The present invention relates to a flow control device and a flow control method.
The present invention is based on a self adjusting or autonomous valve as disclosed in WO 2008/004875 A1 and operating by the Bernoulli principle, belonging to the applicant of the present invention.
Devices for recovering of oil and gas from long, horizontal and vertical wells are known from U.S. Pat. Nos. 4,821,801, 4,858,691, 4,577,691 and GB patent publication No. 2169018. These known devices comprise a perforated drainage pipe with, for example, a filter for control of sand around the pipe. A considerable disadvantage with the known devices for oil/and or gas production in highly permeable geological formations is that the pressure in the drainage pipe increases exponentially in the upstream direction as a result of the flow friction in the pipe. Because the differential pressure between the reservoir and the drainage pipe will decrease upstream as a result, the quantity of oil and/or gas flowing from the reservoir into the drainage pipe will decrease correspondingly. The total oil and/or gas produced by this means will therefore be low. With thin oil zones and highly permeable geological formations, there is further a high risk that of coning, i.e. flow of unwanted water or gas into the drainage pipe downstream, where the velocity of the oil flow from the reservoir to the pipe is the greatest.
From World Oil, vol. 212, N. 11 (11/91), pages 73-80, is previously known to divide a drainage pipe into sections with one or more inflow restriction devices such as sliding sleeves or throttling devices. However, this reference is mainly dealing with the use of inflow control to limit the inflow rate for up hole zones and thereby avoid or reduce coning of water and or gas.
WO-A-9208875 describes a horizontal production pipe comprising a plurality of production sections connected by mixing chambers having a larger internal diameter than the production sections. The production sections comprise an external slotted liner which can be considered as performing a filtering action. However, the sequence of sections of different diameter creates flow turbulence and prevent the running of work-over tools.
When extracting oil and or gas from geological production formations, fluids of different qualities, i.e. oil, gas, water (and sand) is produced in different amounts and mixtures depending on the property or quality of the formation. None of the above-mentioned, known devices are able to distinguish between and control the inflow of oil, gas or water on the basis of their relative composition and/or quality.
With the autonomous valve as disclosed WO 2008/004875 A1 is provided an inflow control device which is self adjusting or autonomous and can easily be fitted in the wall of a production pipe and which therefore provide for the use of work-over tools. The device is designed to “distinguish” between the oil and/or gas and/or water and is able to control the flow or inflow of oil or gas, depending on which of these fluids such flow control is required.
The device as disclosed in WO 2008/004875 A1 is robust, can withstand large forces and high temperatures, prevents draw dawns (differential pressure), needs no energy supply, can withstand sand production, is reliable, but is still simple and very cheap.
The device or valve as disclosed in WO 2008/004875 A1 is possibly the best option today. Still there might be problems cutting off both water and gas in the same valve. It might also be a problem to cut off water in the case of low viscosity oil. In addition the present invention could provide a slower or even permanent change in the characteristic of the device or valve as disclosed in WO 2008/004875 A1. Instability may be a potential problem with said device or valve due to the fast response of the body or disk and the long time constant to the inflow into the screens. Long time delays generally have potential for instability in regulation systems. With the prior art valve as disclosed in WO 2008/004875 A1 there is also a lack of possibility to permanently seal off a section of the well if only water is produced.
US 2008/149323 discloses a material sensitive downhole flow control device. US 2007/044962 discloses a system for isolating flow in a shunt tube, using a swellable material. US 2006/175065 discloses a water shut off method using a material that swells in the presence of a specific substance or substances.
The method and apparatus according to the present invention is set out in independent claims 1, 8, 11 and 22. A further aspect of the present invention is set out in claim 9.
Preferred embodiments of the invention are stated in the dependent claims.
