ENHANCED RESERVOIR CHARACTERISATION BASED UPONBOREHOLEIMAGES SAADALLAH GEOCONSULTANT AS A. SAADALLAH Dr.& Misjonsveien 39, N-4024 Stavanger Norway Tel. + (47) 51 52 62 65 (office)DIPMETER Email: firstname.lastname@example.org website: www.saadgeo.comDATA
WARNING !THIS PRESENTATION WASPREPARED IN 2005IT HAS TO BE UPDATED BYINCLUDING NEW TOOLS (such asthose of Weatherford) AND OTHERELEMENTS OF INTERPRETAION
ENHANCED RESERVOIRCHARACTERISATION BASED UPONBOREHOLE IMAGES & DIPMETERDATAOVERVIEW
1 Introduction2 Dipmeter Tools3 Imaging Tools4 Borehole Map5 Stereographic Projections6 From Raw Data to Geologically Interpretable Outputs7 Basic Interpretation8 Clastic Reservoirs9 In Situ Stress Issue10 Fractured Reservoirs11 Key Features to keep in mind12 Key References
From Logging & Petrophysicpoint of viewtoa Geologic Mapping of theBorehole Wall concept
From Logging & Petrophysic point of view to a GeologicMapping of the Borehole Wall conceptCurve:ONE value (Rock Propriety)vs.ONE Depth (MD)
From Logging & Petrophysic point of view to a GeologicMapping of the Borehole Wall conceptCurve: a value (Rock Propriety) vs. Depth (MD)Dip needed very early inLogging industry (Seismic notyet performed or/and poor, Oilgoes up!)
From Logging & Petrophysic point of view to a GeologicMapping of the Borehole Wall conceptCurve: a value (Rock Propriety) vs. Depth (MD)Dip needed very early in Logging industry (Seismic not yetperformed or/and poor, Oil goes up!)Dip needs a set of at least 3measurements of the SAMEFEATURE: Dipmeter tool: 4curves
From Logging & Petrophysic point of view to a Geologic Mapping ofthe Borehole Wall conceptCurve: a value (Rock Propriety) vs. Depth (MD)Dip needed very early in Logging industry (Seismic not yetperformed or/and poor, Oil goes up!)Dip needs a set of at least 3 measurements of the SAME FEATURE:Dipmeter tool: 4 curvesTechnology improvements: more data,magnetometers, accelerometers, transmissionof data (pulse within mud) IMAGINGTOOLS: ca 100 000 measurements per MeterMD: MAPPING OF THE BOREHOLEWALL.
From Logging & Petrophysic point of view to aGeologic Mapping of the Borehole Wall conceptCurve: a value (Rock Propriety) vs. Depth (MD)Dip needed very early in Logging industry (Seismicnot yet performed or/and poor, Oil goes up!)Dip needs a set of at least 3 measurements of theSAME FEATURE: Dipmeter tool: 4 curvesTechnology improvements: more data,magnetometers, accelerometers, transmission ofdata (pulse within mud) IMAGING TOOLS: 100000 measurements per Meter MD: MAPPING OFTHE BOREHOLE WALL.
1250 Dips measured (2004) a fractured reservoir
From 1 Dip in 1 day (1969Sidi Ferruch Algiers)To1250 Dips measured (2004fractured reservoir)
From FEW toTHOUSANDS ofMEASUREMENTSThat’sDIGITAL GEOLOGY
New ways of thinking,managing data, processing,interpreting…and moreand more data…in realtime …new challenges forgeoscientists
Logging History Mile Stones: 1927 Figure 1.The first electric log was obtained Sept. 27, 1927, on the Diefenbach 2905 well, Rig.No. 7, at Pechelbronn,Alsace, France.The resistivity curve was created by plotting successive readings.
