Screen Pipe for Thick Oil Thermal Recovery in Horizontal Well Completion
A screen pipe, comprises a base pipe with a plurality of oil inlet holes arranged on an outer wall of the base pipe; wherein the screen pipe comprises: a plurality of reinforcing ribs are disposed on an outer circumference wall of the base pipe along an axial direction of the base pipe; a wrap wire is winded at intervals on the plurality of reinforcing ribs along a circumferential direction of the base pipe; and a triangular block shaped foam iron is filled in a space between two adjacent reinforcing ribs of the plurality of reinforcing ribs. When the present invention is in use, the thick oil enters into the gap between the wrap wire and the drive pipe through the wrap wire gap. After filtration by the foam iron, the thick oil enters into the base pipe through the inlet hole, realizing pumping and transportation of the oil.
The present invention relates to a screen pipe, and more particularly to a screen pipe for thick oil thermal recovery in horizontal well completion.
BACKGROUND OF THE INVENTIONOil resources exist in naturally formed oil reservoir, and the exploitation technology varies with different types and inherent characteristics of the reservoir. Thick oil, also called heavy oil, refers to heavy crude oil with high viscosity, high density, and high contents of colloid and asphalt, namely high viscosity heavy crude oil. Generally, the wax content of crude oil is low; therefore, the viscosity of crude oil is high and the flow resistance is large, making it difficult to recover crude oil.
Thick oil is an important constituent of hydrocarbon energy, and its characteristics are as follows: (1) Thick oil contains high levels contents of colloid and asphalt and low content of light fractions. Meanwhile, the relative density and viscosity of thick oil increase with the increase in the contents of colloid and asphalt. (2) The viscosity of thick oil is particularly sensitive to temperature. The viscosity decreases sharply with the increase in temperature, and such phenomenon is more significant in crude oil with high viscosity. (3) Thick oil contains many heteroatoms such as sulfur, oxygen, and nitrogen. (4) The content of paraffin in thick oil is generally low. However, a small number of oilfields are “double-high oil fields” with high contents of both asphalt and paraffin, and is characterized by having crude oil with high viscosity and high solidifying point. (5) The properties of crude oil in the same thick oil reservoir often vary greatly between different well sections of a vertical oil layer and between different wells on the same plane.
In China, the reserve of thick oil is rich, and the annual output of thick oil is accounted for about 10% of the total crude oil output. According to China's second national resource evaluation data, thick oil resources are about 8198.710 tons. However, under stratum temperature, thick oil is too viscous to flow, making it difficult to recovery thick oil by conventional methods. Because thick oil is too viscous and its mobility ratio over water is too high, the effect of common crude oil recovery method on thick oil recovery is very limited.
At present, the methods for improving recovery ratios of thick oil adopted in oil fields in China are mainly steam stimulation and steam flooding. However, while the recovery rate of thick oil may be up to 60% after steam stimulation and steam flooding, nearly 40% of thick oil is still not recovered after the multiple cycles of stimulation and steam flooding. After steam flooding on thick oil reserves, temperature and pressure of the oil layer change significantly, followed by changes in residual oil saturation between pores and residual oil distribution in the wells. However, owing to shallow burial and loose cementation of the oil layer, phenomenon such as casing damage, screen pipe damage, packer damage or sanding tend to occur during the recovery of horizontal wells and severely affect the recovery of horizontal wells.
BRIEF SUMMARY OF THE INVENTIONTherefore, the present invention provides a screen pipe for thick oil thermal recovery in horizontal well completion, for facilitating the rapid recovery of thick oil and avoiding clogging and damage of the screen pipe.
According to some embodiments of the present invention, a screen pipe for thick oil thermal recovery in horizontal well completion comprises a base pipe with a plurality of oil inlet holes arranged on an outer wall of the base pipe. A plurality of reinforcing ribs are disposed on an outer circumference wall of the base pipe along an axial direction of the base pipe; a wrap wire is winded at intervals on the plurality of reinforcing ribs along a circumferential direction of the base pipe; and a triangular block shaped foam iron is filled in as pace between two adjacent reinforcing ribs of the plurality of reinforcing ribs. When the present invention is in use, the base pipe is placed in the horizontal section of the horizontal completed well; thick oil enters into the gap between the wrap wire and the drive pipe through the wrap wire gap, and enters into the base pipe through the inlet holes after filtration by the foam iron, realizing pumping and transportation of the oil.