The present invention will be further described in the following by means of examples and with reference to the drawings, where:
a) shows, in larger scale, a cross section of the control device according to WO 2008/004875 A1, b) shows the same device in a top view.
a) and b) shows the prior control device 2 of WO 2008/004875 A1 in larger scale. The device consists of a first disc-shaped housing body 4 with an outer cylindrical segment 5 and inner cylindrical segment 6 and with a central hole or aperture 10, and a second disc-shaped holder body 7 with an outer cylindrical segment 8, as well as a preferably flat disc or freely movable body 9 provided in an open space 14 formed between the first 4 and second 7 disc-shaped housing and holder bodies. The body 9 may for particular applications and adjustments depart from the flat shape and have a partly conical or semicircular shape (for instance towards the aperture 10.) As can be seen from the figure, the cylindrical segment 8 of the second disc-shaped holder body 7 fits within and protrudes in the opposite direction of the outer cylindrical segment 5 of the first disc-shaped housing body 4 thereby forming a flow path as shown by the arrows 11, where the fluid enters the control device through the central hole or aperture (inlet) 10 and flows towards and radially along the disc 9 before flowing through the annular opening 12 formed between the cylindrical segments 8 and 6 and further out through the annular opening 13 formed between the cylindrical segments 8 and 5. The two disc-shaped housing and holder bodies 4, 7 are attached to one another by a screw connection, welding or other means (not further shown in the figures) at a connection area 15 as shown in
The present invention exploits the effect of Bernoulli teaching that the sum of static pressure, dynamic pressure and friction is constant along a flow line:
When subjecting the disc 9 to a fluid flow, which is the case with the present invention, the pressure difference over the disc 9 can be expressed as follows:
Due to lower viscosity, a fluid such as gas will “make the turn later” and follow further along the disc towards its outer end (indicated by reference number 14). This makes a higher stagnation pressure in the area 16 at the end of the disc 9, which in turn makes a higher pressure over the disc. And the disc 9, which is freely movable within the space between the disc-shaped bodies 4, 7, will move downwards and thereby narrow the flow path between the disc 9 and inner cylindrical segment 6. Thus, the disc 9 moves down-wards or up-wards depending on the viscosity of the fluid flowing through, whereby this principle can be used to control (close/open) the flow of fluid through of the device.
Further, the pressure drop through a traditional inflow control device (ICD) with fixed geometry will be proportional to the dynamic pressure:
where the constant, K is mainly a function of the geometry and less dependent on the Reynolds number. In the control device according to the present invention the flow area will decrease when the differential pressure increases, such that the volume flow through the control device will not, or nearly not, increase when the pressure drop increases. A comparison between a control device according to the present invention with movable disc and a control device with fixed flow-through opening is shown in
This represents a major advantage with the present invention as it can be used to ensure the same volume flowing through each section for the entire horizontal well, which is not possible with fixed inflow control devices.
When producing oil and gas the control device according to the invention may have two different applications: Using it as inflow control device to reduce inflow of water, or using it to reduce inflow of gas at gas break through situations. When designing the control device according to the invention for the different application such as water or gas, as mentioned above, the different areas and pressure zones, as shown in
Fluids with different viscosities will provide different forces in each zone depending on the design of these zones. In order to optimize the efficiency and flow through properties of the control device, the design of the areas will be different for different applications, e.g. gas/oil or oil/water flow. Hence, for each application the areas needs to be carefully balanced and optimally designed taking into account the properties and physical conditions (viscosity, temperature, pressure etc.) for each design situation.
The spring element 18 is used to balance and control the inflow area between the disc 9 and the inlet 10, or rather the surrounding edge or seat 19 of the inlet 10. Thus, depending on the spring constant and thereby the spring force, the opening between the disc 9 and edge 19 will be larger or smaller, and with a suitable selected spring constant, depending on the inflow and pressure conditions at the selected place where the control device is provided, constant mass flow through the device may be obtained.
When producing oil and/or gas the conditions may rapidly change from a situation where only or mostly oil is produced to a situation where only or mostly gas is produced (gas breakthrough or gas coning). With for instance a pressure drop of 16 bar from 100 bar the temperature drop would correspond to approximately 20° C. By providing the disc 9 with a thermally responsive element such as a bi-metallic element as shown in
The above examples of a control device as shown in
Embodiments of the present invention are shown in
More specifically
The main inventive idea is thus to use a material that changes it properties (volume and/or elastic modulus) under the presence of a given chemical substance. The material should be integrated in the valve or control device 2 to modify the inflow characteristics over time that the viscosity discrimination might not work very well for, in particular the presence of water.
The shut off mechanism can thus be based on two principles:
There is a material that changes property in a sheltered area of the valve or control device 2. The simplest example is a polymer that swells under the influence of water. Such polymers can e.g. double their volume when exposed to water. The process takes time as the water needs to diffuse into the polymer. The increased volume behind the disc or body 9 expels flow from the flow channel and hence modifies the valve or control device 2. In the case of much water the swelling backing material 24 can fill the complete space behind the disc or body 9 and hence permanently nearly block the valve 2.
