GEOL40310_LectureA11_Development3_2023.pdf

Geol 40310 Fossil Fuels and Carbon Capture & Storage (CCS) Lecture A11: Reservoir Development and Production 3: facilities and management Autumn 2023-24 T. Manzocchi, University College Dublin 1 1 Lecture A11: Reservoir Development and Production 3: Facilities and management The field production...

Geol 40310 Fossil Fuels and Carbon Capture & Storage (CCS) Lecture A11: Reservoir Development and Production 3: facilities and management Autumn 2023-24 T. Manzocchi, University College Dublin 1 1 Lecture A11: Reservoir Development and Production 3: Facilities and management The field production plan Oilfield production Platforms Surface facilities: separation, infrastructure, platform Oil Refining & Gas Processing Gas development examples: Corrib, ConocoPhillips Southen North Sea. Production profiles for oil and gas reservoirs Wells: Well flow rates. Horizontal and Multilateral wells Logging while drilling and geosteering – Wytch Farm Field Example. Well completions and workovers – Nelson Field Example. Abandonment and decommissioning 2 Geol 40310 Lecture A11 1 Cash flow during the field life cycle Oil production rate 500 400 300 200 100 0 -100 -200 -300 -400 -500 0 5 10 15 20 15 20 25 100 Decommissioning 200 Production Development 300 Appraisal Gaining Access Cumulative cash flow (million $) 400 Exploration 500 0 -100 -200 -300 -400 -500 0 5 10 25 Time (years) Jahn et al. (2008) 3 The Field Development Plan Field sanction Following appraisal and a positive feasibility study, a Field Development Plan is prepared. This is the engineering, operational and economical specification of the project, and must be sanctioned before detailed work can commence. 4 Geol 40310 Lecture A11 2 Well head Oilfield Production platforms Production Utilities Surface facilities are installed on a platform, which can be on land, on the sea-bed, floating or fixed. Choice of platform depends on facility requirements and environment. Buzzard Field Fixed Platform, UK Wytch Farm, Poole Harbour. Semi-submersible Thunder Horse platform, Deep water GOM 5 Schiehallion floating production, storage and offloading (FPSO) vessel. 6 Geol 40310 Lecture A11 3 Surface facilities Compressor gas Well Head Separator Stock tank oil water Reservoir • • • What comes out of the wells is a combination of oil, gas, water and undesirable material (e.g. H2S, sand, etc.). The proportions of these can change significantly over the production life of the reservoir, and must be predicted up-front if massive re-engineering costs are to be avoided. The fluids must be separated, treated and exported for sale or safe disposal. 7 Surface Facilities - separation Simple separator 8 Geol 40310 Lecture A11 4 Surface Facilities - treatment • • • • • • Water de-oiling: the separated water may contain oil in greater proportions than are permitted by the disposal standards. This must be removed. Oil degassing: Remove the volatile components of the oil to satisfy the true vapour pressure requirements – need oil to remain liquid! Oil dehydration: Usually the requirement for crude oil is < 0.5% water. Dew-point conditioning of gas: Remove liquid components to prevent liquid drop-out during transportation and because liquids are more valuable anyway. Contaminant removal (typically H2S and CO2). Gas compression: To the desired pressure before it is used (exported for sale or re-injected in the reservoir) 9 Oil Refining Whitegate oil refinery, Cork 10 Geol 40310 Lecture A11 5 Gas processing Onshore Offshore 11 Corrib Field production and processing: Sub-sea completion and pipeline to onshore processing plant (Ballinaboy terminal) Corrib controversy: route of pipeline to Ballinaboy terminal, Onshore vs. offshore processing. 12 Geol 40310 Lecture A11 6 Downstream Gas Processing – space and throughput allows for more comprehensive treatments 13 Theddlethorpe Gas terminal Victor Platform Lincolnshire Offshore Gas Gathering System Juliet Field sub-sea tieback to Pickerill A platform 14 Geol 40310 Lecture A11 7 ConocoPhillips withdrawal from the UK sector 2015 2018 2019 15 Lecture A11: Reservoir Development and Production 3: Facilities and management Platform Surface facilities: separation, infrastructure, platform Oil Refining & Gas Processing Production profiles for oil and gas reservoirs Wells: Well flow rates. Horizontal and Multilateral wells Logging while drilling and geosteering – Wytch Farm Field Example. Well completions and workovers – Nelson Field Example. Abandonment and decommissioning 16 Geol 40310 Lecture A11 8 Typical production profile – gas reservoir Gas Production rate: Billion cubic feet / year Production rate Gas • • e.g. Kinsale head Field Because of the infrastructure required to transport gas and the lack of storage options, lengthy supply at a particular rate as part of the gas sale agreement underpins gas production. This has lead to typical gas production profiles designed to provide ca. 60% of reserves in a plateau period lasting about a decade. 