The present invention relates to apparatus for enhancing the production of oil from subterranean oil reservoirs with the aid of electric current and, in particular, apparatus for enhancing the performance of the method described in U.S. Pat. No. 7,325,604, issued Feb. 5, 2008, the entire contents of which are incorporated herein by reference.
As set forth in more detail in U.S. Pat. No. 7,325,604, the oil bearing formation is tapped by drilling a downhole into the oil-bearing formation and providing a downhole liner to form an open conduit for the removal of oil. The liner is foraminous in order to permit the oil to enter the conduit throughout the length of the liner. It has been found that the production of oil is enhanced by connecting a negative electrode to the liner and introducing a second electrode in proximity to the formation. A voltage difference is established between the first and second electrodes to create an electric field across the formation. As shown in the patent, the downhole is drilled and the liner is installed and is connected to a casing which is anchored at the surface above the formation. At its lower end, the casing is connected to the proximal end of the liner and is operatively connected to the bore of the liner. The casing mounts a pump for the extraction of the oil produced by the well. The casing and the liners form a series of interconnected conduit sections which have joints along their lengths between the proximal distal ends of the drilling hole. It has been found that the joints between the conduit sections sometimes separate or deteriorate to a point where there is a substantial loss of voltage between adjacent conduit sections, and a possibility of leakage between the sections of the conduit sections and the surrounding underground formation.
The present invention provides a electrical jumper for bridging the joints between the adjoining conduit sections to insure electrical conductivity between the conduit sections, reducing the loss of voltage which may occur when the joints deteriorate.
More specifically, the present invention provides a jumper composed of interconnected tubings adapted to be centered in the adjoined conduit sections on either side of the joint.
The tubings have a central bore which permits the flow of oil from the downhole into the casing where it is withdrawn by the conventional pump which is mounted at the bottom of the casing. The oil is pumped to the surface by the pump through piping.
In accordance with the invention, centering devices are provided about the outer perimeter of the tubings to center the same within the bores of the conduit sections, the centering devices including means to establish an electrical conductivity between the liner and the tubing.
In a preferred embodiment of the invention, the centering device includes a pair of rings encircling the tubing. The rings are connected by an array of bowed springs spaced circumferentially about the rings. Each bowed spring bows outwardly between the rings to resiliently bear against the interior bore of the conduit section in which it is mounted. Each ring encircles the outer circumference of the tubing, one of the rings being anchored to the tubing and the other of the rings being free to be displaced longitudinally of the tubing to allow radial expansion and contraction of the bowed springs.
The invention may also insure enhanced electrical conductivity by providing electrical contacts on the bowed springs where they bear against the internal bore of the associated conduit section to enhance the electrical conductivity between the bowed spring and the ring which is electrically connected to the tubing, for example by welding.
The jumper may be modified to reduce oil leakage through the joint between the interiors of the conduit sections and the surrounding underground formation.
The invention will be described in greater detail with reference to the accompanying drawings in which:
Referring to
In accordance with the invention, it has been found that the electrical continuity between the liner and the casing may be impaired, and it is desirable to provide a jumper to assure electrical continuity between the conduit sections. To this end, as shown in
Each centering device comprises a pair of rings 64 and 66 encircling the tubing. One of the rings 64 is electrically connected to the tubing 54, for example by a weld joint 65, whereas the opposite ring 64 is slidable on the underlying tubing. The two rings 64 and 66 are interconnected by leaf springs 68 which span between the rings and are bowed outwardly to engage the interior wall of the surrounding conduit section. The bowed leaf springs are arranged in a circular array about the entire circumference of the connector 62 and are biased outwardly into firm engagement with the interior wall of the surrounding conduit section. The displaceable ring 66 may be displaced longitudinally of the tubing to increase or decrease the projection of the outer perimeter of the array of bowed springs 68, as required by their engagement with the interior surface of the conduit section. To ensure electrical contact between the springs and the tubing, the medial portions of the leaf spring 68 are provided with electrical contacts 70 which assure electrical contact between the springs and the tubing. The electrical path between the contacts 70 and the connected ring 64 is through the spring itself, but if desired, an additional electrical path may be provided to assure electrical conductivity from the conduit section through the contact to the ring 64 and the underling tubing. It has been found desirable to design the jumper so that the bores of the tubings are between 40-55% of the bore of the associated conduit section, leaving room for the centering devices in the annular space surrounding the liners.
With reference to the embodiment shown in
The overall length of the jumper 80 is shorter than the jumper 60 so that it will pass through the curvature between the extension 84 and the upper end of the casing at the surface. The casing follows an arcuate path from the surface to the extension 84 and the length of the jumper is tailored to pass along the arcuate path without jamming. In other respects, the jumper 80 is similar to the jumper 60 having distal and proximal tubings 92 and 94 interconnected by a joint 93. The tubings 92 and 94 have centering devices comprising fixed rings 94 and slidable rings 96 which are interconnected by bowed springs 98 disposed in a circular array between the rings 94 and 96. The bowed springs 98 are provided with electrical contacts 100 similar to the contacts 70 described in connection with
Preferably, each embodiment of the invention is designed to complement the conduit sections into which the jumper is installed. Preferably, each tubing has a bore which is between 40-55% of the bore of the associated conduit section to provide an annular space surrounding the tubings. In the embodiment of
While particular embodiments of the present invention have been herein described, it is not intended to limit the invention to such disclosures but changes and modifications may be made therein and thereto within the scope of the following claims.