Abstract: The Adventures of Drilling and Conducting Experiments Through a Major Fault Zone in Eugene Island 330, Offshore Louisiana, Gulf of Mexico

Lana B. Billeaud, Roger N. Anderson, Peter Flemings, Steven Losh

The Global Basins Research Network (GBRN), an integrated network of scientists with expertise in the fields of geology, geophysics, geochemistry, and geological and reservoir engineering, in a cooperative agreement with the Department of Energy, is testing the hypothesis of fluid migration through fault zones and into conventional reservoirs. The GBRN is actively drilling a well extension from the Pennzoil Eugene Island 330 A platform to penetrate a major fault zone and conduct experiments within the fault zone. Pennzoil has seen anomalous production in the conventional reservoirs within this field. The objectives of this venture are to locate moving streams of hydrocarbons in the process of migration; determine if oil production can be maximized by drilling into a conduit in the faul zone that directly connects the deeper, geopressured source accumulation to the presently producing reservoirs; and develop techniques for production and exploitation of these conduits within fault zones.

The GBRN is drilling the "Pathfinder" well into the highest stress concentration portion of the "A" fault to conduct several experiments, collect data to analyze and model the fault zone dynamics, and deliver flowing hydrocarbons to the surface. The Pathfinder well spudded on October 17, 1993. The experiments are as follows:

1. Whole Coring Program: Six 30 to 60^prime whole cores will be taken. One whole unaltered core will be taken prior to entering the fault zone, for comparison, and the other five cores will be taken within the fault zone treading new ground in whole coring;

2. Open-Hole Wireline Logging: A series of state-of-the-art logs will be run including: Dipole Sonic Imager, Array Induction Tool, Formation Micro-Imager, Geochemical Reservoir Analysis Tool, and Nuclear Porosity Logging Tool;

3. Sidewall Cores: A total of 180 sidewall cores will be taken in this well targeting shale and sand zones of interest;

4. Modular Formation Tester: One formation tester run will take 12 pressure readings above, through, and below the fault zone for pressure dynamics data;

5. Stress Test: Two stress test zones, one stress test below the fault zone and one within the fault zone, will be data-fraced to obtain the formation fracture pressure data;

6. Frac-Pack Completion, Production Test and Pressure Transient Test: From the well data gathered, a determination will be made if there are commercial hydrocarbons within the fault zone. If the data indicate the possibility of commercial hydrocarbons and/or if the shear and compressional sonic logs indicate sand control is necessary, we plan to use the new technology frac-pack gravel pack to complete the zone for extended production life. If the data indicate non-commercial status and/or the shear and compressional sonic logs indicate a competent formation strength, the lRIS/DataLatch system will be used without sand control for testing the zone. Both systems will require a tubing-conveyed perforating. The testing will include a 5 day flow test with fluid samples collected, then a 4 ay pressure transient limits test with surface read-out to estimate reservoir geometry of the fault zone conduit.

The techniques used in drilling and conducting these experiments will be presented along with the results of the data gathered from the well and an update on the production from the fault zone. The results from this well will aid in the understanding of (1) fluid-flow processes resulting in transient rupture and expulsion of hydrocarbon-charged fluids from geopressured strata, (2) fault-zone pressure dynamics, and (3) modeling of dynamic fluid-flow processes within the fault zone.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994