Identification of Crude Oil Source Facies in Railroad Valley, Nevada, Using Multivariate Analysis of Crude Oil and Hydrous Pyrolysis Data from the Meridian Spencer Federal 32-29 Well

CONLAN, LINDA M., and ROBERT D. FRANCIS, California State University, Long Beach, CA

Comparison of biological markers of a hydrous pyrolyzate of Mississippian-Chainman Shale from the Meridian Spencer Federal 32-29 well with two crude oils produced from the same well and crude oils produced from Trap Springs, Grant Canyon, Bacon Flats, and Eagle Springs fields indicate the possibility of three distinct crude oil source facies within Railroad Valley, Nevada.

The two crude oil samples produced in the Meridian Spencer Federal 32-29 well are from the Eocene Sheep Pass Formation (MSF-SP) at 10,570 ft and the Joana Limestone (MSF-J) at 13,943 ft; the pyrolyzate is from the Chainman Shale at 10,700 ft. The Chainman Shale pyrolyzate has a similar composition to oils produced in Trap Springs and Grant Canyon fields. Compared to those oils, the MSF-SP oil has a high relative abundance of C(31)-C(35) hopanes and gammacerane [C(30)], low relative abundance of tricyclics, and a pristane/phytane ratio less than 1, similar to the Eagle Springs oils. MSF-J oil has a high ratio of tricyclic to the C(31)-C(35) hopanes and virtually no gammacerane [C(30)], which is similar to oils from Bacon Flats field.

Applying multivariate statistical analysis to biological marker data shows that the Chainman Shale is a possible source for oil produced at Trap Springs because of the similarities between Trap Springs oils and the Chainman Shale pyrolyzate. It is also apparent that MSF-SP and oils produced in the Eagle Springs field have been generated from a different source (probably the Sheep Pass Formation) because of the presence of gammacerane (C30). MSF-J and Bacon Flats appear to be either sourced from a pre-Mississippian unit or from a different facies within the Chainman Shale because of the apparent differences between MSF-J and Chainman Shale pyrolyzate.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)