FIELD OF INVENTION

This invention relates to oil and gas production. More particularly, the present invention relates to a device for compartmentalizing a horizontal open-hole section to two production flows and keeping the two flows separate. BACKGROUND OF INVENTION

Completion is a process in oil and gas production for getting an oil reservoir ready for production or injection. Basically, a completion process involves connecting the reservoir to the surface by providing a conduit for well stimulation treatments, isolating the producing reservoir from other zones, and protecting the integrity of the reservoir. There are many choices of completion type in the art can be used for different oil reservoir management plans. Examples of completion type may include open-hole completion, liner completion, and perforated cased hole completion. Among the various choices of completion type, open-hole completion is one of the most well-established types of completion since early days of the oil and gas industry. No casing or liner is cemented in place across the production zone in an open-hole completion, and in most design, sand-control and/or flow-control means are incorporated. Such formation is particularly popular in horizontal well completion, in which cemented installation is much costlier and technically difficult.

Horizontal well is a high-angle well drilled by placing a long wellbore section within the reservoir. In most situations, the well is rarely perfectly horizontal but tend to be near horizontal. A horizontal well usually comprises a tangent section drilled along a deviated well path to a kick off point just above the reservoir section. From there, the well is drilled at an increasingly higher angle toward an entry point which lands on the reservoir. Thereafter, the well continues at a near-horizontal orientation within the reservoir until a desired length of penetration is reached.

Comparing to the conventional vertical well open-hole completion, horizontal well open-hole completion enlarges significantly the contact with the reservoir, thus increasing the production capacity. Although horizontal well completion is much more expensive to drill and prone to failure, it is still economically and productively attractive as its increment in production rate is disproportionately higher than its cost. Hence, engineers are finding solutions to overcome the technical disadvantages of horizontal well completion to maximise its economic value.

One major drawback of a horizontal well is the pressure drop occur along the horizontal wellbore as fluid flows from the toe section of the well to the heel section of the well. Such effect is known as the heel-to-toe effect wherein unequal flow of fluid along the well path is caused by such differential in pressure. Hence, this may lead to water or gas coning at the heel section which may eventually result in an early end to the well productive life, leaving a substantial reserve left unrecovered near the toe section of the well.

In order to solve the problem of the heel-to-toe effect, some horizontal wellbores are segmented into at least two zones with control of fluid flow within each zone to ensure the fullest flow rates and maximum oil recovery. Conventionally, the wellbore is segmented into two zones and fluid flow in each zone is isolated from each other by the technique of tubing-casing dual or dual tubing strings. This involves identifying a possible mid-point for positioning a bottom seal which segments the reservoir into two zones, and stinging a tailpipe all the way to the bottom seal. Such conventional stinging technique usually encounters extreme string weight loss. It is difficult to locate the bottom seal and isolating the wellbore, unlike the conventional vertical completion which can rely on weight as an indicator. Hence, buckling of string or pipe may occur as a result of friction generating between the pipe and the horizontal wellbore. Nevertheless, multiple zone horizontal well completion is still of a huge interest in the field. Therefore, there exists a need for a solution to solve all of the abovementioned problems.

SUMMARY OF INVENTION

This invention objects to provide a solution to the problems.

The present invention describes a device for splitting the production section of the horizontal well completion assembly comprising a hollow body dimensioned to fit closely within the production casing such that a first fluid flow is constraint within the body; and a plurality of apertures for allowing a second fluid flow through the space between the string of tubing and the production casing.

Preferably, the device comprises a plurality of longitudinal vanes extending from the outer surface of the hollow body to contact with the inner surface of the production casing to direct the second fluid flow through the apertures. Alternatively, the vanes can be replaced by a plurality of ribs extending from the periphery of the hollow body to contact with the inner surface of the production casing to direct the second fluid flow through the apertures. In one embodiment, the device may comprise both ribs and vanes, and preferably the vanes are integral of the ribs.

Preferably, each of the vanes has a means for preventing movement between the production casing and the device. Such means for preventing movement between the production casing and the device can be in the form of a shoulder to engage with a protrusion on the inner surface of the production casing.

Preferably, the upstream end of the hollow body has a screw-threaded portion to form a connection between the hollow body and the inner surface of the production casing. A sealing ring is preferred to be provided towards the screw-threaded portion to prevent corrosive fluid from contacting the screw thread.

Preferably, the downstream end of the hollow body is configured or structured in a way that a means for connecting the string of tubing is provided.

