Page 193 - Basic Well Log Analysis for Geologist

‘VL TESTER PRETATION CASE STUDIES

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Case Study 4
Pennsylvanian Upper Morrow Sandstone

Anadarko Basin
An area covering several counties in the Anadarko basin V F/2000 are: at a depth of 7,444 ft = 14: at 7,446 ft = 9;
is assigned to you. It is your responsibility to map and and at a depth of 7,448 ft = 11.
develop hydrocarbon prospects and oversee all company The sonic porosity formula is:
activity in these counties.
_ A _ Atna
As you pursue the assignment, you review many logs
bs = Ate — Atya
from previously drilled wells; some are producing and some
are dry and abandoned. One particular dry and abandoned Other important information you use to pursue your
well captures your attention, because its induction log has evaluation is: Ry = 0.527 at Ty Ry = 0.1L at Te Ty =
good resistivities and its sonic log has good porosities. The 130°F; F = 0.81/27; and surface temperature = 70°F.
well wasn’t tested before its abandonment. However, it was Volumetric recoverable oil reserves are calculated with
logged with an induction electric log (Fig. 85) to determine the following parameters: drainage area = 160 acres; BOI
resistivities of the invaded (R;) and uninvaded (R,) zones, = 1.3; recovery factor (RF) = 0.15; porosity = 16%; water
and a sonic log (Fig. 86) to determine sonic porosity. saturation (S,) = 57.5%; thickness (h) = 8 ft.
Before you can calculate water saturations Archie, a An analysis by the company’s engineering department
value for R,, ts needed. You decide to find a value for Ry by leads to a judgement that, if it appears the well will be
using the SP log and charts (see Fig. 1], Chapter II). productive, it can be re-entered. An estimated cost for
Because water production is a local problem but water re-entry and completion of the well is $275,000. With a

samples are not available, you decide to check the amount gross product price of $32.00 per barrel and a lease which
of water the well may produce. To do this, irreducible water has a 3/l6th royalty, what do you estimate as a return on
saturation (S,, j,) values are plotted versus water saturation investment?
Arehie (Sy) and a water-cut crossplot is constructed (charts Use the Pennsylvanian Upper Morrow Sandstone Log
for water-cut percent are in Appendix 4). Irreducible water Evaluation Table (work Table D) to complete your
saturation values calculated by the formula Sy, i = evaluation.

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