WO2013109331A1

WO2013109331A1 - Offshore heavy oil production

Info

Publication number: WO2013109331A1
Application number: PCT/US2012/062846
Authority: WO
Inventors: Donald Maclean; Johannes Christiaan LANFERMEIJER
Original assignee: Single Buoy Moorings Inc
Current assignee: Single Buoy Moorings Inc
Priority date: 2012-01-20
Filing date: 2012-10-31
Publication date: 2013-07-25
Anticipated expiration: 2014-07-20
Also published as: MX353097B; BR112014017820A8; BR112014017820A2; SG11201404250VA; GB2514934B; GB201412825D0; CA2862123A1; CN104246121A; MX2014008753A; KR20140128339A; GB2514934A

Description

OFFSHORE HEAVY OIL PRODUCTION

Some undersea hydrocarbon reservoirs contain a high proportion of heavy crude oil (hydrocarbons), so output from the reservoir (over a period of a plurality of days) comprises over 50% hydrocarbons of a density above thai of water and with a high viscosity. Such heavy crude oil generally contains at least 60 carbon atoms per molecule and/o has a viscosity on the order of magnitude of over 0.5 poise. Other liquid hydrocarbons (light oil or light liquid hydrocarbons) generally have about 5 to 10 carbon atom per molecule (light oil). Hydrocarbons i!h less than 4 or 5 carbon atoms per molecule are generally gas Heavy oil hydrocarbons are difficult to treat and are difficult to pump into and out of storage tanks The heavy crude can be cracked In refineries to produce light oil (generally oil having a specific gravity less than water and with a low viscosity) which is usually the most desirable hydrocarbons, but considerable effort is required to handle and transport the heavy erode to the refinery. A system that could bo used at an offshore heavy crude oil production facility to crack heavy crude Oil so as to facilitate its transport and transfer through pipes to a further ref sning and treatment facility, would be of value.

In accordance w th the present Invention, a floating hydrocarbon production facility is provided that. Is anchored to the sea floor to lie near an offshore heavy hydrocarbon reservoir, which treats the heavy hydrocarbons to facilitate their transport, transfer through pipes, and further treatment The facility includes a separation station that separates the well effluent into light liquid o k heavy crude oil, gaseous hydrocarbons, water, and solid materials (e.o sand).. The heavy oil (oil with a specific gravity greater than water and generally with a API of less than 20) passes to a cracking station on the floating facility that cracks, or breaks down, the heavy crude oil Into light crude oil. Such cracking can be accomplished in a number of ways. One approach is to use thermal cracking, such as "sleam cracking" in which steam at about 800^* C^* (650 to 1000° C) is applied to the crude oil Another approach is to spray preheated heavy oil at a hot iluiolzed cataiysl to break down the oris into various light oils (referred to as a FCC process, or process that uses fluidked carbon cracking). The cracking methods require large amounts of hot pressured stearn and produce more hot stearn- The processes aiso require considerable amounts of electricity . Much of the pressured stearn produced sn the cracking process is used to drive a steam engine (piston or turbine) that, in turn, drives an electric generato Water from the sea is used in operating the stearn engsne (to provide water that converts to steam _; and to cool the stearn alter it passes through the steam engine), and in the cracking process.

There are many othe known methods fo cracking heavy oil.

The novel features of the invention are set forth with particularity in the appended claims. The invention wiii be bes understood from the following description when react in conjunction with the accompanying drawings

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Fig, 1 is a diagrammatic view of an offshore hydrocarbon production faculty of the present invention, with a tanker shown in a reduced size.

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Fig. 1 iiiusuates a production facility 0 of the invention, which includes a floating structure 2 which carries treatment equipment that produces and heats heavy crude oih or heavy hydrocarbons, from an undersea reservoir or well 14. Heavy crude oil can be considered to be oil having an API (American Petroleum institule) rating of less than 20, so the oil boats on water. Such Oil generally has a high viscosity such as on the order of magnitude of at least 0.5 poise, &ηύίύΐ has hydrocarbons with at least 60 carbon atoms per molecule. Fluid from the seafioor reservoir passes through an electrically-energized pump 20 that lies within tubing extending down to the well or that lies In the downhole casing. The pump pumps the fluid through a riser 22 up to the vessel or other floating structure 12 at the sea surface. Part of the oil is light oil that passes through a conduit 30 from a cracking stalion 32, towards a "Christmas tree" 33 on the seabed and helps m lifting heavy crude oii from the well. Heavy ess and gas from the reservoir pass through a condus? 34 to a separation station 38. The separation station 38 separates out gas .which optionally flows through conduit 40 to a gas turbine power generator set 75. The set 75 Is an engine-generator sei that uses steam (which may be produced by gas) to drive a generator 74 thai: generates electricity. Produced water flows through a pipe 42 to a settling tank 44, Other non-hydrocarbon material such as sand and stones, are released Into the sea after treatment