The present invention also describes a horizontal well completion assembly comprising a horizontal section across an oil reservoir, the section having sand screens for filtering solid particulates from oil entering the section; a production casing extending from one end of the horizontal section to the surface; a bottom seal mounted within the horizontal section for segmenting the horizontal section into two; a first string of tubing extending from the bottom seal to the surface and carrying a first fluid flow; a second string of tubing extending from a point within the production casing to the surface and carrying a second fluid flow; a dual packer mounted within the production casing for simultaneously supporting the two strings of tubing; and a device according to any of the preceding claims mounted within the production casing near the horizontal section for supporting the first string of tubing while allowing the second fluid flow to pass through.

The preferred embodiment of the invention consists of novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings and particularly pointed out in the appended claims; it being understood that various changes in the details may be effected by those skilled in the arts but without departing from the scope of the invention or sacrificing any of the advantages of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated. FIGURE 1 shows a simplified illustration of a horizontal open-hole completion assembly.

FIGURE 2 is a perspective view of the device. FIGURE 3 illustrates two fluid flow paths through the device of FIGURE 1.

FIGURE 4 is a partial cross-sectional view of the device being installed in a

production casing. FIGURE 5 is a partial cross-sectional view of the device being installed in a

production casing.

FIGURE 6 is (A) a left side view of FIGURE 3 and (B) a right side view of

FIGURE 3.

FIGURE 7 is a cross-sectional view of the device being installed in a section of a horizontal completion assembly.

FIGURE 8 illustrates two fluid flow paths through the device of FIGURE 6. DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings. However, it is to be understood that limiting the description to the preferred embodiments of the invention and to the drawings is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

This invention relates to oil and gas production. More particularly, the present invention relates to a device for compartmentalizing a string of tubing within a horizontal open-hole completion assembly with two production flows and keeping the two flows separate.

To aid in illustration and better understanding of the invention, a horizontal open-hole completion assembly is described in the following description in a simpler manner by referring to FIGURE 1 without excluding other possible or conventional use of devices, parts, or techniques. Generally, the completion assembly comprises a substantially horizontal section (11) within an oil reservoir or production zone (not shown) with a guide shoe (16) mounted at the end of the horizontal section (11) to serve as an end point of the completion assembly. The end of the horizontal section (11) is commonly known as the toe section (14) while the beginning of the horizontal section (11) is commonly known as the heel section (15). Following the heel section (15) is a tangent section (12) with a deviated well path which leads to the surface (not shown). Sometimes, a vertical section (13) leading from the tangent section (12) may be provided before the well path reaches the surface.

Production casing (7) is provided along the tangent section (12) up to the surface leaving the horizontal section (11) substantially bare. Sand screens (17) are installed along the horizontal section (11) till the toe section (14) to isolate unwanted solid particulates from entering the well path. Conventional flow control devices (not shown) may be installed to keep the oil flow in one direction towards the surface. To segment the production zone into two, a bottom seal or a seal bore extension (18) is mounted at a possible mid-point of the horizontal section (11) with a first string of tubing (9) sting to ensure oil flow from a first segment (not shown) of the production zone being isolated from the second segment (not shown). A second string of tubing (10) is provided somewhere in the tangent section (12) to receive oil flow from the second segment of the production zone. Both strings of tubing (9, 10) are simultaneously supported within the production casing (7) using a conventional dual packer (19) mounted therein.

As depicted in the“Background of Invention”, stinging an extended tubing (9) to the mid-section of the horizontal section (11) is difficult due to the extreme horizontal length that can cause excessive drag and lose all tubing (9) weight. This phenomena will create difficulties in locating and isolating the zones. In order to solve this problem, the invention provides a solution by segmenting the first string of tubing (9) in to two separate portions and providing additional support for the first string of tubing (9) thus removing any possible occurrence of loss of tubing weight while keeping two oil flows separate. This cannot be done by using a conventional single packer for supporting the string of tubing which will block oil flow from the second segment of the production zone. Further, it is technically difficult and uneconomical to extend the length of the second string of tubing (10) and locate another dual packer within the production casing (7).

The invention discloses a device (100) for supporting or compartmentalizing a string of tubing within a production casing (7) of a horizontal open-hole completion assembly. Such device (100) not only is able to support the string of tubing but can also allow two fluid flows to pass through without mixing. The device (100) may be mounted at any point of the production casing (7) but is normally positioned above or at the start of the horizontal pay zone with its inner string (9) extended all the way to the mid-point section of the horizontal pay zone to provide a reasonable structural integrity of the assembly. For purpose of illustration, one end of the device (100) closer to the surface will be referred as the“heel end” and the other end of the device (100) will be referred as the“toe end”.

