EP0818603B1 - Oil pumping method and facility - Google Patents

Abstract

Installation for pumping a liquid from an underground source consists of a shaft (10) from the surface (12) to the source (14) that includes a chamber (40) that extends over its entire length, at least one casing pipe (18) passing through the chamber and communicating with it, and a valve assembly (34). The assembly (34) is used to selectively connect the chamber with a source of gas at a 1st pressure (36) that enables the liquid to fill the chamber and a source of gas at a greater 2nd pressure (38) to empty the chamber, the liquid being pushed back to a 1st outlet (30) through the casing pipe. A valve (52) mounted in the casing pipe (18) and a 2nd pipe (58;70) leads to a 2nd outlet (74). The flap valve reacts to the density of the fluid surrounding it so that a 1st liquid is pushed back to the 1st outlet and a 2nd liquid of higher density is directed to the 2nd outlet (74) through a 2nd pipe (58;70).

Description

The present invention relates to a pumping process a liquid effluent and, more particularly to a process pumping hydrocarbons from an oil well.

The present invention also relates to a pumping plant for petroleum effluent from from an underground source.

In some oil wells, the natural flow of hydrocarbons from the bottom to the surface is insufficient for allow or maintain commercial production. this is due either to the high viscosity of the hydrocarbons, or to too low natural pressure at the bottom of the well, or still a combination of the two. Water inflows into the wells can also limit the natural flow of hydrocarbons. In order to allow the production of the well on a commercial scale use a assistance system or well activation system. Through example, we can mount a pump at the lower end a production tube located in the well, where you can provide a gas injection system at the bottom of the well. The latter type of installation more commonly called "gas lift", used to lighten the column of hydrocarbons located in the well to facilitate its ascent to the surface.

However, these two assistance systems require the use of apparatus or installations in the well, place where temperatures and pressures are very high and where the surrounding environment can be very corrosive. These conditions at the bottom of the well cause failures or malfunctions of the activation equipment which, given its location in the well, require long and costly interventions. In addition, during these interventions the production of the well is stopped, which results in additional financial losses.

Another assistance system consists in pumping the hydrocarbons made from the surface. The document EP-A-579497 describes a method of pumping liquid from one end of a well to a outlet at the opposite end of the well, where regulates the gas pressure in one or more chambers so that they fill up with liquid. Then a pressure of superior gas is applied to each chamber in order to move the liquid and send it to the outlet. Each chamber is fitted with controlled inlet and outlet valves from level sensors to control the direction liquid flow. According to this document, the rooms can either be overlaid on top of each other inside the well, either be arranged side by side in a point near the exit of the well.

The positioning of the chambers superimposed in the well has advantages in that it allows to have a less bulky installation and energy efficiency optimized. However, this type of installation presents disadvantages since the superimposition of the rooms, each being provided with various valves and level detectors, requires one or more chambers to be removed from the well when there is a breakdown or failure in one of the lower rooms. In addition, the use of multiple rooms, each equipped with valves and detectors levels, makes maintenance forecasts difficult installation.

Document US-A-1,499,589 describes a method of pumping a effluent from a weak eruptive oil well. According to this process, the effluent fills an annular space defined between the wall of the well and a production casing which extends from the bottom of the well to the surface. Once annular space filled with effluent, gas under pressure is sent from the surface into the upper end of this space, causing displacement of the effluent and its up to the surface from the inside of the casing.

However, this type of process has drawbacks in which it ignores the fact that most of effluents from an oil well, contain, especially at the end of the deposit's life, a significant amount of water which can cause natural production to stop of the well, or limit the effectiveness of the gas lift. It is desirable to be able to separate water from hydrocarbons, bottom of the well, so that it can only rise to the surface hydrocarbons.

The subject of the present invention is an installation for pumping allowing the implementation of the pumping process. In order to achieve this object, the invention proposes a installation for pumping a liquid from a source underground including a well extending from the surface towards the liquid source, the well comprising a chamber extending substantially over its entire length, at least a casing crossing the chamber and communicating with it, and a set of valves for selectively placing the room in communication with a gas source at a first pressure allowing the liquid from the source to fill the chamber, and a source of gas to a second pressure greater than the first pressure, in order to empty the chamber, the liquid being returned to a first outlet by flow through the casing, characterized in what it includes, in addition, a valve mounted in the casing , and a second conduit leading to a second outlet, the valve being susceptible to react to fluid density which surrounds it in order to be able to repress a first liquid towards the first outlet, a second liquid, of density more important, being driven back to the second exit by the second conduit.

