José Vásquez Senior Petrophysicist

12 July 2017

Gestión alternativa de Saturación de crudo en reservorios de agua fresca. Ejemplos del Este de Colombia

Presenter: Jose Vasquez

Studies:

• Mechanical Engineer

• BSc Forestry Engineering

• MBA

Schlumberger

• 15 year in Wireline (data acquisition)

• 8 years as Field Engineer

• 7 years in management, sales & technical support

• 8 years in PetroTechnical Services

(log data processing and interpretation)

• OH Interpretation

• CH Interpretation

Sponsors & Gratitude

• Attendees

• SGP

• Schlumberger

MOTIVATION

Dealing with Oil Saturation computation in fresh water reservoirs?

Low sensitivity to Sw

of conventional methods. Eastern Colombia

… but as you will see, not only for fresh water

Dealing with Oil Saturation computation in fresh water reservoirs?

Fresh Water HC Colombian Reservoirs This case is based on SPE paper SPE-177095. Thanks to Ulises Bustos, Schlumberger Petrophysicist for sharing his knowledge and the related material.

Driver

• SW • Primary objective in reservoir evaluation

• Economics of a project

• Mandatory

• Accuracy

• Low Uncertainty

Poor Precision

Accurate

Yields

Good Precision

Inaccurate

Windows

Driver (2)

• Historically, Sw based on resistivity • Archie

• Or derived forms of Archie

• Limitations in Colombian Reservoirs

• Fresh Water (<10,000 ppm)

• Variable Clay Mineralogy

• Carbonate Cements

• HC with wide range of composition

• Gas

• Light Oil

• Heavy Oil

• Movable oil identification is critical factor

Driver (3)

• Siliclastic reservoir rocks with variable matrix properties • Impact on formation porosity

• Drilling Challenges • Active Tectonism

• Significant variations in stress fields

• Depleted reservoirs in mature fields

• Narrow window for drilling

• Higher risks for OH logging (WL or LWD)

Driver (4)

• Wells drilled without any logging • Risk reduction

• Cost reduction

• CH logging provides the only evaluation option

• HC evaluation

• Reservoir Volumetric determination

• Reservoir management

• Economics

-0,2

0

0,2

0,4

0,6

0,8

1

1,2

300 3000 30000 300000

UNCERTAINTY OF SW VS SALINITY MIN DISTR. RANGE MAX DISTR. RANGE

FSAL [ppm]

Sw [v/v]

Understanding sensitivity to Sw The problem of conventional analysis in fresh water

Existing Techniques

• C/O Logging • Common techniques CH logging in Colombia

• High statistics, calibration

• Slow acquisition

• Slim, Large Borehole effect

• >15% Porosity

• Requires Lithology knowldege

Source: Oilfield review,

Summer 1996

Fanny-1 well, Ecuador

Existing Techniques (2)

Sigma Logging

• Sigma = f(Chlorine) • Requires FSAL

• Poor sensitivity to HC in fresh water or variable salinities.

• Requires accurate knowledge of Sigma Matrix

• Requires good knowledge of PHIT

• Very limited applications in most of on-shore Colombian reservoirs

Application of Advanced Spectroscopy

• New methodology for Hydrocarbon Saturation from: • Advanced spectroscopy measurements

• Total Organic Carbon (Cradock et. Al, 2013)

• PHIT

Source: Oilfield Review

Application of Advanced Spectroscopy

• Advantages compared to previous C/O logging interpretation methods: In the new method Saturation is: • based on the conversion of dry weight organic to

hydrocarbon saturation and does not require an extensive calibration database.

• Independent of salinity effects

• Independent of clay or other lithology effects

Hydrocarbon Saturation (Sh) from TOC

• TOC found primarily in: • Kerogen

• Bitumen

• Hydrocarbons

• Oil

• Gas

Photomicrograph Showing Type II Kerogen

• In Unconventional reservoirs • TOC becomes a critical

determination for pay zones identification

• In conventional reservoirs • TOC is occupying pore space

• VHC within Porosity

From TOC to Hydrocarbon Saturation (Sh)

• TIC = (0.12 Wcalcite + 0.13 Wdolomite + 0.104 Wsiderite + …)

• TOC = TC – TIC

• TOC = MCorg / Mma

• MCorg = Xhc * Mhc

• Mhc = ρhc * Vhc

• Shc = Vhc / ФT

From TOC to Hydrocarbon Saturation (Sh)

• Shc = Vhc / ФT

• Shc = Mhc / (ρhc * ФT )

• Shc = Mcorg / (Xhc * ρhc * ФT )

• Shc = TOC * Mma / (Xhc * ρhc * ФT )

• Shc = TOC * ρma * Vma / (Xhc * ρhc * ФT )

Shc = TOC * ρma * (1 - ФT ) / (Xhc * ρhc * ФT ) Measured by

Advanced

Spectroscopy

Hydrocarbon

properties

Measured by porosity tool

Case Study #1: Open Hole Dielectric-Spectroscopy

TOC

Lithology

Saturations Salinities

Dielectric Dispersion

A

B

Oil ?

Water?

Contacts?

Oil_Dielec-1 in. DOI

Oil_Dielec-4 in. DOI

Oil_Spectros-10 in. DOI

Spectroscopy-Dielectric: Deeper Saturation

Profiling to understand Oil Mobility

Sw from RT

Dielectric basic Principle & application

Principles:

• Multifrequency EM signal

107 – 109 GHz

• Water: high permittivity

• Sensitive to Water Volume

Applications / Capabilities:

• Water filled Porosity

• Water Salinity

• Clay CEC

• Textural Parameters: m & n

• Anisotropy

• High Resolution (2 & 4”)

Case #2: Open Hole Spectroscopy reveals high matrix density, complex lithology and otherwise bypassed oil

Case #3: Cased Hole C/O vs Advanced Spectroscopy comparison

Conventional slim C/O log

• 3 passes @ 100 fph

• 25 hours log plan

• 70-80% oil Saturation

• Sgas= 0%

Central Southern Colombia

Case #3: Cased Hole C/O vs Advanced Spectroscopy comparison

Advanced

Spectroscopy in CH

• 1 Single Pass @

530 fph.

• < 2 hours log

• Reasonable

agreement with

conventional slim

C/O.

• In zone C higher

So is obtained.

Case #3: Cased Hole C/O vs Advanced Spectroscopy comparison

Time efficient

results obtained

with advanced

spectroscopy.

• Good

agreement

when compared

to slim C/O

• 10 times faster

• Detailed

lithology

• TOC

Case #4: Cased Hole Light Hydrocarbon sands & complex lithology

Only zones A &

B with So ~50-

65%

Change in

Salinity above X

Complex

lithology with

Matrix density

higher than 2.65

g/cc

THANK YOU & QUESTIONS ?

Thank you!

Any Questions?