Source Rock Characterization Method for Petroleum Exploration

Abstract

ABSTRACT A procedure and apparatus have been developed for rapid source-rock characterization. Based on the paralysis of small rock samples, it makes possible the determination of :various types of source rockstheir degree of evolution (immature, oil zone, gas zone)their petroleum potential The method can be performed on cores or cuttings either in the laboratory or at a well site (especially aboard offshore drilling vessels), and in this case it can be used to detect oil shows. Generally the procedure uses ground rock, but it is also possible to operate directly with small cuttings without any prior treatment. Aboard the GLOMAR CHALLENGER (LEGS 48 and 50) the apparatus was especially used as a safety tool to reveal rapidly the presence of oil shows. INTRODUCTION In the field of petroleum exploration, one of the most important aspects is to be able to recognize the various types of source rocks in a geological series which, under the effect of increasing temperature during burial, produce petroleum compounds. As a matter of fact, the quantity and character of the hydrocarbons which have been produced depend on the character of the organic matter originally deposited in these source rocks as well as on subsequent thermal evolution, i.e. temperature and geological time. Recent research 1,, on kerosene (insoluble organic matter) from sediments sampled in various basins has shown that the physical chemical analysis of these kerosene makes it possible to classify the various types of organic matter and to estimate their oil and gas potential together with their degree of evolution. Do not fulfill the requirements of petroleum exploration which requires the analysis of a large number of sediment samples by simple, cheap and rapid methods. The basic knowledge acquired from the study of various types of kerosene has been used to develop a rapid method applied to characterize the different qualities (types) of organic matter directly on sedimentary rocks and to estimate their oil potential and their degree of evolution. This method is based on the selective detection of hydrocarbon compounds and of one of the principal oxygenated compound (C02) produced by paralysis under normalized conditions of organic matter contained in sediments. The paralysis technique has already been used by various authors (4, 5,6,7,8) for studying organic matter in sedimentary rocks. CHARACTERIZATION OF VARIOUS TYPES OF KEROGEN Elementary analysis of kerosene shows that the major atomic constituents are carbon, hydrogen and oxygen. The H/C and O/C atomic ratios utilized in a diagram of the type established by Van Reveled for coal shows that the samples corresponding to the same quality of organic deposits are situated on a curve called "evolution path". (fig. 1)