Using the Technology

Examples in Conventional Reservoirs and Marine Shales

  The basic idea of our technology is simple. Oil converts to natural gas catalytically, promoted by trace metals in sedimentary rocks. We can predict the amount of gas generated in a rock (% Gas) from its catalytic activity (Activity), which we measure, and the rock’s estimated temperature at depth (Figures 1 & 2).

Example 1: Predicting Gas in Reservoir Rocks, Gulf of Mexico Model

   Consider two reservoirs, A1 and B1, both targeted for drilling at 13,000 ft. Assuming they have hydrocarbons, which has the highest probability for oil (assuming there is no market for gas in this basin)? Both are deltaic sandstones, and we have well cuttings from reservoirs in the basin. An Activity Log of each well gives A1 with an Activity of 10 ppb (parts-per-billion active metal) and B1 with 100 ppb. We then use Figure 1, the Model for deltaic basins, to predict oil in A1 (40% Gas) and 100% gas in B1.

 

Figure 1. Deltaic Basin Model, Gulf of Mexico.  

Example 2: Predicting Gas in a Marine Shale, Palo Duro Basin, Texas.

  The Palo Duro is similar to the Ft Worth basin in several respects, and we were interested in approximating its shale-gas potential compared to the Ft Worth Basin. We obtain cuttings from old wells in Brisco, Floyd, and Motley Counties from the Bureau of Economic Geology here in Houston, and analyzed them for Activity. The Barnett Shale Model for Ft Worth basin had correctly predicted % Gas in Montague, Wise, and Johnson Counties (See Activity Logs and Figure 2). We used this Model and the Activity Logs (Activity vs Depth) and maturities of the Palo Duro to sketch the stratigraphic and geographic opportunities for shale gas in the Bend Group shales of the Palo Duro. The analysis gave a clear picture (proprietary) of the basin’s gas potential relative to the Barnett Shale in Ft Worth Basin. This evaluation was completed in 4 weeks at a cost of under $10,000.

Figure 2. Barnett Shale Model, Ft Worth Basin. The curve marked M is the Activity Curve for Montague County, W is the curve for Wise County, and J is the curve for Johnson County. The Model correctly predicts oil in Montague, wet gas in Wise and dry gas in Johnson.

Activity Logs

  Activity Logs are well logs showing rock activity with depth. They are generated from cuttings, typically four or five samples within a stratigraphic unit. Activity Logs of strategic wells will map oil and gas in three dimensions, thus highlighting opportunities for hydrocarbon-specific (oil or gas) drilling. This is totally new in exploration, with powerful implications where oil or gas carries a premium.

  Figure 3 shows the oil to dry gas trend in the Barnett Shale, Ft Worth Basin. Wells in three counties within the trend were selected for analysis, one from Montague County in the north where the Barnett contains oil, the second south of it in Wise County with wet gas, and the third southeast of it in Johnson County producing dry gas. The three Activity Logs are shown in Figure 4, superimposed for comparison. Taking average activities from the logs, and average maturities in these wells (Wise and Johnson are ~ 1.1% Ro, Montague ~ 0.9% Ro), the Model in Figure 2 correctly shows oil for Montague, wet gas for Wise, and dry gas for Johnson.

Figure 3. Map of the Barnett Shale (Mississippian) in the Ft Worth Basin showing the oil to dry gas trend across the basin. Courtesy of Dan Jarvie, Humble Geochemical Services.

Figure 4. Activity Logs of Three Wells in the Barnett Shale, Ft Worth Basin.

  Two things stand out in these logs. First, the well in Montague County is uniformly inactive, which explains why oil is the dominant hydrocarbon in this region of the Barnett. Second, there are large stratigraphic variations in activity (~ 30% variance) over narrow depth intervals in both Wise and Johnson Counties. It is not analytical variance because the Assay’s reproducibility is within ~ 5%. We believe it is reflecting the oxic/anoxic variations in depositional environments. Consistent with this interpretation, we see a strong correlation between rock Activity and the Rock-Eval ratio HI/(HI+OI) (Figure 5).

  Activity Logs add new stratigraphic information to standard logs, namely the rock’s capacity to convert oil to gas at depth. Like other rock properties, Activity is easily correlated between wells and mapped basin-wide. Coupled with the Models in Figures 1 & 2, Activity maps are powerful predictors of hydrocarbon composition in un-drilled reservoirs.

Figure 5. Marine shales from Bend Group (Penn), Palo Duro Basin, Texas. The data reflects over 2,000 ft of section from Amerada Bernie well. Activity calculated from cuttings obtained from Bureau of Exconomic Geology, Houston. High values of HI reflect reducing condition that should activate metals and high values in OI reflect oxic environments that should deactivate metal.

 

Frank Mango, PhD
Founder, President, and CEO
Petroleum Habitats, LLC
281-497-0384
f mango@petrohabs.rr.com
www.petroleumhabitats.com