Study On Comprehensive Evaluation Method Of Volcanic Reservoir By Logging In The Eastern Sag From Liaohe Depression

Because of the Tanlu Fault,many tectonic movements have occurred in the Eastern sag of Liaohe depression since the Cenozoic,all of which were accompanied by volcanic activity with different intensities.So there volcanic rock widely develops.The volcanic rocks are dominated by basalt and trachyte.In recent years,the exploration and development are mainly concentrated in the Es3 reservoir.In this paper,based on the logging data,combined with drilling core and mercury injection data,the volcanic reservoirs of the Es3 Formation of Eastern Sag from Liaohe Depression are studied in four parts: logging identification of volcanic lithology and lithofacies,quantitative calculation of volcanic rock reservoir physical properties,reservoir pore distribution and heterogeneity of volcanic facies and controlling factors of volcanic reservoir.Logging identification of volcanic lithology and lithofacies: combined with reservoir interpretation needs and feasibility of logging identification,the volcanic rocks are classified.The well logging curves which are impressible to the lithology are obtained,and the logging response characteristics are summarized.The crossplot and least squares support vector machine are used to recognize them.On this basis,the corresponding relationship between volcanic facies and logging response characteristics is established by the calibration of volcanic facies in core well.Quantitative calculation of volcanic rock reservoir physical property: in accordance with stages,the value of volcanic rock skeleton is obtained.Pore-fracture model is selected to calculate the physical parameters.Then Based on the relationship between capillary pressure curve and permeability,the relationship between permeability and capillary pressure curve is established.After the complex conversion of electrical imaging logging,the interval distribution of porosity which is similar to that of the NMR bin is formed.The capillary pressure curve of pore structure is the main tool for qualitative and quantitative evaluation;the NMR logging after conversion,can get continuous capillary pressure curve which can be very good for the pore structure of reservoir continuity interpretation and evaluation.Reservoir pore distribution and heterogeneity of volcanic facies: Based on the study of volcano diagenesis,reservoir space types,reservoir pore structure characteristics,the various facies / sub facies pore distribution characteristics are detailed analyzed,so as to establish the qualitative relationship of the volcano lithofacies and reservoir pore distribution and heterogeneity.Controlling factors of volcanic reservoir: based on the data of porosity and permeability,the standard of reservoir classification and evaluation is established.Based on the core test,well logging interpretation and oil testing,this paper discusses the influence of lithology,lithofacies and fracture on the reservoirs.(1)Logging identification of volcanic lithology and lithofacies in the Eastern Sag form Liaohe DepressionSelecting typical lithology data,the characteristics of volcanic lithology logging response in this area are summarized;and a set of suitable lithology identification chart is made for the area.The cross-plot of neutron and density can well distinguish basalts,and the cross-plot of natural gamma versus deep lateral resistivity can well identify basalts and trachyte.Using the least squares support vector machine,the lithology identification model of volcanic rock is established,and the combination of the two methods is a good solution to the problem of lithologic identification.Through the observation of cores and slices,5 lithofacies and 14 sub-facies have been divided.According to the variation of logging curves,the morphological characteristics,the contact relation between the top and bottom and the analysis of the cross-plot and the imaging logging,10 lithofacies / sub-facies such as explosive facies(pyroclastic flow,surge sub-facies),effusive lava flow facies(hyaloclastite,tabular flow,compound flow sub-facies),extrusive dome facies(inner zone,intermediate zone,and outer zone sub-facies),volcaniclastic facies(resedimented volcaniclastics,epiclast-bearing volcanogenic deposits sub-facies)were recognized.(1)The logging curves shape of explosive facies is similar,and it's not easy to distinguish;the pyroclastic flow subfacies is characterized by welding,and pyroclastic surge subfacies is with various beddings.This is the main feature of the difference between the other subfacies.(2)The conventional logging curves can be well identified and divided for the effusive facies;the hyaloclastite subfacies has high CNL,and the tabular flow subfacies is with smoothed logging curves of DEN,CNL and AC,and the compound flow subfacies is with finger-shape logging curves.According to cross-plot ot GR-CNL and ?(CNL)-?(DEN),the three types of lithofacies can be well distinguished.(3)From inner zone to outer zone of the extrusive facies,the resistivity and density decrease.According to the GR-RLLD cross-plot,the three subfacies can be well classified.(4)According to the GR curve,the volcaniclastic facies can be roughly divided into two types of subfacies,which can be divided into two types according to the stratification characteristics of the re transported volcanic sedimentary subfacies.The resedimented volcaniclastic deposits is with horizontalbeddings,that results in the two types of subfacies can be divided more accurately.