Production History, Depositional Environments and Future Hydrocarbon Potential for Main Pass Blocks 4, 10, and 49 in Louisiana State Waters

Exploration for oil and gas in the Main Pass area since 1948 has resulted in the discovery of 23 fields (State waters). Production in this area has been from the Upper Miocene (Bigenerina A & B, Discorbis 12, and Textularia) and the upper portion of the Middle Miocene (Cibicides carstensi,Textularia W and Bigenerina humblei) with most production coming from sands to depth of 12,000 feet. Available data till the end of December 2006 show Main Pass 4, discovered in 1984, to have produced 942,598 bbls. of liquids and 13,119,251 mcf of gas. Main Pass 10, discovered in 1999 has produced 190,316 bbls. of liquids and 14,426,933 mcf of gas, while Main Pass 49, discovered in 1985, produced 619,146 bbls.of liquids and 57,135,283 mcf of gas.

Wells drilled in this area encounter the typical Gulf Coast sequence of sedimentary facies which begins with a massive sand facies, followed by alternating sands and shales below which is found the deep water shale facies. Numerous east-west trending south dipping faults with anticlinal closures on the downthrown side control most of the hydrocarbon accumulation. Electric log signatures show that typical deltaic depositional environments are found in these fields with distributary mouth bars, channel sands, crevasse splays and subdeltas being common. These sand bodies are limited in areal extent and separated from each other. Sands originating in the same genetic environment have similar log signatures and thus have the potential of being misrepresented as the same sand though they are different and separated bodies and should be individually tested for hydrocarbon production. The existence of numerous thin bypassed stratigraphically isolated sands and deeper Middle Miocene sands offer excellent opportunities for successful commercial exploitation for additional reserves of oil and gas with technical advances combined with the current high cost of energy in the world market.