Changes

Determining the porosity and true resistivity of a zone is the first step in converting the raw log data into estimated quantities of oil, gas, and water in a formation. These estimated quantities are used to evaluate a zone and to determine whether a well completion attempt is warranted. As important as this log-derived information is, however, it should not be applied without the inclusion of other data. This statement is, perhaps, obvious, but it can't be overemphasized. A geologist should always consider every item of relevant data, such as drill stem tests, sample shows, mud-log analysis, nearby production, etc., before making a decision to set pipe.

Determining the porosity and true resistivity of a zone is the first step in converting the raw log data into estimated quantities of oil, gas, and water in a formation. These estimated quantities are used to evaluate a zone and to determine whether a well completion attempt is warranted. As important as this log-derived information is, however, it should not be applied without the inclusion of other data. This statement is, perhaps, obvious, but it can't be overemphasized. A geologist should always consider every item of relevant data, such as drill stem tests, sample shows, mud-log analysis, nearby production, etc., before making a decision to set pipe.

It is exceedingly rare that a log contains more reservoir than nonreservoir information, and when one is unfamiliar with an area or wants to broadly reconnoiter an area, a scanning technique that sorts reservoir from nonreservoir can be helpful, even with access to computer-aided processing. A good scanning technique not only identifies the reservoirs, but can also give the geologist hints as to potential pay and wet zones. Remember that in the interpretive process, the identification of wet zones is as important as the discovery of those containing hydrocarbons, because the comparison of the tow helps clearly identify both the presence and amount of the hydrocarbons.

It is exceedingly rare that a log contains more reservoir than nonreservoir information, and when one is unfamiliar with an area or wants to broadly reconnoiter an area, a scanning technique that sorts reservoir from nonreservoir can be helpful, even with access to computer-aided processing. A good scanning technique not only identifies the reservoirs, but can also give the geologist hints as to potential pay and wet zones. Remember that in the interpretive process, the identification of wet zones is as important as the discovery of those containing hydrocarbons, because the comparison of the two helps clearly identify both the presence and amount of the hydrocarbons.

[[file:Mth16Ch7Figure7-1.jpg|thumb|300px|{{figure number|1}}Flowchart for scanning logs to identify zones of interest (both pay and wet). ¹ Zones that appear to be shales might be radioactive productive zones. ² Shaly zones might produce oil or gas even if they have low resistivity.<ref name=AsquithandKrygowski_2006>Asquith, G., and D. Krygowski, 2006, Basic Well Log Analysis, 2nd Edition: AAPG Methods in Exploration 16, 244 p.</ref>]]

[[file:Mth16Ch7Figure7-1.jpg|thumb|300px|{{figure number|1}}Flowchart for scanning logs to identify zones of interest (both pay and wet). ¹ Zones that appear to be shales might be radioactive productive zones. ² Shaly zones might produce oil or gas even if they have low resistivity.<ref name=AsquithandKrygowski_2006>Asquith, G., and D. Krygowski, 2006, Basic Well Log Analysis, 2nd Edition: AAPG Methods in Exploration 16, 244 p.</ref>]]