SCA receives many queries about the “The Ten Habits of Highly Successful Oil Finders“. Since applying the best practices that are the foundation of the 10 Habits will help you, or your company, reduce the number of dry holes you drill, SCA has written a column elaborating each of the Habits. Here is the column for Habit 4.
Successful oil finders use all of the AVAILABLE data to ensure that they have reasonable and accurate subsurface interpretations.
Many years ago, I had the pleasure of attending an AAPG fieldtrip with my friend Robert M. Sneider, AAPG Sidney Powers Medalist and discoverer of the giant Elmsworth deep basin gas area. Knowing that Bob had made a small fortune buying mature fields, I asked him to let me in on the secret to his success. His answer was:
“If a company selling a field has their exploration and production offices in different cities, I will almost certainly buy the field. If their offices are in the same city but different buildings, I will probably buy their field. If they are in the same building, but different floors, I may buy their field. But if they are on the same floor, I won’t even look at the field”
I was at first disappointed by that answer, as it did not seem the sort of technical secret I could use to duplicate his success. Truth be told, I did not really understand the significance of his statement until years later when I took SCA’s class “Applied Subsurface Geological Mapping”. In that class, Dan Tearpock showed an example from a company that had drilled two dry holes in the middle of a producing field.
The field was located in an extensional tectonic setting and the trap consisted of a number of fault blocks associated with a major growth fault (Figure 1). The reservoirs consisted of deltaic sandstones and were producing under a depletion drive mechanism. Fault Blocks B, C, and F were producing. Well No. 19 in Fault Block D was completed in a different horizon. After the completion of this new map, the company planned wells for both Fault Blocks D and E to drain the resources in these blocks. The data available were 3-D seismic, wells, and production and pressure information.
Based on the map the company drilled both wells, which proved to be uneconomic wells (cement storage facilities). After the wells were P&A’d, a detailed review was conducted using a variety of geological techniques including Quick Look Techniques, as presented in the textbook Quick Look Techniques for Prospect Evaluation by Tearpock, (contributing authors Bischke and Brewton), and as taught in several SCA training courses.
Figure 1: Proposed Locations for Fault Blocks D and E
A critical review of the map indicates a number of problems. For example, the contours in Fault Block C do not honor Well No. 20. Fault Block F dips toward the south, whereas all of the other blocks dip toward the north. The fault that separates Fault Block F from Fault Block E has no vertical separation just south of Well No. 57. There is contour incompatibility across a number of faults. There is a major screw fault (see QLT textbook) separating Fault Block E from F, and there a number of other geological problems. Based on the number of map errors, management should never have approved the wells.
But the interpreters made an even more critical mistake; they failed to use all of the available data. Well No. 13 was drilled into the fault gap. Had the interpreters calculated and used restored tops from this well for the mapped horizon, they could have better constrained their map. More significantly, had they worked more closely with the reservoir engineers, they would have learned that the producing fault blocks were producing under a depletion drive mechanism, and that Fault Blocks B and F had significantly overproduced the volumetrically calculated reserves. Well No. 57 had already produced 150% of the calculated reserves for Fault Block F and was down 50% of original pressure. Reservoir B had also out-produced the volumetrically calculated reserves, and the pressure was significantly lower than original pressure. Where was this excess gas coming from?
This question was answered when the two prospects were drilled. Fault Block E had the same reduced pressure as Fault Block F, and Fault Block D had the same pressure and Fault Block B. Additionally, the remaining reserves in these two fault blocks were insufficient to complete the two drilled wells.
It was when Dan Tearpock made the comment in the mapping class that “had the interpreters worked more closely with the reservoir engineers on the pressures and production, these two dry holes could have been avoided.” I finally saw the wisdom in Bob Sneider’s answer to my question of long ago. When the interpreters and engineers are not together, they are not communicating. When interpreters and reservoir engineers are not communicating, companies leave behind reserves, or drill unnecessary dry holes.
In our industry, failure to use all of the data is one of the most common causes of dry holes.
Geologic and analog databases are two of the more commonly under-utilized data types. Knowledge of the various fold geometries, and their relationship to the faults that form them are powerful tools for helping make accurate maps. Likewise, a strong understanding of depositional models is needed to properly interpret and map reservoirs. Analog databases, such as C&C Reservoir’s DAKS database (http://www.ccreservoirs.com/) can provide useful information for validating your reservoir interpretation and for constraining your reserve estimates.
So, to be a successful oil finder, be sure to use all of the available data!
Want to learn how to use all of the data? SCA’s “Applied Subsurface Geological Mapping” class will help you to integrate all of the available data to make accurate subsurface maps. Our “Clastic Reservoirs: Interpretation and Prediction” class will show you how to use all of the data, including analog data bases, to make accurate reservoir maps. SCA has an exciting training line-up featuring short courses tailored to the requirements of upstream professionals. Review our online training calendar and take the next step towards ensuring your oil finding career is a successful one for many years to come.