The present invention has the advantage of using an installation, whose maintenance is infrequent, especially for the components installed in the well, and which can be done in a simple way from the exit of the well.

• la figure 1 est une vue schématique en coupe d'un puits selon un premier mode de réalisation de l'invention ;
• la figure 1A est une vue en détail d'un élément de la figure 1 ;
• la figure 2 est une vue schématique en coupe d'un deuxième mode de réalisation ; et
• la figure 3 est une vue schématique en coupe d'un troisième mode de réalisation qui est une variante de celui de la figure 1.

Other characteristics and advantages of the present invention will emerge on reading the following description, given by way of explanation but not limitation, made in relation to the appended drawings in which:

• Figure 1 is a schematic sectional view of a well according to a first embodiment of the invention;
• Figure 1A is a detailed view of an element of Figure 1;
• Figure 2 is a schematic sectional view of a second embodiment; and
• FIG. 3 is a schematic sectional view of a third embodiment which is a variant of that of FIG. 1.

In FIG. 1, a well generally represented at 10, which, in the example illustrated, is an oil well, extends from the surface 12 of the ground, which can be the bottom of the sea, to a layer of reservoir rock 14. Well 10 is provided with a casing 16, extending along the well, and with a production tubing 18 extending from surface 12 to a point below a seal 20, called "packer", mounted in the casing in a leaktight manner at a point located a few meters, or a few tens of meters, below of the reservoir rock 14. A conduit 22, provided with a valve check valve 24, is arranged in a seal assembly 26, or packer, mounted in the well around the casing 18 at a point above the rock layer 14. The casing 18 comprises, at a point located approximately 100 m from surface 12, a safety valve 27 disposed immediately above a second packer 28 advantageously mounted in the well. AT its upper end, the casing 18 comprises an assembly of production valves 29, or "Christmas tree" intended for control the production rate of the well, and ensure its security. This set of valves communicates with a conduit production 30 forming the outlet of the well. In addition, the casing 18 comprises, towards its lower end, a valve non-return 32 intended to allow the liquid to flow only towards exit 30.

On the surface 12, a distribution system, formed by example of a set 34 of control valves is connected to a low pressure gas source 36, and a gas source high pressure 38. The pressure from each of the two sources of gas 36 and 38 is chosen according to the characteristics of the well, for example its depth, or the pressure of the deposit. As will be described in more detail below, these characteristics change over time, during the well production. Also, is it necessary to modify the gas pressures used correspondingly, in function of time.

The set of valves 34 communicates with the space annular 40, or chamber, defined between the casing 16 and the casing 18 and delimited by the packer 28 and the set of joint 26 by safety valves 42 and a conduit 44 which passes through a tubing suspension joint 46 or "tubing hanger" mounted at the upper end of the well. A annular space safety valve 48 can be mounted at the end of conduit 44.

The seal assembly 26 is provided with a device allowing the re-injection of water, which, in the example illustrated, is a valve 52, shown in more detail in FIG. 1A. This valve 52 comprises a tubular body 54, substantially coextensive with the casing 18 and provided with lateral openings 56, four in the illustrated example, which put the space annular 40 in communication with the lower end 58 tubing 18. This lower end 58 is provided with a non-return valve 60 which allows the flow of fluid, coming from the annular space 40, in the direction of the arrow 62 towards an aquifer underlying reservoir 14, no represented. The valve 52 includes a ball 64 which is adapted to abut on a seat 66 formed in the body 54, thereby closing the passage to the end lower 58 of the casing 18. The density of the ball 64 is chosen to be superior to that of hydrocarbons liquids from reservoir rock 14, but lower to that of water. Located near 0.9, this density results in ball 64 floating in water, but, when in the presence of hydrocarbons, it descends on seat 66, thus closing the end lower 58 of the casing 18. A conduit 50, on the whole seal 26, allows access to the valve 52 for possible maintenance operations.

