Neal G. Skinner

Rock removal using high-power lasers for petroleum exploitation purposes

This paper describes the experimental results of selective rock removal using different types of high power lasers. US military owned continuous wave laser systems such as MIRACL and COIL with maximum powers of 1.2 MW and 10 kW and wavelengths of 3.8 and 1.3 mm respectively, were first used on a series of rock types to demonstrate their capabilities as a drilling tool for petroleum exploitation purposes. It was found that the power deposited by such lasers was enough to drill at speeds much faster than conventional drilling. In order to sample the response of the rocks to the laser action at shorter wavelengths, another set of rock samples was exposed to the interaction of the more commercially available high power pulsed Nd:YAG laser. To isolate the effects of the laser discharge properties on the rock removal efficiency, a versatile 1.6 kW Nd:YAG laser capable of providing pulses between 0.1 millisec and 10 millisec in width, with a maximum peak power of 32 kW and a variable repetition rate between 25 and 800 pulses/sec was chosen. With this choice of parameters, rock vaporization and melting were emphasized while at the same time minimizing the effects of plasma shielding. Measurements were performed on samples of sandstone, shale, and limestone. It was found that each rock type requires a specific set of laser parameters to minimize the average laser energy required to remove a unit volume of rock. It was also found that the melted material is significantly reduced in water saturated rocks while the drilling speed is still kept higher than conventional drilling.

Downhole fiber optic sensing: the oilfield service provider’s perspective

There is increasing interest in the petroleum industry in the application of fiber-optic sensing techniques. In this paper, we review which sensing technologies are being adopted downhole and the drivers for this deployment. We describe the performance expectations (accuracy, resolution, stability and operational lifetime) that the oil companies and the oil service companies have for fiber-optic sensing systems. We also describe the environmental conditions (high hydrostatic pressures, high temperatures, shock, vibration, crush, and chemical attack) that these systems must tolerate in order to provide reliable and economically attractive reservoir-performance monitoring solutions.

Laser Drilling: Drilling with the Power of Light Phase 1: Feasibility Study

A laser drilling research team was formed from members of academia, industry and national laboratory to explore the feasibility of using modern high-powered lasers to drill and complete oil and gas wells. The one-year Phase 1 study discussed in this report had the goals of quantifying the amount of pulsed infrared laser energy needed to spall and melt rock of varying lithologies and to investigate the possibility of accomplishing the same task in water under atmospheric conditions. Previous work by some members of this team determined that continuous wave lasers of varying wavelengths have more than enough power to cut, melt and vaporize rock. Samples of sandstone, limestone, and shale were prepared for laser beam interaction with a 1.6 kW pulsed Nd:YAG laser beam to determine how the beams size, power, repetition rate, pulse width, exposure time and energy can affect the amount of energy transferred to the rock for the purposes of spallation, melting and vaporization. The purpose of the laser rock interaction experiment was to determine the threshold parameters required to remove a maximum rock volume from the samples while minimizing energy input. Absorption of radiant energy from the laser beam gives rise to the thermal energy transfer required for the destruction and removal of the rock matrix. Results from the tests indicate that each rock type has a set of optimal laser parameters to minimize specific energy (SE) values as observed in a set of linear track and spot tests. In addition, it was observed that the rates of heat diffusion in rocks are easily and quickly overrun by absorbed energy transfer rates from the laser beam to the rock. As absorbed energy outpaces heat diffusion by the rock matrix, local temperatures can rise to the melting points of the minerals and quickly increase observed SE values. The lowest SE values are obtained in the spalling zone just prior to the onset of mineral melt. The current study determined that using pulsed lasers could accomplish removing material from rock more efficiently than continuous wave lasers. The study also determined that reducing the effect of secondary energy absorbing mechanisms resulted in lower energy requirements in shale and, to some extent, in sandstones. These secondary mechanisms are defined as physical processes that divert beam energy from directly removing rock, and may include thermally-induced phase behavior changes of rock minerals (i.e., melting, vaporization, and dissociation) and fractures created by thermal expansion. Limestone is spalled by a different mechanism and does not seem to be as affected by secondary mechanisms. It was also shown that the efficiency of the cutting mechanism improved by saturating porous rock samples with water, and that a laser beam injected directly through a water layer at a sandstone sample was able to spall and melt the sample.

Adapting optical technology to dynamic energy prices: fiber-optic sensing in the contemporary oil field

The oil and gas industry is continually striving to produce more hydrocarbons and reduce waste. Many sensing techniques using optical fiber have been developed over the last three decades for all stages of well development. This paper reviews these optical sensing technologies, with emphasis on new applications and business drivers. Expected performance parameters of these new technologies are discussed, including their accuracy, resolution, stability, and operational lifetime. Environmental conditions, such as high temperatures, shock, vibration, crush, and chemical exposure, are also discussed. These optical technologies are expected to provide safe, reliable, cost-effective, and unprecedented monitoring solutions.

Downhole fiber optic sensing: the oilfield service provider's perspective: from the cradle to the grave

For almost three decades, interest has continued to increase with respect to the application of fiber-optic sensing techniques for the upstream oil and gas industry. This paper reviews optical sensing technologies that have been and are being adopted downhole, as well as their drivers. A brief description of the life of a well, from the cradle to the grave, and the roles fiber-optic sensing can play in optimizing production, safety, and protection of the environment are also presented. The performance expectations (accuracy, resolution, stability, and operational lifetime) that oil companies and oil service companies have for fiber-optic sensing systems is described. Additionally, the environmental conditions (high hydrostatic pressures, high temperatures, shock, vibration, crush, and chemical exposure) that these systems must tolerate to provide reliable and economically attractive oilfield monitoring solutions are described.