ABSTRACT

Low resistivity, low contrast (LRLC) pay sands in the Gulf of Mexico Basin are being found and produced now. In the past these intervals were often overlooked, considered wet or tight. These LRLC intervals which contain significant reserves, can be recognized today through proper identification and evaluation techniques using well logs, and samples/cores.

LRLC pay sands in the Gulf of Mexico Basin have been recognized for many years. However, their economic importance has only recently been demonstrated. With the finding of other LRLC zones in clastic basins throughout the world, (e.g., North Sea, Indonesia, West Africa, and Alaska) evaluation and production of these zones has taken new importance. These not so obvious pay zones have shown to be of large areal extent and contain many thousands of barrels of hydrocarbons. Thus, proper evaluation and understanding of these zones has become essential.

The principal geologic causes of LRLC are: 1) laminated intervals, 2) dispersed clay, 3) structural clay, 4) altered framework grains, 5) grain size, and 6) others.

The major depositional systems containing LRLC reservoirs are: 1) channel fills, 2) delta front and toe deposits, 3) shingled turbidites, and 4) deep water fans including levee-channel complexes.

This knowledge along with knowledge of wireline tools and responses can be used to build petrophysical models that can evaluate these LRLC reservoirs.