Complementary Core Information
Assignment Core Information
You are the project geologist responsible for a well in which some full diameter core has been acquired. Summarize the various options and formats for core photographs, briefly describing some of the main interpretation applications.
Solution
Options for core photography range from black and white to color photography, as well as photographs taken under ultraviolet light. Photographs are often taken of the core before it is slabbed, with any residual hydrocarbons still in place, as well as of the slabbed core. The color and ultraviolet light photographs tend to complement one another, the former recording what the eye sees and the latter revealing oil fluorescence indicating hydrocarbons.
In reservoirs that are fractured, enhancement of the fracture pattern can sometimes be observed in the color and ultraviolet light photographs. Photographs are often taken at 1 ft (30 cm) intervals along the core. In other cases, the cores are grouped into lengths of 15 or 20 ft (4.5 or 6.1 m) and a single photograph is made of the entire sequence. Multiple footage pictures can enable visualization of changes in the core bedding and structures that indicate differences in permeability, porosity and the depositional environment.
Assessment Core Information
1. The data derived from detailed, natural fracture studies in recovered cores are subsequently used to do what? (Select all that apply.)
A .Assist in the planning of well completion and stimulation by identifying fractured intervals. Correct ✔
B .Determine the optimal direction of horizontal development wells in unconventional reservoirs requiring fracking. Correct ✔
C .Locate development wells with favorable fracture permeability. Correct ✔
D .Assist in the structural analysis of hydrocarbon accumulations as they relate to fault orientation and location. Correct ✔
2. Which of the following describe the pyrochromatography method? (Select all that apply.)
A .Provides a distinction between gas productive, oil productive and non-productive zones. Correct ✔
B .Can only be used for offshore hydrocarbon accumulations.
C .Is useful for evaluating reef formations. Correct ✔
D .Causes the fluids to leave the core sample and be swept into a chromatograph for fingerprinting. Correct ✔
3. By what processes are oil fluid samples obtained for the analysis of their API gravity? (Select all that apply.)
A .From the core by centrifuging Correct ✔
B .Drill stem tests Correct ✔
C .Wireline formation tester fluid samples Correct ✔
D .Ditch cuttings
4. What minerals can cause high gamma ray readings in a core gamma ray log? (Select all that apply.)
A .Zinc
B .Thorium Correct ✔
C .Potassium Correct ✔
D .Uranium Correct ✔
5. In the cation exchange process, cations are exchanged between what two elements?
A .Sandstones and limestones
B .Sandstones and clays
C .Coring fluids and clastic rocks
D .Clay surfaces and surrounding water Correct ✔
6. What types of secondary cement, when in significant quantities in sandstones, can cause the grain densities to vary from standard values? (Select all that apply.)
A .Siderite Correct ✔
B .Calcite Correct ✔
C .Quartz
D .Silica
7. A good understanding of the differences in the horizontal and vertical permeabilities of reservoirs is extremely important for what subsurface interpretation activity?
A .Time to depth seismic data conversion
B .Seismic fault interpretation
C .Dynamic reservoir modeling Correct ✔
D .Basin modeling
8. What are the advantages of knowing the salinity of the pore waters? (Select all that apply.)
A .Indicate the extent of coring filtrate flushing. Correct ✔
B .Determine if the pore water is drinkable.
C .Enable accurate water saturation calculations using well logs. Correct ✔
D .Estimate the vertical sweep efficiency of reservoirs. Correct ✔
9. Under what conditions are cores normally photographed? (Select all that apply.)
A .Color photographs under ultra-violet light Correct ✔
B .Black and white photographs under natural light Correct ✔
C .Color photographs under natural light Correct ✔
D .Black and white photographs under infra-red light
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