Patent Application
20080067129
In the disclosure that follows, in the interest of clarity, not all features of actual implementations are described. It will of course be appreciated that in the development of any such actual implementation, as in any such project, numerous engineering and technical decisions must be made to achieve the developers' specific goals and sub goals (e.g., compliance with system and technical constraints), which will vary from one implementation to another. Moreover, attention will necessarily be paid to proper engineering and programming practices for the environment in question. It will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the relevant fields.
In this description, the terms “up” and “down”; “upward” and “downward”; “upstream” and “downstream”; and other like terms indicating relative positions above or below a given point or element may be used to clearly describe some embodiments of the invention. However, when applied to apparatus and methods for use in wells that are deviated or horizontal, such terms may refer to a left-to-right, right-to-left, or other relationship as appropriate.
Electromagnetic treatment devices as described above are electronic, physical treatment devices. In general, the devices create an electric, magnetic, and/or electromagnetic field that causes scale to form in solution rather than plate on the walls of the pipe. It has been determined that in hydrocarbon solutions containing paraffin and other wax-like substances, these crystals of scale also act as sites for the paraffin to adhere rather than depositing on the walls of the pipe. Because scale must be present for such devices to prevent wax deposition, in wells or pipelines that do not include scale forming compounds, injection of such compounds permits the use of electromagnetic treatment devices to prevent paraffin deposition. Chemical injection is generally known in the art, but a simplified description is described below.
An exemplary embodiment for use in an oil well is illustrated schematically in
In a typical chemical injection installation, chemical injection mandrel 110 with chemical injection valve 112 is installed as part of the production tubing string 104. Chemical injection line 108 is run from the chemical injection mandrel 110 to the surface to act as a conduit for the injected fluid. Reverse-flow check valves (not shown) are installed at the point of injection to prevent flow from the production tubing entering the injection flow path. A high-pressure pump, capable of overcoming the downhole pressure, is installed on the surface to pump the chemical injection fluid to the injection point. Furthermore, one or more injection points may be provided along the production tubing.
At the injection point (or points), the chemical injection components are used to introduce a solution containing scale forming compounds into the well. This solution, which may be known as a catalyst fluid, may take a variety of forms. Among such fluids are aqueous solutions of calcium, carbonate, bicarbonate, calcium carbonate, and/or calcium bicarbonate. Barium sulfide in aqueous solution may also be used. A variety of other scale forming chemicals, in both aqueous or non-aqueous solution, will also be apparent to those skilled in the art. The essential property of such compounds is that they be capable of forming seed crystals of scale in the presence of electromagnetic fields induced by electromagnetic treatment device 114, which is connected to the production tubing at the surface. These seed crystals give the wax a site to adhere that otherwise would not be present, thereby preventing the wax from depositing on the walls of the pipe.
The wax, thus effectively suspended in the production hydrocarbons, may be removed at the surface or terminus. One mechanism of paraffin removal is filtration. Alternatively, the paraffin deposits will typically float on top of the produced hyrdrocarbons, and thus the production hydrocarbons may be drawn off the bottom of a suitable tank or settling basin. Either technique provides substantial cost and complexity savings over the prior art techniques of paraffin removal from the production tubing, which were discussed above.
Alternatively, it is not necessary to include chemical injection line 108. For example, the catalyst fluid may be injected directly into the well annulus. When annular injecting it is generally preferred to coat the surfaces exposed in the annulus and to inject greater quantities of catalyst fluid at first. As will be appreciated by one skilled in the art, this type injection is used successfully throughout the oilfield for various treating applications.
Additionally, the techniques disclosed herein are not limited to oil wells. Flowlines and pipelines may be treated in similar fashion. For example,
One skilled in the art will appreciate that the amount of catalyst fluid and the concentration of scale forming compounds therein would be determined as a function of the hydrocarbon fluid volume being treated and the amount of paraffin forming hydrocarbon therein.
When using a treatment device as described in the Stefanini patents referenced above, the nominal operation frequency of the device is about 200 kHz. Other details of operation may be gathered from the Clearwell International Specifier's Guide, which is incorporated by reference in its entirety.
Although specific embodiments and variations of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations that may have been suggested in the present disclosure, may be made to the disclosed embodiments without departing from the scope of the invention as defined by the appended claims. The foregoing description and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
