Abstract

The paper is an update to the current status of laser drilling technique - the first fundamental change to rotary drilling. We begin with a brief note on history of physical tests in 60's and 70's which were limited by the laser technology and low power available at that time. Seven lasers have been identified for potential use in the upstream oil industry. Each rock type has a set of optimal laser parameters to minimize specific energy as observed in the linear track tests. Current efforts are focused on underwater laser drilling.

Next, stress has been put on the basic scientific principles that can bring laser drilling within reach of an industry-supported prototype. Hence, the methods of delivering laser radiation and rock removal from wells drilled followed by parameters like feasibility, economics, benefits and environmental impact related to laser drilling have been discussed.

Laser drilling is found to be more efficient, cleaner way to drill and perforate wells through hard rock formations encountered at greater depths. The effects of the laser rock interaction on permeability have also been studied. Laser perforation resulted in permeability improvements. One of the major advantages of laser drilling is its potential to reduce drilling time. Lasers cut drilling time by not contacting the rock, eliminating the need to stop and replace a mechanical bit. Finally, we end with a discussion on the wider scope of laser technology for on-site tasks including cutting windows for side exiting casing or laterals, extended perforations that connect additional reservoir rock to the well bore, and removal of objects lost down hole that would normally require drill out or fishing operations.

Introduction

Almost three decade old experiments and studies had declared laser drilling as technically unviable. The earliest studies were directed at enhancing tunneling machines used in mining industry by use of lasers. Lasers available at those times were of very low power, produced large wavelengths and were unsafe for industrial use. Naturally, laser drilling was never considered feasible for the oil industry either. There was a great resistance by the oil industry when cable tool drilling was replaced by the rotary drilling. It involved the huge efforts from the rich, powerful and influential innovative people to bring such a change in the drilling practices. Laser drilling technique will have to cross major obstacles before it can be accepted as the first fundamental change to rotary drilling methods.

Laser

The Laser devices are those which convert one form of energy into photons which are electro magnetic radiations. Advances in laser technology supplemented by research and experimentation on laser-rock-fluid interactions have launched laser drilling as a bright option for the oil community. Following seven lasers have been identified to be useful from the oil industry perspective [2]:

  1. Hydrogen Fluoride and Deuterium Fluoride Laser:These have operating wavelength range of 2.6 - 4.2 micrometer. MIRACL was used for reservoir rocks test.

  2. Chemical Oxygen Iodine Laser:Operates at wavelength of 1.315 micrometer. It is possible to destroy missiles with its help that too with a great precision and high range. Such high precision and range can be successfully used to tackle a number of well problems.

  3. Carbon dioxide Laser:Operates at wavelength of 10.6 micrometer with average power of 1MW. It can operate in both continuous and pulsed wave mode. However, because of its large wavelength, attenuation occurs through fiber optics.

  4. Carbon monoxide Laser: Operates at wavelength of 5–6 micrometer. It can also operate in both continuous and pulsed wave mode. Its average power is 200KW.

  5. Free Electron Laser: In CW mode, this can be tuned to any wavelength and is considered as high power laser for future. Thus its wavelength can be adjusted in case of reflection, blackbody radiation, etc.

  6. Neodymium: Yttrium Aluminum Garnet Laser:Operates at 1.06 micrometer wavelength with power of 4KW.

  7. Krypton Fluoride (excimer) Laser:Operates at 0.248 micrometer wavelength with power of 10KW. It can be operated in RP mode. In this laser, the atoms of Krypton and Fluoride in KrF molecule are in excited state.

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