12 Reservoir technolgy August Classification: Internal

Transcription

1 12 Reservoir technolgy August 2015 Classifi Internal

2 Reservoir Engineering Fluid types How is oil produced Fluid flow in porous media Drainage strategies Well solutions and IOR toolbox Classifi 2

3 Reservoir Engineering Fluid types How is oil produced Fluid flow in porous media Drainage strategies Well solutions and IOR toolbox Classifi 3

4 HydroCarbons or just Oil and Gas? HC are a complex mixture of: Methane CH 4 C1 Ethane C 2 H 6 C2 Propane C 3 H 8 C3 Butane C 4 H 10 C4 Pentane C5 Hexane C6 Heptane C7 Octane C8 C9 and the heavier C10+ and contaminants N 2, CO 2, H 2 S Oil or Gas depends on chemistry and physics To answer we need phase diagrams: p vs. T and p vs. V Classifi 4

5 Hydrocarbon names and Sales products Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane Oil unstable Oil stable stable Condensate LPG Sales gas and LNG NGL Rich gas C10+ C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 Classifi 5

6 Hydrocarbons (oil/gas) From reservoir to surface RESERVOIR SURFACE GAS p EXPANSION + NGL/CONDENSATE OIL p SHRINKAGE + DISSOLVED GAS Classifi 6

7 Reservoir Engineering Fluid types How is oil produced Fluid flow in porous media Drainage strategies Well solutions and IOR toolbox Classifi 7

8 How is Oil Produced? Drill a well and perforate Well Head Pressure: p WH Start producing by opening up the well head choke Oil flows into the well and to the surface due to excess energy in the reservoir the bottom hole pressure (p BH ) is higher than the well head pressure (p WH ) + the fluid column weight (ρgh) i.e. p BH p WH > ρgh (+ p friction ) For some reservoirs artificial lift is necessary Gas lift (reduce ρgh) Downhole pump (increase p BH ) When the well flows there is also a pressure drop from the reservoir and into the well (drawdown), p r p BH > 0 H Bottom Hole pressure: p BH Reservoir Pressure: p r Classifi 8

9 How is Oil Produced? The production rate q [Sm 3 /d], depends upon: Drawdown (p r - p BH ) Permeability k Well Head Pressure: p WH Contact Area A between the wellbore and the sands. Viscosity of the fluid: m H Bottom Hole pressure: p BH Reservoir Pressure: p r Classifi 9

10 Reservoir Engineering Fluid types How is oil produced Fluid flow in porous media Drainage strategies Well solutions and IOR toolbox Classifi 10

11 Fluid properties Viscosity (the ease by which a fluid can flow through a porous medium) Typical values for NCS reservoirs (at reservoir conditions, cp): μ w = < 0.2, 0.6 > μ o = < 0.2, 2.0 > μ g = < 0.01, 0.05 > Density (ρ = m/v) Typical values for NCS reservoirs (at reservoir conditions, g/cc): ρ w 1 ρ o = < 0.6, 0.9 > ρ g = < 0.2, 0.4 > Heavy oil: μ o = < 10, millions > Honey: μ h = ρ w > ρ o > ρ g hence gas is always on top, water at bottom and oil in between Viscosity depends on temperature (and pressure) Density depends on temperature and pressure (gas changes much more than liquids) Classifi 11

12 Single Phase Fluid Flow Permeability A measure of the ease by which a fluid can flow through a porous medium Reservoir quality Permeability (k) md Excellent > 1000 Very good 250 to 1000 Good 50 to 250 Moderate 15 to 50 Sources of information 1) Log 2) Plug/core 3) Well test (mini/standard/extended) 4) Cuttings Beware of heterogeneities Water injection into oil reservoir: Poor < 15 Classifi 12

13 Two Phase Fluid Flow Relative permeability Water displaces oil K o,eff = K * k ro K w,eff = K * k rw Measured on core plugs (or use analogue data) 0. 6 k ro k rw S orw : lowest possible value of mobile oil Typical values of S orw : < 0.15, 0.25 > Classifi

14 Recovery Factor / Sweep Efficiency RF = Pore scale displacement x Volumetric sweep x Cut-offs Ability of recovery process to displace oil from accessed rock Degree to which injected fluid accesses all the rock Physical & commercial constraints affecting end of life (i.e. water cut limit) S or Mobility ratio Heterogeneity Connectivity Faults/Barriers Wells Thickness Dip/ gravity Classifi 14