(2)Quantitative calculation of volcanic rock reservoir physical properties in the Eastern Sag form Liaohe DepressionIn accordance with stages,the value of volcanic rock skeleton is obtained.Pore-fracture model is selected to calculate the physical properties.The relationship between permeability and Swanson parameters and Capillary-Parachor parameters is tried to be established.The results show that the relationship between Swanson parameters and permeability is better.After the conversion of the electrical imaging logging data,the distribution of porosity is made which is similar to the NMR porosity bins.Based on the T2 of NMR logging,the relationship between the capillary pressure curve and the nuclear magnetic resonance logging is established,and the related parameters are calculated which used to evaluate the pore structure of reservoirs.(3)Reservoir pore distribution and heterogeneity of volcanic facies in the Eastern Sag form Liaohe DepressionThe diagenesis of volcanic rocks can be divided into early period diagenesis and late period diagenesis.Early period diagenesis determines the formation and distribution of primary pores,and it sums up 8 types of diagenesis in total which are volatilization release,condensing constriction,quenching effect,devitrification,phenocryst burst effect,quasi-syngenetic hydrothermal sedimentation,welding effects,and compaction and cementation.Among the 8 types of diagenesis,volatile release,condensing constriction,quenching effect,devitrification,phenocryst burst effect,play a leading role for the formation of the primary porosity reservoirs.Late period diagenesis influences the transformation of primary porosity and the formation of secondary pores.and it sums up 7 types of diagenesis in total which are filling effect,dissolution effect,tectonic effect,weathering erosions effect,cryptoexplosive brecciation cementation and compaction.Among them dissolution and tectonism have the greatest influence on the formation of secondary pores.By observing cores and thin sections,8 categories reservoir space in volcanic rocks are identified in the Eastern sag of Liaohe Basin.There are 4 types of primary reservoir space,such as pore,frame pore,contraction fissure and cracks fissure,frame pores and contraction fissure contribute most to the reservoir.There are also 4 types of secondary reservoir space,which are dissolution pore,dissolved fracture,tectonic fracture,crypto-explosion fracture.The dissolution pore and tectonic fracture play a leading role in the effective reservoir of volcanic rocks in the area.Through a large number of mercury intrusion test results,it is found that the throat diameter of the Cenozoic volcanic rocks in the Eastern Sag is mainly between 0.02~50?m.The average pore throat diameter of trachyte reservoir is between 0.1~1?m,and the average pore throat diameter of basalt is 0.2~1?m.The pore structure of trachyte and trachyte volcanic breccia is better than that of basalt;the pore structure of vesicular basalt reservoir is better than that of massive basalt.Furthermore,on the basis of the porosity distribution of electrical imaging and the porosity bin of the NMR,combined with the mercury injection test data,5 facies and 14 sub-facies are conducted reservoir heterogeneity study in the Eastern sag of Liaohe Basin,results show that: The diatreme subfacies,pyroclastic flow subfacies,compound flow subfacies,outer zone subfacies and intermediate zone subfacies have larger pore structure.The pore size distribution is relatively concentrated and the connectivity is good in the diatreme subfacies,pyroclastic flow subfacies,outer zone subfacies and intermediate zone subfacies.The pore size distribution of compound flow subfacies is heterogeneous,the lagre and small pore size are alternately developed,and the connectivity is poor.The sub facies of diatreme,pyroclastic flow,and hyaloclastite are mainly composed of single lithology,and longitudinal and lateral heterogeneity is weak.Subfacies with bedding distribution have moderate vertical heterogeneity and weak lateral heterogeneities,such as fall deposits subfacies,surge sub-facies,resedimented volcaniclastics and epiclast-bearing volcanogenic deposits sub-facies.Layered distributed subfacies have strong vertical heterogeneity and weak lateral heterogeneities such as tabular flows sub-facies,extrusive facies.The compound lava flows sub-facies is composed of spatially varying lithology with different physical properties,and the longitudinal and lateral heterogeneity is strong.(4)Controlling factors of volcanic reservoir in the Eastern Sag form Liaohe DepressionBased on 3 quantitative parameters of porosity,permeability and throat radius,as well as oil level and oil testing data,the intermediate basic igneous reservoir is divided into 4 categories.Type ? is composed of high porosity and medium permeability reservoirs(porosity ??10%,permeability ??1×10-3?m2,maximum throat radius Rd?0.63?m).Type ?is mainly composed of medium porosity and low permeability reservoirs(?=5%~10%,?=0.1~1×10-3?m2,Rd=0.04~0.63?m).Type ?is composed of low porosity and low permeability reservoirs(?=3%~5%,?=0.1~1×10-3?m2,Rd?0.04).Type ? is composed of extra low porosity and permeability reservoirs(??3%,??0.1,Rd?0.04).The intermediate and mafic igneous rocks in the Estern Ssg of Liaohe Depression controlled lithology,lithofacies and fracture.Trachyte reservoir is better than the basalt reservoir.Different lithofacies / subfacies lead to different types of reservoir space and different combinations,which affect the reservoir properties and effectiveness of volcanic reservoirs.The favorable facies belts in the study area are mainly the outer zone,intermediate zone,pyroclastic flow and pyroclastic flow subfacies.More close to the fracture,the tectonic fractures more developed,and the more favorable reservoirs developed with better physical properties.