The Genetic Mechanism And Interpretation Of Low Resistivity Oil & Gas Zone In Langgu Depression

The petroleum exploration and development has been going on for about 40 years in Langgu depression. It is very difficult to distinguish oil & gas zone from the water zone electrically because the resistivity of low resistivity oil & gas zone are usually lower than or close to that of.the water zone nearby the oil & gas zone. The causes of the oil & gas zone with low resistivity of Langgu depression are very complex .In recent years, following the development and expansion of the application in new methods and technology of the logging interpretation, the technology of the logging interpretation for the mechanism of oil & gas saturation with low resistivity have been enhanced constantly.Based on the relationship between low resistivity oil & gas zone in Langgu depression and structure, sedimentation, reservoir heterogeneities, the article discussed the regulations in distribution and the genetic mechanism of low resistivity oil & gas zone. Low resistivity oil & gas zones are identified availably by selecting the logging and oil test data and applying the qualitative and quantitative methods .The studies show that structure and sedimentation control regulation of low resistivity oil & gas zone in Langgu depression, and the distribution has certain regularity and randomicity . The confining quality of the fault and formation water mineralization intensity control low resistivity oil & gas zone on structure. The sedimentary facies and the sedimentary cycle control low resistivity oil & gas zone on sedimentation . The diagenism and the clay minerals affect low resistivity oil & gas zone on reservoir heterogeneities.The types and the mechanisms of formation of low resistivity oil & gas zone in different zone of different place in Langgu depression varies from each other. The fine grain lithology of reservoirs , the complexity pore structure and high shaliness and the enrichment of the clay minerals result in the increase of the irreducible water saturation of reservoir and additional conductivity of shale which is the main cause of oil & gas zone resistivity reduction,the other causes of oil & gas zone resistivity reduction are the oil-water correlation change, thin reservoir and drilling fluid invasion.Many identifying methods (lateral correlation and non-resistivity curve surimposition and movable water analysis, etc.) are used to interpret low resistivity oil & gas zone in Langgu depression, which is analyzed and evalued comprehensively, for the sake of decreasing multi solution problem in the course of interpretation,with the qualitative estimation integrating the quantitative interpretation, multi-methods processing interpretation integrating the crossplots and oil and gas shows integrating the log response.