Changes

==Production logs==

==Production logs==

The main applications of the production logs include

The main applications of the production logs include

===Flow detection in and around pipe===

===Flow detection in and around pipe===

[[file:production-logging_fig1.png|left|thumb|{{figure number|1}}Temperature survey showing two gas entries and the geothermal gradient.]]

[[file:production-logging_fig2.png|thumb|{{figure number|2}}Noise log responses to fluid movement downhole.]]

Temperature surveys are the most common surveys to locate fluid movement downhole. Small entries and even flow in channels behind pipe can be detected. Generally, if a well is not flowing, the temperature of the fluid in the borehole will eventually approach the formation temperature, called the ''geothermal gradient''. When a well is produced, formation fluids enter the borehole and move uphole. Gasses typically cool when entering the borehole while liquids do not. In either case, their movement uphole is easily detected by deviations of the borehole temperature from the geothermal gradient. [[:file:production-logging_fig1.png|Figure 1]] illustrates a typical temperature survey response to two gas entries into a well.

Temperature surveys are the most common surveys to locate fluid movement downhole. Small entries and even flow in channels behind pipe can be detected. Generally, if a well is not flowing, the temperature of the fluid in the borehole will eventually approach the formation temperature, called the ''geothermal gradient''. When a well is produced, formation fluids enter the borehole and move uphole. Gasses typically cool when entering the borehole while liquids do not. In either case, their movement uphole is easily detected by deviations of the borehole temperature from the geothermal gradient. [[:file:production-logging_fig1.png|Figure 1]] illustrates a typical temperature survey response to two gas entries into a well.

[[file:production-logging_fig2.png|thumb|{{figure number|2}}Noise log responses to fluid movement downhole.]]

[[file:production-logging_fig3.png|left|thumb|{{figure number|3}}Tracer velocity shot technique and injection profile.]]

Noise logs are also used to evaluate fluid movement downhole. Unlike temperature surveys, noise logs are not run continuously across the interval of interest. Instead, a number of stationary readings are taken at different depths downhole. The movement of fluids, especially gasses, generates turbulence or noise, which gets louder as the flow rate or pressure drop increases. [[:file:production-logging_fig2.png|Figure 2]] shows how a noise log can be effective at detecting movement downhole. In this schematic diagram, a source, sink, and restriction to flow are the noise sources. The frequency spectrum of the noise is also observed to further improve the understanding of flow downhole.

Noise logs are also used to evaluate fluid movement downhole. Unlike temperature surveys, noise logs are not run continuously across the interval of interest. Instead, a number of stationary readings are taken at different depths downhole. The movement of fluids, especially gasses, generates turbulence or noise, which gets louder as the flow rate or pressure drop increases. [[:file:production-logging_fig2.png|Figure 2]] shows how a noise log can be effective at detecting movement downhole. In this schematic diagram, a source, sink, and restriction to flow are the noise sources. The frequency spectrum of the noise is also observed to further improve the understanding of flow downhole.

Radioactive tracer surveys use a tool composed of an ejector capable of ejecting shots of radioactive tracer material into the flow stream, usually of an injection well. Such an instrument has either one or two gamma ray detectors spaced below the ejector. By various techniques, the operator chases the ejected radioactive material as it moves with the injected fluid. By noting the position, time, and size of the tracer signal, an accurate overview of the injection profile can be established. Special techniques are also available to detect injected fluid channeling through the cement to undesirable zones. A schematic diagram of a tracer tool is shown in [[:file:production-logging_fig3.png|Figure 3]].

Radioactive tracer surveys use a tool composed of an ejector capable of ejecting shots of radioactive tracer material into the flow stream, usually of an injection well. Such an instrument has either one or two gamma ray detectors spaced below the ejector. By various techniques, the operator chases the ejected radioactive material as it moves with the injected fluid. By noting the position, time, and size of the tracer signal, an accurate overview of the injection profile can be established. Special techniques are also available to detect injected fluid channeling through the cement to undesirable zones. A schematic diagram of a tracer tool is shown in [[:file:production-logging_fig3.png|Figure 3]].

