Study On Comprehensive Logging Evaluation Method For Fluid Properties Of Dense Reservoirs

As low-saturation reservoirs are discovered in major oil fields,low-saturation reservoirs have received increasing attention from researchers.It is found through research that low-saturation reservoirs are poor in physical properties and complex in pore structure,belonging to low-porosity and low-permeability reservoirs.Secondly,the low-saturation reservoirs in different blocks of different oilfields have different genetic factors,and the geological background of such reservoirs is quite complicated.The mechanism is diversified,and it is difficult to clarify the cause of low saturation.The low-saturation reservoir has a large range of oil and water,the oil and gas saturation is low,and the reservoir is saturated due to complex genesis.It is difficult to calculate accurately,and there are technical bottlenecks in the detailed evaluation of oil and gas.Due to the complexity of low-saturation reservoirs,conventional logging evaluation methods have great incompatibility in such reservoir evaluation.Taking the low-saturation reservoir in the XX block of the Taipei Sag in the Tuha Basin as an example,based on a large number of well logging data and core experimental data,the systematic nature of the low-saturation reservoir was carried out based on the geological background and the status of exploration and development.Research and achieve the following results:Based on the analysis of rock lithology and pore characteristics and the analysis of core experiments,the causes of low saturation of the study area were analyzed based on the geological background,sedimentary environment and accumulation characteristics of the study area.The low saturation of the study area is mainly caused by low-amplitude structure,poor reservoir physical property,complex pore structure,reservoir heterogeneity,and secondly,rock wettability also has certain influencing factors.The study found that the low-saturation reservoirs in different blocks have different genesis,so different blocks need to be targeted for the specific environment of the block.Therefore,for the study of the causes of low saturation,we can start from the following aspects:(1)structural factors;(2)accumulation factors;(3)reservoir factors;(4)sedimentary environment.Based on the rock-rock experiment,it is found that the conductivity law of the low-saturation reservoir in the study area satisfies the Archie characteristics,and non-Archisian characteristics do not appear.However,when applying the Archie formula to calculate the saturation,it is found that the error of the calculation of the specific interval is large,and it is found through further research.For low-saturation reservoirs,saturation is greatly affected by the large difference in the distribution of water salinity in the formation and the influence of clay minerals and hydrocarbons.In order to eliminate the influence of these influencing factors on saturation,the variable resistivity Archie model is proposed based on the Archie formula.The application effect is good,and the interpretation accuracy is improved from the conventional 21% error to 9%.In order to finely evaluate the oil-water layer,it is difficult to solve the problem of difficult division of oil and water layers in low-saturation reservoirs and difficult identification of fluid properties.According to the capillary pressure test,the reservoirs are divided into two categories: Class I good reservoirs;Class II bad reservoirs.Based on the oil-water phase infiltration data,based on the theory of the oil-water two-phase flow Darcy law,a model of water production rate and water saturation is established.On the basis of the experimental analysis of the test oil core,the lower limit standard of effective reservoir in the study area was established.Finally,the fine evaluation criteria of the oil and gas aquifer in the low saturation reservoir of the study area were determined,and the test results of the test oil test showed that the application effect was very good.