The method of implementing the installation thus described is the next :

First, the annular space 40 is put in communication, by the set of control valves 34, with the low pressure gas source 36. The low pressure prevailing in the annular space 40 allows the mixture of hydrocarbons and water forming the effluent, coming from the reservoir layer 14, to go back up inside the well, through valve 24 and conduit 22, filling the annular space 40 to an intermediate level 67 upper, and thus driving the low pressure gas from the reservoir towards its source. The installation is not equipped oil level sensors, this level intermediate is determined according to the characteristics tank, gas pressure and time. Time necessary for the oil to reach its level stabilization is very long, we use a level intermediate, below the maximum possible level, that the hydrocarbons reach after a predetermined time.

The effluent from the reservoir rock 14 comprises a mixture of hydrocarbons and water. During the period of filling the annular space 40, the hydrocarbons separate from the water, which, being more dense, collects towards the lower end of the annular space 40. The ball 64 of valve 52, being in the water, rises from its seat 66 and opens the passage from the annular space 40 to the aquifer, which however cannot fill the annular space due to valve 60.

Once this filling / separation time has elapsed, all control valves are actuated to isolate the annular space 40 of the low gas source pressure 36 and put it in communication with the source gas 38 at high pressure. The gas pressure in the upper end of the annular space 40 acts on the hydrocarbons and water and tends to push them back to the bottom from the well, the non-return valve 24 preventing liquids from return to tank 14.

When the effluents in the annular space 40 are moved down by the high pressure gas, the water finding towards the lower end of the annular space through valve 52 towards the aquifer in the direction of arrow 62, the interior of well 10 being isolated from the aquifer by seal 20. Once the water has been moved from the annular space, and the oil gets to the lower end, the ball 64, located in a less dense medium, descends to its seat 66, closing the passage to the aquifer. Once this passage is closed, the hydrocarbons displaced by the high pressure gas pass by an opening 68 formed in the casing 18 at a point below the valve 32 and go up towards the outlet 30 at the surface 12. It should be noted that, depending on the profile evolution of the pressure in the annular space 40, and well characteristics (aquifer pressure, pressure at the wellhead, ...), the expulsion of the two phases can be do it simultaneously.

Thus, according to the invention, a significant part of the water from reservoir 14 will be re-injected into an aquifer underlying, thereby significantly improving the content of effluent oil raised to the surface.

An intermediate level is determined according to the back pressure on the discharge line, pressure of the gas, geometric characteristics of the well and time. Indeed, the time required for the hydrocarbons reach a level of stabilization, level which must be find above opening 68 to avoid a high pressure gas recirculation is again very long. Also, we use an intermediate level, above the minimum possible that the oil reaches after a predetermined time. Once this time is up, all of the valves 34 are actuated again and the space annular 40 is isolated from the high pressure gas source 38 and put in communication with the low pressure source 36. Thus, the gas pressure in the annular space 40 decreases quickly, allowing liquids from the tank to get back to filling this space 40. Then the cycle of the operation described above is repeated. Like pressure of the well changes over time, it is necessary to proceed to periodic measurements of the static pressure of the well in order to correspondingly modify the pressures of gas.

In order to obtain a smoothing over time of the production of hydrocarbons, but also high gas consumption pressure, one can have two or more wells, or well assemblies, connected to a common outlet 30, arranged so that when it is in the purge phase, the others are in the filling phase. The number of wells, or well sets, will then be determined based on compared durations of the two phases, so as to optimize the overall production throughput.

In Figure 2 is shown an installation for a oil well which, unlike that of Figure 1, does not have an underlying aquifer to which the water coming from the reservoir rock 14 can be driven back. Sure this figure, the elements common with those of the installation of figure 1 carry the same figures of reference.

As shown in Figure 2, the casing 18, instead to be extended by a lower end 58, communicates, inside the seal assembly 26, with a second casing 70. This second casing 70 extends from the assembly of seal 26, through packer 28 and opens in a chamber 72 delimited between the packer 28 and the suspension seal 46 casing. This room 72 communicates with a device common re-injection, or evacuation of water (not represented) by a conduit 74 provided with a safety valve 76. If the well is not equipped with a packer 28, the second casing 70 extends to the surface.

