, it is easy to cause the pump to get stuck and affect the stability of drainage

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