Logging History Mile Stones: 19471941: logging took another major step forward with theintroduction of the Spontaneous-PotentialDipmeter.1947: This measurement was improved further with theResistivity Dipmeter1952: Continuous Resistivity Dipmeter
Logging History Mile Stones:Imaging Tools1968 BHTV (BoreHole TeleViewer) Mobil Acoustic...1986: FMS (Formation MicroScanner) Schlumberger Electric...1991 FMI (Fullbore Formation Microscanner) Schlumberger...1994 RAB (Resistivity at the Bit) LWD Schlumberger...2001 OBMI (Oil Base MicroImager) Schlumberger...NEXT: high resolution imaging LWD tools (technical issue totransmit data while drilling solved: WO (2007??)Followed by other logging companies: Baker Hughes, Halliburton
MAIN DIPMETER TOOLS Logging Company Main TechnicalTool Name Resolution Name & Mud Characteristics EnvironmentSHDT 8 microresistivity electrodes on Schlumberger’s tool(Stratigraphi 4 pads (2 per pads) Water-base mudc Dipmeter) Sampling: 0.1 inHEXDIP Vertical 6 microresistivity electrodes on Baker Hughes’ tool(Hexagonal resolution: 1-2 6 pads Water-base mudDiplog) cmSED (Six 6 microresistivity electrodes on Halliburton’ toolArm 6 pads Water-base mudDipmeter)
HIGH RESOLUTION IMAGING TOOLSElectrical and Acousticof the main logging companies in petroleum industry BAKER HUGHES: - STAR (electrical & acoustic) - CBIL HALLIBURTON: - XRMI (EMI) - CAST SCHLUMBERGER: - FMI (FMS) - UBI
Main Characteristics of Electrical Imaging ToolsUse electrical responses of the formation to create Images.Pad-based Microresistivity (conduct. mud),sensitive to poor pad contact. Depth of investigation: 1 in.Resolution linked with electrical contrast:Bedding ca. 1 cm; Fracture ca. 1 mm (Resistivity Contrast) EMI FMI STAR 6 Pads, 2 rows 4 Pads & Flaps 6 PadsArm configuration 2 X 12 Sensors 2 X 12 Sensors 25 SensorsSensors 150 192 144Coverage 58% of 8.5” 75% of 8.5” 56% of 8.5”Logging Speed 1800 ft/hr 1800/1500 ft/hr 1200/2400 ft/hrX-, Y-Spacing 0.2 in. 0.1-0.2 in. 0.1 in.
Main Characteristics of Acoustic Imaging ToolsAcoustic response of the formation to build up imagesRotating transducer (Transmitter-Receiver)Ultras. pulse 250-500 kHz. Water- and Oil-based mud,100% borehole coverage, sensitive to borehole shape,Depth of investigation: 0, Travel Time and Amplitude AttenuationResolve feature down to 1 in. CAST UBI CBIL 200 samples/rev 7.5 Rot /Sec 6 Rot/SecMeasurements 180 samples /rev 12 (STAR) 250 samples/rev 1 in. 2100 ft/hrVertical Sampling 0.3 in 0.4 in 800 ft/hr 0.2 inrate & Logg. speed 1200 ft/hr 0.2 in 400 ft hr 2400 ft/hrImage Resolution 0.4 in at 250 kHz 0.2 in at 500 kHz
BoreHoleMapBoreholeToolProjection: BoreholemapTool within the Borehole: RBAttitude of a plane in SpaceAttitude of an axis in SpaceBoreholemap representation: SinecurveTadpole
BoreHoleMap: OrientationBorehole AxisDEVI: Deviation (inclination): Angle 00-90 Deg (from vertical to horizontal axis)HAZI: Borehole axis azimuth: Angle 000-360 Deg (from N-000- to N -360 clockwise)MD: Measured DepthTool Axis (Sonde Axis)DEVI: Sonde Deviation: Angle 00-90 Deg (from vertical to horizontal axis)Sonde DEVI = Borehole DEVIP1AZ: Ref PAD (PAD1): Azimuth PAD1 = Angle 000-360 Deg from North (000) orfrom the BOREHOLE HIGH SIDE clockwiseMD: Measured Depth
