| Yitong basin is a strike slip - extensional basin limitted by sheared sliding movement. Two evolution stages had been undergone for it by earlier right lateral tension - shear and later left lateral compression shear. There are more sedimentary systems in basin, and fan delta,lacustrine deposit, gravity flow deposit are important. The sediment system has characteristics of near to source,rapid deposition and poor sorting ,etc. The basin type,evolution, structural feature,fault system, sedimentary system and sand body distribution are all complex, so as to be unclear in the mechanisms of oil and gas accumulation process and inadequate in the degree of exploration for us. For the reasons, the proved reserves is less than 15% of the predicting geological reserves.Chaluhe fault depression is the largest depression in area in Yitong basin. It is difficult to identify oil-, gas- and water-bearing formation for the reasons which lead to the reservoir logging properties is unclear, as follow: the firstly, there are types of reservoir and oil- and gas-bearing formation in the depression. Heterogeneity in porosity, permeability, pore throat structure of reservoir is greatly. The secondly, properties of crude oil, formation water and drilling mud are complex, such as the lower oil density and salinity of formation water; The thirdly, versatile drilling mud properties lead to reservoir damage acutely. The fourthly, logging system is complex, and so on.For above reasons, the nucleus points of the paper are as follow:①to analyze reservoir features deeply;②to build up relations among lithology,porosity and permeability, degree of hydrocarbon bearing and logging measurement parameters(so called the four-properties's relation) ;③to find out geological control factors on logging features ;④to explore the best method to identify oil-, gas-and water-bearing formation;⑤to summarize the pool types and distribution.The research about reservoir has been made by using lab data. The conclusion is as follow: (1)The lithology of reservoir is mainly sandy conglomerate, siltstone and muddy siltstone are in second position; thirdly is fine sandstone and pebbled fine sandstone, and the moderate-coarse sandstone is little. (2) The oil-bearing degree is mainly fluorescence level, secondly is oil trace, oil immersion and oil patch are little. The coarser is sandstone, and the better in oil show is it. (3) It is low-moderate porosity and low-medium permeability for reservoirs. There is only a little good quality reservoir in basin. Generally speeking, the coarser is sandstone in grain size, and the better in porosity and permeability is. The deeper in burial depth is, the more intensity is in diagenesis,and more poor in porosity and permeability is, but porosity and permeability of the reservoir increases slightly in the secondary pore zone in deeper burial formation. (4) The main santstone type is lithic arkose,arkose and feldspathic litharenite, K-feldspar is in rich. Magmatic debris is inportant, and the compositional and texture maturity are lower. (5)lt is volatile-light,middle-low viscosity oil for crude oil feature; formation water salinity is lower, most of formation water salinity is less than 10000ppm, changes greatly, and it inclines to increases with depth. (6)The five groups of the reservoir can be divided.From depression margin to center, (1) The line of facies is about alluvial fan, fan delta plain, fan delta front, pro-fan delta and offshore -shallow lacustrine; (2) Lithology change is about grain-supported sandy conglomerate, matrix-supported sandy conglomerate, sandstone, fine sand and siltstone; (3) Grain- size of sandstone decreases, and the porosity and permeability of sandstone decreases with the increase of calcareous cementitious intensity and decrease of the effect of mud pebble in sandstone; (4) The tendency of that formation water salinity increases reflects that the shallow reservoir on basin margin obviously is affected by the leaching of meteoric fresh water due to the tectonic uplift and erosion.The study the four-properties's relation has shown that the types of oil-, gas- and water-bearing reservoir includes oil and water layer with normal resistivity (oil layer's resistivity is higher, water layer's resistivity is lower), oil layer with relatively lower resistivity, oil layer with water,water layer with high resistivity in Chaluhe fault depression. Because of the effect of lithology and fresh water of lower salinity, sandy conglomerate water layers with high resistivity has been occurrence commonly in the study area.It is showed by study that the key geologic factors affecting reservoir electrical property features are as follow: lithology, formation water salinity, calcareous cementition, hydrocarbon saturation,etc. Calcareous cementition can cause lower interval transit time and high resistivity; lower formation water salinity can cause high resistivity; high shale content can cause high interval transit time and lower resistivity;coarse grain can cause lower interval transit time and high resistivity; so the electrical property features is complex,some factors cover up fluid' s electrical response.Based on the above study,under the complex geological conditions,geological constraint is the basis of correct fluid identification.On the study of reservoir feature, fluid feature, electrical behavior, the interpretation modelsof reservoir parameters are set up by using core and logging data. Fast identification methods(such as Rxo/Rt-SP overlapping, neutron-density porosity overlapping, Sp—Rt cross plot), crossplot chart methods (AC—Rt cross plot chart, Rw—Rt cross plot chart, AC—Rt/Rw, Sw—Sw(?),Φ—Φ×Sw) have been used,and proved being effective. Considering the sand-conglomerate reservoirs develop, bad quality of borehole, complex mud property , etc.According to array induction logging, time-lapse logging, laterologging data combined with the result of resistivity forward and inversion modelling, resistivity calibration of reservoir about mud invasion is studied. The results of resistivity forward modelling reflect that deep lateral and deep induction resistivity changes from high-invasion to low-invasion with the water saturation increasing when fresh muds invase reservoirs; deep lateral and deep induction resistivity have shown lower-invasion in spite of high or low water saturation, and deep induction is affected significantly when brine muds invase reservoirs. Dual induction log or dual lateral logging almost are low-invasion no matter what oil layer or water layer is in the study area by the the practical logging data. This reflects the influence of mud invading on the induction logging and lateral logging responses is not obvious, and reservoir water saturation is high. The tested resistivity has high value and low-invasion when oil saturation is high by the response of resistivity radial characteristic of array induction logging and lateral logging when fresh mud invases reservoirs; the resistivity first increases and then decreases when oil saturation is low, the resistivity is low and low-invasion in water layer; the invasion radial profile is low-invasion in spite of water layer or oil layer when brine mud invases reservoirs.According to static step profile model and resistivity geometric factor theory, VB computer language is used to program the resistivity inversion program. The recognition accuracy has been improved after comparing the identification charts before and later of resistivity invasion correction. Two kinds of identification methods(include SP curve shape and resistivity radial-contrast method) are added newly, according to the research results on profiles of formation resistivity when the mud filtrate invades reservoirs.Using a combination of above methods to recognize the fluid, several profiles of pool have been made in different secondary tectonic units. Based on above study, the characteristics of pool distribution in Chaluhe depression is summarized as follow:(1) In plane, close to depression center, reservoir lithology is mainly siltstone, sand body is continuous, lithologic pool type is main; lithology is mainly sandy conglomerate and moderate-coarse sandstone close to the depression boundary; fault pool type is main; structural pool type is main close to source and fault; structural-lithological reservoir type is main away from source and fault;(2) Because of the fault screened, oil-bearing properties in the downthrow block of fault is batter, that is to say, the trap of ridge of antithetic fault controls oil concentration;(3) Affected by tectonic reworking, hydrocarbon preservation condition is poor in tensional area, such as boundary and slope area;(4) Comprehensively, the structure, deposition, fluid inclusion, temperature-pressure system, formation water chemical characteristics, SP reverse ,etc. data reflect the top of Liangjia structural belt is the good petroliferous properties and is faint under later reformation; the top of Wanchang structural belt is strongly later reformation, the area of around structural belt is faint later reformation; Gudian slope is litter hydrocarbon accumulate by strongly later reformation.
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