In Fig. 1. heavy crude oil entering the separation station 36 is delivered through outlets 51 . 53 o oonduits 507 52 to the station 32 , which is a cracking station that converts heavy crude oil to light crude oil. The cracking station uses hot (e.g .SOCr C) sand to break down heavy crude arid uses a small amount of hydrocarbon gas and diluent to imtsaily generate neat and steam. The process reuses the sand and creates additional heat which creates additional steam. Applicant uses the additional steam, as described below.

Applicant provides a heavy oii storage tank, or buffm 60 that receives heavy crude oil from the separation station 36 and thai can delive heavy crude oil to the cracking station 32, Optimum operation of the cracking station 32 requires a steady flow of heavy crude oil into the station. When the flow through the conduit 34 deceases, this shortfall is made up by the flow of oil horn the buffer tank 60 to the cracking station The buffer tank preferably l as a capacity to store more oii than the average flow of oil into the cracking station In one minute (more than 1 ,000 gallons and preferably more than 5,000 gallons). Heavy crude that has been cracked at the cracking station Info light oIL Is delivered through conduit 61 to a light oil storage tank 62, and from the light ού storage tank the oil flows through a transfer system 64 to a tanker 66 _: or to an export pipeline on the sea bed (no!, shown). The tanker 66 carries the oil to a distant refining facility where appropriate amounts of oii of selected densities are combined. The fact that oii m the storage tank 62 Is light oil means that if can be readily loaded into the tanker 66. as by passing through a pipeline, and later unloaded and further processed, Such further processing can he used to obtain the desired mix of light oils and additives, etc. The cracksnq station 32 uses hot sand and/or steam to heat incoming heavy crude oil at 52 to crack it, with the process creating additionai heat which is carried away by additional steam, Applicant uses the steam to produce electricity. The steam produced by the cracking station is delivered through a conduit 70 to a steam powered engine 72, which can be a sieam engine that has pistons or which can include a steam turbine The vessel can nave boilers (78) thai use hydrocarbons to create steam dur ing startup of the process. The steam powered generator is connected to an electrical generator 74 that generates electricity Alternatively, a closed loop beat transfer system can be used to deliver the steam to apparatus that heats It and delivers the heated steam to the engine 72.

Steam is produced by the cracking station only after a period of operation (e.g. quarter hour). During this time, applicant uses hydrocarbon gas that flows through conduit 40 to drive an engine-generator set such as 75 wherein electuary Is obtained from the generator 74.. The gas can be ignited and used to energize the same engine 72 or an auxiliary one. in the present embodiment a steam generator Is used, but as an alternative, steam from vessel steam boilers 78 can be used to stad up the process.

Applicant passes excess steam at the engine 72 through a conduit 82 to the buffer tank 60 to heat heavy crude therein so it flows more easily. Excess heat also can be used to heat light oil in the light oil tank 82. it Is well known that steam exiting a steam engine is usually cooled In order to decrease its pressure so there is a large pressure differential between incoming and outgoing steam. Applicant uses a seawa!er lift pump system 80 to deliver sea water to a fresh water generator 84 that uses beat to produce clean water (most salt removed). Trie clean water Is passed to the steam engine to cool the exiting steam and to produce clean water for the steam engine. Electricity from the generator 74 is used to power pumps thai pump fluids Into various stations. These Include the pump 20 that pumps heavy crude up through a riser., an offloading pump that pumps light oil to the tanker 86 that carries oil away from the floating structure 12. and a seawater lift pump 80 that provides water to the steam engine.

