Raster log technology revolutionizes geologist's workflow

Raster well-log technology, based on bitmap log images with applied depth calibration, is revolutionizing how geologists work at Apache Corp.’s Midcontinent division in Tulsa.

The division has gone from 100% paper-based geologic workflows to a staff fully committed to a computer-based approach to log storage, management, and interpretation.

The workflow has gone from geologists and technicians searching for, photo copying, hand annotating, and hand correlating well logs, to a team of geologists accessing their well-log information digitally across a client-server network.

After being in place for more than 1 year, raster technology has increased the staff’s well-log-related geologic task productivity by five to ten times over the old paper methods.

Every geologist who has had a chance to use the technology is currently using it; the few who are not are waiting for data to become available in their work areas.

Technology buy-in

Apache’s Midcontinent division, focused primarily on acquisitions and development of an extensive property base in Oklahoma and Texas, became aware several years ago that raster well-log software and data could assist geologists in basic geologic workflows.

The company was skeptical about the concept, however, due to the sheer volume of wells in the mature Midcontinent region that required conversion to a depth-calibrated, raster format.

Apache decided to evaluate the technology when the depth-calibrated raster data became available.

The acquisition of 2,000 oil and gas producing properties in northwest Oklahoma and the Texas Panhandle from Crescendo Resources LLC in early 2000 prompted Apache’s decision to move forward with an evaluation of raster well-log technology.

With the acquisition, the company’s Midcontinent division had an inventory of 250,000 acres of gross lease holdings from which to prospect. Senior management, in addition, issued a challenge to the division’s nine geoscientists to identify and drill 240 wells in 2000.

Apache’s geologic team faced a monumental geotechnical challenge, with the need to collect and correlate logs over a wide subsurface area in the Anadarko basin of western Oklahoma and the Texas Panhandle.

Raster well-log technology, which A2D Technologies calls smartRASTER data and smartSECTION software, offered a solution to the problem.

Raster technology matures

Well-log raster or bitmap images that have associated depth intelligence or applied depth calibration, called smartRASTERs, have become an industry standard format.

With the imported data, cross-section software can automatically annotate depth-related data, such as production tests, to well logs. Geologists can also pick formation tops and store them within the software application database.

Interpretive Imaging introduced smartRASTER technology to the industry in 1996, with the company merging with A2D Technologies in 1999.

A2D pioneered cross-section software, called smartSECTION, which was the first to read smartRASTER images.^{1 2}

Over the past 2 years, several additional commercial software packages, including Landmark Graphics Corp.’s GeoGraphix, GeoPlus Corp.’s Petra, Neuralog Inc.’s Neurasection, and Digi-Rule Inc.’s CrossView, have begun supporting depth-calibrated raster, well-log data import.

Paper to rasters

Migrating from 100% paper-based workflow to a new computer-based approach was an enormous decision for Apache. In deciding to move forward the company needed to address two very significant concerns.

1. How would the company acquire the data?
2. If Apache invested in the data and software, would the geologists accept the new technology or continue working with paper?

During acquisition of the data, the challenge was to justify the expense of purchasing depth calibrated, well-log images or smartRASTERs from A2D.

Alternatively, Apache could have incurred the internal costs of creating its own depth-calibrated rasters from noncalibrated well-log images, which it could have purchased at lower cost from three other image vendors that it considered during the decision phase.

In some areas, Apache had A2D’s smartRASTER, depth-calibrated, well-log images. In other areas the company experimented with using its support staff to depth calibrate the less expensive basic images.

It became apparent to the company, due to intensive staff time required to build a database internally, that it would be cost effective to purchase the smartRASTERs.

The geologists could get right to work, since the rasters would already be depth calibrated.

Company management could not overstate the second concern.

Apache was considering making a significant investment in data, software, and staff time. The investment would be wasted if the team of geologists, many of whom had more than 20-years of experience, were not going to use the new technology.

The concern of whether the Apache geologists would use the intelligent well-log raster technology soon faded once the company made it available to them.

Their degree of acceptance is directly related to the amount of data available in the geologist’s area of responsibility.

In areas where raster logs were available and loaded into the software for entire counties, the geologists embraced the new technology immediately.

In other areas, where only a portion of the data was available, geologists were forced to work back and forth between the paper and computer world.

Geologic workflow

The software and data combination allowed geologists to perform traditional paper-based workflows, but much more efficiently.

The software allowed them to continue doing the basics of geologic workflow, without major changes or the need to learn a complicated software system.

For example, the set of tasks performed by geologists who work on Texas Panhandle region properties emphasizes the details of subsurface interpretation.

