Nozzle for jet drilling

#1. Field of the Invention

#This invention pertains to drilling of holes through the earth. More particularly, a nozzle is provided for drilling of drainholes from wells and other small-diameter holes.

#2. Description of Related Art

#For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features and wherein:

#FIG. 1 illustrates a cased well and a drilling apparatus for drilling through a casing and drilling a drainhole in a reservoir.

#FIG. 2 illustrates an experimental set-up that can be used to test jet bits.

#Referring to FIG. 1, one embodiment of a drilling apparatus, such as disclosed in U.S. Pat. No. 6,263,984, hereby incorporated by reference, is illustrated. Nozzle jet drill 20 has been used to drill through casing 12 and cement 14 and is used to continue drilling lateral hole or drainhole 16 through reservoir 18. Nozzle jet drill 20 is attached to elastomeric tube 22, which in turn is connected to flexible steel tube (coiled tubing) 24 at connection 23. Upset tubing (rigid) 26 may be used to place bit diverter 28 in the well. The bit diverter is designed to turn a jet bit attached to an elastomeric tube through about a 90 degree turn, more or less. Diverter 28 may be a funnel tube guide which contains a wider top and narrows down to an outlet hole at the bottom, where a constriction (not shown) may be placed to enable a drill to kick-off. Alternatively, diverter 28 may be placed in casing 12 using well known wire line placement methods without the use of upset tubing 26 in the well. A recessed replaceable blasting plate (not shown) made of hard material such as tungsten carbide or the like, may be used to protect the funnel tube guide during the initial drilling through the wall of casing 12. Coiled tubing 24 extends to the top of well 10 and may coil onto reel 30.

#Drilling fluid may be pumped down the well by pump 34. Drilling fluid may contain abrasive particles, preferably ranging from about mesh 20 to about mesh 140. A water-soluble polymer such as J362, available from Dowell/Schlumberger, may be used in the concentration range of about 10 pounds to about 40 pounds per 1,000 gallons of liquid to keep the abrasive particles suspended and to lower friction pressure loss during flow of drilling fluid through tubing 22 and 24. Concentration of abrasive particles may be selected depending on drilling conditions, but normally concentrations up to about one-half pound of abrasive per gallon may be used. Chemicals such as KCl and HCl may be added to drilling fluid to assure that the fluid is compatible with the reservoir rock. Preferably, the fluid pumped is filtered to minimize plugging of orifices in a bit and fluid may be heated to decrease friction loss during flow downhole. Flow rate of drilling fluid may vary widely, but may be, for example, about 10 gallons per minute

#A suitable high-pressure pump such as pump 34 is a Kerr Pump, such as KP-3300-XP, of triplex design with ceramic plungers. It will provide over 4,000 psi at rates from 4.8 GPM to 21.5 GPM. A 24-horsepower unit should suffice for most shallow-well applications; that is, for well depths less than 2500 feet. Other common high-pressure triplex pumps with ratings to and above 10,000 psi may be used. Elastomeric tube 22 may be a Gates Rubber Company 6M2T product, product number 4657-1554, which has a minimum burst pressure of 16,000 psi, an inner diameter of 0.375 inch, and outer diameter of 0.69 inch, and a minimum bend radius of 2.5 inches. Other such tubes may be used having higher pressure ratings and smaller minimum bend radius or smaller hydraulic hose capable of withstanding burst pressures up to 10,000 psi or more may be used. An intermittent pressure valve may be placed downstream of pump 34 to enable the introduction of pressure pulses into the drilling fluid that will be transmitted to drill 20. The pulsed pressure waves from the drill may be detected at the surface or in the bore hole by geophones 38 and used to monitor the position of drill 20, using known techniques. Direction-indicating instruments such as a gyroscope, magnetometer or accelerometer(s) or combinations of these instruments may be placed near bit 20 and information from such measurements may be transmitted to surface while drilling using known measurement-while-drilling (MWD) techniques, such that the operator is informed of the initial direction of the nozzle-jet into the formation and its subsequent direction. Normally, the operator will desire to maintain lateral hole 16 within reservoir 18 as drilling proceeds.