In the prior art, steam flooding technology has been used in the recovery of thick oil. In steam flooding, a steam injection well and a production well are set above an oil reservoir; steam is continuously injected into the steam injection well to heat the strata around the wellbore and the crude oil in the strata. A steam zone gradually expanding with the injection of steam is formed in the strata near the wellbore. The steam can reduce oil saturation of the steam zone to a lower degree, and drive the flowable crude oil (that is, the difference between original oil saturation and residual oil saturation) out of the steam zone. Meanwhile, in the horizontal section of the horizontal completed well, the steam moves vigorously toward an updip direction; and as driven by gravity, the heated crude oil moves toward a downdip direction. With the increase in temperature of the crude oil, oil-water and gravel mixture in the horizontal section of the horizontal completed well would boil, causing denudation of the crude oil (by disturbance caused by boiling of the mixture). In the present invention, the oil-water and solid mixtures begin to enter into a base pipe from the horizontal section of the horizontal completed well. A wrap wire is a full metal bar and winded at intervals on the plurality of reinforcing ribs to form a primary filter unit for solid gravels with large diameter in the oil-water. A foam iron forms a second filter unit for solid gravels with small diameter to realize the purpose of sand control for the base pipe. Moreover, when change in production pressure of the horizontal section of the horizontal completed well occurs due to the influence of liquid pressure and heat contained in the oil-water, a second filter zone formed between two adjacent reinforcing ribs of the plurality of reinforcing ribs would be compressed. However, a triangular block shaped foam iron is filled in the second filter zone; when deformation of the foam iron occurs under stress, a plurality of flow channels with irregular geometric shapes would still form in the second filter zone to allow the oil-water mixture to pass through. In addition, when stressed, pore channels in the foam iron change slightly, making it difficult to fully block the pore channels. Meanwhile, as the foam iron has a certain degree of flexibility, the pore channels in the foam iron would recover when elastic deformation is restored so that the seepage capacity of the second filter zone can be maintained to ensure successful recovery of the thick oil.
According to another embodiment of the present invention, the screen pipe for thick oil thermal recovery in horizontal well completion further comprises a plurality of strengthening ribs annularly disposed on the wrap wire along the axial direction of the base pipe. In the horizontal section of the horizontal completed well, the wrap wire is pressured by the oil layer, and the pressure varies constantly with the change in oil layer temperature. That is, during sudden changes in the pressure, the wrap wire is extremely vulnerable to damage. However, in the present invention, a plurality of strengthening ribs are annularly disposed on the wrap wire, providing a stable support for the primary filter unit formed by the wrap wire to cope with the constantly changing production pressure in the horizontal section of the horizontal completed well and extend the service life of the wrap wire.
According to yet another embodiment of the present invention, the outer wall of the wrap wire is coated preferably with TiALN-WC/C coating. As the friction coefficient of the TiALN-WC/C coating is only 0.1, the TiALN-WC/C coating can significantly reduce friction loss between the solids, such as gravel, and the wrap wire when the solids continuously contact the wrap wire. Meanwhile, the TiALN-WC/C coating is self-lubricating, greatly ensuring the service life of the wrap wire in the horizontal completed well.
According to yet another embodiment of the present invention, the base pipe further comprises a connector, wherein each of two ends of the base pipe is connected with a blind pipe through the connector respectively. Preferably, according to the actual needs in oil recovery, the base pipe is connected with the blind pipe though the connector for facilitating the pumping and transportation of crude oil. The present invention abandons direct welding of the blind pipe to the base pipe as adopted in the conventional art when laying the pipeline so as to facilitate the replacement of damaged wrap wires without having to replace the base pipe and wrap wire entirely, therefore reducing the production cost in thick oil recovery.
For making the above and other purposes, features and benefits become more readily apparent to those ordinarily skilled in the art, the preferred embodiments and the detailed descriptions with accompanying drawings would be put forward in the following descriptions.
The present invention would become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
The present invention would now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.
