Vsp Sv Lesson 7 Homework

Presentation on theme: "Borehole Seismic Introduction"— Presentation transcript:

1 Borehole Seismic Introduction

2 Overview Introduction Seismic Signals in the borehole
Borehole EnvironmentBorehole survey typesBorehole seismic deployment

3 What is a VSP?A VSP or Vertical Seismic Profile is the process of recording seismic data in a wellbore environment. The geophones are vertical in the earth versus horizontal along it as in surface seismic.

4 Borehole Seismic Surveys
CheckshotVertical IncidenceWalkaway3D-VSPDBSeisOffset VSPSalt ProximityZero OffsetLWD ToolSeismicMWDIntegrated Seismic SurveysGECO LONGVAOSLOPressure &TemperatureFlow &Phase4C SensorsBorehole seismic surveys : the past, the present and the futureCheckshot surveys - The time taken for seismic energy generated from an explosive source to propagate downwards is measured at receivers positioned at key formation tops. From this information it is possible to calculate the formation interval velocities.Zero Offset VSPs - Geophones are evenly distribution along the well bore. As well as providing travel-time and velocity information from a single source positioned at the well-head, it is possible to measure the reflectivity of each horizon and build up a single trace seismic image at the wellbore.Moving Source VSPs or Walkaway VSPs - Here the geophone is stationary, with the sources moving, firing every 25 metres along a 6km line. As the boat traverses, a profile of reflected seismic energy for each horizon is built up, and is shown by the green and blue lines. This generates a 2D image of the sub surface underneath the path of the source line.This technique can be extended to 3D, by acquiring many 2D profiles at different offsets.Although acquiring 3D-VSP data-sets has been around since the late 1980s, until now positioning the data correctly both spatially and in depth (known as migration) has been done strictly using 2D techniques.Schlumberger over the past few years have improved their depth migration algorithm from 2D to 2.5D (used for the Brent survey acquired by Shell, and featured in a recent First Break) and now have a full 3D migration algorithm.Integrated Reservoir Technology The future challenge will be the application of integrated reservoir evaluation and monitoring technology in which 4D-4C borehole seismic surveys will be one of the key components for the complete reservoir monitoringNEXT SLIDE : Rationale for 3D VSP

5 IntroductionSeismic Signals in the boreholeBorehole EnvironmentBorehole survey typesBorehole seismic deployment

6 Seismic Signal in the Borehole
TimeDowngoing direct arrivalReflected upgoing primaryDowngoing multipleReflected upgoing multipleDepth

7 Vertical Seismic Profile
Time-DepthSeismic ReflectionsTimeTime-DepthDepth

8 One-Way Time vs. Two Way Time
Surface SeismicVSPTWT = OWT + TTTimeReflectionTWTTransitTime (TT)TTReflectionTime (OWT)OWTTTDepth

9 Borehole MultiplesUpgoing Multiples

10 Borehole MultiplesDowngoing Multiple

11 Borehole MultiplesAll Multiples

12 Tube Wave Energy Source
Tube waves are generated when surface waves from the source come in contact with the borehole fluid and become a guided wave traveling up and down the borehole.As the tube wave travels vertically in the borehole it pushes the wall horizontally.When the geophones are properly clamped to the borehole wall most of the tube wave energy will be seen in the horizontal geophones.At changes in the borehole dimensions some of the tube wave energy will be reflected back to the surface. This will also occur when the energy reaches the bottom of the hole.

13 Tube Waves Raw Data One-Way Time Depth Vertical Channel Tube wave
Horizontal ChannelVertical ChannelTube waveYXHODOGM

14 Surface Seismic Comparison
VSP DataOffsetDepthOne-Way TimeTwo-Way Time

15 IntroductionSeismic Signals in the boreholeBorehole EnvironmentBorehole survey typesBorehole seismic deployment

16 Resonance types & effects
Resonance generates signal distortionCoupling resonance effectModal resonance effect

17 Resonance Attenuation
Reduce tool dimension & massIncrease tool application forceOptimize contact geometryCombined toolsShakerCoupling contactsGeophonesIsolatingspringsVersatile Seismic Imager - VSIIsolated geophone package: 3.5 lbsPositive mechanical anchoringCombinable Seismic Imager - CSIIsolated geophone package: 20 lbsPositive mechanical anchoringArray Seismic Imager - ASIIsolated geophone package: 9 lbsMagnetic clamping

