Patent Application
20180106144
The field of the invention is determination of which of several producing zones is producing water when multiple zones are on production at the same time so that the water producing zone can be isolated and more particularly using tracers to pinpoint the water producing zone.
Frequently when a well is completed there are perforations in multiple zones in a single formation or discrete zones in spaced apart formations that are created. The formations may be put on production one at a time or at the same time. At some point in time the well can start to produce undesirable materials such as water. When that happens the response is frequently isolation of such a zone to redirect production from other zones that do not have this issue. At times it is challenging to pinpoint exactly where the water is coming from. Sometimes water migrates through the formation and it is produced at a different access point in the wellbore. It would be desirable to be able to pinpoint the source of water production to be able to close off the right zone or zones in the formation.
Part of well completion can be hydraulic fracturing where fluid and solids are pumped at high pressure into the formation to fracture the formation to enhance subsequent production. The fracture fluid under pressure creates the fractures that are then propped open by the solids contained in the fracture fluid stream. Typically these solids are called proppants and are frequently at least in part sand.
Tracer fluids are used during production to aid analysis of the nature of the fluids being produced as a way to determine if the produced fluids are the fluids expected from the producing formations. Some examples of dye tracers are U.S. Pat. No. 6,729,400; 7,028,773; 6,564,866; 8,141,633; 6,016,191; 7,347,260 and 7,658,226.
The present invention uses tracers that are of recognizable different colors in different zones and preferably embeds the tracer in coated proppants. If the undesired fluid is produced in a specific zone, the coating on the tracer is removed to let the tracer escape to the surface. Since each zone is fractured with different color tracer, surface personnel can pinpoint the specific zone that is producing the undesired fluid and steps can be taken to close that zone off
These and other advantages of the present invention will become apparent from the following description and drawings. Those skilled in the art will further appreciate other aspects of the invention from a review of the detailed description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention can be determined by the appended claims.
Different zones are fractured with proppant containing tracer dye of different colors that is encapsulated in the proppant. The presence of an undesired material such as water removes the coating to allow the uniquely colored tracer dye to be released during production. Surface personnel note the color of the dye and associate a specific zone that is producing the undesired material. Steps are taken to close off the offending zone as production continues from the other zones in the borehole. Detection of cross flow between zones can also be accomplished if the same color is still produced after the zone associated with its color is isolated.
For a detailed description of the preferred embodiment of the invention, reference will now be made to the accompanying drawings wherein:
It should be noted that while only two zones are illustrated to explain the concept, that multiple zones each with a unique color of tracer dye can be used. Furthermore, the proppant 20 or 22 can form only a portion of the proppant pumped under pressure into a respective zone. The zone needs to have its fractures held open even when the undesirable material is being produced so only some of the proppant can carry the dye tracer while the remaining proppant can be of a type or types that are well known in the art. While 20 or 22 can be actual proppant, it can also be simply tracer dye encapsulated for containment without serving a proppant function at all. In this case the presence of unwanted material being produced such as water will remove, dissolve or otherwise disable the coating allowing the tracer dye to be released to flow to the surface. A meter M can be used to take continuous or periodic readings on the produced fluid to spot the presence on the tracer dye in the produced fluid. Such a meter can be a spectrometer that can discern the different colors of the dye in the produced fluid so that the location of the production of the undesired material, such as water, can be determined and the needed valve such as 16 or 18 can be closed off with a wireline or coiled tubing mounted shifting tool schematically illustrated as 24. As shown in
Those skilled in the art will now be able to appreciate that the method of the present invention allows the location of production of unwanted water or other materials to be pinpointed in a multizone borehole so that a particular zone can be isolated promptly. Sometimes water can migrate from one zone to an adjacent zone so that more than one zone may need to be closed off before there is no longer an indication of the dye tracer. The method can be used to detect migration of water or other materials from an injection well into a production well or other applications.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
