Small-diameter layered sand-prevention water injection full-well backwashing integrated pipe column and method

Abstract

The invention discloses a small-diameter layered sand-prevention water injection full-well backwashing integrated pipe column and method. Each subsystem comprises a production casing pipe, a top expanding packer, a bottom expanding packer and a sand-prevention water-injection backwashing unit, wherein sand-prevention water-injection backwashing unit comprises an inner-layer water-injection pipe column and an outer-layer sand-prevention pipe column; the subsystems are overlapped layer by layer to realize multi-layer layered sand prevention water injection; the axial section of the side wall ofthe lower end of the expanding packer is of a Y-shaped bifurcate structure, a sleeve of a water distributor is connected with an inner side branch of the Y-shaped bifurcate structure, and the water distributor is fixedly connected with an outer side branch of the Y-shaped bifurcate structure at the lower end of the expanding packer; the water distributor with a larger outer diameter is put into the sleeve of the water distributor with a larger inner diameter, so that the problem of combining sand prevention and water injection concentric double pipes in a small-diameter sleeve is effectively solved; and a system structure of each layer of up-and-down expanding packer, each layer of screen pipe up-and-down sand blocking packer and each unit up-and-down well washing mechanism is adopted, cooperative work is achieved, and layered sand prevention, layered water injection and full-well backwashing are achieved.

Description

technical field [0001] The invention relates to the technical field of downhole process pipe strings for oil field production, in particular to a small-diameter layered sand control water injection full well backwashing integrated pipe string and a method. Background technique [0002] Unconsolidated sandstone reservoirs are the main force of oilfield development. During development, there are development difficulties such as loose reservoirs, easy sand production, multiple layers encountered in a single well, and large differences in physical properties between layers. It is a main technical means of reservoir formation energy. At present, the mechanical layered sand control and layered water injection technology is mainly used in offshore oil fields. Since the production casing is 7in and above, the wellbore size is relatively large. The matching layered water injection string can realize layered sand control, layered water injection and full well backwashing. However, f...

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Problems solved by technology

The patent application with the application number 201811006392.7 "A layered sand control and layered water injection integrated pipe string and its lowering" discloses a process string that realizes the two functions of layered sand control and layered water injection, but here In the patent application, when the water injection well is due to procedures such as measuring and adjusting, stopping injection, and backwashing, the formation pressure fluctuations are likely to encourage the formation to spit out sand. Blocked by sand return, it is impossible to realize the regular full-well backwashing function required by the water injection process; and the water distributor and the screen are directly connected in series, and the screen adopts an annular structure with a sandwich wall, and the outer diameter of the screen is large, so it cannot meet this requirement. Requirements for layered sand control layered water injection and whole well backwashing of small diameter production casing

The patent application with the application number 201810883804.9 "A Device and Method for Layered Sand Control Water Injection and Backwashing in One String" discloses a process string for realizing the three functions of layered sand control water injection and backwash well in one string, but in In this patent application, the water distributor is placed in the screen pipe, so that the water injection string can be inspected and repaired separately in the later stage. However, under the condition of a small-diameter cased well, as mentioned above, the existing water distributor cannot be placed in a small casing. The inner diameter of the screen or oil pipe is small, and it is impossible to repair the layered water injection string after the layered mechanical sand control; at the same time, the patented technology uses a multi-section perforated screen for the purpose of setting and sealing the top of the sand control outer string Hanging seals and layered packers at all levels, but when backwashing the well, the perforated screen at the top becomes a shortcut for the backwashing well circulation, and can only realize the backwashing of the tubing section of the water injection string, and the layered water injection string It is difficult to effectively backwash the well

[0003] Therefore, at present, for onshore oilfields mainly exploited with small-diameter production casings, limited by the small size of the wellbore and the large outer diameter of the existing water distributor, it is generally used to run directly into the layered water injection string without sand control, or to use chemical After the sand control, the layered water injection string is lowered to perform layered water injection, but the chemical sand control effect is not good for multi-layer long wells, and under the erosion of large-volume water injection, the effective period of sand control is short, resulting in In the case of well surveying, stop injection or backwashing, sand is produced in the formation, and the water injection string is buried in the sand, so long-term water injection cannot be performed, the operation frequency is high, the operation volume is large, and the cost is high

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