Wells – Processes – Vibrating the earth or material in or being placed in the...
Reexamination Certificate
1998-12-01
2001-02-13
Bagnell, David (Department: 3672)
Wells
Processes
Vibrating the earth or material in or being placed in the...
C166S177200
Reexamination Certificate
active
06186228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods and apparatus for enhancing the production of liquid hydrocarbons from subterranean formations penetrated by well bores utilizing one or more sonic energy transducers in the well bores.
2. Description of the Prior Art
The production of liquid hydrocarbons from producing formations and reservoirs is generally assisted to a great extent by naturally occurring forces such as the expanding force of compressed gases, the buoyant and driving force of approaching water and the force of gravity. Primary recovery techniques utilize these forces to cause the liquid hydrocarbons to migrate from subterranean formations into one or more well bores penetrating the formations. Unfortunately, the natural forces are typically only sufficient to allow a small percentage of the total liquid hydrocarbons in formations and reservoirs to be produced.
Secondary recovery techniques are generally employed to recover more of the liquid hydrocarbons in subterranean formations. These techniques utilize extraneous energy forces to supplement the naturally occurring forces in the formations to force the liquid hydrocarbons from the formations into well bores. The extraneous forces can be generated from a large variety of sources including gas injection, steam injection, water injection and the like. These secondary recovery techniques are typically initiated after the primary forces within a formation or reservoir have been at least partially exhausted.
Water flooding is one example of a secondary recovery technique that has been successfully employed in different types of formations. Generally, in accordance with water flooding techniques, one or more injection wells and one or more production wells are utilized. An aqueous solution is injected through the injection wells in order to drive liquid hydrocarbons to the production wells where they are produced. Many modifications to basic water flooding techniques have been developed including the use of certain chemicals and materials in the injection water to help displace the liquid hydrocarbons from the formation. For example, gelling agents are often employed to increase the viscosity of the water and thereby increase its efficiency in driving the oil to the production wells. Surfactants have also been employed to reduce the surface tension of the liquid hydrocarbons and thereby facilitate their production.
Another secondary recovery technique that has been employed to increase the recovery of oil involves the use of low frequency vibration energy. Low frequency vibration from surface or downhole sources has been used to influence liquid hydrocarbon recoveries from subterranean reservoirs. This type of vibration at source-frequencies generally less than about 2000 Hz has been referred to in the literature as sonic, acoustic, seismic, p-wave, or elastic-wave stimulation. For example, stimulation by low frequency vibration has been effectively utilized in some cases in Russia to improve oil production from water flooded reservoirs. Examples from the literature suggest that low frequency stimulation can accelerate or improve ultimate oil recoveries. Explanations for why low frequency stimulation makes a difference vary widely. Examples of such explanations include that the vibration causes the coalescence of oil droplets to reestablish a continuous oil phase, the dislodging of oil droplets so that they can flow as liquid fines, the reduction of capillary forces by altering surface tensions and interfacial tensions and the release of gas which is absorbed at the rock surfaces or dissolved in the water and/or oil phases. For example, U.S. Pat. No. 5,184,678 to Pechkov et al. issued Feb. 9, 1993 discloses a method and apparatus for stimulating fluid production in a producing well utilizing an acoustic energy transducer disposed in the well bore within a producing zone. It is stated in the patent that the acoustic wave radiation transmitted into the producing formation reduces the viscosity of liquid hydrocarbons therein whereby they more readily flow to the well bore.
It is fairly well known that ultrasonic waves can improve and/or accelerate oil production from porous media. The problem with ultrasonic waves is that in general, the depth of penetration or the distance that ultrasonic waves can move into a reservoir from a source is very limited (like less than a few feet), whereas low frequency waves can travel great distances through rock (hundreds to thousands of feet).
While sonic liquid hydrocarbon flow stimulation methods and apparatus have achieved some success in stimulating or enhancing the production of liquid hydrocarbons from subterranean formations, the acoustic energy transducers used have generally lacked sufficient acoustic energy intensity to be significantly effective. Thus, there are continuing needs for improved methods and apparatus which use sonic energy to enhance the production of liquid hydrocarbons such as oil and gas condensate from subterranean formations.
SUMMARY OF THE INVENTION
The present invention provides methods and apparatus for enhancing the production of liquid hydrocarbons from subterranean formations penetrated by well bores which meet the needs described above and overcome the deficiencies of the prior art.
The methods of the present invention are basically comprised of the steps of placing an acoustic energy transducer actuated by at least one electric powered magnetostrictive actuator in a well bore within a liquid hydrocarbon producing formation. Thereafter, acoustic energy in the form of pressure waves is caused to be emitted from the acoustic energy transducer through the liquid hydrocarbons in the formation whereby the surface tension of the liquid hydrocarbons is reduced and the liquid hydrocarbons flow more freely to the well bore.
The electric powered magnetostrictive actuator utilized in the transducer is preferably comprised of a drive rod formed of a terfenol alloy. A coil surrounding the terfenol rod creates an alternating magnetic field in the rod which causes the rod to extend and contract to a greater degree than other types of drive rods. The terfenol drive rod is connected to a flexible element which imparts high intensity acoustic pressure waves to fluids surrounding the well bore for relatively long distances therefrom.
When the liquid hydrocarbons produced are in the form of relatively viscous oil, in addition to the acoustic transducer at least one ultrasonic energy transducer activated by an electric powered magnetostrictive actuator is placed in the well bore and caused to emit ultrasonic wave energy to the liquid hydrocarbons flowing into the well bore whereby the viscosity of the liquid hydrocarbons is temporarily reduced. This reduction in viscosity allows the liquid hydrocarbons to more freely flow through the well bore.
In applications where there is not sufficient pressure drive to cause the liquid hydrocarbons to flow to the surface, an electric powered liquid hydrocarbon pump can be placed in the well bore within the producing formation. The pump can be connected to a string of production tubing disposed in the well bore or to coiled tubing therein. The pump and one or more of the above described sonic energy transducers are connected to a wire line which is in turn connected to a power source and control unit on the surface.
Thus, depending upon the particular application, the type of formation involved and the type of liquid hydrocarbons produced, one or more acoustic energy transducers, one or more of both acoustic energy transducers and ultrasonic energy transducers or one or more of both types of transducers and a liquid hydrocarbon pump are utilized in a well bore penetrating a producing formation.
The apparatus of this invention for enhancing the production of liquid hydrocarbons from a subterranean formation penetrated by a well bore includes a conduit disposed in the well bore for conducting produced liquid hydrocarbons from the subterranean formation to the surface. An electric powere
Fraim Michael Lee
Maloney Daniel R.
Reese Dave E.
Wegener Dennis C.
Zornes David R.
Bagnell David
Dougherty Jennifer R.
Haag Gary L.
Phillips Petroleum Company
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