17 Production rate Typical production profile – oil reservoir Plateau Decline Buildup Rejuvenation Decline Time (years) e.g. Ekofisk field: Extreme example of field rejuvenation • • Oil is more easily stored and transported than gas, and cash flow considerations favour quicker production (but may require more expensive surface facilities and more wells). A typical oilfield production profile has a peak production period of 2-5 years, followed by decline and perhaps rejuvenation, followed by abandonment when operating costs exceed production profit. 18 Geol 40310 Lecture A11 9 How many wells do you need? Height (ft) above OWC 2km Water cut Liquid rate (bbl/day) Oil production rate Water injection rate (data available only till 1999) Water production rate Water cut i.e. the fraction of total liquid production that is water Nelson Field, UKCS Producers Injectors 400 7100 200 0 Number of wells: Desired peak production rate Estimated initial well flow rate. But how is the initial well flow rate estimated? 19 Well Head Separator PWH PS PR Pwf Reservoir Flowing Bottom-hole Pressure (𝑃𝑤𝑓 ) Flow into a well PR 0 0 Flow rate Flow into well: 𝑞𝑜 = PI(𝑃𝑅 − 𝑃𝑤𝑓 ) Productivity index is a function of the formation permeability, the fluid viscosity and the extent of permeable interval. Determining it is a fundamental objective of well testing. 20 Geol 40310 Lecture A11 10 Well Head Separator PWH PS PR Pwf Reservoir Flowing Bottom-hole Pressure (𝑃𝑤𝑓 ) Flow up a well PR PWH 0 0 Flow rate Stable Flow up well: 𝑞𝑜 ∝ R(𝑃𝑤𝑓 −𝑃𝑊𝐻 ) Wellbore radius 21 Initial well flow rate Well Head Separator PWH PS PR Pwf Reservoir Flow into well: 𝑞𝑜 = PI(𝑃𝑅 − 𝑃𝑤𝑓 ) Flowing Bottom-hole Pressure (𝑃𝑤𝑓 ) Steady-state flow is achieved when: flow up the well = flow into the well. This defines the initial operating conditions assuming incompressible fluids PR PWH Steady-state flow 0 0 Flow rate Flow up well: 𝑞𝑜 ∝ R(𝑃𝑤𝑓 −𝑃𝑊𝐻 ) 22 Geol 40310 Lecture A11 11 Horizontal wells Horizontal wells have the advantages of: - Longer reservoir sections, leading to higher production indices - The ability to connect laterally discontinuous features (fractures, fault-blocks). - Define the direction of flow (will be perpendicular to the well). The geometry and heterogeneity of the reservoir are crucial determinants on whether horizontal wells will be beneficial, and in many cases vertical wells are more use. 23 Multilateral wells • • • Multilateral increase the advantages associated with horizontal wells. More demanding to drill and complete: greater rewards but greater risk and cost. Slow to gain widespread use: most popular in Russia and the Middle East https://www.slb.com/~/media/Files/resources/oilfield_review/ors98/win98/key.pdf Multulateral productivity in the South Shaybah Field Source: Saudi Aramco 24 Geol 40310 Lecture A11 12 loogging run 2 loogging run 1 Drilling and logging • • A comprehensive suite of wireline logs is run in open-hole before the casing is set. Before the advent of LWD in the early 90s, therefore, the only real-time information came from the cuttings and the mudlog. 25 Logging While Drilling (LWD) and Directional Drilling Bristow (2002) 26 Geol 40310 Lecture A11 13 2015: State-of-the art LWD including up- and down- Resistivity http://www.weatherford.com/products-services/drilling-formation-evaluation/drilling-services/lwd-geosteering 27 Pushing the envelope with Horizontal Drilling: The Wytch Farm Field, Mid-1990s. Total reserves. ca. 500 million barrels. Sherwood Sandstone depth ca. 1200m. BP operated field. http://www.southampton.ac.uk/~imw/jpg-PetroleumGeology/11PGS-Wytch-Wells-Trajectories.jpg 28 Geol 40310 Lecture A11 14 Concepts for Wytch Farm offshore Development Artificial Island Extended Reach Wells Extended-reach wells were chosen because there would be less impact on the environment and development would cost less than half and occur three years earlier https://www.slb.com/~/media/Files/resources/oilfield_review/ors97/win97/ex_drilling.pdf 29 Wytch Farm Well M11: The first 10 km reach well 1km 1km oil Side-tracked to maximise length in the most productive unit of the Sherwood sandstone. Brought on-stream at a rate of 20,000 BOPD. 20m 200m 30 Geol 40310 Lecture A11 15 Well completions • • Completions provide communication between the well and the reservoir (the lower completion) and between the well and the wellhead (the upper completion). Lower completions range from very simple open holes to highly