Petroleum Formation Evaluation -6

7/31/2019 Petroleum Formation Evaluation -6

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PANDIT DEENDAYAL PETROLEUM UNIVERSITYSCHOOL OF PETROLEUM TECHNOLOGY

B.TECH. SEMESTER - VI

ASSIGNMENT - 6

Course: Petroleum Formation evaluation (PE 308)

Problem 1: The following figure (A) shows a cross plot of and density in a sandstonereservoir containing a water zone, a hydrocarbon zone and a gas zone. The points associated with

gas zone have been identified. Construct on figure an interpretation chart similar to figureprovided (Fig.B).

(i) What is the estimated value ofma?(ii) What do you estimate w to be?

(A)

(B)


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Problem 2: In a well (Problem above), the water resistivity is known to be 0.18 ohm-m in azone at 115

0F. Assuming that the water contains NaCl only, what value ofw does this imply?

(i)

What is the value of Sw in the water zone, using this new input?(ii) The induction log clearly sees this zone as 100% water: However, the drillingfluid is oil-based mud. What does this say about the relative depth of

investigation of the measurement?

Problem 3: From the data of the following table, estimate the capture cross section of waterin capture units.

(i) Estimate the capture cross section in capture units, of salt water with 100 kppmNaCl dissolved. How well does it agree with the following figure


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Problem 4:Using the data from the logs in the given figure and assuming that the injectionwater was fresh, compute the salinity of the connate water at the depth X150.


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Problem 5:The following figure is a log of a tight (low porosity) carbonate section. Usingthe neutron-density cross plot, identify zones of the different matrix types present in this section

of the well


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Problem 6:Consider the following set of data taken sections of a clean sandstone reservoir. Although the

sandstone is free of clay, it does contain some pyrite. The question to answer is: how close does

the manual cross-plot technique get you to the true porosity.

The table format provided here will help to complete the task. Note the column of matrix density

values, which have been determined from core analysis. Make a plot of porosity obtained from

the density tool alone under two different conditions: using the core-measured grain density, andusing the cross plot grain density (ma)n-d. For both calculations, assume that the formation fluid

has a density of 1.20 g/cm3


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Problem 7:To verify the identification of the sets of matrix lines in the Pe plot of the following figure,

compute the b and Pe values for 50% porosity limestone, dolomite and sandstone. Consider two

cases of pore fluid, water and CH2. The appropriate values for computations are from the tableprovided below:


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TABLE: Density and photoelectric parameters for various minerals (FromBertozzi, Ellis and Wahl)


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Problem 8:From the log of the following figure calculate the apparent matrix values maa and Umaa and

hence the percentage of quartz, calcite and dolomite (assuming no clay).


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Problem 9:With reference to the following three figures, which tool combination would you prefer to use

for lithology determination in a carbonate reservoir containing limestone and dolomite?

Specifically, what are the maximum errors tolerable in a 5% porous limestone so that it is notmisidentified as a dolomite? For each pair of cross plots, you can evaluate the maximum

tolerable error by either of the measurements or assume a simultaneous error of the two.


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Petroleum Formation Evaluation -6