ORIENTATION of the BOREHOLE MAPY-AXIS: - Borehole High Side 0 90 180 270 3600 - Tool Frame Y-Axis: MD - North& MDX- AXIS: - Borehole Perimeter& Azimuthal X-Axis: Azimuthal & Perimeter
ORIENTATION of the TOOL WITHIN the BoreholeTool ROTATES (around the AXIS) itsEXACT position INSIDE the BOREHOLEhas to be known at EVERY measurementRB: Relative Bearing:Angle between the referenced-arm (P1AZ) and a fixed feature(North, High side of the Borehole) is recorded atevery measured point
Core Goniometry Methodology1. - Projection of core-features onto a borehole map2. - Projection of a planar-feature onto the borehole map (Fault…)3. - Projection of a linear-feature of a surface onto the borehole map (Striation on Fault-Surface)
Projection of Core: Borehole MapOrthogonal projection ontoa cylindrical surface = Borehole Map A reference line parallel to the core axis = master calibration line with the MD = Y-Axis Perimeter =2PR = 3600 = X-Axis (cm & Deg)
Projection of a Planar-feature PR DIP-AZIMUTH Sine curve TOP PR Sine curve BOTTOM =DIP-AZIMUTH Perimeter =3600 900 1800 2700 360-00 =2PR PR/2 PR 3PR/2 2P R-0 cm DIP-AZIMUTH (cm or Deg) relative to the master calibration line Master Calibration Line
Projection of a Planar-feature DIP Sine Curve Amplitude DZ 900 1800 2700 360-00 PR/2 PR 3PR/2 2P R-0 cm DZ Tang DIP = Core Diameter
AXIS On Borehole MapFault Surface with Striation (Sandstone clast) in Shale
Projection of a Linear-featureof a Surface onto the Borehole Map PR DZ 900 1800 2700 360-00 PR/2 PR 3PR/2 Tang DIP = DZ 2P R-0 cm Diameter of the Core DIP-AZIMUTH of the line relative to the master calibration line
Projection of a Linear-featureof a Surface onto the Borehole Map 900 1800 2700 360-00 PR/2 PR 3PR/2 2P R-0 cm DIP-AZIMUTH of the LINE relative to the master calibration line
N (000Deg)TADPOLE 0 Deg 90 Deg 10/135 Deg W (270 Deg) E (090 Deg) 15/225 Deg S (180 Deg)
Compass Rose 360/0 348.75 011.25 326.25 033.75 045 N-S 315 .S W N..N NN 056.25 E-S W- W- N.N SW S..S 303.75 NW -S E- EE E N W. NW .SW 078.75 281.25 -E. E-W SE E. N270 E-W E-W 090 W. W NW 258.75 W. S -E. E. NE- SE 101.25 NW N..N NN .SW SW -S E E- 123.75 W- W-S N E -S 236.25 S..SE N.N S 135 225 N-S 146.25 213.75 168.75 191.25 180Dipping Striking Dipping Striking348.75…011.25: N E-W 168.75…191.25: S E-W011.25…033.75: N.NE W.NW-E.SE 191.25…213.75: S.SW W.NW-E.SE033.75…056.25: NE NW-SE 213.75…236.25: SW NW-SE056.25…078.75: E.NE N.NW-S.SE 236.25…258.75: W.SW N.NW-S.SE078.75…101.25: E N-S 258.75…281.25: W N-S101.25…123.75: E.SE N.NE-S.SW 281.25…303.75: W.NW N.NE-S.SW123.75…146.25: SE NE-SW 303.75…326.25: NW NE-SW146.25…168.75: S.SE E.NE-W.SW 326.25…348.75: N.NW E.NE-W.SW168.75…191.25: S E-W 348.75…011.25: N E-W
From RAW Data toGEOLOGICALLYInterpretable Outputs
Main ProcessesRaw data, microresistivity measurements recorded by electrode tool,need to be processed:Speed correction,Magnetic declination correction,Depth shift offset (when it is needed)Generation of image/dip logs.