With reference to FIGURE 2-6, the device (100) comprises a hollow body dimensioned to fit closely or tightly within the production casing (7) such that a first fluid flow (9A) from the first segment of the production zone is constraint within the hollow space (8) of the body. The first string tubing (9) carrying the first fluid flow (9A) is separated into two sections joint together using the device (100) to form a complete string of tubing. Various techniques of connection known in the field can be employed and will not be discussed in details herein. At least an aperture (1), and preferably a plurality of apertures (1), is provided to allow a second fluid flow (10A) from the second segment of the production zone to pass through and maintain within the space between the production casing (7) and the first string of tubing (9). This can be done by having the first string of tubing (9) connected to the device (100), particularly to the hollow space (8) of the hollow body and the apertures (1) being spaced around the hollow space (8). A non-limiting example (not shown) of such device is a donut-like article having an inner diameter dimensioned to allow connection of the first string of tubing and a plurality of apertures spaced around the hollow centre.

According to the preferred embodiment of the invention, the device (100) comprises a plurality of longitudinal vanes (4) extending from the outer surface of the hollow body is provided to closely engage with the inner surface of the production casing (7), and apertures (1) are formed between the vanes (4). Accordingly, a portion of the hollow body may not be able to closely or tightly engage with the inner surface of the production casing (7), but the engagement will be relied on the vanes (4). Alternatively, the apertures (1) can be formed by having a plurality of ribs (not shown) extending from the periphery of the hollow body at its heel end to closely contact with the inner surface of the production casing (7). It is possible to have both ribs and the vanes (4) extending from the hollow body and if so, preferably, the ribs and the vanes (4) are an integral unit so that the engagement between the inner surface of the production casing (7) and the hollow body can be greater. The existence of the vanes (4) naturally divides the second fluid flow (10A) into a plurality of flow paths, each of the flow paths is in between two vanes (4), such that in overall the second fluid flow (10A) is directed towards the apertures (1). It shall be noted that the apertures (1) are isolated from the hollow space (8) of the hollow body so that the two fluid flows (9A, 10A) can be kept separated and not to be mixed. As described by the preferred embodiment of the invention, the device (100) comprises a screw-threaded portion (2) at the heel end of the hollow body to form a fastening connection between the hollow body and the inner surface of the production casing (7). Accordingly, a portion of the heel end of the hollow body is in a close engagement with the inner surface of the production casing (7) while the rest of the hollow body with the vanes (4) extending from its outer surface having a relatively smaller dimension is not. Optionally, the whole portion of the heel end with close engagement with the production casing (7) is provided with screw thread (2), but preferably only a part of the portion is screw-threaded. It is important to prevent the screw thread (2) from contacting with the second fluid flow (10A) which can cause erosion on the screw thread (2). Hence, a sealing ring (3) is provided on the portion of heel end with close engagement and between the screw-threaded portion (2) and the ribs/vanes (4). Such sealing ring (3) can also prevent seepage of the second fluid flow (10A) through the screw- threaded portion (2). In accordance to the preferred embodiment of the invention, the vanes (4) comprises a means (5) for preventing movement between the production casing (7) and the device (). Particularly, the means (5) can also aid in locating the device () within the production casing (7). Preferably, the means (5) is a shoulder (5A) that engages with a protruding structure on the inner surface of the production casing (7). Optionally, the vanes (4) can be provided with a further shoulder (5B) as a secondary point of reference for locating the device ().

Preferably, the toe end of the device () is provided with a means or configuration (6) to allow connection of one section of the string of tubing, particularly the first string of tubing (9), to the hollow body. The string of tubing (9) can be connected to the toe end of the device (100) by various techniques. In one example, the string of tubing (9) can be mounted on the inner surface of the hollow body. In another example (not shown), the hollow body can be partially inserted and mounted within the string of tubing. Yet in another example (not shown), the string of tubing can be connected to the periphery of the hollow space in an end-to-end fashion. FIGURE 7-8 shows a cross-sectional view of the device (100) being installed in a section of a horizontal completion assembly with a section of the string of tubing (9) being connected to the toe end of the device (1), according to an exemplary embodiment of the invention. Likewise, the other section of the string of tubing (9) can be connected to the heel end of the device (100) with a like technique to form a complete string of tubing, and the connection will not be illustrated in details in FIGURE 7-8.

Although the invention has been described and illustrated in detail, it is to be understood that the same is by the way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.