Radiant energy – Geological testing or irradiation – Well testing apparatus and methods
Reexamination Certificate
2000-08-16
2003-04-22
Hannaher, Constantine (Department: 2878)
Radiant energy
Geological testing or irradiation
Well testing apparatus and methods
C250S265000
Reexamination Certificate
active
06552333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and methods for use in the production of hydrocarbons. In another aspect, the present invention relates to apparatus and methods for examining gravel packs utilized in completed hydrocarbon wells. In even another aspect, the present invention relates to apparatus and methods for determining the quality of gravel packs utilized in completed hydrocarbon wells.
2. Description of the Related Art
Oil and gas wells are often completed in unconsolidated formations containing loose and incompetent fines and sand which migrate with fluids produced by the wells. The presence of formation fines and sand in the produced fluids is disadvantageous and undesirable in that the particles abrade pumping and other producing equipment and reduce the fluid production capabilities of the producing zones in the wells.
Heretofore, unconsolidated subterranean zones have been stimulated by creating fractures in the zones and depositing particulate proppant material in the fractures to maintain them in open positions. In addition, the proppant has heretofore been consolidated within the fractures into hard permeable masses to reduce the potential of proppant flowback and migration of formation fines and sands through the fractures with produced fluids.
Thus, it is not hard to imagine that in the production of hydrocarbons from a subterranean formation penetrated by a wellbore, it is often necessary to address the problem of the production of fine particulate materials with the desired well fluids. Such fine particulate materials can cause abrasive wear on well components such as pumps, valves and tubular goods resulting in costly replacement. Additionally, these particulates must be separated from the desired well fluids before transport, processing or sale. Further, these particulate materials can accumulate in the wellbore and in the near wellbore area and greatly reduce or completely stop further production of the fluids of value.
Minimizing the production of particulate materials such as formation sand without reducing well productivity has long been the goal of sand control operations. Toward that goal, various technologies have been used including resin consolidation, gravel packing, overbalanced perforating with resin consolidation and the like.
For example, gravel packs which include sand screens and the like have commonly been installed in the wellbores penetrating unconsolidated zones. The gravel packs serve as filters and help to assure that fines and sand do not migrate with produced fluids into the wellbores.
In a typical gravel pack completion, a screen is placed in the wellbore and positioned within the unconsolidated subterranean zone which is to be completed. The screen is typically connected to a tool which includes a production packer and a cross-over, and the tool is in turn connected to a work or production string. A particulate material which is usually graded sand, often referred to in the art as gravel, is pumped in a slurry down the work or production string and through the cross over whereby it flows into the annulus between the screen and the wellbore. The liquid forming the slurry leaks off into the subterranean zone and/or through the screen which is sized to prevent the sand in the slurry from flowing there-through. As a result, the sand is deposited in the annulus around the screen whereby it forms a gravel pack. The size of the sand in the gravel pack is selected such that it prevents formation fines and sand from flowing into the wellbore with produced fluids.
Gravel pack technology has its own set of problems and limitations. These include problems in assuring placement uniformity and efficiency. Often, if not utilized correctly, or under certain circumstances, gravel packs also have the undesired side effect of reducing well productivity.
Specifically, a problem which is often encountered in forming gravel packs, particularly gravel packs in long and/or deviated unconsolidated producing intervals, is the formation of sand bridges in the annulus. That is, non-uniform sand packing of the annulus between the screen and the wellbore often occurs as a result of the loss of carrier liquid from the sand slurry into high permeability portions of the subterranean zone which in turn causes the formation of sand bridges in the annulus before all the sand has been placed. The sand bridges block further flow of the slurry through the annulus which leaves voids below the bridges formed. When the well is placed on production, the flow of produced fluids is concentrated through the voids in the gravel pack which soon causes the screen to be eroded and the migration of fines and sand with the produced fluids to result.
It is well known, that to be effective, the gravel pack must comprise densely packed sand without voids or cavities in the sand. If portions of the annulus around the screen are not packed completely with sand, formation fluids containing formation sand will quickly erode the screen, leading to a gravel pack failure. Further, if the gravel pack initially is not densely packed, subsequent compaction caused by, for example, flow of the formation fluids, can result in voids and cavities within the gravel pack.
There has been much prior art relating to evaluation of gravel packs.
U.S. Pat. No. 4,423,323, issued Dec. 27, 1983 to Ellis, et al., discloses a neutron logging method and apparatus for determining a formation characteristic free of environmental effects. Specifically, a neutron logging tool is passed through the borehole while irradiating the formation with neutrons. Neutrons exiting the formation are detected with neutron detectors and count rate signals are generated. In response to these signals, an indication of porosity, substantially independent of error due to tool standoff from said borehole wall, is produced. In addition, values of tool standoff are also generated. These standoff values are then filtered to reduce statistical variations and are used to generate improved indications of porosity. A further aspect is the determination of tool standoff, effective cement/casing thickness, or gravel pack quality from the relation between the logarithms of the count rates and the empirically derived response curves without an explicit down-hole measurement.
U.S. Pat. No. 4,587,423, issued May 6, 1986 to Boyce, discloses a method for gravel pack evaluation utilizing a logging tool with a gamma source and gamma detector. Using a Monte Carlo modeling of gravel pack conditions in a completed borehole, a straightforward expression for the determination of percent packing as a function of known or measurable borehole quantities is derived, from which an accurate quantitative gravel pack log may be obtained for purposes of evaluating gravel pack quality.
U.S. Pat. No. 4,783,995 issued Nov. 15, 1988, to Michel et al., discloses an apparatus and method for logging the density of a gravel pack installation in a drill hole while the gravel pack installation tool is being withdrawn from the drill hole. After the apparatus is recovered at the earth's surface, the density log is recovered by means of a dedicated surface readout module. The logged data of the density of the gravel packed zone is examined for voids in the gravel pack. If any such void is indicated from the data, remedial action can be taken promptly while the gravel pack equipment is still at the drill hole site.
U.S. Pat. No. 4,950,892 issued Aug. 21, 1990 to Olesen, discloses a method and tool for investigating a gravel pack located in the annulus between the tubing/screen and the casing of a borehole. The method includes moving a logging tool through the tubing/screen over the depth region of the gravel pack. The logging tool includes a neutron source able to emit neutrons at such an energy that their interaction with a first set of atoms indicative of the gravel pack quality causes the production of gamma rays, and at least one gamma ray detector. The method also includes deriving a measurement of the number
Gadeken Larry L.
Shultz Ward E.
Storm Bruce H.
Gabor Otilia
Halliburton Energy Service,s Inc.
Hannaher Constantine
Vinson & Elkins LLP
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