Trisakti 2013 Teknik Reservoir Lanjut

DRIVE MECHANISM

Dr. Ir. Rachmat Sudibjo 1

TEKNIK RESERVOIR LANJUTTeknik Perminyakan - TrisaktiINTEGRATED PETROPHYSICS

Integrating geoscience disciplines to achieve dynamic reservoir description

Integrated Petrophysics

RESERVOIR DESCRIPTION

CORING

CONVENTIONAL CORE

PETROGRAPHIC ANALYSIS Thin Section Petrography

microphotographs illustrates the typical components of a sandstone reservoir

Poorly sorted sandstone

Oolitic limestone

Scanning Electron Microscopy Analysis

Useful Porosity

Some micro porosity may not be observed in conventional core analysis. Most porosity indicating logs see unconnected porosity, but the sonic log may not see any or all of the microporosity.

FLUID SATURATION

CAPILLARY PRESSURE

RELATIVE PERMEABILITY

LOGGING UNIT

DRILLING FLUID INVASION

Resistivity Response versus Depth of Investigation

THE PETROPHYSICAL MODEL

General Rules For Picking Log Values

In thick beds, pick average values(heavy black vertical lines) ===>Old style induction log, layer roughly15 feet (5 meters), pick peaks and valleys;other logs, pick averages ===>

FORMATION VOLUME FACTOR Bo = 1 1.4 Bw = 1 1.1Bg = 0.005- 0.007Volume @ kondisi reservoir / volume @ kondisi permukaan (standar)

Sangat praktis untuk konversivolume dari kondisi reservoirke permukaan dan sebaliknya

Juga dapat digunakan untuk mengkonversi unit volumedari bbl > scf etc27teknik reservoir lanjut - RS -teknik perminyakan - trisakti

MONETIZATION (VOL. STANDARD)

material balance: diperlukan konversi dari volume reservoir ke volume permukaan (standard)

28teknik reservoir lanjut - RS -teknik perminyakan - trisakti$$$$$$Basic Conceptsteknik reservoir lanjut - RS -teknik perminyakan - trisakti29Pressure gradientteknik reservoir lanjut - RS -teknik perminyakan - trisakti30

During a period of sedimentation, grains of sediment are continuously building up, in a water environment, the pore spaces between the grains were, therefore, filled with water. If the pore throats through the sediment are interconnecting all the way to surface, the pressure of the fluid at any depth in the sediment will be same, i.e. formation pressure. This pressure depends only on the density of the fluid in the pore space and the depth (hydrostatic pressure), independent of the pore size or pore throat geometry. hydrostatic pressure. Formation gradient pressure is generally equal to 0.433 psi/ft for freshwater. Deviations from this gradient and its associated pressure at a given depth are considered abnormal pressure.

Formation Pressure Definition Normal Hydrostatic PressureThe vertical pressure at any point in the earth is known as the overburden pressure or geostatic pressure. The overburden pressure at any point is a function of the mass of rock and fluid above the point of interest. In order to calculate the overburden pressure at any point, the average density of the material (rock and fluids) above the point of interest must be determined. The average density of the rock and fluid in the pore space is known as the bulk density of the rockOverburden Pressure Lithostatic PressureOverburden Pressure

Normal pressure gradientP grad water = 0.433 psi/ftP grad oil = 0.35 psi/ftP grad gas = 0.08 psi/ft

teknik reservoir lanjut - RS -teknik perminyakan - trisakti34


Fluid contactstekres lanjut teknik perminyakan - trisakti36

Pressure gradient in Reservoirteknik reservoir lanjut - RS -teknik perminyakan - trisakti37

Penentuan fluids contacts tekres lanjut teknik perminyakan - trisakti38

teknik reservoir lanjut - RS -teknik perminyakan - trisakti39OWCPEAK STRUCTUREGOCWater GradientOil GradientGas GradientCwCoCgPo = PwPo = PgDepthPressureDifferential Density EffectsThis effect is encountered when a gas reservoir with a significant dip is drilled. Because of a failure to recognize this potential hazard, blowouts may occur.

teknik reservoir lanjut - RS -teknik perminyakan - trisakti41OWCPEAK STRUCTUREGWCWater GradientOil GradientGas GradientPo = PwPg = Pw.Well TestDepthPressure Reserve Estimation Methods

1. Volumetric Method

Early stage of reservoir development Geology, Geophysics, Rock and Fluid properties Recovery Factor (RF) assigned arbitrarily No time dependency, No Production data Reservoir limits for reserve classification

Structure on top of production well

BHP vs Depth

BHP vs depth (upper & lower bonds of prediction confidence at @ 80%

the shift across the boundary between good and poor quality sand (Capillary chart)