Main ProcessesSpeed correction,convert data, recorded vs. time into data vs. depth&correct depth offset due to oscillations along the axis tool.Oscillations are caused by irregularities of the borehole or in fact dueto the none-constant speed of the tool while running the logs.Generally, a sliding window of 10 ft is used for an average cable speedof 1600 ft/hr.
SPEED CORRECTION: is applied to correct for erratic tool motion & convert data recorded in time to depth 0 90 180 270 3600 T8 T3 0.2 in. T2 T2-7 2-7 T1 T1Y Axis: MD T0 T0IN THEORY: Tool moves up the IN REALITY: Tool moves ERRATICALLY upborehole recording measurement-sets the borehole recording measurement-sets atAt regular timing (T0 – T3) regular timing (T0 – T3)
Main ProcessesMagnetic declination correction,applied to inclinometry measurementsrecorded by the tool (relatively to themagnetic North) to convert them toGeographic North.
Main ProcessesDepth shift offset (when it is needed)Correlation of GR from another Run (Wireline Log) & GR from FMIGeological Feature determined from other sources
Main ProcessesGeneration of imagesStatic normalised images (called Static Images):computation carried out in a window covering all thelogged section.Dynamically normalised images (called Dynamic Images):sliding window (5 Ft).Scale in the range white-yellow-brown-dark :white-yellow: minimum conductivityTobrown-dark: maximum conductivity.
Measurementsrecorded by padsduring the runRepresented byresistivity curvesspecific to eachpadare correlatedduringthe process(spikes)
Correlationprocess will fit aplane & computeits dip/dip-azimuth
Processing Dipmeter Data:-1 m sliding window (1600 ft/hr average cable speed- Corresponding step: 0.5 m- Search angle 70 Deg
Processing Dipmeter Data:-1 m sliding window (1600 ft/hr average cable speed- Corresponding step: 0.5 m- Search angle 70 Deg Max. Search Window Step length Angle relative Computed log Comments length (cm) (cm) to borehole name Deg. Computed log used for Hex100X50X8 interpret dips 100 50 80 0 stored in a new log named INTERPR100 60 30 60 Hex60X30X60 20 10 40 Hex20X10X40
Dip Log:Computed Dips OnlyHigh & Low ConfidenceNoisePoor Data Intervals
From Atlas of Borehole Imagery Ed L.B. Thompson Aapg 2000
QUALITY CHECKFrom LOADING To FINAL INTERPRETATION
QC: Depth Match, Static & Dynamic ImagesGeological Features: Bed Boundary, Bedding Static Image Dynamic Image GR CalipersRHOBNPHI
Other Points:Repeat Section (200 ft MD)Tool Rotation (less than one turn per 30 ft)Slip-Stick BehaviourRaw data in original format (LIS, DLIS)Field Print (orientation, Pad#, MagneticDeclination Value, Correction (Not Done)
IF OrientationDon’t Fit with Previous Field Model ?Comparison with OTHER RUNSGeology is the BEST QCTool has picked the “wrong” North?Rotation of the Dip Log, around the borehole axis(Same Methodology as in Core Goniometry)Assume the Same Error during all the RUN
ROTATIONVertical BoreholeDIP remains the SameDIP-Azimuth Changes
INTERPRETATION Step 1Collecting Geologic Data-1) Diptype Listing-2) Image Quality-3) Zonation Based on Image FabricHighlighting:-4) Lithology (Sedimentology) Facies-5) Deformation Facies
DIPTYPE LISTING:3 Geologic Surface Types:-1) Sedimentologic-2) Structural-3) In Situ Stress Features
Identification of Geological FeaturesPicked out directly from images &/or inferredSedimentological features:- Bedding planes Structural-Dip, Paleo-Horizontal Dip- Cross-bedding Paleo-Transport Directions, Deposi-- Unconformities tional environments- Image facies Help define reservoir unitsTectonic features:- Faults: Fault-block rotation, strike-slip component- Fractures: Fracture analyses of reservoir: Fracture population characterisation, fracture densities, Maximum fracturing directions- In-situ Stress features: Breakout, Tensile FracturesIn Horizontal wells: syncline & anticline structures, younging direction, Bedding-plane-correlation to constrain reservoir zonation
