Geophysical Connections: The Power to Provide
By Lynda Nolen, Bishop & Associates Inc.

Start your car, turn up the heat, or jump into a hot shower. For most of us, these simple operations all entail the use of oil or natural gas. What most of us don’t realize is the vast amount of money, time, and manpower that is involved in providing the world with an uninterruptible supply of both of these precious commodities.

In 2011, it is estimated that aggregate capital expenditures on global oil and gas exploration will reach almost $490 billion, close to an 11% increase over 2010. Although in most countries, the economic downturn of 2009 reduced year-over-year demand, the astonishing rebound in 2010 has once again sent oil and gas prices climbing. Present estimations indicate global demand for oil and gas will grow at over 2% yearly for the next five years, with the greatest demand coming from emerging economies. A key factor in the sustainability and growth of this industry sector has been improvements in exploration, production, and processing activities. Among these improvements has been the increase in electronic content.

Today, the use of electronics has encroached on all aspects of the geophysical market, from seismic exploration to production to processing. Key among these electronic improvements is the use of connectors to transfer both signal and power. Connectors are found in numerous applications in the geophysical industry. One of the most predominate is in the field of seismic exploration.

Seismic exploration is the search for subsurface deposits of crude oil, natural gas, or minerals. It involves the recording, processing, and interpretation of non-natural or artificial shock waves induced below the earth’s surface. These shock waves allow seismic surveys to be produced that detail the underground structure of a particular area. In seismic exploration, seismic energy is recorded digitally and then transferred above ground, where it is converted to an analog signal for interpretation.

 Seismic exploration can be performed on land or in a marine environment. There are two primary types of seismic exploration deployed in geophysical applications. One involves refraction technology, while the other involves reflection technology. Refraction seismology is based on the arrival time of the initial, artificially induced burst of seismic energy at a variety of distances. It measures the way sound waves bend as they encounter different layers of the earth. Reflection seismology concentrates on the movement of the ground after the initial ground motion. It analyzes the reflection from subsurface interfaces, including their angle of inclination, similar to echo sounding used in radar systems and submarines. Although reflection seismology is more expensive than refraction to perform, because of the high cost associated with oil and gas excavation, and the fact reflection seismology provides more detailed information, it is the primary type of exploration used in geophysical applications.

In land exploration, artificial seismic energy, and in turn, sound waves, are created by either pounding the earth’s surface with a vibrator or thumping truck or by exploding small dynamite charges in shallow holes called boreholes. Borehole logging, also referred to as well-hole logging, allows very sensitive probes to be dropped below the earth’s surface, so that a variety of information can be obtained. This information includes subsurface temperature, depth of water table, location and altitude of fractures, sediment porosity/permeability, and formation thickness. The instruments that gather this information are called geophones or seismometers. Geophones act as the receivers, listening and recording the sound waves as they return. By comparing the rate and the strength of the sound waves generated by the artificial seismic energy that is reflected back from the underlying rocks, with the exact time and location of the source and the location of the geophones, detailed information can be gathered.

In marine exploration, similar to land exploration, specially designed instruments called hydrophones gather the information that is passed on for analysis. Unlike land exploration, where the seismic energy is generated by thumping or small dynamite charges, in marine applications, sound waves are generated using compressed air or water, and shot from guns. As the sound waves are reflected off of the various sub-bottom sediment layers, their signals are recorded by the hydrophones. In both land and marine geophysical exploration, transducers, either motion sensor type or pressure response type, are used to convert the seismic energy into the electrical signals that are passed through the connectors to the recording and analyzing equipment.

Hydrophones are generally configured in three basic formats. The first format consists of hydrophones arranged in a pattern on a submerged surface, and is often referred to as surface reference. The second format has the hydrophones bottom-mounted in lines or grids and is commonly referred to as bottom reference. The third format, which is commonly referred to as submerged buoyant or streamers, consists of an array of hydrophones mounted to a flexible hose that is towed through the water. Each of the different formats is designed for a specific water depth, sea bed condition, and type of data gathering. The third format, streamers, is the most prevalent in marine exploration.

Streamers are composed of several sections coupled together by special connectors that provide the mechanical, electrical, and/or optical continuity for the conductor pairs from the hydrophones and the depth transducers. The section closest to the boat is classified as the lead-in section, while the sections between the live sections, which carry the hydrophones and transducers, are classified as strength members, and extend the length of each streamer section from one live section to the next. Streamers are assembled in sections, with each section approximately 75 meters long. Extended end to end, streamers often are thousands of meters long.

In addition to geophysical exploration, connectors also play a crucial role in many other geophysical applications. Connectors are used extensively in reservoir monitoring. Using different types of sensors, connectors provide information on pressure, flow, and resistivity, ensuring that wells are operating efficiently and safely. They are used in artificial lift systems and blowout preventer systems, and on pumps, oil rigs, and drilling platforms, This does not even include the number of connectors used in refinery operations, many which have to carry ATEX or IECEx approval.

Connectors used in geophysical applications all must be able to withstand the rigors of a harsh, often brutal, environment. Connectors used in land exploration and drilling applications often must be capable of handling both low (-55°C) and high temperatures (+200°C), and high pressure (25,000 PSI). Connectors used in marine exploration and drilling applications, in addition to low/high temperature and pressure situations, must be able to offer complete protection from the ingress of water, plus handle the effect of salt water and other corrosive mediums. Although the equipment used to gather the information, whether in a stationary land location or aboard a vessel, is often protected from these temperature, pressure, and corrosive extremes, the connection must still be rugged enough to handle other factors, such as vibration and moisture.

Based on specific applications, connectors used in geophysical applications include:

  • Mil-spec type circular connectors with bayonet or threaded coupling

  • Push/pull circular connectors

  • Industrial M12-type connectors

  • Single and multi-pin standard and hermetically-sealed, feed-through connectors

  • Rectangular I/O connectors, including micro-miniatures, USB, RS232, and RS422

  • Ethernet connectors

  • Severe duty, fiber optic connectors

  • RF connectors

  • Terminal blocks

Many connectors, because of their intended application, are pre-assembled by the connector manufacturer as overmolded cable assemblies. Others are field or customer terminated. Special accessories, like rubber boots that protect engagement threads from corrosion, and locking mechanisms that prevent disengagement of energized connectors, are also used extensively.

 

Irrelevant of the application, the use of high-grade harsh environment connectors in geophysical applications will continue to grow. What is going to drive specific connector types will be the goal to improve and increase production, as reserves become smaller and more complex. Other factors that will also increase connector usage will be growing pressure to protect the environment, demanding greater and more sensitive monitoring systems, as well as the desire to embed control and communication features into existing products. Although fiber optic connectors and cable assemblies presently represent a very small percentage of the connector types used, the benefits fiber offers, including increased signal capacity in smaller wire bundles, immunity to crosstalk, electrical isolation, and the ability to withstand higher temperatures than standard logging tools, will increase demand, over time.

Lynda Nolen
Product Specialist, Bishop & Associates Inc.
 Lynda Nolen has been in the interconnect industry for over 30 years. She has worked in sales, sales management, marketing, and product management for such companies as TRW Electronics Components Group, Sunbelt Components, Cinch Connectors, Arrow Electronics, PEI Genesis, and Delphi Interconnect. Nolen has extensive experience in competitive cross-referencing, drawing, web and catalog review, new product introduction programs, harness and connector assembly programs, account management, and customer service programs. Lynda received her Bachelor of Arts degree from Roger Williams University in Rhode Island in 1979, and has completed various electrical engineering courses.

 
 
 
 
 

Bishop & Associates, Inc. © 2011