Abstract: Possible Role for Nitrogen in Formation of Petroleum Deposits

George A. Sellers

A hypothetical mechanism built on observations garnered from the literature may explain the primary migration of petroleum constituents through fine-grained source rocks. It is suggested that ammonia and possibly organic nitrogen compounds, diagenetically produced from organic matter or transported to basins in detrital clays, are stored in various sedimentary materials which are mutable under epigenetic and eometamorphic conditions. The proposed temporary repositories for the ammonia are clays, organic matter, and biogenic carbonate materials. The stored ammonia and amino compounds may be released over a range of depths by several processes: dewatering of expandable clays, reconstitution of largely smectitic mixed-layer clays to predominantly illitic mixed-layer clays, t ermal alteration of the humic-acid fraction of the organic matter, or recrystallization or dissolution of biogenic carbonate deposits. The resulting ammonia solutions may be concentrated sufficiently to enhance the mobilization of petroleum constituents through fine-grained source rocks to reservoirs. Ammonia measured at concentration levels from several tenths of a gram to 2 g per liter in reservoir brines is cited as possible evidence for this process.

AAPG Search and Discovery Article #90976©1976 AAPG-SEPM-SEG Pacific Section Meeting, San Francisco, California