Location of Points of Water Entry in Oil Wells
- D. Silverman (Stanolind Oil and Gas Co.) | A.R. Brown (Stanolind Oil and Gas Co.)
- Document ID
- Society of Petroleum Engineers
- Transactions of the AIME
- Publication Date
- December 1948
- Document Type
- Journal Paper
- 286 - 304
- 1948. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 4.1.5 Processing Equipment, 5.2 Reservoir Fluid Dynamics, 1.6.9 Coring, Fishing, 3.1.1 Beam and related pumping techniques, 4.1.2 Separation and Treating, 3.2.4 Acidising, 3 Production and Well Operations, 4.2.3 Materials and Corrosion
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Equipment and methods for locating the points of entry of salt water into oilwells are described. These techniques make it possible to delineate accuratelythe top and bottom boundaries of water zones whether bottom water orintermediate zones of production. Data are given on tests by this survey methodon a number of producing wells. Complete results were obtained on wells showingwater percentages ranging from high values to as little as 10 pct salt water. Anumber of the wells tested were plugged back and the results are reported indetail. While not all the work-overs were successful, evidence, including theresults of reruns by this survey method, points to failure of the plug-backoperations. The data provided in the tests discussed show, contrary to generalopinion, that a large percentage approaching 50 pct of the wells showedintermediate water instead of bottom water. Furthermore, approximately a thirdof the wells tested showed multiple zones of water production. The equipmentcomprises a long pipelike assembly carrying 10 pairs of electrodes spaced aparta distance of 4 ft. A surface- controlled solenoid-operated switch is providedto connect each of the individual pairs of electrodes in turn to asingle-conductor steel-armored cable by means of which the conductivity of thefluid in the vicinity of each of the electrode pairs can be continuouslyrecorded at the surface. Any number of electrode pairs and any spacing can beused. This assembly is lowered on tubing and placed in position opposite thesection of the well to be studied. A conventional rod pump is used to producethe well for the survey. The pump inlet is placed below the lowest electrodepair. The well is conditioned by pumping out the salt water normally standingin the well and introducing fresh water into the annulus at the surface. Whenthe resistivity of the water standing in the well has been increased to asufficiently high value, the in flowing fresh water is stopped and the drawdown operation of the survey is started. As the fluid head is lowered bypumping, fluids flow into the well and the entry of salt water is indicated bythe change in resistivity of the fresh water opposite the zones of waterentry.
The process can be repeated as often as necessary with little effort andwithout moving any well equipment to be sure that the fluids produced from eachzone are representative of the true reservoir content.
The oil industry has been concerned from its inception with the control offluids entering its wells. In order to effect the greatest economy of operationand to get the greatest economy of operation and to get the greatest totalproduction of petroleum liquids out of the ground, the flow of gas and watermust be controlled and often extensive workovers are planned and carried outfor this purpose. This has become even more important in recent years becauseof the need for the conservation of natural resources.
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