Well Logging Interpretation And Evaluation Of Low-permeability Mixosedimentite Reservoir

With deepening exploration and development of Qaidam basin,the complex reservoir has become an important object of exploration and development in the future,and we need to deal with more logging problems with more difficulties.The mid-shallow layer,represented by Xiao Liangshan in northwest Qaidam basin,have very complex and diverse characteristics of reservoir as its special deposition,diagenesis and geological conditions,especially the characteristic of peperite is obvious.The lithology is divided into clastic rock(silty mudstone,argillaceous siltstone)and carbonate rocks(limestone,marl,micritic limestone,algal limestone,etc.),all kinds of lithology with thin layer and thin interbed.In addition to the algal limestone and siltstone,there are very few single lithologic reservoirs.It is very difficult to identify the lithology with logging.Effective evaluation method of reservoir is hard because the reservoir space is small and permeability is poor.The heterogeneity of reservoir result in complex relationship between the porosity and permeability,which cause the interpretation model of high precision too hard to build up in conventional methods;Formation skeleton's contribution to the logging information are greater than the pore,which lead the characteristics of electrical logging of oil,water and dry layers too small,and oil and water layers are difficult to qualitative and quantitative evaluation.So the evaluation of complicated background and low permeability lithologic reservoirs become an important area of logging research.Based on Xiao Liangshan in case,this paper firstly put forward a reservoir classification and logging identification methods based on the quantitative characterization of the pore structure factor.On the basis of the reservoir classification evaluation,study different types of effective thickness of the reservoirs(chapter 3).Secondly,set up lithologic identification method based on the gradual stripping methods,and realize lithology quantitative evaluation(chapter 4).Thirdly,based on the core states to scale logging information,establish the quantitative evaluation models of static parameters like shale content,porosity and permeability.Among them,the model of permeability quantitative evaluation based on the reservoir quality factor belongs to the feature skill,which achieved good results(chapter 4).Fourthly,integrated application of logging,mud logging data,which established qualitative and quantitative identification method of multi-attribute fluid properties using different data,making the interpretation coincidence rate increased by 5% in the study area(chapter 5).In the end,based on the above methods,established a set of suitable technologies for low permeability reservoir logging evaluation of the peperite,thus improved the discovery rate and the interpretation coincidence rate,which promoted the increase of reserves in the northwest of Qaidam basin.