Introduction
What are the reservoir rock properties?
The importance of reservoir rock & fluid properties
How fluids flow through the reservoir rock and how this flow can be altered to produce greater recovery and profits
Provides good understanding in reservoir management, Simulation and EOR, etc.
Reservoir Fluid Properties?
What are reservoir fluids? Crude oil Natural gas or Drinkable water?
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Reservoir Rocks
Oil created by the source rock won’t be useful unless it winds up being stored in an easily accessible container, a rock that has room to “suck it up”
A reservoir rock is a place that oil migrates to and is held underground.
Examples of reservoir rocks includes:
Sandstones Limestone and /or Carbonate rocks
Characteristics of Reservoir Rocks
A good reservoir rock must have porosity in which petroleum can exist. Even though a reservoir rock looks solid to the naked eye, a microscopic examination reveals the existence of tiny openings in the rock, called pores.
Another characteristics of reservoir rock is that it must be permeable. That’s the pores of the rock must be connected together so that hydrocarbons can move from one pore to another
Source of data: Coring Coring are processes used to recover formation
samples from petroleum reservoirs.
Reservoir rock samples are used for reservoir description and definition, reservoir characterization and to enhance both geological petrophysical nature of the reservoir.
Physical sample of reservoir rock core is essential to evaluate the two most significant characteristics:
the capacity and ability of the reservoir rock to store and conduct petroleum fluids through the matrix.
In addition, data on formation’s lithology and production potential are obtained through coring program.
ROCK MATRIX AND PORE SPACE
Rock matrix Water Oil and/or gas
Framework
Matrix
Cement
Pores
Sand (and Silt) Size Detrital Grains
Silt and Clay Size Detrital Material
Material Precipitated Post-Depositionally,During Burial. Cements Fill Pores andReplace Framework Grains
Voids Among the Above Components
FOUR MAJOR COMPONENTS OF SANDSTONE
MATRIXFRAMEWORK
(QUARTZ)
FRAMEWORK(FELDSPAR)
PORE
0.25 mm
CEMENT
FOUR COMPONENTS OF SANDSTONE
PDC Cutters
Fluidvent
Drill collarconnection
Inner barrel
Outer barrel
Thrust bearing
Core retainingring
Core bit
CORING ASSEMBLY AND CORE BIT
Unlike a normal drill bit, which crushes the rock into small pieces, a core bit can be visualized as a hollow cylinder with cutters on the outside.
The cylinder of rock that is cut by the bit is retained within the core barrel by an arrangement of steel fingers or slips.
Core diameters are typically from three to seven inches and are usually about 90 feet long.
Coring
• Whole core sampler
• Side-wall core sampler
Whole Core Photograph,Misoa “C” Sandstone,
Venezuela
WHOLE CORE
Photo by W. Ayers
SIDEWALL SAMPLING GUN
Core bullets
Core sample
Formation rock
The sidewall sampling tool can be used to obtain small plugs from the formation. The tool is run on a wireline after the hole has been drilled. Some 20 to 30 bullets are fired from each gun at different depths.
The hollow bullet will penetrate the formation and a rock sample will be trapped inside the steel cylinder. When the tool is pulled upwards, wires connected to the gun pull the bullet and sample from the borehole wall.
Sidewall cores are useful for identifying hydrocarbons zones, when viewed under UV light. Qualitative inspection of porosity is possible; however, the cores may have been crushed during the collection process, so quantitative sampling of porosity is questionable.
SIDEWALL CORING TOOL
Coring bit
Samples
A newer wireline tool actually drills a plug out of the borehole wall, thus avoiding crushing of the sample.
Up to 20 samples can be individually cut and are stored inside the tool.
WHOLE CORE ANALYSIS vs. PLUGS OR SIDEWALL CORES
WHOLE CORE
Provides larger samples
Better and more consistent representation of formation
Better for heterogeneous rocks or for more complex lithologies
Smaller samples Less representative of heterogeneous
formations Within 1 to 2% of whole cores for medium-to
high-porosity formation In low-porosity formations, from core plugs
tends to be much greater than from whole cores
Scalar effects in fractured reservoirs
WHOLE CORE ANALYSIS vs. PLUGS OR SIDEWALL CORES
PLUGS OR SIDEWALL CORES
Coring
core plug
whole core
INFORMATION FROM CORES
Porosity
Horizontal permeability to air
Grain density
Vertical permeability to air
Relative permeability
Capillary pressure
Cementation exponent (m) and saturation exponent (n)
Standard Analysis Special Core Analysis
*Allows calibration of wireline log results
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