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By: Dionisio Mufuma [Universidade Agostinho Neto] Simão Diavita Garcia [Norwegian University of Science and Technology] Dondo Salomão [Statoil Angola] The Travel from Wireline / LWD raw data to a reservoir summary : An Educational Exercise about Petrophysical Well Evaluation

dsfinal Apresentation (SPWLA) 20012

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By:

Dionisio Mufuma [Universidade Agostinho Neto]

Simão Diavita Garcia [Norwegian University of Science and Technology]

Dondo Salomão [Statoil Angola]

The Travel from Wireline / LWD raw data to a reservoir summary : An Educational Exercise about Petrophysical Well Evaluation

Outline

• Introduction

• Well Location

• Data acquisition and quality control

• Reservoir properties determination

- volume of shale

- porosity

- resistivity of formation water

- temperature gradient

- saturation, fluid contacts and permeability

• Reservoir summary

Introduction

• The World is energy dependent

After crude oil is removed from the ground, it is sent to a refinery by pipeline, ship, or barge. At a refinery, different parts of the crude oil are separated into useable petroleum products. Crude oil is measured in barrels (abbreviated "bbls").

• Exploration is the activity to find hydrocarbons

• Hydrocarbons are the main energy source

The Congo Basin is the sedimentary basin that is the drainage of the Congo River of west equatorial Africa.

Well Location• Congo Basin

• Well name: Cazenga

• Reservoir: Sandstone

• Time of deposition: Oligocene

Data Acquisition• Well Log: a continuous measurement

of formation properties with electrically

powered instruments to infer properties

and make decisions about drilling and

production operations.

www.Slb.com

• Wireline log: is the data acquired by running tools on a cable from a winch after the hole had been drilled.

• LWD (Logging While Drilling) is the general term we use to describe the systems and techniques for gathering downhole data while drilling a well

Log Quality Control

• Check on tool Calibration before and after logging operations

• Check if measurement made by tool is similar to those made in nearby wells.

• Check log response from cased intervals and formations such as anhydrite and salt

• Check if recorded data are correctly labeled, scaled and well presented.

• Use Repeat Section to ensure that recorded parameters are the same.

• Compare Histograms of main and repeat runs made over the same depth after depth shifting.

• Depth shift, merge and log edition can be made.

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Reservoir properties determination

• (Asquith et al. 2004 ): … shale is more radioactive than sand or carbonate, gamma ray logs can be used to calculate volume of shale in porous reservoirs.

• Volume of shale (Vsh) , fraction , % or decimal V/V :

• Volume of shale (Vsh) calculated values:

We have used linear model

Reservoir properties determination

• Porosity

Reservoir properties determination

• We have used Density porosity, (DPHI).

• Porosity calculated values:

Reservoir properties determination

• Resistivity of formation water(Rw)

• The Pickett plot may be used over a known water bearing section for Rw determination.

Reservoir properties determination

• Water saturation computation require knowledge of formation water resistivity

• Resistivity of formation water ( Rw)

• Rw may be calculated by using theTemperature and salinity over the water bearing Zone.

**TVDSS= true vertical depth Subsea

Where: Rw is water resistivity; T is the temperature and NaCl is the total NaCl concentration in ppm

Reservoir properties determination

• Water Saturation: is the amount of pore volume in a rock occupied by formation water

Formulas that we used:

Reservoir properties determination• Water Saturation (Sw), Unit: fraction, %, decimal V/V

• Hydrocarbon Saturation

Sh=1-Sw

We have used Nord Sea model

• Water saturation calculated values

Reservoir properties determination

• Fluid contact and density

Oil Water Contact (OWC). May be in 3475m TVDSS

Reservoir properties determination

• Permeability (K)• Permeability (K) : is the ability of a rock to transmit fluids.

•K is measured in darcys or millidarcys

• Related to porosity but not always dependent

Formulas :

Reservoir properties determination

2012-04-09

Reservoir properties determination• Permeability calculated values

We have used

Reservoir Summary

AV= average; SWIRR= Irreducible Water Saturation ; BVW= Bulk Volume of Water; SH= Hydrocarbon Saturation ;PERM= Permeability; V/V decimal; M/M decimal ; MD= milldarcy .

Sand_A

Sand_B

Oil

water

References• Asquith, G., and Krygowski, D., 2004, Basic well log analysis second edition, AAPG. Methods in exploration series, no.16, America Association of Petroleum•Schlumberger, 1989. Log Interpretatio nPrinciples/ Applications (availablethroughClassfronter)

• Daniel A. Krygowski, ,2003, Austin Texas USA : Guide to Petrophysical Interpretation

Web:www.Onepetro.orgwww.wellEval.comwww.hlliburton.comwww.worldoil.comwww.Knovel.comwww.epmag.comwww.Slb.com