Monitoring - Production Logging Testing

Water entry/exit locations and sources
Non-performing perforations
Flow behind casing or tubing
Crossflow
Leaks in tubing or casing
Unproductive/receptive intervals for stimulation
Packer leaks
Lost-circulation zones

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Temperature: Temperature can be used for injection evaluations although interpretation can be difficult.

Pressure: The pressure sensor can be used to determine wellbore pressures for critical well control applications, to evaluate friction losses and for pressure transient measurements.
Flow: Flow along the wellbore is measured, commonly with a spinner. The spinner is a fan blade type device that is rotated by the fluid movement in the borehole.
Dielectric (Water Holdup): This is used for inferring components in the production stream and, for PWRI, would be more useful in an offset producer where water cut has increased.
Gamma Ray:The gamma ray is used for adjusting the depths of the production logs with other logs to a common basis, to follow injected radioactive material in the borehole to determine flow profiles and velocities and to trace tagged frac sand.
Casing Collar Locator (CCL):The casing collar locator (CCL) is used as a means of depth correlation and can be used to locate perforations, packers, x nipples, gas lift valves, screens, and other mechanical components.

The borehole flow rates should exceed some minimum value (e.g. 10 feet per minute in fluid or 28 feet per minute in gas). Check with the vendor. Charts are available to convert production in barrels per day to flow rates in different sizes of pipe. The tool velocity also adds or subtracts from the spinner rate and is used to calibrate the spinner and determine the spinner threshold.
Line speed is a critical component in most production logging. It is important to remember that the spinner is only indicating what is happening in the borehole where the spinner is positioned and that the production dynamics of boreholes may vary greatly, causing the spinner to sometimes give unreliable results especially in multi-phase wells. While many vendors will indicate that they have self-diagnosing/correcting gauges, make every effort to keep the survey reasonably slow and uniform.
Particularly if you are considering any sort of pressure transient evaluations to look at properties of individual layers, be certain to have adequate gauge sensitivity and environmental tolerance. In critical applications, consider dual gauges.
It is not unheard of for gauges to become "gummed up." Schmoo in some Alaskan wells, including material backflowing/squeezing out during shut-in has been known to impair gauge function.
As with most survey operations, it is not too difficult to be fooled during interpretation. Be especially careful with interpretation of thermal data. If possible, always do a warmback survey, to help to discriminate between actual fractures taking fluid, fractures that wander along the length of the wellbore and annular channels.
If you are doing dielectric surveys on your producers, capacitance sensors response to percent of water mixes is not linear and when water becomes the dominant percent of the mixture it becomes difficult to discriminate any the percent of water and oil in the mix (some sources indicate that the oil cut needs to be greater than 3% to be detected).

Production logging tools and services are offered by a variety of vendors – with broad geographical coverage and levels of sophistication. The table below is a partial list.

Company Location URL

Baker Atlas Worldwide http://www.bakerhughes.com/bakeratlas/reservoir_production/polaris_index.htm

Cardinal Surveys Company Odessa, TX, Hobbs, NM http://www.cardinalsurveys.com/default.asp

Expro International Group PLC 2001 Aberdeen and other offices worldwide http://www.exprogroup.com/casedholeservices/epl.htm

Halliburton Worldwide http://www.halliburton.com/spe98/flow2000.asp

Kuster Company F.T.I. Inc. Long Beach, CA and other worldwide offices http://www.kusterco.com/

Lee Tool Division of Schlumberger Canada Ltd. Red Deer, Alberta http://www.leetool.ab.ca

Madden Systems Incorporated Odessa, TX; Houston, TX;
New Orleans, LA http://www.maddensystems.com/index.htm

Maxim Technology Limited Wales, UK www.maximtech.co.uk

Oildata Wireline Services Limited Nigeria http://www.oildatainc.com/index.html

Read Well Services Bergen, Norway; Aberdeen, UK; Doha, Qatar http://www.readgroup.no/group/index.asp

Schlumberger Worldwide http://www.connect.slb.com/index.cfm?id=id4638

Spartek Systems Sylvan Lake, Alberta http://jaguar.rttinc.com/~spartek/index.htm

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