Structure map on top of porosity

Minimum cut off:permeability = 1 mdPorosity = 2-4% (carbonate) = 7-10%(sandstone)

Isopach map of total net sand

Net oil isopach above HKW

Isopach of total net oil sand

Perhitungan Kandungan Minyak (OOIP) Secara Volumetric

52 Reserve Estimation Methods

2.Material Balance

Later stage of development Geological data, Rock and Fluid properties, Production data RF is calculated Time dependantDRIVE MECHANISMSOLUTION GAS DRIVE: RF= 10-15%GAS CAP GAS DRIVE RF = 15 25%WATER DRIVE RF = 20 40%GRAVITY DRAINAGE RF = 15 30%

54teknik reservoir lanjut - RS -teknik perminyakan - trisakti

SOLUTION GAS DRIVE

Solution Gas DriveCrude oil under high pressure may contain large amounts of dissolved gas. When the reservoir pressure is reduced as fluids are withdrawn, gas comes out of the solution and displaces oil from the reservoir to the producing wells. The efficiency of solution gas drive depends on the amount of gas in solution, the rock and fluid properties and the geological structure of the reservoir.

Recoveries are low, on the order of 10-15 % of the original oil in place (OOIP). Recovery is low, because the gas phase is more mobile than the oil phase in the reservoir.

Solution gas drive reservoirs are usually good candidates for water-floodingGAS CAP DRIVE

Gas Cap DriveThe initial reservoir pressure is below the bubble point, so there is more free gas in the reservoir than the oil can retain in solution.This free gas, because of density difference, accumulates at the top of the reservoir and forms a cap. In gas cap drive reservoirs, wells are drilled and completed in the oil producing layer of the formation. As oil production causes a reduction in pressure, the gas in gas cap expands and pushes oil into the well bores. WATER DRIVE

Water DriveMost oil or gas reservoirs have water aquifers. When this water aquifer is continuously fed by incoming water, then this bottom water will expand as pressure of the oil/gas zone is reduced because of production.

The expanding water also moves and displaces oil or gas in an upward direction from lower parts of the reservoir, so the pore spaces vacated by oil or gas produced are filled by water.

The oil and gas are progressively pushed by water towards the well bore. Recovery factor may reach 50% of the original oil in place (OOIP)GRAVITY DRAINAGE

Gravity Drainage

Gravity drainage may be a primary producing mechanism in thick reservoirs that have a good vertical communication or in steeply dipping reservoirs. Gravity drainage is a slow process because gas must migrate up structure or to the top of the formation to fill the space formerly occupied by oil. Gas migration is fast relative to oil drainage so those oil rates are controlled by the rate of oil drainage.COMBINATION DRIVE

Material Balance MethodUnderground withdrawal (oil + gas + water) = Expansion of oil+ dissolved gas (A)+ Expansion f gas-cap gas (B)+ Reduction in HCPV (C)+ water influx (D)

Material Balance Method - Basic Principle A = Increase in HCPV due to the expansion of the oil phase (oil +dissolved gas). B = Increase in HCPV due to the expansion of the gas phase (free gasin the gas cap). C = decrease in HCPV due to the combined effects of the expansion of the connate water and the reduction in reservoir pore volume. D = decrease in HCPV due to water encroachment (from aquifer)

MATERIAL BALANCEN =

N=vol. minyak @ standarG=vol. gas @ standarW=vol. air @ reservoirm=vol.gas/vol.minyak@reservoirNp=prod.minyak@standarGp=prod. gas@ standarWp=prod. air @ standarWe=intrusi air @ reservoirBo, Bg, Bw= unit vol. menyesuaikan65teknik reservoir lanjut - RS -teknik perminyakan - trisaktiMATERIAL BALANCEsimultaneous drivesN =

66teknik reservoir lanjut - RS -teknik perminyakan - trisaktiMATERIAL BALANCEsimultaneous drivesN =

DDI = Depletion Drive IndexSDI = Segregation Drive IndexWDI = Water Drive Index DDI+SDI+WDI = 1

67teknik reservoir lanjut - RS -teknik perminyakan - trisaktiStraight Line MBEMBE can be modified as equations of straight lines, which can be applied to different types of reservoirs (Havlena Odeh).

