Statistical and geostatistical study of Rn and hydrocarbon components of a soil gas monitoring system: an application to surface hydrocarbon exploration

Abstract

This work addresses three topics: (1) the study of the joint areal distribution of the Rn and hydrocarbon components of soil gases over a large region overlying some known hydrocarbon reservoirs in the southern part of Hungary; (2) the relationships between the positive anomalies of Rn and hydrocarbon components of soil gases to the existing reservoirs; (3) suggestions for new targets for surface hydrocarbon exploration based on the results. Given the very low correlation coefficients between the Rn and hydrocarbon components of the soil gases, factor analysis was used to reveal a background process controlling the common migration of hydrocarbon and Rn components. The lateral distribution of the factor scores were studied using sequential Gaussian distribution. The E-type grid generated from 100 realizations indicated several positive anomalies at the surface. Indications with a larger than 0.7 probability were kept for further analysis. Seismic sections of a 3D survey support the comparison of the surface locations of these anomalies and the surface projections of the known reservoirs. The results proved the connection between the known reservoirs and the Rn and HC components of soil gases. From the positive verification, regions with a high probability positive anomaly of factor scores, but without any reservoir counterparts may be suggested as targets for further surface hydrocarbon exploration.