TRENDS: PROVIDING VALUE-ADDED TECHNOLOGY

L. C. Lawyer
Chevron Corp.
Houston

The oil industry has been through major changes in the past 10 years. We have seen an activity high in the early 1980s, which was stimulated by oil price predictions that went as high as $70/bbl. By 1985 we saw oil prices plunge to $8/bbl, causing numerous reorganizations and mergers.

Today we find ourselves in a business environment in which large oil companies are reducing their exploration budgets in the mature basins of the U.S. and Canada in favor of more-attractive opportunities in frontier plays, usually overseas.

These same companies are taking a hard look at their existing fields with the objective of increasing operating efficiency by sales, trades, and purchases. Nonperforming properties are sold or exchanged for properties that are within the supported infrastructure.

Before a property can be considered for divestment, it must be evaluated on the basis of current reserves and potential for additional reserves. This process of restructuring producing properties is often referred to as "property enhancement."

The result of property enhancement is the identification of core producing properties. Resources and efforts are then focused on the core properties to maximize production and reserves.

This is today's business environment. Our challenge is to provide value-added technology that will support exploration and production business objectives. Expenditures for technology should be treated like any other expenditures, with calculations of expected payouts and anticipated rates of return. An evaluation of risk should also be made.

in other words, solid economic justification is required. This justification is particularly true in production, where expenditures and results are more closely coupled.

THE 3D EXAMPLE

The use of 3D seismic data to assist in reservoir management is a striking example of value-added technology.

Bay Marchand field in the Gulf of Mexico was discovered by Chevron in 1949. In the mid-'80s, Chevron acquired a high quality 3D seismic survey. Needless to say, there was a certain amount of risk involved in that decision, since Bay Marchand is an old field and well into the decline phase.

Seismic acquisition was difficult because of shallow water and the many producing obstacles. Extensive planning and coordination with the geophysical contractor, Western Geophysical, resulted in the acquisition of a truly excellent survey.

After an integrated analysis of all the pertinent data, which involved many engineers, geologists, and geophysicists, development work was carried out which completely reversed the decline of the field (Fig. 1)

Production in the field had dropped to 16,000 b/d when the decision was made to conduct the 3D survey. Today Bay Marchand is producing nearly 40,000 b/d.

Another good example of value-added technology is found in the methods used to acquire 3D marine seismic data.

Just a few years ago, 3D acquisition was an extension of 2D data acquisition. To get 3D data, you simply shot a series of closely spaced 2D lines. Typically the spacing between lines was about 50 m, although in the early days of 3D the lines were more widely spaced.

Today, many seismic vessels are outlifted with two or three cables and two source arrays instead of the normal method of one cable and one source array. With the boat configured this way, six lines are recorded with each pass of the boat instead of just one as with 2D methods.

Consequently, we are able to record a 3D survey in approximately one sixth of the time it would take if we were trailing one cable and one source.

However, there are difficulties with this configuration. Each cable may be as long as 6,000 m and cost $2.5 million. Cables are fragile and subject to being bitten by sharks and cut by shrimp boats. Also, each source array is made up of a number of air guns. Getting this much hardware and cabling on and off the back of a relatively small vessel is a challenge in itself.

Acquiring more data in less time implies one dimension of value-added technology. An added dimension would be to acquire more data with higher precision.

To obtain the high quality surveys that are required for reservoir management, the location of the boat, every geophone group along the cable, and the source arrays must be known with great accuracy for each shot taken. To locate the boat with the desired accuracy, many radio positioning methods have been employed.

The most advanced method is called Global Positioning System, or simply GPS. With this satellite-based system, locations can easily be determined to an accuracy of 5 m. The method is not only accurate but rapid and low-cost.

In addition to satellite receivers on the boat, receivers are also placed in the tail buoys of the cables being towed to accurately determine the location of the end of each cable. The configuration of the cable below the water is determined by sonic transceivers deployed along the cable and on the hull of the boat.

The travel times between these points are continuously measured to yield their relative locations (Fig. 2). The source arrays are located in a similar manner.

In summary, a large amount of technology is employed to acquire the high quality 3D surveys which are essential to the resultant value-added interpretation.

SEARCH TIME

It is estimated that geologists and geophysicists spend an average of 60% of their time searching for data (Fig. 3). This effort adds little value to their work.

By cutting down on data search time and using the speed of an interactive workstation, it is not unrealistic to expect an order of magnitude increase in productivity. But again, this is only one dimension of the value-added benefit of interactive workstations:

In addition to the productivity increases, an interpreter with a workstation will be able to improve his interpretation using techniques not available with batch methods. Examples of these are signal enhancement, inversion, velocity modeling, amplitude analysis, and geologic modeling.

Geologic modeling includes checking on bed lengths, area or volume conservation, restorations of various kinds, and other appropriate modeling techniques. In summary, using workstations will result in a superior interpretation in a much shorter time period, providing a tangible value-added benefit.

Integration of data between various applications is also essential.

This means taking all of the data into consideration during the interpretation, not just seismic data.

Effective data management and integration require standards, and this is where the geophysical industry and the entire petroleum industry seem to have problems.

Except for a few cases such as tape formats, we have done a very poor job of setting standard formats for our data. There are industry efforts under way to change this. Efforts such as Petrotechnical Open Software Corp., Open Software Foundation, and the IBM Mercury project are trying to create some order out of our data chaos. To standardize on a single data model is a very large challenge of the '90s, but if achieved, it will benefit everyone and have great added value.

CONCLUSION

These are but a few examples of the technology and techniques that are around today or will be around in the near future which produce added value. Other geophysical technology is competing in the marketplace, and some of it has a good chance to pay out.

A few examples are tomography, shear wave splitting, vertical seismic profiling, EOR monitoring, and downhole seismic sources.

In summary, the challenge of the '90s is to provide both production and exploration with the value-added technology necessary to meet their business objectives.