CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application that claims priority to Chinese Application Serial No. 201911418591.3 filed on Dec. 31, 2019, the disclosure of which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to the technical field of tubing, and in particular, to a multichannel composite coiled tubing (CCT).

BACKGROUND

Coiled tubing is widely used in workover, drilling, completion, logging and other operations in oil and gas fields, which runs through the whole process of oil and gas production and is known as a “universal operation machine”. However, coiled tubing has only a single channel, and thus has limitations when operating in oil and gas fields, especially in layered water injection. Because of the complex geological conditions, most of the oil fields in China have strong reservoir heterogeneity and great differences in reservoir porosity and permeability. If unified water injection is adopted directly, it will cause too much water absorbed in the high-permeability layer and insufficient or even no water absorbed in the middle and low-permeability layers. Consequently, the high-permeability layer will have poor oil displacement and the injected water may inrush, leading to premature flooding of the oil well. As for the medium and low-permeability layers, they will have a lower recovery factor and become a remaining oil-enriched area. Therefore, layered water injection is generally adopted for multi-layer reservoirs at home and abroad. The current layered water injection method usually uses tubing as the main channel for water injection. An eccentric water injector is suspended at the bottom of the tubing, and the eccentric water injector is connected to the ground control system through a cable. The water injection and the test of the formation pressure are completed through the cables. The tubing needs to be connected one by one during the running process, and the cable is bound to the outside of the tubing. The operation and test procedures are complicated, the pressure is difficult to measure, and water injection additives cannot be selected to match different reservoirs.

SUMMARY

The present invention provides a multichannel CCT. The present invention effectively solves the problems in the prior art that the operation and test procedures are complicated, the pressure is difficult to measure and water injection additives cannot be selected to match different reservoirs.

To achieve the above purpose, the present invention provides the following technical solutions: A multichannel composite coiled tubing (CCT) includes three inner pipes and an insulator, where the insulator is provided therein with a plurality of the inner pipes; the insulator is nested inside a sheath; a protective layer is welded outside the sheath; a compressive layer is welded outside the protective layer; a plurality of armored tubes are bonded to the outside of the compressive layer; a fiber layer is bonded to the outside of the armored tubes; a filler is provided among the armored tubes between the fiber layer and the compressive layer; an anti-corrosive layer is bonded to the outside of the fiber layer.

According to the above technical solution, there are 15-35 armored tubes arranged in a ring shape.

According to the above technical solution, a conduit is embedded in the side of the inner pipe inside the insulator, and a shield layer is adhered to the outside of the conduit.

According to the above technical solution, an armored layer sleeves the outside of the inner pipes.

According to the above technical solution, the shield layer is a shield net and the conduit is a copper wire.

A method for preparing a multichannel CCT includes the following steps:

S1. analyzing a service condition and a function of the three-channel-combined coiled tubing;

S2. performing material selection, mechanical property design and structure selection of the tubing;

S3. performing fine wrapping, heat pipe internal protection and thermal treatment molding;

S4. inspecting and testing after production; and

S5. applying after inspection and testing are qualified, and recording the data.

According to the above technical solution, in step S2, the mechanical property design covers tensile strength, crushing strength and internal pressure strength of the tubing;

the material selection includes: designing a structural parameter of the multichannel tubing for layered water injection according to a general flow requirement of coiled tubing operation; determining an outer diameter of the multichannel tubing, and a geometric size, a tensile capacity and a pressure bearing capacity of each channel; selecting an optimal multichannel arrangement scheme to organically combine the channels of the coiled tubing to avoid the problems of low space utilization, difficult processing, large gap, easy loosening and sliding, where through the material selection and structural design, material and production costs are reduced;

structure selection: during use, the coiled tubing is in a plastic deformation state, and repeated lifting and descending will cause relative displacement of the channel and damage the product structure; the production technology of multichannel tubing for layered water injection is actively explored according to the existing production technology of coiled tubing and cables, so as to achieve manufacturing feasibility goals such as functional design, structural design and continuous design.

According to the above technical solution, in step S3, the inner pipe and the conduit are placed in a mold; then a raw material of the insulator is cast into the mold, and an outer layer is sleeved and cast; finally the molding is detected.

According to the above technical solution, in step S3, the inner pipe and the armored layer are fixed; then a raw material of the insulator is cast into a mold, and an outer layer is sleeved and cast; finally the molding is detected.

According to the above technical solution, the data in step S5refers to cost reduced.

Compared with the prior art, the present invention has the beneficial effects of scientific and reasonable structure and safe and convenient use.

1. The operation and test procedures are simple, the pressure is easy to measure, and a water injection additive can be easily selected to match different reservoirs. In addition, the coiled tubing is insulated, satisfying pressure transmission and logging through two cables.

2. A compressive layer and an armored tube are convenient for extending the life of the tubing. The armored tube and a fiber layer improve the toughness and softness of a pipe gallery, which can adapt to different terrains. An anti-corrosive layer improves the service life of the tubing.

3. The service conditions and functions of the three-channel-combined coiled tubing are analyzed to realize normal data acquisition. Material selection, mechanical property design and structure selection are performed to realize reasonable material use. The optimal multichannel arrangement scheme is selected to organically combine the channels of the coiled tubing to avoid the problems of low space utilization, difficult processing, large gap, easy loosening and sliding. Through the material selection and structural design, the material and production costs are reduced.

4. The costs are reduced while normal use is ensured.

