Borehole communication via drill strings in oil wells

The performance of multichannel and single channel accelerometers used as uphole communication receivers is studied. Using measured channels from the drill string testbed, it is shown that one tri-axial accelerometer can provide nearly uncorrelated signals when compared to two single channel accelerometers. Having uncorrelated signals at the uphole receiver provides a diversity which in turn can lead to an increase in the communication system performance. The use of a strain sensor as a receiver in borehole communication is proposed. Using measured channels from the drill string testbed, the performance of a strain receiver with a single-accelerometer receiver is compared. The results show that the strain receiver has better performance than the single accelerometer receiver, and is further demonstrated that the strain channel impulse response has a better structure than a single-accelerometer channel impulse response. Furthermore, the multichannel reception using several receivers with the aim of improving communication system performance is studied. The combination of a strain sensor and a tri-axial accelerometer as a four-channel receiver is proposed. Given the complexity of studying the strain channel and the three acceleration channels analytically, experiments are conducted to obtain these channel impulse responses. The channel measurements show that these wireless channels are nearly uncorrelated and therefore can provide a diversity gain. This is further confirmed by the low bit error rates that this system provides. Comparison with single channel receivers shows the usefulness of the proposed system for wireless communication via drill strings

Acoustical Communications for Wireless Downhole Telemetry Systems

This dissertation investigates the use of advanced acoustical communication techniques for wireless downhole telemetry systems. Using acoustic waves for downhole telemetry systems is investigated in order to replace the wired communication systems currently being used in oil and gas wells. While the acoustic technology offers great benefits, a clear understanding of its propagation aspects inside the wells is lacking. This dissertation describes a testbed that was designed to study the propagation of acoustic waves over production pipes. The wireless communication system was built using an acoustic transmitter, five connected segments of seven inch production pipes, and an acoustic receiver. The propagation experiments that were conducted on this testbed in order to characterize the channel behavior are explained as well. Moreover, the large scale statistics of the acoustic waves along the pipe string are described. Results of this work indicate that acoustic waves experience a frequency- dependent attenuation and dispersion over the pipe string. In addition, the testbed was modified by encasing one pipe segment in concrete in order to study the effect of concrete on wave propagation. The concrete was found to filter out many of the signal harmonics; accordingly, the acoustic waves experienced extra attenuation and dispersion. Signal processing techniques are also investigated to address the effects of multipaths and attenuation in the acoustic channel; results show great enhancements in signal qualities and the usefulness of these algorithms for downhole communication systems. Furthermore, to explore an alternative to vibrating the body of a cemented pipe string, a testbed was designed to investigate the propagation aspects of sound waves inside the interior of the production pipes. Results indicate that some low-frequency sound waves can travel for thousands of feet inside a cemented pipe string and can still be detected reliably

Applications of aerospace technology to petroleum extraction and reservoir engineering

Through contacts with the petroleum industry, the petroleum service industry, universities and government agencies, important petroleum extraction problems were identified. For each problem, areas of aerospace technology that might aid in its solution were also identified, where possible. Some of the problems were selected for further consideration. Work on these problems led to the formulation of specific concepts as candidate for development. Each concept is addressed to the solution of specific extraction problems and makes use of specific areas of aerospace technology

DOWNHOLE RF COMMUNICATION: CHARACTERIZATION AND MODELING OF WAVEGUIDE PROPAGATION IN A FLUID-FILLED DRILL PIPE

Current technologies for downhole communication in oil and gas drilling applications are severely limited in data rate and latency. This work proposes that a system based upon guided wave propagation could be designed to utilize a wireless, radio frequency (RF) signal to yield tens of megabits per second of data transfer. To determine the feasibility of the proposed system, a test setup was built to measure attenuation of RF signals transmitted through a pipe filled with various drilling fluids. A finite element analysis model was also built to further investigate waveguide propagation of electromagnetic signals in a fluid filled pipe. The measurement setup was validated using fluids of known dielectric properties. A number of a drilling base fluids and oil-based fluids were measured and their dielectric properties calculated. The feasibility of the proposed communication system is not promising for liquid based fluids. However, there is significant potential in an air-based system

