GIS in Exploration
Texaco Exploration looked for better ways to explore for oil and gas and found them on the computer
by Don Lyle
When Texaco wanted to improve its exploration techniques, it turned to a geographical information system (GIS). It found a better way to capture and share information with a greater number of people, but it went through some growing pains in the process.
Based on maps, a GIS provides a picture that brings out relationships among objects—whether they are on the surface or in the subsurface. It provides an ideal setting for people of different disciplines to focus all their talents on a project′s big picture.
Speaking at the annual ESRI Petroleum User Group Conference in Houston, Greg Slutz offered a personal case study. Slutz has worked for Texaco for 23 years, and he has worked in exploration computer operations for 20 of those years. During the past seven, he has applied GIS technology to operations of the company’s international exploration division, headquartered in Bellaire, Texas.
Modeling the Project—Texaco used GIS to locate the wellsite. It then used the contoured map to build a 3D picture of the terrain. That allowed the oil and gas exploration company to use computer-aided design tools to build a model of the proposed wellsite at the exact location it will occupy. It also shows positions for mud ponds and other rig-side installations. Diagram courtesy of Texaco Exploration and Production Inc.
In setting up an efficient exploration technique, Texaco needed to capture structured and unstructured data, share that data easily with asset team members, assemble cumulative databases to pass on lessons learned, and coordinate a variety of databases. A GIS offers that kind of power and flexibility, he says.
Texaco used ESRI′s Arc⁄Info and ArcView to capture the different types of data used in exploration. First it loaded digitized surface geology maps and a digital elevation model derived from topographic contours for the project area. That formed the foundation for the layers of information that would follow. The company then went to the corporate database to bring in seismic shot points and well locations. Next, it added Landsat and SPOT satellite images. It added cultural information about the area from digitized government maps, and early in the process, it added earthquake epicenter locations from the Internet. Earthquake data gave the company information about thrust sheets in the region, Slutz says. As the data was loaded, the development team made it available to the explorationists on the ArcView desktop GIS.
Much time and effort has been spent developing techniques that add value to the exploration effort.
Greg Slutz, Texaco
The benefits started with people in the field. ″We put together small field maps they could take to the field,″ he says. The exploration people took those maps to the sites and added their own information. They brought the new information back, and it joined the original data in the databases fed into the GIS engine. Those teams took digital photos of outcrops, video strips of the topography, video shots of core samples, even notes on field observations. All that was linked to form a complete picture of the region, gather all the information about potential exploration targets into the GIS and make it available to everyone with an interest in the project.
As the exploration progressed, GIS became an invaluable tool in the prospect area′s ongoing evaluation. The exploration crew used the multiple levels of information to plan seismic acquisition in the rugged, mountainous area. They used the information for control in their interpretations of the subsurface. They used it to find and scout potential drilling locations, and they used it as a common talking ground in exchanging information with the regional Texaco field office.
Once the GIS was set up, they used it to prepare maps and 3D displays. One 3D display of the mountainous terrain helped the exploration team explain to the front office why the seismic collection was so expensive, Slutz says. They created a simulated flyover of the surveyed area. The team also could use the information planted in the databases to answer questions about the project area. All they needed to do was open the database underlying the geographical area they were investigating at the time.
One of the GIS gathering system′s strengths was the easy coordination of different disciplines. Once the seismic was shot, the GIS development team added the seismic lines to the GIS so the geophysicists could coordinate the seismic with the other exploration information. As the seismic crews captured more data, formation strike and dip information were added to the growing database. The team wrote scripts that allowed them to accurately represent this data in time sections in Landmark SeisWorks. That gave them a more accurate interpretation of the seismic as it helped tie the seismic readings to the outcrops recorded by the field geologists. Using tools in the GIS package, they could plot all the surface data in a single place, from the present-day earth surface color-coded by elevation to surfaces identified by formation tops in the seismic survey. And they could coordinate that with rivers and present-day cultural information.
The team continued building information into the GIS visual and tabular databases. Procedures and scripts were developed to add geologic intelligence to the data and export it to 3D modeling packages such as Geosec and EarthVision.
GIS displays also addressed concerns of the engineers and the environmental experts. A more accurate 3D model of the subsurface gives exploration analysts of all disciplines better odds of correctly evaluating target formations, traps, drilling targets and even long-term field exploitation and improved production techniques. If all the information goes into the GIS databases, the learning curve remains intact. The departure of a key person or the loss of a vital piece of information can′t disrupt it.
A more accurate 3D model of the subsurface gives exploration analysts of all disciplines better odds of correctly evaluating target formations, traps, drilling targets and even long-term field exploitation and improved production techniques.
The survey crew provided the data that allowed the company to put together a 3D representation of the drillsite, including pits, machinery, the rig location, roads in and out, and adequate room to maneuver trucks. Because of the inherent differences in computer-aided design (CAD) data and GIS data, the CAD data had to be converted into a form the GIS could use. Once the team converted the CAD program to the GIS format, the 3D rendering helped Texaco evaluate the feasibility of the drillsite, Slutz says. Using the GIS′ 3D modeling capabilities, the proposed wellsite was modified to show what it would look like after the facilities were built. The changes included cut and fill operations necessary to remove a section of a hillside and the construction of mud pits.
Beyond that, the 3D representation gave support crews information they needed to do their jobs more efficiently. It also gave them the opportunity to recommend improvements. For example, he says, ″GIS is being used by the communications team to help design the most cost-effective system, helping to determine the need for satellite dishes or line-of-sight transmitters.″
Texaco has started the well, but Slutz has not received any information about the well′s success since it has not yet reached the exploration objective.
GIS gave the team:
- improved integration of activities;
- better support for evaluation and analysis;
- more support for the team-based organization;
- a means to save time and money; and
- a way to improve knowledge transfer.
Still, he says, ″Our use of GIS has been a learning experience. As of yet, we have not fully transferred the process over to the explorationists using ArcView. Significant effort is still required by GIS specialists using the more powerful Arc⁄Info to load and manipulate the information. A significant time commitment to QC (quality control) the data integrity is also required. Much time and effort has been spent developing techniques that add value to the exploration effort.″
Overall, the process has been a good one for Texaco. The GIS core improved the company′s ability to integrate information that supports its exploration activities. That, in turn, resulted in a significant savings of time and money as it gave the company the ability to use all of the existing information in analysis and evaluation. The program brings together a wide array of types of information and organizes them at a central, easily accessible location. Even people at remote locations can access the information easily and quickly.
″We believe that GIS will become increasingly important to the success of exploration and will further enhance Texaco′s knowledge management capabilities,″ Slutz says.
Reprinted from Hart′s Oil and Gas World, June 1999