Publications

Surface geochemical petroleum exploration is defined as the search for migrated surface hydrocarbons and their alteration products. Geochemical surveys document hydrocarbon microseepage that originates from buried petroleum reservoirs and/or source rocks. Results from geochemical surveys and research studies document that hydrocarbon microseepage occurs in areas with active petroleum systems, is common, widespread, predominantly vertical, and dynamic. Direct geochemical exploration techniques analyze small quantities of hydrocarbons that occur in the pore space of soils, are adsorbed onto clay minerals, or are incorporated within soil cements. Indirect methods detect seepage-induced changes to soil and sediments. Microbes play a profound role in the oxidation of migrating hydrocarbons, and are directly responsible for many surface manifestations of petroleum seepage. Onshore and offshore hydrocarbon microseepage surveys in southeast Asia require careful planning and implementation due to extreme variations in topography and surface conditions. Based on effective logistical and security considerations, geochemical surveys have proven ideal for this regions diverse exploration regions. To optimize recognition of seepage anomalies, sampling patterns and quantities must reflect survey objectives, expected size and shape of targets, and expected variation in surface measurements. Defining background values is an essential part of anomaly recognition and delineation. Undersampling and/or the use of improper sampling techniques is a major cause of ambiguity which may lead to interpretation failures. Geochemical exploration data have found their greatest value when integrated with geological and geophysical data. The integration of surface and subsurface exploration methods leads to better prospect evaluation and risk assessment because prospects associated with microseepage anomalies are 4-6 times more likely to result in a commercial discovery than prospects with no associated seepage anomaly. Recent southeast Asia case studies from Philippines and Indonesia will be presented.