Patent Application
20100078414
1. Field of the Invention
This invention relates to underground drilling methods and apparatuses. In one aspect, this invention relates to non-vertical drilling methods and apparatuses for drilling non-vertical boreholes. In one aspect, this invention relates to the use of lasers as a means for augmenting the mechanical drilling process. In another aspect, this invention relates to the use of lasers as a means for augmenting the functionality of a mechanical drill bit used in drilling underground. In yet another aspect, this invention relates to the use of lasers as a means for facilitating the use of coiled tubing for drilling underground. In yet another aspect, this invention relates to use of laser as a means for cleaning the walls of drilled wells and removing formation damage from drilling fluid.
2. Description of Related Art
Conventional underground drilling is typically carried out using a rotary drill bit attached to a drill string. During the drilling operation, a drilling fluid is injected into the borehole for removal of debris generated by the drilling process. The drill bit is typically constructed from alloy steel and comprises pieces of carbide or diamond on the surface to break up the material being drilled. The two most common types of drill bits are fixed cutter and roller cone bits. The drill bit is attached to a drill string which consists of one or more sections of steel pipe connected together and rotated from above ground. Alternatively, the drill bit may be attached to a continuous steel pipe, known as coiled tubing, fed from a reel. In the case of coiled tubing, the drill bit is rotated by a downhole motor that is commonly hydraulically driven.
Coiled tubing is substantially more flexible than the connected pipe sections of a drill string. Depending upon the underground reservoir characteristics, holes may be drilled vertically, sideways, vertically then sideways, or vertically and then horizontally. It is not uncommon to make multiple side tracks from a single horizontal borehole into the underground formation to increase recovery. In most applications, particularly when drilling in harder materials, it is necessary to apply a certain amount of force on the drill bit to achieve the desired drilling speed. In vertical boreholes, when using a substantially rigid drill string, the force on the drill bit is controlled by a combination of the weight of the drill string above the bit and additional push or pull force applied to the drill string above ground. However, this method of force becomes less effective when drilling non-vertically, i.e. curved holes, side tracking or horizontal drilling, and even less effective when using a more flexible drill string such as coiled tubing, most notably when drilling in very hard materials such as granite. Methods have been developed to improve the drilling speed in these applications. The most common of these is the use of a tractor, which anchors to the surface of the drilled hole upstream of the bit while the downstream drill string is powered forward using electrical or hydraulic force. Although effective in many applications, the tractor systems are very expensive and have difficulties maneuvering through softer formations where the surface breaks down and is not able to provide the requisite anchoring. In addition, conventional drilling systems require a greater number of trips down the borehole as well as tools to stimulate the well after it has been drilled, clean the well surface, and measure formation properties.
The use of lasers for the purpose of producing boreholes to enable the extraction of liquid and gaseous fuels from underground formations is well-known in the art. U.S. Pat. No. 4,066,138 to Salisbury et al. teaches an earth boring apparatus mounted above ground that directs an annulus of high powered laser energy downwardly for boring a cylindrical hole by fusing successive annular regions of the stratum to be penetrated at a power level that shatters and self-ejects successive cores from the hole.
U.S. Pat. No. 4,282,940 to Salisbury et al. teaches an apparatus for perforating oil and gas wells. Using this method, a high-powered coherent light beam is axially directed along the borehole to a predetermined depth and deflected along a beam axis. The beam is focused to concentrate at each of a plurality of spaced focal points along the deflected beam. This, in turn, is said to provide a significant increase in the distance that calculated oil or gas bearing formations can be perforated, thereby increasing the yield by more conventional means.
The use of lasers for drilling is also taught by U.S. Pat. No. 4,113,036 to Stout in which underground boreholes are drilled through a formation from a plurality of vertical boreholes by use of laser beams to form a subsurface, three-dimensional bore passage pattern for in situ preparation of fossil fuel deposits to be recovered and a laser beam is projected vertically through an angularly adjusted tubular housing inserted into each borehole from which a reflected drilling beam is laterally directed by an angularly adjusted reflector to form a bore passage; U.S. Pat. No. 3,871,485 to Keenan, Jr. in which a laser beam generator positioned in a wellhole is electrically connected to an inhole voltage generator actuated by drilling mud or other liquid passing through a laser beam housing connected to the drill string and a reflecting crystal for the laser beam is positioned within the laser beam housing to reflect the beam in an elliptical pattern across the formation to be penetrated; U.S. Pat. No. 4,090,572 to Welch in which a laser beam for drilling gas, oil or geothermal wells in geological formations and for “fracing” the pay zones of such wells to increase recovery is projected into a borehole along a beam guide so as to make available laser energy adequate to melt or vaporize the formation under downhole conditions; and U.S. Pat. No. 5,107,936 to Foppe in which a gap defining the outer profile of a borehole is melted down and the drill core surrounded by this gap is extracted at intervals through the melting zone.
It is one object of this invention to provide an apparatus for facilitating the use of coiled tubing in the underground drilling of boreholes.
It is one object of this invention to facilitate the underground drilling of non-vertical boreholes.
It is another object of this invention to provide a method and apparatus for borehole cleaning and stimulation.