The method of implementing the installation of the figure 2 is substantially similar to that of the installation of the figure 1. Once the annular space is filled effluent, and that the separation of hydrocarbons from the water is done, sending high pressure gas into the annular space 40 displaces the liquids downwards present in this space. At first, the water finding at the lower end of the annular space is pumped back to the water re-injection device by through the second conduit 70, the chamber 72 and the conduit 74, the valve 52 being open. It is to highlight that, during this phase, the static pressure exerted on the water by the hydrocarbon column, present in space annular, is added to the gas pressure in annular space. This additional static pressure facilitates the ascent of water to the surface.

Once the oil level has dropped up to the valve 52, the ball 64 closes on its seat 66. A from this moment, the hydrocarbons are driven back by the high pressure gas, through opening 68 and of the casing 18, towards the outlet 30. The rest of the process is similar to that relating to the installation in FIG. 1. As in the previous example, the expulsion of the two phases can be done simultaneously.

The pumping method and installation according to the invention may apply to subsea wells or wells earth, as well as vertical or inclined wells. He is at note that this device also allows separation at less partial of the gas dissolved in the effluent from the reservoir 14, the gas thus separated rising through the conduit 44, to the low pressure gas tank 36.

Alternatively, the physical separation between phases being carried out at the bottom, the discharge towards the surface could be achieved by a single conduit, the arrival of phases in sequence allowing their individualized treatment at the wellhead level, in order to send the phases towards their respective exits.

The embodiment of FIG. 3 differs from that of the Figure 1 in that the pumping installation is intended for pump water separated from hydrocarbons towards the rock reservoir 14 instead of sending it to an aquifer like this is the case in the installation of figure 1.

In figure 3, the elements already present in figure 1 have the same reference numbers.

As shown in Figure 3, the end 58 of the casing 18 opens immediately below the seal assembly 26, in a chamber 80 defined in the lower end of the well 10. Perforations 82, formed in the reservoir rock layer, open in the chamber 80. The reservoir rock layer has a thickness more important than that of the embodiment of the Figure 1 and has a very high permeability.

The pumping process implemented using the installation of FIG. 3 is substantially similar to that of Figure 1. After the separation phase, water is towards the lower end of the annular space 40 and the valve 52 is open. When gas from the high pressure source 38 is sent to annular 40, the water is discharged by this gas through the valve 52 and the along the end 58 of the production casing 18 towards the room 80. Then the water enters, in the direction of the arrows 84, in the lower part of the rock layer 14 by the lower perforations 82. Also, once the water propagated in the rock layer 14, it tends to move, or expel the hydrocarbons present in the rock towards the chamber 80, then in the annular space 40.

Claims (4)

1. An installation for pumping a liquid coming from an underground source, comprising a well (10) extending from the surface (12) towards the liquid source (14), the well comprising a chamber (40) extending substantially over its entire length, at least one casing (18) passing through the chamber and communicating therewith, and an assembly of valves (34) designed to bring the chamber selectively into communication with a source of gas at a first pressure (36) allowing the liquid coming from the source to fill the chamber and a source of gas at a second pressure (38) greater than the first pressure in order to empty the chamber, the liquid being forced back towards a first outlet (30) by flowing through the casing, characterised in that it additionally comprises a clack valve (52) mounted in the casing (18) and a second conduit (58; 70) leading to a second outlet (74), the clack valve being capable of reacting to the density of the fluid which surrounds it in order to be able to force back a first liquid towards the first outlet (30), a second liquid, of greater density, being forced back towards the second outlet (74) via the second conduit (58; 70).
2. An installation according to claim 1, characterised in that the clack valve (52) comprises a ball (64) arranged to seal off a seat (66) in the second conduit (58; 70), the density of the ball being of the order of 0.9.
3. An installation according to claim 1 or claim 2, characterised in that the second outlet consists of an aquifer.
4. An installation according to claim 1 or claim 2, characterised in that the second outlet consists of the source (14) of the liquid.

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