The Search for Oil and Gas

The digital recording and processing of seismic data in the oil industry took quantum leaps in the mid-1960s, making possible a new method of interpretation by allowing geophysicists to measure the “relative wave amplitudes” between seismic traces for the first time.  Up to that point, seismic techniques only helped map subsurface structures and identify possible oil traps.  Operators still had to take the risk of drilling to find oil and gas.  But the new digital seismic data offered the enticing possibility of directly detecting hydrocarbons on the seismic record.  “Direct detection” was based on the principle that the acoustic impedance of a loosely cemented rock filled with hydrocarbons was different from that of a similar water-filled rock, and with advanced digital methods, this difference often could often be detected as an “amplitude anomaly” or “high-amplitude reflection” on the seismic record.  Shell Oil and Mobil Oil were the first companies to identify and quantify such anomalies, and factor them into their bids for offshore leases.  Mobil referred to them as “hydrocarbon indicators.”  Shell called them “bright spots,” a term widely adopted in the industry.

The bright spot story at Shell Oil began with  the 1967 offshore Louisiana and 1968 offshore Texas lease sales.  In mapping the subsurface structure on Prospect 370 using some of the best seismic data available at that time, Mike Forrest, a staff geophysicist in New Orleans, observed what he called a “strong seismic reflector” on the top of the structures, where production would most likely be found.  He also observed strong seismic reflectors on the crests of structures in the Plio-Pleistocene trend in both offshore Texas and Louisiana.  In the spring of 1969, he produced a study that correlated the seismic data on six to eight fields with well logs.  Shell’s exploration vice president R.E. McAdams ordered the Exploration and Production Research Center (EPRC) on Bellaire Blvd. in Houston to establish an Amplitude Analysis Project team in the Basic Measurements and Theory Section at the Bellaire lab to test and verify Forrest’s empirical observations.  Dr. David DeMartini, a EPRC researcher assigned to the New Orleans office to help understand the physics, did early calibration studies using wireline log measurements of velocity and density and wrote computer programs to calculate the expected effects of fluid substitution on porous rock densities, wave velocities and reflection coefficients using Gassmann’s equation and also to interpret the probabilities of various fluid saturants from calibrated seismic amplitude measurements and these calculated values using Bayes’ rule in late 1969 and 1970.  Gene McMahan also did calibration studies in 1969 and 1970 and was the first person to casually use the term “bright spot.”  During this same period, management spread the technique of bright spot interpretation to other exploration divisions with mixed success.

In the December 1970 federal lease sale offshore Louisiana, Shell Oil exploration managers applied bright spot evaluation for the first time, in a significant way, in its offshore bidding.  Under the leadership of Geophysics Manager Dick Grolla, Aubrey Bassett, a geophysicist in the offshore division, wrote a program to quantify the amplitude changes and gas sand thickness so potential oil and gas reserve estimates could be made.  Leighton Steward, the 1970 Geologic Lease Sale Coordinator, used bright spot interpretation to estimate oil and gas reserves on the Eugene Island 330 prospect, which would become the largest field discovered in federal waters on the Louisiana-Texas shelf.  In preparation for the  next major sales, in September and December 1972, researchers at the Bellaire laboratory improved deconvolution and made correlations with velocity and density logs from wells and also demonstrated the quantitive predictions of Gassmann’s equation with ultrasonic frequency velocity measurements made on cores.

Over the next several years, bright spot technology improved considerably and became a very reliable tool for exploration in all geologic provinces and at greater depths than initially thought.  Shell Oil scanned almost every prospect in the Gulf of Mexico for bright spots and made bids based on quantitative measurements of seismic amplitude and sand thickness.  By reducing the potential for drilling a dry hole and modifying the weighting of risk, bright spot interpretation allowed Shell to put more money into its lease bids and more than make up for it in decreased drilling costs.

The Mobil story began in 1964, when a production geologist working in Mobil’s New Orleans Division wrote a letter regarding the correlation between high-amplitude reflections and a major producing zone in the South Marsh Island Block 23 field.  Mobil geophysicists later noted other high-amplitude reflections associated with structural culminations on prospects offered in several state and federal lease sales between 1965 and 1970.

