This invention relates to pumping produced fluid such as oil from a first formation zone in a well, employing a jet pump being supplied with a power fluid comprising one or more liquids. More specifically the invention is directed to installing a jet pump into an oil well with the objective of utilising the energy available from one oil producing formation to improve the production rate from the first formation with lower flowing pressure. Although other well completions will be able to utilise this invention, it is especially suitable for wells completed according to the so-called Coiled-Tubing-Assisted Pumpdown concept, in which simultaneous production from several separate oil producing formations in a horizontal well is made possible and effective. This concept, herinafter referred to as CTP, is the subject of a pending U.S. patent application, number 07/689.547.

Prior art patents exist as U.S. Patent number 1,547,194, which involves the use of gas from a reservoir to lift oil by aeration and subsequent reduction of hydro¬ static head, and patent number 3,746,089, which involves the use of reservoir energy to lift oil from another lower zone by simple comingling. Reference is also made to patent numbers 3,234,890, 4,390,061, 4,441,861, 4,605,069, 4,664,603, 4,744,730, and 4,790,376, all of which involve jet pumping with the help of power fluid supplied from the surface. In contrast thereto the present invention involves exclusively power fluid supplied from a formation having a higher flowing pressure than the formation from which it is desired to produce oil.

The novel and specific features of this invention are defined in the claims.

The jet pump is intended to be installed into a so- called sliding sleeve unit, itself installed in a tubing extension of the well for the purpose of allowing access to

oil production flowing into the well casing through perfor¬ ations, this produced fluid being confined by two produc¬ tion packers. One or more other oil producing formations are similarly confined lower in the well and are allowed access to the tubing extension through similar sliding sleeves equipped with retrievable so-called Concentric Standing Valves.

The jet pump itself in known methods, as described in the abovementioned U.S. patents, is intended to be operated with power fluids supplied from the surface via either the well's tubing or its annulus. It is a feature of the present invention that the power fluid is supplied from a formation in the well itself with a higher flowing pressure. This is a situation that is especially probable in a horizontal well, which may intersect producing formations with widely differing characteristics.

This invention provides for the possibilities that the high-pressure formation is either above or below the formation which requires additional energy. The high pressure formation may produce oil, water or a mixture, and in this case, the resulting produced fluid will have a lower proportion of water and correspondingly more oil. In a standard CTP completion, such a zone would be choked and its energy wasted. For the case where the high-pressure formation is below the weak formation, the lifting process is referred to as straight jet pumping, and where the high-pressure formation is above the weak formation, the process is referred to as reverse jet pumping. It will be understood that in a substantially horizon¬ tal well "above" and "below" should be taken in relation to the surface end of the well, i.e. "below" is further away from the surface as seen along the well.

The jet pump itself in accordance with the present invention is mounted in an adapter which is designed to be run into the well using the Coiled-Tubing-Assisted Pumpdown

technique. However, other installation methods may be used if the well is equipped accordingly.

The following description will explain more in detail the various functions and configurations of the invention, with reference to the drawings in which:

Fig. 1 schematically shows a typical horizontal well intersecting several productive formations of differing production capacities due to higher or lower flowing pressures, where it may be desired to increase the contribution from a zone with a low capacity. Fig. 2 shows the principles of a jet pump installed in the special type of completion necessary, where production from a low pressure zone is increased by the installation of a straight jet pump, which is operated by flow from the lower, high pressure zone. Fig. 3 shows an embodiment of a straight jet pump adapter installed in an appropriate sliding sleeve together with a shifter mandrel and lock mandrel which in this case provide for locating and locking in and opening of the sliding sleeve, Fig. 4 shows the straight jet pump adapter of fig. 3 in larger scale and indicates how fluid flow through the central bore imparts its hydrodynamic energy to fluid entering through side ports, and thereby from the ports of the sliding sleeve, Fig. 5A shows a similar view of an embodiment of the reverse jet pump adapter, in which fluid from the sliding sleeve's ports enters the central bore and imparts its hydrodynamic energy to fluid entering from below, and Fig. 5B shows a cross section A-A as indicated in Fig. 5A.

In Fig. 1, a typical horizontal well is shown inter-

secting several separate zones of a reservoir. These zones are denoted Zl, Z2, Z3, Z4 and Z5 in fig. 1. The well comprising a vertical wellbore 1 a bend part and a hori¬ zontal well part 2 is drilled from a surface location 5. In this case the horizontal well part 2 is of particular interest, since it penetrates a formation 10 having production zones Z1-Z5 as mentioned. 10A is a form of diagram illustrating the orientation and size of these zones, with corresponding arrows 3 indicating the formation flow rates from the various zones.

One of these zones Z4 exhibits disappointingly low productivity due to a low flowing pressure, while an adjacent zone Z5 receives, for example, pressure support from a nearby water injection well. If left to produce naturally, production from the strong lower zone Z5 will dominate the well's production capacity and the low- pressure zone Z4 will not be properly depleted before the strong zone Z5 is flooded by injection water. A standard CTP completion resolves this problem by choking the strong zone, thereby dissipating its reservoir energy. There is then danger that another zone will dominate production and the low-pressure zone will still be unable to produce enough for satisfactory depletion. Conventional artificial lift methods will not be able to improve this situation because of the problems of access to the lower zone and the fact that the well is horizontal and normal well main¬ tenance techniques with wireline is not possible.

In Fig. 2, a solution is presented using the principles of this invention. Schematically shown in this figure are a well casing 8, a tubing extension 9 and three production zones 11, 12 and 13 with arrows indicating production flow through casing perforations (not shown) .

