Unconventional Resources Assessment of La Luna Formation in the Middle Magdalena Valley Basin, Colombia

Abstract

La Luna Formation, a Cretaceous sequence in the Middle Magdelana Valley basin (MMVB) of Colombia, is described as calcareous shales and limestones, black in color, with high foraminifera (Globigerina) content, and with calcareous and phosphate concretions. Formation members are named Galembo (calcareous shales with limestone layers and nodules), Pujamana (claystone, mudstone, gray shale and cherts) and Salada (black shales, black mudstones, black calcareous claystone, black limestone layers and concretions with pyrite). The total organic carbon (TOC) values for Galembo range from 1.09% to 11.90% and for Salada from 2.15% to 11.90 with Type IIS kerogen. Liquid hydrocarbons would be present in the northern and central part of MMVB, and condensates and dry/wet gases are related to the southern MMVB areas. Biomarker analyses reveal variations in redox and predominant marine organic matter deposited under anoxic and high water salinity conditions. The average SEM total area porosity for Galembo is 8.5% and 8.11% for Salada members. The depositional environment is shallow marine, restricted middle shelf. Four major third order stratigraphic cycles corresponding to the three La Luna Formation members are proposed during an overall sea level rise towards the La Luna Formation top. This primary assessment indicates a good potential for a shale oil/gas system, where good organic matter content is present, the formation reached maturity levels for hydrocarbon generation and has relatively high porosity for oil and/or gas storage. The thicknesses in outcrop vary from 180–720 ft. for Galembo, 300–400 ft. for Salada and 500 ft. for the transitional Pujamana member.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015