In early 1970, Bob Hirsch, Mobil’s New Orleans Division Exploration Manager, organized a meeting in New Orleans to review evidence for the direct detection of hydrocarbons on seismic data.  Attendees included Sandy Blattner, Chief Geophysicist New York; Dr. Al Musgrave with the Exploration Services Center (ESC); and Dr. Bob Watson with the Field Research Laboratory (FRL).  A task force was formed for the purpose of developing specific criteria for recognizing and grading what were to be called, at Blattner’s suggestion, Hydrocarbon Indicators or HCI’s.  ESC and FRL agreed to the development of special date processing programs for amplitude preservation and polarity identification.

A follow-up meeting held in Dallas during the summer of 1970 included attendees from most of Mobil’s larger exploration offices.  Examples of HCI’s from the Gulf of Mexico and offshore Nigeria were shown.  Later meetings included data from other locales with examples of phase-shift and dim-out anomalies.  Mobil’s bids at the December 1970 and subsequent Gulf of Mexico lease sales were almost exclusively based on probabilistic reserve estimates derived from HCI’s.

A number of geoscientists and managers contributed to Mobil’s HCI program.  Notable were Sandy Blattner, Al Musgrave, Bob Watson, Bob Hirsch, Offshore Texas Division Exploration Manager (1972-1975) and Corporate Exploration Manager (1975-1976), Graves Noble, Division Geophysicist in New Orleans (1966-1972) and Regional Geophysicist after 1972, and Lou Kihneman, who followed Hirsch in both New Orleans and Houston exploration managerial positions.  As at Shell, other geologists, geophysicists, engineers, data processors, and researchers also were involved in HCI related activities.  Especially important were the multidisciplinary task forces responsible for various modeling programs including an industry bid model.

Once the technology of bright spots or HCI’s was embraced, it had a giant impact on offshore exploration in the Gulf.  Shell and Mobil first to put money behind the technology in lease sales held in late 1970.  Other companies eventually caught on, helping the industry discover and economically develop fields in water depths extending out to 1,000 feet.  Decreased overall exploration costs afforded by the technology allowed companies to spend more on innovative production technologies, building ever larger steel-jacket fixed platforms in deeper water.

Recognizing the pioneering efforts of the following individuals and companies who contributed to the development of this technology:

Aubrey Bassett, David DeMartini, Mike Forrest, Gene McMahan, H. Leighton Steward, Shell Oil Company; Sanford “Sandy” Blattner, H. Robert Hirsch, Lou Kihneman, Albert “Al” Musgrave, Graves Noble, Bob Watson, Mobil Oil (now ExxonMobil)

The first commercial marine 3D survey was conducted in 1975 by Sun Oil Company and Geophysical Service Inc. (GSI), a division of Texas Instruments (TI). Four technologies enabled the survey, credited as the key to deepwater offshore exploration: First, Dr. Milo Backus of GSI developed 3D seismic technology that enabled use of TI’s Automatic Scientific Supercomputer.

Second, the previously-developed marine Air Gun, was made technically practical by Ben F. Giles who spearheaded the effort to make it work in the field environment.

Third, were software tools required to process the massive volume of data recorded. Performing the research and developing the initial modules were Dr. William A. Schneider and Edward R. Tegland.

Finally, Marvin Murphy placed sensitive compasses in the marine streamer to transmit real-time information about its location as it was towed behind the seismic vessel.

These technologies, combined into a functional system, enabled marine 3D seismic. R. J. Graebner, the technology coordinator, and M. E. Trostle, the operations coordinator, entered into an agreement with Charles (Chuck) Kiely of the Sun Oil Company to achieve the first successful commercial marine 3D survey.

Recognizing the pioneering efforts of the following individuals and companies who contributed to this technology:

Dr. Milo Backus, Ben F. Giles, Robert J. Graebner, Charles (Chuck) Kiely, Marvin Murphy, Dr. William A. Schneider, Edward R. Tegland, and M.E. (Shorty) Trostle, Geophysical Service Inc. (Texas Instruments Inc.), and Sun Oil Company (Kerr McGee Corp.)