F= N (Eo + m Eg + Ef,w) + We Bw

F = summation of production terms: Np [Bo + (Rp Rs) Bg] + Wp Bw (rb)Eo = Oil and Dissolved gas expansion terms [ (Bo Boi) + (Rsi Rs) BgEg = Gas cap expansion term Boi (Bg / Bgi 1)Ef,w = rock and water compression/expansion terms (1+m) NBoi --------------- (cw Swc + cf) p + We Bw (1 Swc)

MBE- Definitions of VariablesProduction dataNp = Cumulative oil produced (stb)Gp = cumulative gas produced (scf)Wp = Cumulative water produced (stb)Rp = Gp/Np = Cumulative produced gas-oil ratio (scf/stb)Reservoir Datapi = Initial mean pressure in the reservoir (psi)p = current mean pressure in the reservoir, (psi)Swc = connate water saturation, (fraction)cf = Compressibility of formation (psi-1)Fluid PVT DataBgi = Initial gas volume factor at pi (ft3/scf)Bg = Gas volume factor at current pressure p (ft3/scf)Boi = Initial oil volume factor at pi (rb/stb)Bo = Oil volume factor at current pressure p (rb/stb)cw = Compressibility of water (psi-1)Bw = Formation volume factor of water at current pressure p (rb/stb)Rsi = solution gas-oil ratio at initial pressure pi (scf/stb)Rs = solution gas-oil ratio at current pressure p (scf/stb)No gas cap, no water drive70

No gas cap71

No water drive72

No gas cap73

No water drive74

WATER INFLUX

DDI = Depletion Drive IndexSDI = Segregation Drive IndexWDI = Water Drive Index DDI+SDI+WDI = 1

75teknik reservoir lanjut - RS -teknik perminyakan - trisaktiWATER INFLUX

STEADY STATE : SCHILTHUIS

MODIFIED STEADY STATE : HURST

UNSTEADY STATE : VAN EVERDINGEN & HURST 76teknik reservoir lanjut - RS -teknik perminyakan - trisaktiWATER INFLUX

77teknik reservoir lanjut - RS -teknik perminyakan - trisaktiWATER INFLUX

k= konstanta water influx [bbl/day/psi] dp= (pi-p) di batas reservoir / aquifer [psi]

c= konstanta water influx [bbl/day/psi dp= (pi-p) di batas reservoir- aquifer [psi] a = konstanta konversi waktu [f. unit waktu] B= konstanta water influx [bbl/day/psi] dp= penurunan tekanan [psi] Q(t)=dimensionless water influx78teknik reservoir lanjut - RS -teknik perminyakan - trisaktiWater InfluxVan Everdingen (re/rw = 2 4)teknik reservoir lanjut - RS -teknik perminyakan - trisakti79

Van Everdingen (re/rw = 2 4)teknik reservoir lanjut - RS -teknik perminyakan - trisakti80

Van Everdingen (re/rw = 5 10)

Reserve Estimation Methods

3.Decline Curve Analysis Later stage of development, production rate undergoes natural decline Mostly Production data, no Pressure data RF is calculated Time dependant

Decline curve of an oil well

Advantage of Decline CurvesDecline curves are the most common means of forecasting production. Theyhave many advantages:Data is easy to obtain,They are easy to plot,They yield results on a time basis, andThey are easy to analyze.Exponential DeclineIf the conditions affecting the rate of production of the well are not changed byoutside influences, the curve will be fairly regular, and, if projected, will furnishuseful knowledge as to the future production of the well.

in the exponential decline, the wells production data plots as a straight line on a semilog paper. The equation of the straight line on the semilog paper is given by:

q = qi .eDt

Where:q = wells production rate at time t, STB/dayqi = wells production rate at time 0, STB/dayD = nominal exponential decline rate, 1/dayt = time, day

Hyperbolic Decline

If the wells production data plotted on a semilog paper concaves upward, then it is modeled with a hyperbolic decline. The equation of the hyperbolic decline is given by:

q=qi(1+bDi.t)-1/b

Where:

q = wells production rate at time t, STB/dayqi = wells production rate at time 0, STB/dayDi = initial nominal exponential decline rate (t = 0), 1/dayb = hyperbolic exponentt = time, day

Harmonic Decline

A special case of the hyperbolic decline is known as harmonic decline, where b is taken to be equal to 1. The following table summarizes the equations used in harmonic decline:

q=qi/(1+bDi.t)

Where:

q = wells production rate at time t, STB/dayqi = wells production rate at time 0, STB/dayDi = initial nominal exponential decline rate (t = 0), 1/dayb = hyperbolic exponent = 1t = time, day

Reserve Estimation Methods

4.Reservoir Simulation applied at any stage, more reliable for matured reservoirs Geological, Rock and Fluid properties, Production data More useful as reservoir management tool

FRACT. FLOW & ITS DERIVATIVEteknik reservoir lanjut - RS -teknik perminyakan - trisakti88

FRACTIONAL FLOW EQUATIONteknik reservoir lanjut - RS -teknik perminyakan - trisakti89

WATER FRACTIONAL FLOWteknik reservoir lanjut - RS -teknik perminyakan - trisakti90

FRONT & AVERAGE WATER SATURATIONSteknik reservoir lanjut - RS -teknik perminyakan - trisakti91