SEDIMENTOLOGIC FeaturesListing PARTICULAR to a RESERVOIRRelated to data from other sources (Cores,Petrophysics, Seismic, Field Studies) to helpCORRELATE
QC: Depth Match, Static & Dynamic Images Geological Features: Bed Boundary, Bedding Static Image Dynamic Image GR CalipersRHOBNPHI Bed BoundaryFMI
QC: Depth Match, Static & Dynamic Images Geological Features: Bed Boundary, Bedding Static Image Dynamic Image GR CalipersRHOBNPHI Bedding Bed BoundaryFMI
Foreset, Foreset Boundary & Cross Bedding Calipers GR Foreset Boundary Cross RHOB Bedding Foreset Bed Boundary NPHIFMI
Shale Bedding, SS Bedding & Heterolithic Bedding Calipers GR RHOB NPHI Shale Bedding SS Bedding Heterolithic BeddingFMI
TECTONIC FeaturesListing PARTICULAR to a RESERVOIRRelated to data from other sources (Cores,Petrophysics, Seismic, Field Studies) to helpCORRELATE
Part of a Diptype List (Fractured Reservoir)Diptype Name,(CorrespondentGeological Notion), Description & Correlation with Geologicalcolour used in plots Comments Featureand Fig., andIllustration (Go to Fig#) Narrow or large, and discrete resistive orFAULT conductive anomaly displayed along a sub- planar feature cutting sedimentologic planes. Fault is differentiated from(Fault), Red Also, a clear cut off the bulk resistivity, Fracture.GoToFig11 highlighting a plane considered as a fault plane. The current bedding planes areBEDDING Change in the bulk conductivity along a generally parallel to bed boundary(Bedding), planar boundary at the lowest scale of the and regularly repeated in the bed or image, i.e. centimetre scale. Regularly layer.Green repeated planar features corresponding to Confusion sometimes with ShaleGoToFig12 current bedding planes. Bedding, Bed Boundary and Stylolite
FMI Fault Examples of Geological Features Interpreted as a probable Reverse Fault Bedding plane in the Hangingwall Block Minor Fault The same Bedding plane in the Footwall Block Reverse Minor Fault with a ca 15 cm throw
From Atlas of Borehole Imagery Ed L.B. Thompson Aapg 2000
Younging Direction in Horizontal Well Younging Direction Cross sectionTD of anticline drilled by a Horizontal Well Upward Downward Younging direction inferred from the shape of the sine curveOutward direction Inward direction
Bedding Plan Correlation: a methodology tohelp define reservoir units -INTERVAL without fault Younging Direction picked out -SHORT interval - A BEDDING PLANE , bounding reservoir units picked and choosen as STRATUM GUIDE - Locations where Stratum guide is cut DOWNWARD or UPWARDTo be Performed Carefully! are picked out
Bull’s eye structure in Borehole Images Borehole high side of Horizontal Well: Inward direction Inward direction= Anticline structureOr Outward direction= Inflexion of the well-track (concave profile)
Wood-Grain structure in Borehole Images Borehole high side of Horizontal Well: Inward direction Inward direction= Syncline structureOr Outward direction= Inflexion of the well-track (convex profile)
From Atlas of Borehole ImageryEd L.B. Thompson Aapg 2000
From Atlas of Borehole ImageryEd L.B. Thompson Aapg 2000
Example of Image Fabric Zonation Highlighting Matrix CharacteristicZonation Name & Colourused to flag the Description & Correlation with Commentscorresponding interval, Geological Features and Eventsand Illustration (Fig) This layer might be rich in clay, shale, fine grain thatThinly Bedded Interbedded matrix with thinly bed including might be a horizontal barrier toMatrix (Red) cross bedding. It is possible to pick every 5 fluid displacement.GoToFig11 cm a bedding surface. It can be used to determine the Paleohorizontal dip if necessary. The resistive spots are Conglomerate-shaped matrix with resistive considered as tight or close nodules. This might be related to therefore not used by fluids as conglomerates or not, it has to be calibrated porosity.Nodular Matrix with other data sources (cores, mud logs, On the contrary, the “matrix”(Green) GoToFig12 field studies…). Resistive nodules might be between the resistive spots is related to some anisotropic proprieties of the conductive so it is considered matrix or to some tight features. as actual/potential significant porosity
