Laser communications can enable more efficient and higher bandwidth communications across longer distances than conventional radio frequency (RF) systems. However, beam divergence angles for laser systems are narrower than typical RF systems, and require precise pointing, acquisition, and tracking systems to establish and maintain the link. In addition, typical lasercom links are point-to-point, and not capable of multicast or broadcast. Conventional pointing and tracking (PAT) systems use mechanical gimbals or fast-steering mirrors. Mechanical gimbals may not meet the size, weight, and power (SWaP) constraints for small spacecraft, particularly for multiple concurrent spatially diverse beams. Fast-steering mirrors while compact and efficient have limited aperture size, and many would be needed to provide multiple links over a hemisphere.The Miniature Optical Steered Antenna for Intersatellite Communications (MOSAIC) aims to provide nonmechanical pointing and tracking using liquid lenses, allowing a wide field-of-view and support for multiple concurrent links. Initial work with commercially available liquid lenses showed that liquid lenses can be used in a space environment and assessed spatial coverage. In this work, we model a transmitter using three liquid lenses. One on-axis lens provides focusing capability. Two off-axis and perpendicular lenses provide beam steering, with a fisheye lens amplifying the effect. This provides near-hemispherical pointing up to 170 degrees. We investigate beam quality and divergence using a Zemax model and conduct a link analysis dependent on the beam steering angle and rotation angle. A 25 Mbps link with 200 mW transmit power at 1550 nm (optical C band) and 16-ary pulse position modulation (16-PPM) can be maintained up to 28 km separation with 3 dB margin for an Optotune EL-16-40-TC liquid lens. Losses are primarily due to the liquid lenses limiting aperture size to 16 mm. We also consider the impact of diffusers for increasing numerical aperture through a simple ray transfer analysis and experimental results.
This paper discusses a stimulation optimization case history in the STACK (Sooner Trend, Anadarko Basin, Canadian, and Kingfisher counties of Oklahoma). This area has been active for a number of years, and operators are still trying to figure out how best to drill and complete the asset. This case history will cover a field trial conducted in the Meramec, the Sycamore and the Woodford, and will compare the completion methods of two offset pads, with one pad serving as the pre-optimization offset. These field trials consisted of wellbore spacing tests as well as the implementation of certain design and execution changes. The first major design change was the implementation of an algorithm-based, automated controlled breakdown process designed to improve the uniformity and the cluster efficiency of given stimulation treatments. When stimulations are conducted, it has been consistently demonstrated that a disproportionate number of perforation clusters are not effectively treated during any given stimulation treatment. The implementation of a controlled breakdown process not only allows for a better stimulation efficiency, but also allows for consistent treatment operations across stages and wellbores. The second design change was the application of ultra-fine particulates (UFP) during the initial pad stages of stimulation treatments. Unconventional reservoirs contain some level of complexity in the form of microfractures. Conventional proppants are typically too large to prop those microfractures, which limits how much hydrocarbon can be produced from a given reservoir. UFPs are small enough to enter those microfractures. Likewise, UFPs have been shown to reduce near wellbore friction early in stimulation treatments, which improves operational efficiencies. The third design change was the utilization of a wellhead connection system in place of a traditional zipper manifold. This system reduces equipment on location as well as the complexity of operations when stages on two or more wells are being stimulated in sequence. The operational changes on the post-optimization pad yielded increased efficiencies and reduced costs. The wells also showed a substantial production improvement over the typical curves for the area. The post-optimization wells had a higher rate of return over the pre-optimization pad. The wells where the automated controlled breakdown process was utilized demonstrated a 5 to 15% production increase over comparable offsets on the same pad. The wellhead connection system improved transition times between wellhead swaps during well zipper stimulation operations. The implementation of the breakdown process, the wellhead connection system, and UFPs improved operational efficiencies as well as making treatments more consistent. Observed treating pressures were lower and more consistent when the breakdown process was utilized. This paper demonstrates how the implementation of a controlled breakdown process, wellhead connection system, and UFPs can help improve well economics. Also, the economic potential for the STACK when utilizing an optimized completion is demonstrated.
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