sophisticated, selfregulating “intelligent” wells. Key features are: - Liners (slotted or perforated) provide rigidity and ensure an open hole for production logging. - Packers allow different intervals to be isolated. - Cemented and perforated completions allow particular sections to be targeted. - Wire screen and gravel packs are used to control sand production. - Frac-pack completions inject the gravel into hydraulic fractures in the formation. Smart well. 31 Artificial lift • • • • The purpose of artificial lift is to enable or encourage the hydrocarbons to come to surface. Artificial lift systems add energy to fluids in the well – the reservoir is unaltered Artificial lift may not be needed until later in field life, but if it will be needed it may be costeffective to start it straight away. There are two basic types of artificial lift system: Pumps: These provide a mechanical means of pushing or pulling the fluids to surface. Gas lift: Gas is injected into the well to lower the density of the hydrocarbon so it will rise. Beam pump Electric submersible pump Gas lift system 32 Geol 40310 Lecture A11 16 Well interventions (workovers) • • • • • • A workover is any operation done within the wellbore after the initial completion. Re-entering a well can be costly and therefore several workovers are generally performed at the same time. Reasons for workovers include: Unsatisfactory performance: e.g. does the well need restimulating or re-perforating? Mechanical problems: e.g. has the cement of the casing become damaged? Recompletion: Is it sensible to change the locations of the producing zone? Upwards recompletion of a well Initial Production Before Recompletion After Recompletion 33 Workovers in the Nelson Field, UKCS Oil production rate Water injection rate (data available only till 1999) Water production rate Water cut Water cut Liquid rate (bbl/day) Field-wide behaviour: Worked-over well (upwards recompletion) NB: oil production is red on this graph (water production is blue) 1994 1999 2004 2009 34 Geol 40310 Lecture A11 17 Primary, Secondary and Tertiary Recovery Primary Recovery Use the reservoir’s own energy Secondary Recovery Tertiary Recovery (Change the flow paths) (Change the fluid properties) Increase the reservoir’s energy Reduce Hydrocarbon viscosity Water Injection. Gas Injection. Water Alternating Gas Injection Thermal methods Deletion drive Solution gas Drive Improve Sweep and Drainage efficiency Gas Cap Drive Water Drive Improve porescale efficiency Miscible flooding (solvents) Waterflood design. Infill drilling. Horizontal wells. Compaction Drive Chemical flooding Foams, surfactants 35 Primary, Secondary and Tertiary Recovery: Ula Field Primary depletion Secondary Recovery: Waterflooding Tertiary Recovery: Miscible Gas Inection Oil production rate (mbbls/d) Plateau 2 Plateau 1 STOIIP ca. 1 Billion Bbls. 2012 2006 GOR (scf/stb) Start Foam Assisted WAG Extend WAG Scheme First Gas returns Sttart decline Water breakthrough Increased injection rate Start miscible WAG 1996 1986 Gas Injection rate (mmscf/d) Start water injection Watercut (%) Water Injection rate (mbbls/d) Arrested decline Zhang et al. (2013) 36 Geol 40310 Lecture A11 18 Abandonment and Decommissioning Cash Flow for a North Sea Oilfield Exploration, Appraisal, Development Production Decommissioning JPT, Jan. 2015. 37 Abandonment and Decommissioning The Economist 38 Geol 40310 Lecture A11 19 OSPAR (Oslo Paris) Convention for the protection of the marine environment of the North-East Atlantic. Inventory of offshore installations Since 1998 the dumping, and leaving wholly or partly in place, of disused offshore installations is prohibited within the OSPAR maritime area. Permission may, however, be given to leave installations or parts of installations in place. 39 Well abandonment Isolate hydrocarbon-bearing intervals. Protect aquifers. Isolate overpressured zones. Ca. 40% of UKCS decommissioning costs are associated with well Plugging and Abandonment. Jahn et al. (2008) 40 Geol 40310 Lecture A11 20 Platform decommissioning Fixed steel platform, Valemon Field (Statoil) 41 Pioneering Spirit World’s largest ship launched in 2014, capable of removing platforms in a single lift 382 m long, 124 m wide vessel was built in South Korea by Daewoo Shipbuilding & Marine Engineering (2011–14) at a cost of €2.6 billion (US$3 billion), and commenced offshore operations in August 2016. Removal of the Repsol-operated Yme mobile offshore production unit in the Norwegian North Sea, on August 22, 2016 42 Geol 40310 Lecture A11 21 Stages of work in a reservoir Appraisal Decommissioning Lectures A4, A5: Exploration Lectures A6, A7, A8: Appraisal Lectures A9, A10, A11: Development & Production 43 Geol 40310 Lecture A11 22