===Quantitative flow evaluation===

===Quantitative flow evaluation===

Quantitative evaluation of flow profiles in injection or producing wells is common. Injection wells are most often evaluated with radioactive tracer techniques, while producing wells, where multiphase flow may be encountered, are evaluated using flowmeters with fluid identification devices.

Quantitative evaluation of flow profiles in injection or producing wells is common. Injection wells are most often evaluated with radioactive tracer techniques, while producing wells, where multiphase flow may be encountered, are evaluated using flowmeters with fluid identification devices.

The most effective technique with radioactive tracers is the ''velocity shot'' technique, illustrated in [[:file:production-logging_fig3.png|Figure 3]]. The tool is stationary during such a test, and the gamma count rate is recorded at the surface. In Figure 3, tests were made above, between, and below the perforations, and the surface recordings are shown to the right of the well sketch. The highest velocity and flow rate are recorded above the perforations, while zero flow is detected in the lowest interval. By measurement of the traveltime between detectors, Δt, and using the known spacing between detectors D₁ and D₂, the flow rates can be calculated and an injection profile constructed, as shown on the right of the figure.

The most effective technique with radioactive tracers is the ''velocity shot'' technique, illustrated in [[:file:production-logging_fig3.png|Figure 3]]. The tool is stationary during such a test, and the gamma count rate is recorded at the surface. In Figure 3, tests were made above, between, and below the perforations, and the surface recordings are shown to the right of the well sketch. The highest velocity and flow rate are recorded above the perforations, while zero flow is detected in the lowest interval. By measurement of the traveltime between detectors, Δt, and using the known spacing between detectors D₁ and D₂, the flow rates can be calculated and an injection profile constructed, as shown on the right of the figure.

In producing wells, spinner flowmeters are used to measure the bulk flow rate, even in multiphase flow conditions<ref name=pt09r2>Anderson, R. A., Smolen, J. J., Laverdiere, L., Davis, J. A., 1980, A production logging tool with simultaneous measurements: Journal of Petroleum Technology, February, p. 191–198.</ref>. Two such flowmeters are shown in Figure 4. The ''full bore flowmeter'' in Figure 4(a) is run continously across the interval of interest, while the basket type flowmeter in Figure 4(b) uses stationary measurements. Although these devices can determine the bulk flow rate, fluid identification tools are required to evaluate the kinds of fluids present in the flow. These fluid identification instruments measure the pressure gradient, bulk density, or capacitance of the flowing mixture. The flowmeter and fluid identification devices are usually run as a combination on the same tool string. Results typical of such a tool string are shown in Figure 5. In this example, zone A produces water, while the zones above it are all gas producers. A plug set between zones A and B will be effective at eliminating the water production in this example.

In producing wells, spinner flowmeters are used to measure the bulk flow rate, even in multiphase flow conditions<ref name=pt09r2>Anderson, R. A., Smolen, J. J., Laverdiere, L., Davis, J. A., 1980, A production logging tool with simultaneous measurements: Journal of Petroleum Technology, February, p. 191–198.</ref>. Two such flowmeters are shown in [[:file:production-logging_fig4.png|Figure 4]]. The ''full bore flowmeter'' in [[:file:production-logging_fig4.png|Figure 4(a)]] is run continously across the interval of interest, while the basket type flowmeter in [[:file:production-logging_fig4.png|Figure 4(b)]] uses stationary measurements. Although these devices can determine the bulk flow rate, fluid identification tools are required to evaluate the kinds of fluids present in the flow. These fluid identification instruments measure the pressure gradient, bulk density, or capacitance of the flowing mixture. The flowmeter and fluid identification devices are usually run as a combination on the same tool string. Results typical of such a tool string are shown in [[:file:production-logging_fig5.png|Figure 5]]. In this example, zone A produces water, while the zones above it are all gas producers. A plug set between zones A and B will be effective at eliminating the water production in this example.

 

 

==Mechanical integrity logs==

==Mechanical integrity logs==