Temperature Surveys in Oil Wells
- C.V. Millikan (Amerada Petroleum Corporation)
- Document ID
- Society of Petroleum Engineers
- Transactions of the AIME
- Publication Date
- December 1941
- Document Type
- Journal Paper
- 15 - 23
- 1941. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 5.2.1 Phase Behavior and PVT Measurements, 5.9.2 Geothermal Resources, 1.14 Casing and Cementing, 4.3.1 Hydrates, 1.6 Drilling Operations, 2.4.3 Sand/Solids Control, 2 Well Completion, 1.11 Drilling Fluids and Materials, 4.3.4 Scale
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Temperature measurement in wells is an old practice and geothermal gradientshave been of interest to geologists for many years. Their application to theoperation of oil wells is a more recent practice. It has long been recognizedthat temperature anomalies occur in drilling and producing wells butthermometers that could obtain a satisfactory record of the anomalies were notavailable.
The normal geothermal gradient is considered as being about one degreeFahrenheit for each 60 ft. of depth. This" normal" gradient varies indifferent areas, but whatever it may be in an area there is little variationfrom the surface to as deep as the drill penetrates. The normal gradient isappreciably changed by gas expanding from the reservoir into the borehole or bythe movement of fluid through a borehole while drilling, producing, orcirculating. It is the resulting anomalies and abnormal gradients from whichconditions in wells can be interpreted. Some of the applications of suchinterpretations are locating the position of oil or gas sands, permeable stratain a reservoir zone, gas-oil contact, source of water, casing leaks, and thetop of cement behind casing.
A thermometer for use in wells must be sensitive and have a low thermal lag.The
sensitivity should permit recording 0.2?F. or less for differentialtemperatures although the actual temperature need not be more accurate thanIOF. The thermal lag
should be as low as rugged construction will permit in order to allow surveysto be made in a minimum of time. Of the several kinds of thermometers, theserequirements are most easily obtained with the vaporpressure, expansion, andelectric-resistance types. Thermometers for use in wells may beself-contained-that is, the complete instrument is lowered into the well and arecord made of the temperature---or the thermal element only may be loweredinto the well and the temperature recorded at the surface. The vapor-pressureand expansion types are more adaptable for a self-contained instrument whilethe electricresistance thermometer is more suitable for surface recording oftemperatures.
The self-contained instrument can be run against high pressure on a single wireline with only one operator required. The instrument and its hoisting equipmentis easily portable and can be mounted on a small car. The disadvantages are asomewhat greater thermal lag and the necessity of completing a run before anytemperature or temperature anomaly is known.
A surface-recording thermometer has the advantage of being somewhat moresensitive and of having a lower thermal lag.
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