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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.
6
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
• 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
• 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
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