A jet pump 15 is shown installed in a sliding sleeve 16 within zone 12, which sliding sleeve is part of a CTP completion. For this type of completion, the different producing zones 11, 12, 13 in the well are isolated by

production packers 11A, 12A, 13A joined by the extension 9 of the well's production tubing. The sliding sleeves such as 16 are installed in this tubing extension 9 and provide access to the isolated formation zones when they are opened. Sliding sleeve units are well known components used in vertical wells.

Reservoir fluid flowing from lower in the well (arrows 23 in fig. 2) with a high flowing pressure is utilised as the power fluid (arrow 23A) for the operation of the jet pump 15. The composition of this power fluid 23A is not critical as long as free gas is not present, and even free gas only affects the pumping efficiency, not its feasi¬ bility. As a result of this method of operating jet pump 15, the flowing pressure of a low-pressure zone 12 is effectively increased and the flowing pressure of a strong zone 13 is decreased, allowing more efficient depletion of the low-pressure zone 12 and a delay in the tendency of the strong zone 13 to be flooded by injected water. The size and configuration of the jet pump 15 can be adjusted within certain limits to give the required balance of production from the two zones. The jet pump 15 must be retrieved to the surface by CTP techniques for this adjustment. The characteristics of jet pumps are well enough known for this to be practical without resorting to trial-and-error. It will be understood that in a well with many zones, there may be more than one zone below the zone where the jet pump is installed. Whether the straight or the reverse jet-pumping technique is used, these multiple zones will act as one, independent of any interaction between them. The pressure and flow rate existing at the bottom of the jet pump adapter will be used to determine the operating parameters of the pumping system.

Fig 3 in axial section shows a practical arrangement of the jet pump and the necessary accessories in a CTP completion. A sliding sleeve unit or section 26 constitutes a short length of the production tubing

extension or housing 26A which is provided with a sliding sleeve element 36 as known per se, as well as side ports 36P. A toolstring 30 comprises components and elements as follows: A lock 31 is used to hold the toolstring 30 in position even when subjected to axial forces from either direction. This lock 31 also enables easy retrieval if the correct pulling tool is used.

The middle element in fig. 3 is a shifter mandrel 35 which serves to locate the toolstring in the correct and predetermined sliding sleeve unit 26, and then to provide the means whereby the actual sleeve element 36 is shifted down, thereby aligning the ports 26P, 36P in the housing 26A and the internal sleeve element 36 and allowing subsequent fluid communication from outside.

The lower element 40 is shown in more detail in Fig. 4. The jet pump 25 itself is enclosed in an adapter housing 40A which by seals 41, 42 isolates the ports 36P in the sleeve unit 36 from above and below. Ports 44 in the adapter housing 40A between the seals 41, 42 allow fluid from the reservoir into an outer chamber 45, where there is a spring-loaded ring 47 which is pushed back (47') by this reservoir fluid when it is flowing, but will not allow reverse fluid flow from the tubing 30A to the reservoir. The produced fluid from the lower zones flows into the pump 25 from below (arrow 48) and is constricted into the jet 25A of the pump, where its pressure is converted into kinetic energy. The resulting low pressure allows the required high flowrate from the outer chamber 45 and therefore from the formation. The fluids from lower in the well and from the formation (arrow 49) opposite the sliding sleeve unit 36 are then combined in the throat section 25C of the pump and their kinetic energy is thereafter con¬ verted back into pressure in a diffuser section 25B. This flowing pressure is lower than the lower zone would have produced at that flowrate but higher than the pressure the

zone opposite the sliding sleeve would have produced at. The pressure is also higher than the pressure would have been if the lower zone would have been choked.

It is possible to install a jet pump adapter housing 50A with a different configuration, as shown in Fig. 5A and 5B. This is the so-called reverse jet pump 60 where the formation opposite the sliding sleeve unit (not shown) provides the power fluid for increasing production from a low-pressure zone lower in the well. Radial flow passages 55 are drilled around the jet section 65 such that fluid flow through the ports in the sliding sleeve is lead to the core of the jet pump 60 and to the jet 60A. Longitudinal flow passages 53A-D allow access from the lower zone of the well to a chamber 6OB surrounding the jet 60A, where the low pressure generated by the high-velocity jet draws produced fluid from the lower zone into the throat 65C. As usual for a jet pump, there is a diffuser section 65B to reduce the velocity of the combined fluids, producing a high flowing pressure to lift these fluids to the surface via the production tubing in the normal manner.

As in the embodiment of Fig. 4, the one in Figs. 5A and 5B comprises seals 51 and 52 around adapter housing 50A, in which there are also radial ports 54.

Access to the jet from the sliding sleeve ports is controlled by a check valve 66 below the jet 60A which can only be opened by high pressure from the formation. A weak spring 67 closes this valve, and high pressure in the tubing, for example while performing CTP operations, will further energise the seal and maintain the check valve 66 on seat. At 66' this valve is shown in its open position with spring 67 compressed.

These descriptions have been made for a CTP well completion, and are equally valid for a similar type of completion intended for Through-Flowline, or TFL, well completions. The same holds true for non-horizontal wells which can be serviced by wireline methods, provided that

they are completed with the different zones isolated from each other by production packers and sliding sleeves. In this case, the other elements in the toolstring will not be the same, but will depend on the configuration of the sliding sleeve used. In addition, the check valves included in the designs of the straight and reverse jet pump elements are not necessary.