Thin-bedded sandstones deposited in channel-levee complexes are extremely important reservoirs in the Gulf of Mexico and other basins around the world. They are often referred to as “low resistivity/low contrast pay” because individual beds are below the resolution of conventional well logs. Fortunately, thin beds can be resolved with borehole image logs, conventional core and other micro-resistivity logs.
This report documents exploration, production and development problems in eight fields in the Gulf of Mexico and one field from Equatorial Guinea, where thin-bedded levee sandstones are the predominant reservoir.
One of the biggest unknowns with these reservoirs is the lateral extent and connectivity of the thin beds. No one could imagine that sandstone beds less than one inch thick could be both laterally continuous and interconnected over thousands of acres. Fortunately, many fields in the Gulf of Mexico have been developed and are producing from these thin-bedded reservoirs and we now have hard data to support these facts.
The producing fields have not only shown that these reservoirs are viable economic targets, but that they can be some of the best producing reservoirs in the deep-water. One of the first deep-water levee reservoirs to be produced in the Gulf of Mexico was Tahoe in late 1993. The first producing well at Tahoe was vertical and produced at rates of up to 27 MMCFGD. The next milestone was to show that these reservoirs could be developed by using “near horizontal” wells.
In July 1996 a 1,338 ft (407.8 m) section of a near horizontal well was completed and started producing at Tahoe. This well produced at rates up to 33 MMCFGD. Several other near horizontal wells were completed after that time at Tahoe and Ram Powell with producing rates as high as 109 MMCFGD and 9,500 BCPD.
As with most reservoirs there are both positive and negative aspects that become apparent after long-term production. This report also documents some of the successes and the failures of wells completed within thin-bedded levee reservoirs and attempts to summarize the reservoir characteristics in order to maximize future production in these types of reservoirs.
The Appendix of this report contains 2-page field summaries of the fields mentioned in the main body of this report. These summaries are arranged alphabetically.