In
In the prior art, steam flooding technology has been used in the recovery of thick oil. In steam flooding, a steam injection well and a production well are set above an oil reservoir; steam is continuously injected into the steam injection well to heat the strata around the wellbore and the crude oil in the strata. A steam zone gradually expanding with the injection of steam is formed in the strata near the wellbore. The steam can reduce oil saturation of the steam zone to a lower degree, and drive the flowable crude oil (that is, the difference between original oil saturation and residual oil saturation) out of the steam zone. Meanwhile, in the horizontal section of the horizontal completed well, the steam moves vigorously toward an updip direction; and as driven by gravity, the heated crude oil moves toward a downdip direction. With the increase in temperature of the crude oil, oil-water and gravel mixture in the horizontal section of the horizontal completed well would boil, causing denudation of the crude oil (by disturbance caused by boiling of the mixture). In the present invention, the oil-water and solid mixtures begin to enter into a base pipe 4 from the horizontal section of the horizontal completed well. A wrap wire 2 is a full metal bar and winded at intervals on the plurality of reinforcing ribs 3 to form a primary filter unit for solid gravels with large diameter in the oil-water. A foam iron 8 forms a second filter unit for solid gravels with small diameter to realize the purpose of sand control for the base pipe. Moreover, when change in production pressure of the horizontal section of the horizontal completed well occurs due to the influence of liquid pressure and heat contained in the oil-water, a second filter zone formed between two adjacent reinforcing ribs 3 of the plurality of reinforcing ribs would be compressed. However, a triangular block shaped foam iron is filled in the second filter zone; when deformation of the foam iron 8 occurs under stress, a plurality of flow channels with irregular geometric shapes would still form in the second filter zone to allow the oil-water mixture to pass through. In addition, when stressed, pore channels in the foam iron 8 change slightly, making it difficult to fully block the pore channels. Meanwhile, as the foam iron has a certain degree of flexibility, the pore channels in the foam iron 8 would recover when elastic deformation is restored so that the seepage capacity of the second filter zone can be maintained to ensure successful recovery of the thick oil.
This embodiment further comprises a plurality of strengthening ribs 1 annularly disposed on the wrap wire 2 along the axial direction of the base pipe 4. In the horizontal section of the horizontal completed well, the wrap wire 2 is pressured by the oil layer, and the pressure varies constantly with the change in oil layer temperature. That is, during sudden changes in the pressure, the wrap wire 2 is extremely vulnerable to damage. However, in the present invention, a plurality of strengthening ribs are annularly disposed on the wrap wire 2, providing a stable support for the primary filter unit formed by the wrap wire 2 to cope with the constantly changing production pressure in the horizontal section of the horizontal completed well and extend the service life of the wrap wire.
As a preferred embodiment, the outer wall of the wrap wire 2 is coated with TiALN-WC/C coating. As the friction coefficient of the TiALN-WC/C coating is only 0.1, the TiALN-WC/C coating can significantly reduce friction loss between the solids, such as gravel, and the wrap wire 2 when the solids continuously contact the wrap wire 2. Meanwhile, the TiALN-WC/C coating is self-lubricating, greatly ensuring the service life of the wrap wire in the horizontal completed well.
As a preferred embodiment, according to the actual needs in oil recovery, the base pipe is connected with the blind pipe 7 though the connector 6 for facilitating the pumping and transportation of crude oil. The present invention abandons direct welding of the blind pipe 7 to the base pipe 4 as adopted in the conventional art when laying the pipeline so as to facilitate the replacement of damaged wrap wires 2 without having to replace the base pipe 4 and wrap wire 2 entirely, therefore reducing the production cost in thick oil recovery.
While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.
Claims
1. A screen pipe for thick oil thermal recovery in horizontal well completion, comprising a base pipe with a plurality of oil inlet holes arranged on an outer wall of the base pipe, wherein the screen pipe comprises:
- a plurality of reinforcing ribs, disposed on an outer circumference wall of the base pipe along an axial direction of the base pipe; a wrap wire, winded at intervals on the plurality of reinforcing ribs along a circumferential direction of the base pipe; and
- a triangular block shaped foam iron, filled in as pace between two adjacent reinforcing ribs, of the plurality of reinforcing ribs.
2. The screen pipe for thick oil thermal recovery in horizontal well completion according to claim 1, wherein further comprising: a plurality of strengthening ribs annularly disposed on the wrap wire along the axial direction of the base pipe.
3. The screen pipe for thick oil thermal recovery in horizontal well completion according to claim 1, wherein an outer wall of the wrap wire is coated with TiALN-WC/C coating.
4. The screen pipe for thick oil thermal recovery in horizontal well completion according to claim 1, further comprising: a connector, wherein each of two ends of the base pipe is connected with a blind pipe through the connector respectively.
Type: Application
Filed: Sep 28, 2016
Publication Date: Feb 28, 2019
Inventor: Changming He (Chengdu)
Application Number: 15/540,263
