Boring or penetrating the earth – Processes – Boring with specific fluid
Reexamination Certificate
2002-03-12
2003-06-24
Tsay, Frank (Department: 3672)
Boring or penetrating the earth
Processes
Boring with specific fluid
C175S067000, C175S424000
Reexamination Certificate
active
06581700
ABSTRACT:
FIELD OF THE INVENTION
This invention is generally applicable to cutting earthen or subterranean formations. More particularly, this invention is applicable to drilling wells such as oil, gas or geothermal wells. Additionally, this invention may be used in drilling and mining wherein tunnels, pipe chases, foundation piers, holes or other penetrations or excavations are made through formations for purposes other than production of hydrocarbons or geothermal energy.
BACKGROUND OF THE INVENTION
The process of drilling a well bore or cutting a formation to construct a tunnel and other subterranean earthen excavations is a very interdependent process that preferably integrates and considers many variables to ensure a usable bore is constructed. As is commonly known in the art, many variables have an interactive and cumulative effect of increasing drilling costs. These variables may include formation hardness, abrasiveness, pore pressures and formation elastic properties. In drilling wellbores, formation hardness and a corresponding degree of drilling difficulty may increase exponentially as a function of increasing depth. A high percentage of the costs to drill a well are derived from interdependent operations that are time sensitive, i.e., the longer it takes to penetrate the formation being drilled, the more it costs. One of the most important factors affecting the cost of drilling a well bore is the rate at which the formation can be penetrated by the drill bit, which typically decreases with harder and tougher formation materials and formation depth. Consequently, drilling costs typically tend to increase exponentially with depth.
There have been many substantially varied efforts to meaningfully increase the effective rate of penetration (“ROP”) during the drilling process and to thereby reduce the cost of drilling or cutting formations by improving drill bit efficiency. Dr. William C. Maurer's book entitled, “Advanced Drilling Techniques” published by Petroleum Publishing Company in 1980 outlines several novel efforts in an attempt to address the issue of increasing the rate of penetration. Further, Dr. Maurer's book illustrates the tremendous interest, breadth of participation and significant money spent attempting to fulfill the long-felt need for substantially improving the ROP.
Three significant efforts of a sustained nature to meaningfully increase ROPs warrant discussion relating to this invention. The first two of these efforts involved high-pressure circulation of a drilling fluid as a foundation for potentially increasing the rate of penetration. It is common knowledge that hydraulic power available at the rig site vastly outweighs the power available to be employed mechanically at the drill bit. For example, modem drilling rigs capable of drilling a deep well typically have in excess of 3000 hydraulic horsepower available and can have in excess of 6000 hydraulic horsepower available while less than one-tenth of that hydraulic horsepower may be available at the drill bit. Mechanically, there may be less than 100 horsepower available at the bit/rock interface with which to mechanically drill the formation.
One of the first significant efforts at increasing rates of penetration was a promising attempt to directly harness and effectively utilize hydraulic horsepower at the drill bit by incorporating entrained abrasives in conjunction with high pressure drilling fluid (“mud”). This resulted in an abrasive laden, high velocity jet assisted drilling process. The most comprehensive work conducted in attempting to use drilling fluid entrained abrasives was conducted by Gulf Research and Development Company. This work is described in detail in a number of published articles and is the subject of many issued patents. This body of work teaches the use of abrasive laden jet streams to cut concentric grooves in the bottom of the hole leaving concentric ridges that are then broken by the mechanical contact of the drill bit. There was ample demonstration that the use of entrained abrasives in conjunction with high drilling fluid pressures caused accelerated erosion of surface equipment and an inability to control drilling mud density, among other issues. Generally, the use of entrained abrasives was considered practically and economically unfeasible. This work was summarized in the last published article titled “Development of High Pressure Abrasive-Jet Drilling,” authored by John C. Fair, Gulf Research and Development. It was published in the Journal of Petroleum Technology in the May 1981 issue, pages 1379 to 1388. Due to this discouraging terminal report, the industry has not meaningfully attempted to further investigate and develop a system to use abrasives for well bore drilling purposes.
A second significant effort to directly harness and effectively utilize the hydraulic horsepower available at the bit incorporated the use of ultra-high pressure jet assisted drilling. A group known as FlowDril Corporation was formed to develop an ultra-high-pressure liquid jet drilling system in an attempt to significantly increase the rate of penetration. FlowDril spent large sums of money attempting to commercially field a drilling system. The work was based upon U.S. Pat. No. 4,624,327 and is well documented in the published article titled “Laboratory and Field testing of an Ultra-High Pressure, Jet-Assisted Drilling System” authored by J. J. Kolle, Quest Integrated Inc., and R. Otta and D. L. Stang, FlowDril Corporation; published by SPE/IADC Drilling Conference publications paper number 22000. Further to the cited publication, it is common knowledge that the complications of pumping and delivering ultra-high-pressure fluid from surface pumping equipment to the drill bit proved both operationally and economically unfeasible. FlowDril Corporation is continuing development of an “Ultra-High Pressure Down Hole Intensifier” as a substitute technology in an effort to commercialize its product. Of note is the fact that FlowDril demonstrated that generating a kerf near the hole gage will produce increased efficiencies for the mechanical action of the drill bit. This is cited in the conclusions stated in the article titled “Ultra-High Pressure Jet Assist of Mechanical Drilling” authored by S. D. Veehuizen, FlowDril Corp; J. J. Kolle, Hydropulse L. L. C.; and C. C. Rice and T. A. O'Hanlon, FlowDril Corp. published by SPE/IADC Drilling Conference publications, paper 37579.
A third significant effort at increasing rates of penetration by taking advantage of hydraulic horsepower available at the bit was developed by the inventor who was issued U.S. Pat. No. 5,862,871 for the process. This development employed the use of a specialized nozzle to excite normally pressured drilling mud at the drill bit. The purpose of this nozzle system was to develop local pressure fluctuations and a high speed, dual jet form of hydraulic jet streams to more effectively scavenge and clean both the drill bit and the formation being drilled. It is believed that these novel hydraulic jets were able to penetrate the fracture plane generated by the mechanical action of the drill bit in a much more effective manner than conventional jet were able to do. Rate of penetration increases from 50% to 400% were field demonstrated and documented in the field reports titled “DualJet Nozzle Field Test Report—Security DBS/Swift Energy Company,” and “DualJet Nozzle Equipped M-1LRG Drill Bit Run”. The ability of the dual jet (“DualJet”) nozzle system to enhance the effectiveness of the drill bit action to increase the effective rate of penetration required that the drill bits first initiate formation indentations, fractures, or both. These features could then be exploited by the hydraulic action of the DualJet nozzle system.
Due at least partially to the effects of overburden pressure, formations at deeper depths may be inherently tougher to drill due to changes in formation pressures and rock properties, including hardness and abrasiveness. Associated in-situ forces, rock properties and increased drilling fluid density ef
Curlett Harry B.
Gregory Marvin Allen
Sharp David Paul
Browning & Bushman P.C.
Curlett Family Ltd Partnership
Helmreich Loren G.
Tsay Frank
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