In the second principle, by introducing said oppositely arranged wedges 25, the edge geometry and hence the reference pressure transmitted to the open space or cavity 14 behind the disc or body 9 is modified. In principle this can also be a jaw (not shown) that cuts off flow. It should be noted that the second principle can be configured to reverse the effect of the valve or control device 2 leaving the edge area the high velocity area which might be advantageous for specific applications.
Some important characteristics are as follows:
Examples of materials that swell in water, but that are little affected by hydrocarbons, are polymers based on e.g. Vinyl alcohol or acrylamid. The more polar, the higher the affinity to water. One example that is highly absorbing or swelling is Sodium polyacrylate. The affinity to water can be tailored to a large extent with the cross-linking. The principles are described in U.S. Pat. No. 3,220,960 (Cross-linked Hydrophilic Polymers and articles made there from). The amount of swelling and the mechanical properties can to a large extent be tailored by the degree of cross-linking.
In addition a further selectivity can be obtained following along the lines of e.g. U.S. Pat. No. 4,591,441 (Method and apparatus for separating oil from water) where a hydrogel is used to have an oil resisting/repelling function.
For higher temperatures and pressures, micro porous materials such as Zeolites (in the extreme in the form of molecular sieves) can be tailored to react with water or potentially water and methane. Generally the volume changes are relatively small, but can exert a considerable force.
Most or all such material systems are in principle reversible. However, the amount of water that is required to induce swelling and how low the amount will have to be for the material to go back to its original shape will vary and many such materials will be too sensitive to water. On the other hand, the application will produce a pressure typically counteracting the swelling mechanically attempting to drain the material and hence counteracting the naturally occurring swelling.
Reference is made to the paper entitled “Swellable Technology Systems Provide A Simple Zonal Isolation Method In The North Sea” by Alf Kolbjørn Sevre and Sverre Anderssen, available from http://bergen.spe.no/publish files/3.3 Easywell S.Andressen.pdf. Typical packers swell permanently in oil, but swelling in water is often reversible. The paper also illustrates another interesting effect that can be utilized; swelling in water can be governed by salinity. For example, the material can change when there is an influx of salty reservoir water. See also U.S. Provisional Patent Application No. 60/976,575 filed Oct. 1, 2007.
Rubber generally swells in oil or under the presence of hydrocarbons. Silicones are good examples of materials that are not influenced by water, but swells considerably with most hydrocarbons.
A large selection of materials for non reversible applications is referenced in WO 2006/003112.
A good example of a reversible swelling material system under contact with oil is: Methyl terminated, and silica and iron oxide filled, dimethyl polysiloxane, which is commercially distributed under the name of Red Silicone Rubber and is produced commercially by companies such as General Electric Company through its GE Silicone division. Reference is also made to U.S. Pat. No. 5,378,889 (Method and apparatus for detecting hydrocarbon fuels in a vapor state with an absorber-expander member).
The reader is referred to the following documents for further examples of the types of material that can be used in an embodiment of the present invention: JP 05123066, EP 1752690 A1, DE 35 39 595 A1, DE 42 11 302 A1, U.S. Pat. No. 6,358,580 B1, EP 0486869 B1, JP 10101850, U.S. Pat. No. 4,532,298, WO 2006/108784 A1 and U.S. Pat. No. 7,228,915 B2
Hence it has been demonstrated that a number of material systems can react reversibly and non reversibly to contact with:
A material with an appropriate property can be engineered and tailored to perform a particular function for a particular application, for a limited range in composition, temperature and pressure.
The main function in the above embodiments is to alter the flow geometry and hence either:
Referring to
Referring to
For each different use case, a detailed engineering consideration is required of the balancing forces involved for a given set of viscosities and chemical property of the phases.
It will be appreciated that the material 24 may also be provided behind the disc 9 in
The present invention is only restricted by the appended claims, and not by the embodiments as described above. In the context of the present invention the term “oil and/or gas production” includes any process related to exploration or exploitation of oil and/or gas (e.g. installation, injection of steam, etc.) and is thus not restricted to a production mode.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/NO2010/000104 | 3/18/2010 | WO | 00 | 11/13/2012 |