Thus, the invention provides a method and system for handling oil that is produced from an offshore reservoir or seabed pipeline that produces primarily (at least 50%) heavy crude oil. The crude oil is produced from the reservoir by a floating structure, or vessel, that includes a cracking station that cracks the crude oil after it has been initially processed to remove water, sand, gas and light oil. The cracking station preferably uses high temperature (e.g. 800^" C) steam to crack the heavy oil to produce light oil or lighter oil (less viscous oil) that can be more easily pumped or otherwise flowed through pipes for processing and transport. Steam created by cracking heavy oil into light oil Is used to energize a steam engine that powers an electrical generator, with sea water used as a coolant for the steam engine. Electricity from the electrical generator powers the cracking station and other facilities, and electricity can be exported to consumers on shore or to another offshore system through a cable.

Although particular embodiments of fee invention have been described and illustrated herein, It is recognized that modifications and variations may readily occur to these skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents,

Claims

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1 , A method for efficiently obtaining fight oil from an undersea reservoir (1 ) which produces a reservoir fluid that contains heavy crude oil, comprising: passing said produced fluid from the undersea reservoir up from sad reservoir through a riser (22) to a structure (12) that floats at the sea surface; passing said produced fluid to a separation station (36) on the floating structure_: and, in sasd separation station separating trie heavy crude oil snto hydrocarbons and non-hydrocarbon material and separating the hydrocarbons into gaseous h drocarbons, light oil and heavy oil -including disposing of said non- hydrocarbon material Into the sea;

flowing said heavy oil to a hydrocarbon cracking station (32) on said floating structure wherein said cracking station is energizeahie m part by electricity_: and energizing said cracking station to crack said heavy crude oil to produce light oil gaseous hydrocarbons, and heat;

using said beat produced by said cracking station to produce pressured steam, using said pressured steam to d i e a steam engine (72)_f using said steam engine to drive an electrical generator (74) _; and using a portion of electricity from said electrical generator to energize said cracking station.

2. The method described in claim 1 including- using said gaseous hydrocarbons to Initially generate steam to drive said electrical generator, before steam Is available.

3. The method described in claim 1 inc udi g:

storing a quantity of heavy crude oil in a heavy crude oil buffer tank (60) that Is connected to said cracking station, to enable the constant flow of heavy crude oil to said hydrocarbon cracking station (32), and using steam from sale steam generator to beat oil in said crude oil buffer tank.

4, The method described In claim 1 wherein.

said cracking station has a crude oil storage tank, and including using steam ··?··

from sa¾d steam generator to heat crude oil In said crude oil storage tank.

5. The met od described in claim 1 including:

using electricity from said electrical generator to energize a sea floor pump (20) that lies no higher than the sea floor to pump fluid from said reservoir to said structure.

6. The method described in claim 1 including:

flowing seawater from said sea and using said seawater as a cooling medium for said steam engine.

7. The method described in claim 1 Including:

using heat from said cracking station to generate freshwater from seawate _: and using said generated freshwater to produce steam.

8. Apparatus for producing hydrocarbons from an undersea reservoir which produces reservoir fluids that contains heavy oil, comprising:

a floating structure (12) that floats at a sea surface, and a user (22) that connects said reservoir to said floating structure:

a separation station (36) on said floating structure which >s coupied to sale riser and which separates fluid from said reservoir into at least heavy oil and non- hydrocarbon material said separation station having a heavy oil outlet (51 _; 53) and said separation station uses electrical power;

a cracking station (32) on said floating structure which Is connected to a heavy oil outlet (53) of said separation station, said cracking station having a light oil outlet (61 ) and a steam outlet (70);

an engine-generator est that receives steam from said cracking station to drive a steam engine and which uses the steam engine to drive an electrical generator (?4h said electrical generator having an electrical outlet connected to said cracking station.

9. The apparatus described in claim 8 including:

a buffer tank (80) which stores heavy oil and which has an inlet connected to said separation station to receive and store heavy oil therefrom and an outiet connected to said cracking station.

10. The apparatus described in claim 8 wherein.

said buffer tank has a storage capacity of more than 1 ,000 gallons.

1 . The apparatus described in claim 9 Including:

a conduit that carries from said steam outlet of said cracking station to said buffer tank to heat heavy oil therein.