These and other objects of this invention are addressed by an apparatus for drilling underground comprising at least one optical fiber for transmitting light energy from a laser energy source to an underground drilling location and a mechanical drill bit having at least one cutting surface and forming at least one light transmission channel aligned to transmit light from the at least one optical fiber through the mechanical drill bit by way of the at least one light transmission channel. This invention can increase the speed and/or efficiency of drilling systems for drilling holes in substances such as concrete, granite, limestone, sandstone, and other rock materials; it can be used for a wide range of drilling operations in substances such as concrete, cement, rock, limestone, marble, quartz, etc.; and it is especially suitable for drilling horizontal boreholes in the ground for producing and recovering oil, gas, water, and geothermal energy. This invention may also be used for drilling smaller holes for logging, for side tracking through existing holes or with reaming bits. It may be used to drill boreholes of a variety of sizes but is especially suitable for drilling holes in the range of about 0.5 inches to about 20 inches in diameter.
In operation, the laser energy is used for spalling or for weakening of the structure of the material to be drilled by softening the material ahead of mechanical drilling. Hard materials such as granite should be significantly easier to drill using a mechanical drill bit after having been presoftened. Drilling fluid, also referred to as drilling mud, may be circulated through and around the drilling tool to cool the system as well as remove the debris. In accordance with one embodiment, a static, dynamic, mechanical, electro mechanical, or other type of separator, such as a cyclone, may be employed to remove contaminants from a portion of the drilling mud, which, in turn, may be used to clear a path ahead of the laser so as to maximize laser energy impingement on the material being drilled. In accordance with one embodiment, a fluid containing at least one of water, air, nitrogen, CO2 or another fluid that is substantially transparent to laser energy may be injected into the laser path to at least partially clear the path ahead of the laser. In yet a further embodiment, debris generated by the laser energy may be analyzed and the results fed into instrumentation to determine the properties of the formation for drilling control to optimize drilling efficiency and maximize well production efficiency. In yet another embodiment, the laser energy may be used for cleaning and stimulation of the borehole.
These and other objects and features of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein:
The invention disclosed herein is a laser assisted drilling system for underground drilling, which includes a laser assisted mechanical drill bit and optical fibers for the transmission of laser energy from a laser source disposed above ground or within the drill string to the drill bit. The advantages of this invention compared with conventional technologies include an increase in drilling speed due to the use of laser energy to spall ahead of the mechanical drill bit the material ahead of the mechanical drill bit being drilled prior to utilization of the mechanical drill bit; the ability to use the laser energy on demand to selectively soften the material only when needed; the ability to use smaller diameter and thinner wall drill strings due to the reduced force on the drill bit, more control over the direction of the drilling, and less tendency of the drill string to buckle, especially with respect to flexible drill strings such as coiled tubing; the ability to provide additional services downhole, such as measurement while drilling (MWD), logging while drilling (LWD), seismic logging, steering of the drill bit, and sweet spot detection due to the available bandwidth for data transmission provided by the optical fiber; and the ability to use the information gathered during the drilling operation for directing the laser assisted drill bit to clean and stimulate the well as the drill bit is removed. In addition, the use of laser energy for well stimulation and cleaning reduces the need for conventionally employed chemicals for these operations, thereby reducing the environmental impact of the drilling and completion operation.
The apparatus of this invention for underground drilling,
As previously indicated, during the drilling operation, a drilling fluid 20, i.e. drilling mud, is provided to the drill bit 15 for cooling of the drill bit and removal of debris from around the drill bit. The drilling mud is conveyed through a mud motor 14 disposed rearward of the mechanical drill bit through which the drilling mud is transmitted to the mechanical drill bit. After cooling of the drill bit, the drilling mud flows around the exterior of the drill string as indicated by arrows 26 up to the top of the borehole, taking with it debris from the area of drilling within the borehole.
Disposed rearward of mud motor 14 in accordance with one embodiment of this invention, is instrumentation package 13 for providing MWD and/or LWD services.
In accordance with one embodiment of this invention as shown in
As previously indicated, mechanical drill bit 15 forms at least one light transmission channel 25 through which light from optical fiber 11 is transmitted to an area ahead of the mechanical drill bit during the drilling operation. In accordance with one embodiment, optical fiber 11 extends through light transmission channel 25 substantially to the leading surface of the mechanical drill bit and, as shown in
In accordance with one embodiment of this invention, mechanical drill bit 15 forms an optical cavity 31 aligned with optical coupling 30 as shown in
In accordance with one embodiment of this invention, shown in
It will be appreciated that during operation of the laser assisted drill bit, debris from the drilling operation may come between the laser energy outlet or outlets from the light transmission channels and the desired formation target, thereby inhibiting the transmission of laser energy to the formation target. In accordance with one embodiment of this invention, shown in
As previously indicated, in addition to transmitting and controlling the laser energy and its direction, the bandwidth available in the optical fibers may also be used to perform additional services such as MWD, LWD, seismic logging and sweet spot detection. Thus, LDW, MDW and other information gathered during the drilling operation may be used to direct the laser assisted drill bit to clean and stimulate the well as the drill bit is removed from the borehole. The use of laser energy for well stimulation and cleaning reduces the need for conventionally used explosives and chemicals for these operations, thereby reducing the environmental impact of the drilling and completion operation. In addition, the laser energy may be used to generate emissions from formations to provide formation property data. Such an application is shown in
While in the foregoing specification this invention has been described in relation to certain preferred embodiments, and many details are set forth for purpose of illustration, it will be apparent to those skilled in the art that this invention is susceptible to additional embodiments and that certain of the details described in this specification and in the claims can be varied considerably without departing from the basic principles of this invention.
