L'utilisation de diagraphies soniques et de profils sismiques 2D pour bâtir un modèle

géostatistique des aquifères salins profonds de la région de Bécancour

M. Claprood, E. Konstantinovskaya, M. Duchesne, B. Giroux, E. Gloaguen, M. Malo, L. Massé, et J. Lavoie

22 April 2010

Using sonic logs and 2D seismic profiles to build a geostatistical model of the deep

saline aquifers of the Bécancour area

M. Claprood, E. Konstantinovskaya, M. Duchesne, B. Giroux, E. Gloaguen, M. Malo, L. Massé, and J. Lavoie

22 April 2010

Long term objectives:

Build geostatistical model of the petro-physical properties of the deep saline aquifers of the Bécancour area.

Simulate different scenarios of porosity and permeability distribution in the saline aquifers to better estimate the potential of CO2 storage at Bécancour.

Monitor the expected fate of the CO2 injected at Bécancour.

but now...Using available geophysical data recorded in the Bécancour area, build the initial geostatistical model.

Outline

1. Geophysical measurements available in Bécancour:• Borehole logs• Seismic 2D

2. Creation of TD Charts with post-stack 2D seismic lines and sonic logs

3. Some thoughts about the initial geostatistical model of the saline aquifers in Bécancour

4. What’s next to improve the geostatistical model of the Bécancour area

Geological Background at BécancourThickness of sedimentary units of the St. Lawrence Plateform increases from NW to SE in the Bécancour area.

The Yamaska Fault, striking SW-NE, is the principal structural element of the area.

Red lines: 2D seismic profiles in the Bécancour area

Blue dots: borehole logs in the Bécancour area

Thick red line: seismic profile M2002

5 km

Geological Background at BécancourInterpretation of profile M2002 recorded SW of the Bécancour area.

Yamaska Fault

NW SE

Geophysics at Bécancour

Geophysics at Bécancour

18 boreholesBorehole logs include sonic, gamma rays, electric, density, porosity, photoelectric.

30 seismic profiles (2D)2D seismic profiles recorded between 1970 and 2008 for oil and gas exploration.

Borehole logs at Bécancour

High number of boreholes (18) and logs allows good characterization of petro-physical properties of the geological units in the Bécancour area.

This will be important to establish better constraints on the petro-physical properties of the geostatistical model of the Bécancour deep saline aquifers.

Sonic logs are recorded at 11 boreholes; some logs are recorded on the whole interval (0m to +1200m depth), while others are restricted to specific geological units.

This complicates the creation of time to depth charts, essential to tie the seismic data acquired in two-way time to logs acquired in depth.

Borehole logs at Bécancour – Sonic Logs (DT)

A241

A239

A196

A242

A198

A246

A250

A247

Borehole logs at BécancourIdentification of stratigraphic units:

GR : high values in cap rock(shales)GR: low values in salineaquifers (limestones)GR: transition from Trentonlimestone to Bmt dolomites

Borehole logs at BécancourUse of GR logs to identify seismic signatures of some geological units.

We have to use thisqualitative method to identify horizons becausewe don’t have access topre-stack seismic data,and because no VSP were available to better estimatethe velocity with depth.

Borehole logs at BécancourUse of GR logs to identify seismic signatures of some geological units.

We have to use thisqualitative method to identify horizons becausewe don’t have access topre-stack seismic data,and because no VSP were available to better estimatethe velocity with depth.

Borehole logs at BécancourUse of GR logs to identify seismic signatures of some geological units.

We have to use thisqualitative method to identify horizons becausewe don’t have access topre-stack seismic data,and because no VSP were available to better estimatethe velocity with depth.

Identification ofseismic signatureswhich correspond to specific geologicalunits.

Dark blue: Trenton limestone; lack of seismic reflections.Light blue - purple – pink – yellow: Strong reflections associated to the Chazy and Beekmantown Groups (dolomite and dolomitic sandstone), and the Cairnside Formation (sandstone).

2D Seismic at Bécancour

Identification ofseismic signatureswhich correspond to specific geologicalunits.

Identification ofstructural features(faults).

Dark blue: Trenton limestone; lack of seismic reflections.Light blue - purple – pink – yellow: Strong reflections associated to the Chazy and Beekmantown Groups (dolomite and dolomitic sandstone), and the Cairnside Formation (sandstone).

2D Seismic at Bécancour

2D Seismic at Bécancour30 seismic profiles recorded between 1970 and 2008.

Pre-stack data not available, restricting the interpretation and the possibility of reprocessing.

2D seismic profiles are used to identify seismic signatures of specific stratigraphic units.

Create time to depth charts (TD charts) to analyze seismic data recorded in time with borehole logs recorded in depth.

Building an initial geostatistical model of the petro-physical properties (porosity, permeability) of the deep saline aquifers in Bécancour.

2D Seismic at BécancourBuilding TD ChartsTD charts are generated by comparing sonic and density logs with seismic signatures corresponding to specific geological units.

TDChart

SonicDT

RHO AI RCVp(m/s)

2D Seismic at BécancourSpatial relations and continuity betweenthe horizons identified on the 2D seismicprofiles.

almost 3D…

This is the best we have so far to buildan initial geostatistical model of the deepsaline aquifers at Bécancour.

Initial Geostatistical ModelCo-kriging formations tops identified at all 18 borehole logs (depth) with horizons identified on 2D seismic profiles (twt).

twt (s)

Initial Geostatistical ModelCo-kriging formations tops identified at all 18 borehole logs (depth) with horizons identified on 2D seismic profiles (twt).

Build the initial gridblock model in depth... sorry, no results to present yet.

A241

Ut – 632mTr – 763m

Bmt – 914m

A239

Ut – 635mTr – 768m

Bmt – 925m

A223

Ut – 644mTr – 755m

Bmt – 908m

A242

Ut – 638mTr – 742m

Bmt – 897m

A196

Ut – 731mTr – 752m

Bmt – 900m

twt (s)

Where to go from now:

Combine the information obtained from borehole logs and 2D seismic to build an initial 3D permeability model of the saline aquifers at Bécancour.

At Bécancour, we need to work with the opposite of what is common in reservoir analysis… lots of borehole logs and 2D seismic data of variable quality. We are presently looking for the best methodology to follow for the construction of the initial model of permeability.

Optimize the analysis of borehole logs... better understand the relations between different logs to increase our confidence on the evaluation of the petro-physical properties.

Where to go from now:

It is expected to record vertical seismic profiles (VSP) this summer to gain better estimation of the distribution of the seismic velocity with depth.

It would be important to consider acquiring 3D data at Bécancour to better define spatial continuity…seismic? magnetotelluric? magnetic? gravity?Difficult to plan because of the actual location of the study site at Bécancour.

Merci!!!