For computerized well log interpretation to be effective in working the Morrow formation, which has mixed carbonate-siliciclastic deposition, the software-data system needed to:

1. Provide quick access to a choice of 1-in. scale resistivity logs for correlation logs and 2 1/2-in. scale neutron density logs for lithology identification.
2. Store, access, post, and annotate electronic scout-ticket data directly onto the well-log depth track.
3. Splice multirun logs together.
4. Allow for on-screen log correlation that simulates paper-based methods.
5. Build structural and stratigraphic cross sections at the local and regional scales.

Programmers had designed the cross-section software to facilitate these workflow details, thus involving geologists in the software design details.

Cross-section construction allows for selection of specific wells, log types, and scales. Each well can include one or more logs that can be displayed on a common scale.

Users can automatically post and annotate production-test data to the logs (Fig. 1- Click here to view pdf Cross section constructed for the Texas Panhandle through the Lower Morrow formation).

The attention to these workflow details in software design and its overall ease of use, account for the Midcontinent geologic team’s rapid acceptance of the technology.

Texas Panhandle

One of the authors filled the role of office champion, supporting acquisition and implementation of raster well-log technology.

He worked the Texas Panhandle properties for the past 5 years. During the first 4 years, he worked the area using the traditional paper-based approach and had correlated four or five key tops across the area from the paper-log database of 2,000 wells.

After receiving most of the log data for the same area in smartRASTER format, he was able to recorrelate the same 2,000 wells in less than 4 months.

During this 4-month period, he not only reproduced the work of the previous 4 years, but also picked several additional tops and created a large number of important regional cross sections.

The ability to create cross sections quickly and hang on different correlation horizons instantly has brought a regional context to the work, which he believes has produced a much higher degree of correlation accuracy.

The enormous time savings and the ability to add several mapping horizons to his studies allowed the author to identify several more prospects.

He now has the goal to correlate every well in his region and work multiple zones, which would be inconceivable with paper.

Improved correlations

Using raster well logs and the cross-section software package, a senior Apache geologist said he was able to subdivide the Granite Wash section of the Anadarko basin into several more mappable zones than could have been possible if the same section were worked with paper-based logs.

This has allowed the geologist to exploit more effectively Apache’s producing acreage in the trend.

He said two tools present in the software, the ability to quickly hang on different datum lines along with the ability to analyze the section from local (zoomed in) and regional (zoomed out) perspectives, improved the correlation framework.

Previously, due to time constraints before Apache began using the raster technology, geologists in the department were limited in the number of cross sections they could construct.

There was a tenfold increase in productivity for regional work and five to tenfold increase for prospecting, since raster technology was distributed.

The ability to create regional cross sections, hung on any datum instantly, and then export tops to its mapping system allows Apache personnel to ask multiple

Computer-assisted regional and prospect scale cross sections and the ability to analyze structural complexities with well-log data have allowed the generation of more cross sections and maps which ultimately improves the quality of our work, said Apache.

Fig. 2 shows the northwest-to-southeast (left to right) structural cross section through the Kinta field area of the Arkoma basin, Okla. A normally displaced faulted section is apparent. Click here to view pdf Kinta field area of the Arkoma basin, Oklahoma

The smartSECTION software calculated and drew the offset correlations automatically.

Geologists are hooked

Apache’s Midcontinent group is always looking for ways to maximize the talents of its professional team.

Before the raster well-log experiment, three promising elements of the raster well-log technology motivated Apache management and staff, as follows:

1. Efficiency. Eliminate cut and paste work habits associated with paper logs.
2. Organization. Provide data storage and access instantly at field and prospect scales.
3. Security. Eliminate data loss or the danger of losing paper logs.

Evidence suggests that Apache realized these three objectives. The Midcontinent geologists used to spend a significant amount of time simply looking for and collecting data in file rooms, log libraries, and other data depositories.

The geologists needed additional time annotating production test data and correlating logs.

With the raster well logs in the company’s regions of interest loaded into the software, the geologists can access any log, have production test data automatically annotated, and immediately start interpreting.

Apache Midcontinent region’s goal is to acquire complete smartRASTER coverage in all focus areas and to provide all geoscientists with access to a functional log database at their desktops.

The company’s client-server network also allows the region’s production and reservoir engineers to access log data at their desktops, enhancing their workflow and productivity, such as searching for recompletion candidates.

Nearly all of Apache’s Midcontinent division geologists have made similar comments since the company adopted depth-calibrated raster technology in mid-2001.

Instant access to logs in their area of interest eliminates time sinks in searching, collecting, and annotating well log information.

References

1. Montgomery, S.L.,"Raster logs may be basis for a geologic workstation," OGJ, Apr. 7, 1997, p. 84.
2. Valusek, J.E., "‘Smart’ raster logs can boost productivity of geologists," OGJ, Apr. 10, 2000, p. 78.

The authors