15 Reservoir Engineering Fluid types How is oil produced Fluid flow in porous media Drainage strategies Well solutions and IOR toolbox Classifi 15

16 C16 Drainage Strategy / Drive mechanism Natural depletion Water injection Gas injection Thermal Chemical Miscible gas WAG Other PRIMARY RECOVERY Pressure depletion; no injection at all. NATURAL DRIVE SECONDARY RECOVERY Injection of fluids for pressure maintanance. PHYSICAL DRIVE TERTIARY RECOVERY Injection of fluids designed to further improve recovery; advanced recovery methods. DESIGN DRIVE IMPROVED OIL RECOVERY (IOR) All measures beyond current plans to improve expected oil/gas recovery. Can include all mechanisms. Drainage strategy Find the best suited mechanism for optimal resource exploitation ENHANCED OIL RECOVERY (EOR) All advanced recovery methods

17 Depletion Aquifer support Initial OWC Oil rate virgin field Water Cut GOR OWC time mature field Classifi 17

18 Pressure maintenance - Water injection Downflank water (denser than oil) injection Oil Oil Water Water Edge water Basal water Classifi 18

19 Pressure maintenance - Gas Injection Upflank gas (lighter than oil) injection Edge gas injection Top gas injection Gas Oil Water Classifi 19

20 Rules of thumb - The Big Picture UR = STOOIP * RF Recovery Factor Low Medium High Oil field by depletion and without aquifer support. (a) Oil field by efficient Water or Gas injection or strong aquifer support. (a) 10% 15% 20% 30% 50% 60% Gas field - by depletion. (b) 60% 70% 80% Classifi 20

21 Number of wells guidelines Different approaches Oil Producers (OP) 1. Well drainage area: 1.5 to 3 km 2. (choose upon compartmentalization, heterogeneity level, NTG) Water/Gas Injectors 1. From experience; the ratio of number of producers to injectors varies from (3:1) to (1:1). 3. Classifi 21

22 Reservoir Engineering Fluid types Fluid flow in porous media Drainage strategy Well solutions and IOR toolbox Classifi 22

23 Well design and completion Benefit vs. Cost Vertical / horizontal / slanted / multilateral wells Commingled vs. dedicated completions Zonal Isolation Packers Inflow control (ICV, ICD) Sand control Sensors Artificial lift (gas lift or ESP) Tubing diameter Water injection into oil reservoir: S or ~0.20 Classifi 23

24 Increased oil recovery Statoil s toolbox in the whole value chain Platform technology Low pressure production Debottlenecking Subsea technology Compression Boosting Drilling and well Advanced wells Well Interventions Standardised well solutions Reservoir management Conventional and advanced recovery methods Geophysical reservoir monitoring Mapping and modeling of complex reservoir formations

25 Reservoir Engineering Toolbox Simulation models versus Analytical methods Reservoir simulation models may help identifying the number of wells required, the optimal completion of wells, the present and future needs for artificial lift, and the expected production of oil, water and gas. In Statoil there is a requirement to have a reservoir simulation model at DG2 level, but most projects have a simulation model at DG1 or earlier. Analytical methods generally cannot capture all the details of the given reservoir or process, but are fast and at times, sufficiently reliable. In modern reservoir engineering, they are generally used as screening or preliminary evaluation tools. Analytical methods are especially suitable for potential assets evaluation when the data are limited and the time is critical. Classif 25 ication

26 Seismic interpretation structure map, faults, etc. Uncertainty analysis static & dynamic uncertainty analysis Calibration field observations, production data, etc. Cooperation between the disciplines is the only way to make the right decisions. Well design well design, drilling schedule, lift curves Geomodeling reservoir properties, pay, continuity, etc. Reservoir engineering simulations grid and model effects drainage strategy, # wells, well types, position Communication is the key to success! Facilities design production, process & export design Petrophysics reservoir properties, fluid saturations, etc. Outcome production profiles + uncertainty project economics - for investment decision Economics oil price & cost assumptions 26 Classifi Internal The subsurface workflow - Security Classificati on: Internal - Status:

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28 Presentation title Presenters name Presenters title Tel: Classifi Internal