The subsurface geology of the Monument Oil Field of New Mexico

The Monument Field is located a few miles east of the south-western rim of the Llano Estacado. The producing structure is a subsurface aticlinal fold which was discovered by combined geology and geophysical surveys. The white Lime Formation, the main reservoir rock, is a part of the Permian system near the western edge of the Permian Basin. The present production comes entirely from the 4th pay, white Lime, which is from 175 feet to 100 feet thick. This 4th pay is a porous, light colored limestone. The gravity of the crude oil is approximately 38 degrees A. P. I. and verges on asphaltic oil at the base. Under present conditions, it is estimated production will continue about 12 years.