I he inυenl.nn relates io device as staled :ι n 1 he b mLroduct ion Lo Claim 1 for the compres ion of ,,.u1 t LphaJ;e fluid, e g unprocessed pet oleum well stream

Ln some industrial processes, such as petroleum production, chemical and petro emi al processes and hot water processes, a means is needed to pre ^uri e complex

]0 fluids consisting of different qas _. fJujd mixtures and possibly solid particles. Conventional technology s based on a separation of the phases, before the gas and fluid phase can be pressurized in isolation.

Equipment is needed which can pressurise any multiphase

15 fluid mixture with solid particles without any form of separat on .

There is a great potential market for such equipment in petroleum production. Considerable financial benefi s are envisaged both in the development and operation of 0 marginal oil and gas fields if untreated well stream could be transported by pipeline directly to processing facilities onshore or on a central platform. If there is insufficient well pressure, or early production is decided upon, the well stream will require pressuri ation . Another advantage of ^r > compressing the well streain is to minimise the complexity of the flow conditions in the transport pipelines.

For most applications there are substantial advantages if the compression equipment is located on the seabed in conjunction with subsea wells. I his places exacting demands 0 on operational reliability and the resultant complexity of the equi pment .

Numerous concepts are currently being developed to try to meet this functional requirement. A common feature of all these designs is that there is machinery with movable

me han c l equipment directly exposed to the well stream. This leads to the following drawbacks:

* There will be erosion damage if there are solid particles in the mixture.

E> * The machinery tolerates small variations in a mixture's gas/liquid ratio.

* The machinery generally operates with poor efficiency.

* The machinery ic characterized by relative complexity.

]0 Purpose of the invention:

1 he main purpose of the invention is to create a device that will increase the pressure in multiphase fluids, thai; can have greater effectiveness, operational reliability and more process parameter flexibili y than known desig ^' ns for ] b similar purposes. 1 he device is to be suited for subsea installation .

Principles of the. invention:

The present invention comprises a device as indicated 20 in the. introduction to Claim 1, with the features presented in the. characterizing part of Claim 1.

The. present invention has the following advantages:

* The erosion damage caused by solids in the mixture 2b will be considerably less than in known designs because all sealing surfaces are. protected by a clean barrier fluid and there is low velocity between the moving mechanical components .

* The present design has no limitations concerning a 30 mixture's gas/liquid ratio.

* The design will operate with high efficiency with all gas/liquid ratios.

* The components used in the. system design are. mainly based on known technology..

3b

The. invention will be described in more detail, with reference to the accompanying drawings, where

h iguro 1 shows I he principles of ^" a device according to I lie invention in a di grammat c drawing

Figure 2 shows a detail o the design in Figure t

1 tie system consists of a cylinder 1 which has a piston

2 inside, the piston 2 is Forced Forwards and backwards by a h igh- ressure drive medium being alternately supplied to two smaller diameter cylinders 3, which Are located υn each side of the main cylinder Piston 2 has cylindrical end pjoces, hereafter called the end pistons, • that act as pistons in tlie cyliriders 3.

Seals b are located between the end pistons 4 and the dri e cyli ders .

The drive medium is supplied under high pressure through a pipe 8 to the compression system. A control system 6 w th cartridge valves ensures that the high. pressure drive medium is alternately supplied to one of the two drive cylinders 3. Each time the pisi on 2 readies one of the end positions, the control system 6 makes a change over. Providing the drive medium is freshwater or seawater, the drive medium can be released to the surroundings through an outlet pipe 9. An alternative i to have the drive medium in a closed system. This means that the return pipe 9 must be connected to the pump unit 13 that pressurizes the drive medium. The pump unit 13 does not have to be in I he immediate vicinity of the compressor system.

The multiphase fluid is fed into the compression system through a pipeline 10, and is led out by a transport pipe though pipeline 11. The respective pipelines &ro connected in series to end surface of the cylinder 1. Check valves 12, 13, 14, 15 are fitted to all pipe connections betω- en pipelines 10, 11 and the cylinder ].

The continuous operating of the device according to the invention can thus be described as identical sequences that Follow each other in time, where a sequence starts From an end position 1 he cycle of a sequences on one side of the piston 2 is similar to the cycle on the other side oF the

piston 2 except that the cycles on the two sides of ι e piston 2 are in opposite phases. ^" I he following description of a sequence is based on the situation shown in Figure. 1, and the sequence is only described for one side of piston 2.

The. sequence starts with a drive unit 2] driving a pump 16 that pumps high -pressure medium through pipe 8 to 1 he change-over valve 6 that controls the drive medium to chamber 20 in cylinder 3, where the. drive medium exerts a force on the end piston 4 in chamber 20. This force is further transferred to the piston 2 so that it is for -d towards the left in Figure 1. When piston 2 moves to the left in Figure 1 this leads to an increase, in pressure in chamber 17 in cylinder 1. When the pressure rise is sufficient, check valve 12 closes and check valve 14- opens, enabling the multiphase medium in chamber 17 to be pumped into pipeline. 11 until chamber 17 is empty, and the. piston 2 reaches its end position to the. left in Figure 1. This causes the change-over valve 6 to reverse and control the drive medium into chamber 19 in cylinder 3 so that a force, is exerted on the end piston 4- in chamber 19 which is again transferred to piston 2 forcing it to the right in Figure 1. This reduces the pressure in chamber 17 and when the pressure reduction is sufficient, check valve 14 closes and check valve 12 opens. This enables the multiphase medium to be pumped into chamber 17 from pipeline 10 until chamber 17 is full and the piston 2 is in the end position on the right in Figure 1. This causes the. change-over valve. 6 to reverse thus forcing the drive medium into chamber 20 in cylinder 3 so that the drive medium exerts a force on the end piston 4 in chamber 20 which is again transferred to the piston 2 forcing it to the left in Figure 1. This increases the pressure in chamber 17 in cylinder 1. When the pressure increase is sufficient, check valve 12 closes and check valve 14- opens enabling the. multiphase medium in chamber 17 to be pumped into pipeline 13 until the piston 2 is back in the initial position shown in Figure. 1, this sequence can then be repeated as long is required.

^" the inlet and the out let foi the product medium on t hc> piston pump are shown In more detail n figure 2 As t is s mm tri al , only half is shown The horizontal piston pump has a double outlet 24-, 25 with two check valves Fitted b ,23. ^" I he main outlet 24 is located at the highest point on the pump. In an expelling stroke the gas will be Forced ">ub first The dead volume of the pump will be reduced so that it only contains a fluid phase, this will linpro-ve 1'ιe volumetric efficiency of the pump. Sand which collects in

10 the bottom of the cylinder is ejected during the pump stroke into a collection pocket at the lowest point 2b in the cylinder. This pocket is emptied after each piston stroke A valve/fixed orifice throt tle s fitted upstream of where pipeline 24- joins the high-pres ure pipeline 11 to reduce

]b the fluid flow through 2b

A control system 6 provides the correct sequence. The control system 6 comprises a number of cartridge valves. Cartridge valves are preferred to slide valves as the former have larger capacity and are more operationally reliable. 0 Another matter is that slide valves require a lubricating hydraulic medium; whereas cartridge valves enable scawaler to be used.