A Survey on Subsurface Signal Propagation

Wireless Underground Communication (WUC) is an emerging field that is being developed continuously. It provides secure mechanism of deploying nodes underground which shields them from any outside temperament or harsh weather conditions. This paper works towards introducing WUC and give a detail overview of WUC. It discusses system architecture of WUC along with the anatomy of the underground sensor motes deployed in WUC systems. It also compares Over-the-Air and Underground and highlights the major differences between the both type of channels. Since, UG communication is an evolving field, this paper also presents the evolution of the field along with the components and example UG wireless communication systems. Finally, the current research challenges of the system are presented for further improvement of the WUCs

SeisCORK engineering design study

The goal of SeisCORKs is to make simultaneous and co-located seismic, pressure, temperature, pore water chemistry and pore water biology measurements in the seafloor. We want to see the small events in the vicinity of the borehole for three reasons: 1) After an event fluid may flow in the formation in response to the changing stress regime. Down to what magnitude of event do the pressure transients in the well respond? 2) Fluid flow causes small earthquakes. One mechanism for example is by changing the temperature of the rocks which expand and contract, altering the stress regime. We want to look for this fluid flow. 3) Laboratory studies of rock deformation show that shear fracture is preceded by the coalescence of interacting tensile microcracks which are observed as “acoustic emissions”. By placing high frequency geophones next to faults it may be possible to observe these “acoustic” precursors to rock failure. Since in reservoirs on land small events appear in the frequency band 400-800Hz, no one has yet tried to observe them in oceanic crust. SeisCORKs also obviate the considerable logistical, administrative, and clearance difficulties associated with scheduling a shooting ship to run offset VSPs. We resolved to start with a “tubing conveyed” SeisCORK configuration consisting of four three-component sondes at 50m separation lowered on the outside of 4.5in casing (or drill pipe) inside 10-3/4in casing.Funding was provided by the National Science Foundation under Contract Nos. OCE-0221832 and OCE-0450318

Making risk-informed decisions to optimize drilling operations using along string measurements with Wired drill pipe a high-speed, high-quality telemetry alternative to traditional mud pulse telemetry.

The ever-increasing demand for energy resources has led to drilling more complex and challenging wells. The information required to navigate through these complex geologies is provided by highly sophisticated sensors embedded in logging-while-drilling and measurements-while-drilling downhole tools. These combined with rotary steerable systems have made it possible to drill highly deviated, extended reach, and multilateral wells with high precision. Drilling operations can be considered high-risk operations due to the large number of sources that can lead to undesirable outcomes. Therefore, data transmission from downhole sensors and communication with downhole tools is vital to drill safely and successfully a well. Mud-pulse telemetry is the most used telemetry method to transmit the data from downhole tools to the surface. However, advancements in sensor technology and the development of new tools have resulted in higher amounts of data needed to be transmitted to the surface to take advantage of the resolution they now provide fully. The reliance on mud-pulse telemetry, which offers relatively low data transmission speed and broadband, has been the limiting factor, often sacrificing higher drilling rates to obtain the required data quality. The introduction of wired drill pipe, capable of delivering bi-directional telemetry at speeds up to 10.000 times faster than traditional mud-pulse, has removed the reliance on mud-pulse, making it possible to obtain memory-mode quality real-time data. Wired drill pipe also enables the use of along string measurements. These measurement tools are placed along the string and gather pressure, temperature, and drilling dynamics data. Thus, it is now possible to understand the downhole environment along the wellbore and not just a few meters behind the bit. This makes it possible to timely identify well control and well stability events, thereby making risk-informed decisions to mitigate the risk of hazardous events and additionally optimizing drilling operations. The objective of this thesis is to provide a description of the drilling process and the tools that have made it possible to drill the wells that nowadays are drilled. Further, it describes different telemetry methods but focuses on mud-pulse telemetry and its limitations. Then, the wired drill pipe system is extensively described, and it is presented the way it allows the integration of measurement tools along the string. Furthermore, it is shown how these tools enable making risk-informed decisions to reduce the risk during drilling operations. The result is safer drilling operations to be achieved while also saving time by reducing the telemetry time, preventing tool failures, and avoiding resource-demanding well remediation operations. Finally, it is discussed how the availability of real-time high-quality data and full bi-directional instantaneous communication with downhole tools has enabled a step towards more automated drilling operations. The combination of high-speed data transfer with machine learning and artificial intelligence has made it possible to develop autonomous drilling services capable of optimizing the well path and reducing well times