TRANSITION ZONEteknik reservoir lanjut - RS -teknik perminyakan - trisakti92

2D FLUID FLOWteknik reservoir lanjut - RS -teknik perminyakan - trisakti93


Microscopic displacementteknik reservoir lanjut - RS -teknik perminyakan - trisakti96

Vertical sweep efficiencyteknik reservoir lanjut - RS -teknik perminyakan - trisakti97


Sweep effeciency

Sweep effeciencyteknik reservoir lanjut - RS -teknik perminyakan - trisakti100

Areal & vertical sweep eff.teknik reservoir lanjut - RS -teknik perminyakan - trisakti101

Displacement efficiencyteknik reservoir lanjut - RS -teknik perminyakan - trisakti102

where S oi = initial oil saturation at start of floodB oi = oil FVF at start of flood, bbl/STB = average oil saturation in the flood pattern at a particular point during the flood

DYKSTRA PARSONS coefficient of K variation (V)teknik reservoir lanjut - RS -teknik perminyakan - trisakti104

V =k50 = median permeability value, mDk84.1 =permeability at 84.1% probabilityPlot of permeability data on log normal paperteknik reservoir lanjut - RS -teknik perminyakan - trisakti105K, mDPercent of sample with higher Permeability5099.990.01

V =

Dykstra Parson, WOR = 1

vMDykstra Parson, WOR = 5

VMDykstra Parson, WOR = 25

VMDykstra Parson, WOR = 100

VM

Water ConingP > 0,433(w -o)hc


Water Coning In A Vertical Oil Well

For an reservoir with an underlying water-zone, and the perforated interval at the top of the oil-zone, a number of researchers have proposed methods for determining the Critical oil flow rate (Qoc).teknik reservoir lanjut - RS -teknik perminyakan - trisakti116The commonly-used methods are: - Meyer-Garders Method- Chaperon's Method- Schol's Method- Hoyland-Papatzacos-Skjaeveland's Method - Sobosinski - Cornelius

All these methods apply to the isotropic reservoir case where horizontal permeability equals vertical permeability, except for Chaperon's more general anisotropic case.Water Coningteknik reservoir lanjut - RS -teknik perminyakan - trisakti117

Water coning & fingeringteknik reservoir lanjut - RS -teknik perminyakan - trisakti118

Water coning in horizontal wellteknik reservoir lanjut - RS -teknik perminyakan - trisakti119

Critical Pressure Drawdown & Production Rateteknik reservoir lanjut - RS -teknik perminyakan - trisakti120P > 0,433(w -o)hc

P = pressure draw down at the well = water specific gravity = oil specific gravityhc = vertical distance from the bottom of well completion to OWCMeyer-Garders Methodteknik reservoir lanjut - RS -teknik perminyakan - trisakti121

0.001535Chaperon's Methodteknik reservoir lanjut - RS -teknik perminyakan - trisakti122

Schol's Methodteknik reservoir lanjut - RS -teknik perminyakan - trisakti123

Hoyland-Papatzacos-Skjaeveland's Methodteknik reservoir lanjut - RS -teknik perminyakan - trisakti124

Metode BOURNAZEL dan JEANSON


0.00137Sobocinski dan Cornelius M < 1, =0.5 M> 1, = 0.6Z : dimensionless cone heighttd : dimensionless time, t: daysteknik reservoir lanjut - RS -teknik perminyakan - trisakti

Contoh perhitunganteknik reservoir lanjut - RS -teknik perminyakan - trisakti127

nomenclatureteknik reservoir lanjut - RS -teknik perminyakan - trisakti128Where: Qoc = critical oil well rate, STB/day h = oil column thickness, ft hp= perforated interval, ft kh= horizontal permeability, md kv= vertical permeability, md ko= effective oil permeability, md (ko= rock permeability x oil relative permeability)re = drainage radius of well, ftrw = wellbore radius, ftBo = formation volume factor of oil o = oil viscosity, cp o = oil density, lb/ft3 w = water density, lb/ft3Note that the critical rate is the oil rate below which water breakthrough will never occur; this rate may be too low for practical and economic reasons.Water coning Input dataOil column thicknessftPerforated intervalftWellbore radiusftDrainage radiusftPermeabilitymDOil relative permeabilityOil densitylb/ft3Water densitylb/ft3Formation volume factorOil Viscosityteknik reservoir lanjut - RS -teknik perminyakan - trisakti129OUTPUT VARIABLES Critical Oil Flow RateSTB/day Meyer-Garder's Method Chaperon's Method Schol's Method Hoyland-Papatzacos-Skjaevelandteknik reservoir lanjut - RS -teknik perminyakan - trisakti130Critical Oil Flow Rate (Anisotropic)STB/day Chaperon's Method

Trisakti 2013 Teknik Reservoir Lanjut

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