Abstract: Method of evaluating the biodegradation, through the action of a bacterial population, of hydrocarbons trapped in a geologic structure. The mass of hydrocarbons present in said structure is determined without taking account of the biodegradation, from data relative to the physical and geometrical characteristics of the structure studied. Then the mass of hydrocarbons consumed by biodegradation is calculated after evaluating the number of bacteria, their hydrocarbon consumption and the structure filling time. The mass percentage of oil disappeared through the bacterial action is deduced from these two masses. Application: determination of the composition of oils in a reservoir and notably location of heavy oils. The method can notably be applied to the evaluation of the economic risk linked with the presence of biodegraded petroleum reservoirs.

Abstract: Method of modeling the biodegradation of hydrocarbons trapped in an oil reservoir or trap through the action of the bacterial population in an underlying aquifer.

Abstract: Method of evaluating the biodegradation, through the action of a bacterial population, of hydrocarbons trapped in a geologic structure. The mass of hydrocarbons present in said structure is determined without taking account of the biodegradation, from data relative to the physical and geometrical characteristics of the structure studied. Then the mass of hydrocarbons consumed by biodegradation is calculated after evaluating the number of bacteria, their hydrocarbon consumption and the structure filling time. The mass percentage of oil disappeared through the bacterial action is deduced from these two masses. Application: determination of the composition of oils in a reservoir and notably location of heavy oils. The method can notably be applied to the evaluation of the economic risk linked with the presence of biodegraded petroleum reservoirs.

Abstract: A method of evaluating the volume ratio of gas to oil (GOR) in the fluids of a well during drilling by direct or indirect measurement of the volumes of gas and oil in the cuttings. The method includes determining the volume of gas (Vg) contained in the drilling fluids by measuring a ratio between a volume of gas produced and a corresponding volume of drilled rock, determining the volume of oil (Vo) by measuring the total organic carbon (TOC) in the drilled rock while taking account of physical characteristics of the drilled rock and of the oil under the surface conditions, and determining said volume ratio (GOR) by calculating the ratio of the previously determined volumes of gas and of oil. The method can be implemented in the field, even on a drilling site, using a Rock-Eval type equipment for example.

Abstract: Method of modeling the biodegradation of hydrocarbons trapped in an oil reservoir or trap through the action of the bacterial population in an underlying aquifer.

Abstract: The invention provides a method for determining the organic matter content of sedimentary rocks from data recorded in the well by at least two well-logging probes measuring different parameters. Two probes are chosen, one for responding in the same direction ot a variation of the water and organic matter content of the rocks, the other for responding very differently to a variation of one or other of these same components, and both so that the iso-organic matter content lines in a three pole diagram are substantially merged whether the third pole is the water pole or the clay pole. The position of the line I(0%) is determined experimentally and the organic matter content is derived therefrom corresponding to each pair of values of the parameters measured in the well. In a diagram where the parameters used depend, for example, on the transit time of sound in the rock and on the electric resistivity of the formations, the iso-content lines form a family of parallel lines.