The geophysical (seismic) recorded signal in three dimensions requires a mathematical adjustment (migration) prior to use in determining potential drill locations. This adjustment, which involves many thousands of computations, requires significant computational power and speed. Prior to the introduction of digital computers into the oil and gas exploration, this process performed on geophysical data recorded in two dimensions was accomplished utilizing non-computer-aided methods. Donald W. Rockwell recognized the requirements and the value of this adjustment and visualized how it could be accomplished. His early original work toward this filed in 1964 resulted in him being granted an U. S. Patent in 1967 (#3,353,151). His patent provided building blocks for the early computer implementation of the mathematical adjustment and its refinement and widespread extensive use in current oil and gas exploration and production activities around the world continue to validate this important development.

Recognizing the pioneering efforts of the following individuals and companies who contributed to the development of this technology:

Donald W. Rockwell

Marine explorationists conduct seismic surveys using reflected sound waves to create an image of the underlying structures. Beginning with simple, 2-dimensional cross sections, the technology has evolved to detailed 3-dimensional seismic images that model the subsurface. Explorationists use the model to decide where to drill. Currently, engineers study the changes in the seismic images over time (so-called 4-D) to track the migration of hydrocarbon through the reservoir. The development of this science has resulted in increasing the probability of finding oil, and in more productive wells. Milo M. Backus at Geophysical Services Inc., later Texas Instruments, played a central role in GSI’s introduction of digital seismology (‘the digital revolution’), and later in GSI’s introduction of high density 3-D seismic surveying. Backus later taught at the University of Texas directing research into the extraction of exploration information from 3-D seismic data, with an emphasis on direct detection of hydrocarbons.

Recognizing the pioneering efforts of the following people and companies who contributed to the development of this technology:

Milo M. Backus Geophysical Services Inc. (now Transocean), University of Texas

In July 1950, a patent was filed for a seismic technique which greatly increased the number of recordings taken from a single reflection point.  These multiple common depth point recordings significantly increased the clarity of the subsurface images by combining or stacking these recordings to reduce noise and multiple reflections.  The technique is recognized as one of the top innovations of seismic technology.  W. Harry Mayne at Petty-Ray Engineering (later Petty-Ray Geophysical) was recognized as having directed this development and many subsequent innovations that dramatically improved the recordings of seismic images.

Recognizing the pioneering efforts of the following people and companies who contributed to the development of this technology:

W. Harry Mayne
Petty-Ray Geophysical (Baker Hughes)

With the development of the 3D seismic field recording and processing capabilities in the early 70s, came the opportunity to develop and implement, in 3D, the imaging of subsurface formation layers using advance computer and software algorithms.  Prior imaging algorithms only allowed the imaging of the subsurface in 2D, which often lacked sufficient clarity in highly complex areas.  The 3D concept of subsurface imaging initially took basically two different paths with the first method employing a multi-step algorithm, which involved imaging closely space parallel lines of seismic data extracted from the recorded 3D data volume.  These intermediate 2D image results were then re-oriented into parallel extracted lines in a perpendicular direction and again the 2D subsurface imaging method applied; however, in the more difficult subsurface areas this imaging output lacked overall clarity.

The second approach became possible with the advance of computer technology and computing speeds in the late 70s and 80s, which resulted in the ability to implement technology for the imaging of the subsurface using a single pass full 3D imaging algorithm.  The technology has continued to evolve allowing the imaging of the subsurface in either the time and or depth domains.  3D subsurface imaging is now one of the key technologies in exploring successfully for oil and gas.

Recognizing the pioneering efforts of the following individuals and organizations that contributed to this technology:
Milo Backus, Jon F. Claerbout, William (Bill) S. French, Kenneth (Ken) L. Larner, William (Bill) A. Schneider, Robert (Bob) H. Stolt, Amoco (now BP), Conoco (now Conoco Phillips), Gulf Oil (now Chevron), Stanford University, Texas Instruments and Western Geophysical.

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