ScaleRudist Shuaiba (Cr)Bu Hasa Field (AbuDhabi)
DEFORMATION FACIESZONATION(Stylolite Associated Fractures, Fracture Zone 1…)
Example of Zonation Highlighting Deformation Features, Stylolite & Karstic Associations, and Poor ImagesZonation Name &Colour used to flag Description & Correlation withthe corresponding Comments Geological Features and Eventsinterval, andIllustration (Fig)Poor Image Image is of poor quality, high to moderate Poor quality of image correspond(Red) uncertainty in the interpreted features of the often to washout intervalsGoToFig11 flagged interval. This zone, subhorizontal might play a positive role in draining fluids Tiny Fractures (up to 20 cm vertical-length) horizontally. sub perpendicular to Stylolite surface, Such feature is known as used by fluidStylolite occurring in the lower side, or upper side or paths in some carbonate reservoirs.Associated both sides of the stylolite surface. Fractures It might be considered as “pipe-layer” are striking in all azimuths (radial) or in parallel to the Stylolite surface.Fractures particular azimuths: it is not clear. If crossed by Fracture Zone or(Green) Sometimes a couple of stylolite surfaces Fractured/Cataclastic zone this mightGoToFig12 with their associated fractures are close increase the draining propriety. enough to constitute a Stylolite Zone The question is about the role regarding vertical path of fluids: obstacle or drain?
Examples:Girdle: Inferred faultsBimodal: UnconformitiesPaleohorizontal dipStructural Dips: Per Units,Logged Section
Structural Dip & / or Paleo-Horizontal Dip: ?“...Dips with constant magnitude and azimuth in a low energy environmentcan be selected. They correspond to the groups of beds, whose bedding planes have notundergone any biogenic or tectonic alteration. It can reasonably be assumed that thesebeds were deposited on nearly horizontal surfaces and that their present dips are theresult of tectonic stresses” Tire de Serra, O. 1985, “Sedimentary environments fromwireline logs”. I call it: PALEO-HORIZONTAL DIP “By Structural dip is intended the “general attitude of beds”. It is the dip that would be measured at outcrop. It is usually the dip seen on seismic reflectors, themselves a generalisation. It avoids any sedimentary structures of any size and is generally considered to represent the depositional surface which also is considered to be horizontal.” Tire de Rider, M. H. 1996 “The geological interpretation of well logs” I call it: STRUCTURAL DIP
The way I see it, and use it in my interpretation:PALEO-HORIZONTAL DIPPaleo-Horizontal Dip, as is suggested by the name, is the dip of bedding planes thatwere originally deposited horizontally. Low energy sediments such as shale, planktonicsediments and coals, in specific conditions, can be assumed to be depositedhorizontally.Such bedding planes may be used to infer tectonic events such as uplift, tilting or faultblock rotation.STRUCTURAL DIPStructural dip is restricted to the mean dip of a lithological formation that can be usedin geological (structural) cross-section, or related to a specific marker that can becorrelated to a seismic one, avoiding detailed sedimentological structures at smallscale. The dip and associated dip-azimuth can be used to infer the geometry of theunits, for structural purposes at rather bigger scale, no matter what its genetic origin,or what events the unit has previously undergone.
Paleo-Horizontal Dip: Interval of Low Energy Deposits
Paleo-Horizontal Dip: Whole Dip-type Populationof Low Energy Deposits
Structural Dip: Several Dip-type Populations: BedBoundary, ...
PALEOHORIZONTAL DIP Implemented to Rotate Out Dips After Rotation Before Rotation