18 Shaker Response

19 IntroductionSeismic Signals in the boreholeBorehole EnvironmentBorehole survey typesBorehole seismic deployment

20 Borehole Seismic History
CheckshotSingle Trace2-D Lateral Coverage

21 Checkshot Surveys Formation Travel Times Formation Velocities
SourceDepth ModelSurfaceSeismicDepth (m)AcousticImpedanceFormationVelocitiesSyntheticSeismogramGeophonesDepth-VelocityModel InputsSurface SeismicCorrelationTime (s)WaveletProcessing

22 Zero Offset VSP Surface Seismic Correlation
SourceDepth ModelSurfaceSeismicDepth (m)Over-pressure Zone PredictionCorridorStackGeophonesMultiple PatternIdentificationWaveletProcessingTime (s)FormationVelocities

23 Vertical Incident VSP Surface Seismic Correlation
WALKABOVEVertical Incident VSPSurface SeismicCorrelationSourcesDepth ModelSurfaceSeismicDepth (m)Lateral Coverage Beneath WellVSPImageGeophonesMultiple PatternIdentificationFault and DipIdentificationTime (s)FormationVelocities

24 Offset VSP Surface Seismic Correlation Fault and Dip Identification
SourceDepth ModelSurfaceSeismicDepth (m)Fault and DipIdentificationVSPImageGeophonesSalt ProximityIdentificationShear WaveAnalysisTime (s)Surface SeismicSurvey Design

25 Imaging Walkaway Surface Seismic Correlation Fault and Dip
SourceWALKAWAYSurfaceSeismicDepth (m)GeophonesFault and DipIdentificationShear WaveAnalysisDepth ModelVSPImageSurface SeismicSurvey Design

26 True Seismic Amplitude
AVO WALKAWAYAVO WalkawaySource PositionsTrue Seismic AmplitudeWith Changing OffsetP-WaveS-WaveP-P and P-SV AnalysisAnisotropy velocity modelQ factor analysisReflector

27 Salt Proximity Survey Provides Accurate Salt Face Image
2D, 2.5D and 3D Imaging Solutions

28 3D VSP Very High Sub-Surface Imaging Resolution
Well 1Well 2Exploration and Development ApplicationsSurface seismic 3D PSDMWell 1Well 2Detailed Preplanning and 3D Modeling Required3D-VSP Depth Migration

29 IntroductionSeismic Signals in the boreholeBorehole EnvironmentBorehole survey typesBorehole seismic deployment

30 Borehole seismic on Wireline
DownholeGeophonesSourceReferenceSensorsRecordingUnitDowngoing WavefrontPitApplicationsAll seismic applicationsOperations - Max deviationdependant of well liquid type & well geometry (example: so far, ASI ran in 77 deg deviation, in Brine)

31 Pipe Conveyed Acquisition
ApplicationsAll seismic applicationsOperationsMax deviation: no limit (113o exp)Ex : 3 * CSI / MDT / Pex / DSIExtendable CSI sub isolates geophones from tool body & pipesWet connectCSIPressure samplingSonicNeutronGamma densityTension subResistivityGamma spectroscopyCompression sub

32 Conventional VSP source
Through Drill Seismic TDSConventional VSP sourceGAC sensorDrill bitTDS Thru-Drill SeisApplicationsAll seismic applications, & particularly...… Position of the drill bit:on the surface seismicfrom the target... Imaging beside the well... Prediction ahead of the bitOperationsData acquisition... Tool Pumped down… Reciprocate between levels… No circulation… Acquisition 10 min maxMin deviation so far = 7 degMax deviation so far = 90 degSaving rig timeTaking effective and fast decisions

33 Logging While Drilling
Drill Bit Seismicsseismic reflectorLWD Toolsea floorMWD telemetrySeismicMWDSensorSurface SystemSourceApplicationsReal Time checkshots...… Position of the drill bit:on the surface seismicfrom the target… Along with ISONIC:Calibration of ISONIC data & RT Synthetic seismogramOperationsSaving rig timeTaking effective and fast decisionsSensorsWeightssea floorDrill Bitseismic reflector

34 Through Tubing Seismic
VSP sourceApplicationsAll seismic applications, & particularly...... Imaging beside the well (coil tubing drilling, well redevelopment, etc)OperationsData acquisition - Stop productionGeophones (GAC)

35 Simultaneous Acquisition
ApplicationsAll seismic applications, & particularly...… Acquiring borehole seismic data before surface processing starts: Velocity anisotropy, Q attenuation, AVO, VSP-guided processing, shear modelOperationTool stays stationary in the wellPlatformJoint acquisitions with GP

Открыть дверь и вызвать сотрудников отдела систем безопасности, я угадал. - Совершенно. Будет очень глупо, если вы этого не сделаете. На этот раз Стратмор позволил себе расхохотаться во весь голос. - Твой сценарий мне понятен.

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