Logging interpretation of volcanic rock reservoir in Songnan gas field

In view of complicated volcanic lithology,versatile matrix parameter,deeply disturbed reservoir fluid because of lithology and mud invasion,this thesis tentatively studies a series of work under the aim of guiding gas field development.Volcanic rocks reservoir belongs to low porosity and low permeability reservoir.Fluid identification faces the problems of difficult distinction between gas and water as the logging response on gas is far lower than the logging response on rock skeleton.Saturation calculation faces the problems of low interpretation precision as various Archie's parameters caused by complicated lithology and pore structures.In view of above problems,we bring forward to a log interpretation method of volcanic rocks that is the mutual independence and mutual authentication between the qualitative interpretation and the quantitative interpretation.In view of gas identification,there are four research directions exploring the gas identification criterion based on logging which are the reconstructions of porosity composite curves identify gas,research on the relative value of resistivity,application of nuclear magnetic logging technology,and analysis of reservoir's gas-bearing and difference in log response.The reconstructions of porosity composite curves to identify gas means change density log curve and acoustic log curve into porosity of density curve and porosity of acoustic curve.Then the gas reservoir can be identified by using the three porosity log curves.Study on the relative value of resistivity means searches the difference value between the deep investigation laterolog and the shallow investigation laterolog.Based on these results,we have completed logging identification of five types of reservoirs and founded qualitative interpretation of volcanic rocks;in terms of quantitative interpretation of the volcanic rocks,as the resistivity log curve is the comprehensive response of lithology and pore structures,using the Archie formula which contains various m value based on resistivity logging response can get more precise gas saturation.The production testing results already testified the conclusion.Based on these research results,the system has set up the criterion of log interpretation on Songnan volcanic rocks reservoirs.Applying these new methods of volcanic rocks reservoirs,several logging prediction of new wells have been proofed.These methods have good application effectiveness.